Recent zbMATH articles in MSC 80https://zbmath.org/atom/cc/802022-11-17T18:59:28.764376ZWerkzeugTime discretization of a nonlocal phase-field system with inertial termhttps://zbmath.org/1496.350252022-11-17T18:59:28.764376Z"Kurima, S."https://zbmath.org/authors/?q=ai:kurima.shunsukeSummary: Time discretizations of phase-field systems have been studied. For example, a time discretization and an error estimate for a parabolic-parabolic phase-field system have been studied by \textit{P. Colli} and \textit{S. Kurima} [Commun. Pure Appl. Anal. 18, No. 6, 3161--3179 (2019; Zbl 1480.35008)]. Also, a time discretization and an error estimate for a simultaneous abstract evolution equation applying parabolic-hyperbolic phase field systems and the linearized equations of coupled sound and heat flow have been studied (see [\textit{S. Kurima}, ESAIM, Math. Model. Numer. Anal. 54, No. 3, 977--1002 (2020; Zbl 1437.65120); Electron. J. Differ. Equ. 2020, Paper No. 96, 26 p. (2020; Zbl 1450.35015)]). On the other hand, although existence, continuous dependence estimates and behavior of solutions to nonlocal phase-field systems with inertial terms have been studied by \textit{M. Grasselli} et al. [Q. Appl. Math. 65, No. 3, 451--469 (2007; Zbl 1140.35352)], time discretizations of these systems seem to be not studied yet. In this paper we focus on employing a time discretization scheme for a nonlocal phase-field system with inertial term and establishing an error estimate for the difference between continuous and discrete solutions.Sufficient conditions for the continuity of inertial manifolds for singularly perturbed problemshttps://zbmath.org/1496.350972022-11-17T18:59:28.764376Z"Bonfoh, Ahmed"https://zbmath.org/authors/?q=ai:bonfoh.ahmed-sSummary: We consider a nonlinear evolution equation in the form
\[
\mathrm{U_t + A_\varepsilon U + N_\varepsilon G_\varepsilon (U)} = 0,
\tag{\(\mathrm{E}_{\varepsilon}\)}
\]
together with its singular limit problem as \(\varepsilon\to 0\)
\[
U_t+ A U+ \mathrm{N} G(U) = 0,
\tag{E}
\]
where \(\varepsilon\in (0,1]\) (possibly \(\varepsilon = 0\)), \(\mathrm{A}_\varepsilon\) and \(\mathrm{A}\) are linear closed (possibly) unbounded operators, \(\mathrm{N}_\varepsilon\) and \(\mathrm{N}\) are linear (possibly) unbounded operators, \(\mathrm{G}_\varepsilon\) and \(\mathrm{G}\) are nonlinear functions. We give sufficient conditions on \(\mathrm{A}_\varepsilon\), \(\mathrm{N}_\varepsilon\) and \(\mathrm{G}_\varepsilon\) (and also \(\mathrm{A}, \mathrm{N}\) and \(\mathrm{G})\) that guarantee not only the existence of an inertial manifold of dimension independent of \(\varepsilon\) for \((E_\varepsilon)\) on a Banach space \(\mathcal{H}\), but also the Hölder continuity, lower and upper semicontinuity at \(\varepsilon = 0\) of the intersection of the inertial manifold with a bounded absorbing set. Applications to higher order viscous Cahn-Hilliard-Oono equations, the hyperbolic type equations and the phase-field systems, subject to either Neumann or Dirichlet boundary conditions (BC) (in which case \(\Omega\subset \mathbb{R}^d\) is a bounded domain with smooth boundary) or periodic BC (in which case \(\Omega = \Pi_{i = 1}^d (0,L_i), \, L_i>0)\), \(d = 1\), 2 or 3, are considered. These three classes of dissipative equations read
\[
\phi_t+N(\varepsilon \phi_t+N^{\alpha+1} \phi +N\phi + g(\phi))+\sigma\phi = 0,\quad\alpha\in\mathbb{N},\\
\tag{\(\mathrm{P}_\varepsilon\)}
\]
\[
\varepsilon \phi_{tt}+\phi_t+N^\alpha(N \phi + g(\phi))+ \sigma\phi = 0,\quad\alpha = 0, 1,\\
\tag{\(\mathrm{H}_\varepsilon\)}
\]
and
\[
\begin{cases}
\phi_t+N^\alpha (N \phi + g(\phi)-u)+\sigma\phi = 0,\\
\varepsilon u_t+\phi_t+N u = 0,
\end{cases}
\alpha = 0, 1
\tag{\(\mathrm{S}_\varepsilon\)}
\]
respectively, where \(\sigma\ge 0\) and the Laplace operator is defined as
\[
N = -\Delta:\mathscr{D}(N) = \{\psi\in H^2(\Omega),\,\psi \text{ subject to the BC}\}\to \dot L^2(\Omega) \text{ or }L^2(\Omega).
\]
We assume that, for a given real number \(\mathfrak{c}_1>0,\) there exists a positive integer \(n = n(\mathfrak{c}_1)\) such that \(\lambda_{n+1}-\lambda_n>\mathfrak{c}_1\), where \(\{\lambda_k\}_{k\in\mathbb{N}^*}\) are the eigenvalues of \(N\). There exists a real number \(\mathscr{M}>0\) such that the nonlinear function \(g: V_j\to V_j\) satisfies the conditions \(\|g(\psi)\|_j\le\mathscr{M}\) and \(\|g(\psi)-g(\varphi)\|_{V_j}\le\mathscr{M}\|\psi-\varphi\|_{V_j}\), \(\forall\psi\), \(\varphi\in V_j\), where \(V_j = \mathscr{D}(N^{j/2})\), \(j = 1\) for Problems \((P_\epsilon)\) and \((S_\epsilon)\) and \(j = 0\), \(2\alpha\) for Problem \((H_\epsilon)\). We further require \(g\in{\mathcal C}^1(V_j, V_j)\), \(\|g'(\psi)\varphi\|_j\le\mathscr{M}\|\varphi\|_j\) for Problems \((H_\epsilon)\) and \((S_\epsilon)\).Shape optimization of a thermal insulation problemhttps://zbmath.org/1496.353832022-11-17T18:59:28.764376Z"Bucur, Dorin"https://zbmath.org/authors/?q=ai:bucur.dorin"Nahon, Mickaël"https://zbmath.org/authors/?q=ai:nahon.mickael"Nitsch, Carlo"https://zbmath.org/authors/?q=ai:nitsch.carlo"Trombetti, Cristina"https://zbmath.org/authors/?q=ai:trombetti.cristinaSummary: We study a shape optimization problem involving a solid \(K\subset\mathbb{R}^n\) that is maintained at constant temperature and is enveloped by a layer of insulating material \(\Omega\) which obeys a generalized boundary heat transfer law. We minimize the energy of such configurations among all \((K, \Omega)\) with prescribed measure for \(K\) and \(\Omega\), and no topological or geometrical constraints. In the convection case (corresponding to Robin boundary conditions on \(\partial\Omega\)) we obtain a full description of minimizers, while for general heat transfer conditions, we prove the existence and regularity of solutions and give a partial description of minimizers.Two equivalent finite volume schemes for Stefan problem on boundary-fitted grids: front-tracking and front-fixing techniqueshttps://zbmath.org/1496.651362022-11-17T18:59:28.764376Z"Gusev, A. O."https://zbmath.org/authors/?q=ai:gusev.a-o"Shcheritsa, O. V."https://zbmath.org/authors/?q=ai:shcheritsa.o-v"Mazhorova, O. S."https://zbmath.org/authors/?q=ai:mazhorova.olga-sSummary: We present finite-difference schemes on boundary-fitted grids for the two-dimensional Stefan problem. It is shown that the proposed numerical schemes constructed by front-tracking and front-fixing techniques are equivalent.A coupled fluid-mechanical workflow to simulate the directed energy deposition additive manufacturing processhttps://zbmath.org/1496.740482022-11-17T18:59:28.764376Z"Beghini, Lauren L."https://zbmath.org/authors/?q=ai:beghini.lauren-l"Stender, Michael"https://zbmath.org/authors/?q=ai:stender.michael"Moser, Daniel"https://zbmath.org/authors/?q=ai:moser.daniel"Trembacki, Bradley L."https://zbmath.org/authors/?q=ai:trembacki.bradley-l"Veilleux, Michael G."https://zbmath.org/authors/?q=ai:veilleux.michael-g"Ford, Kurtis R."https://zbmath.org/authors/?q=ai:ford.kurtis-rSummary: Simulation of additive manufacturing processes can provide essential insight into material behavior, residual stress, and ultimately, the performance of additively manufactured parts. In this work, we describe a new simulation based workflow utilizing both solid mechanics and fluid mechanics based formulations within the finite element software package SIERRA [\textit{Sierra Solid Mechanics Team}, Sierra/SolidMechanics 4.52. User's Guide SAND2019-2715. Techn. Rep., Sandia National Laboratories (2011)] to enable integrated simulations of directed energy deposition (DED) additive manufacturing processes. In this methodology, a high-fidelity fluid mechanics based model of additive manufacturing is employed as the first step in a simulation workflow. This fluid model uses a level set field to track the location of the boundary between the solid material and background gas and precisely predicts temperatures and material deposition shapes from additive manufacturing process parameters. The resulting deposition shape and temperature field from the fluid model are then mapped into a solid mechanics formulation to provide a more accurate surface topology for radiation and convection boundary conditions and a prescribed temperature field. Solid mechanics simulations are then conducted to predict the evolution of material stresses and microstructure within a part. By combining thermal history and deposition shape from fluid mechanics with residual stress and material property evolutions from solid mechanics, additional fidelity and precision are incorporated into additive manufacturing process simulations providing new insight into complex DED builds.OpenFOAM based conditional moment closure (CMC) model for solving non-premixed turbulent combustion: integration and validationhttps://zbmath.org/1496.760102022-11-17T18:59:28.764376Z"Gaikwad, Pranit"https://zbmath.org/authors/?q=ai:gaikwad.pranit"Sreedhara, S."https://zbmath.org/authors/?q=ai:sreedhara.sSummary: This article presents a direct integration of conditional moment closure (CMC), an advanced combustion model with a computational fluid dynamics (CFD) package, OpenFOAM (open-source field operation and manipulation) to solve non-premixed turbulent combustion. Earlier in [``Modelling of methanol and H\(_2\)/CO bluff-body flames using RANS based turbulence models with conditional moment closure model'', Appl. Therm. Eng. 93, 561--570 (2016; \url{doi:10.1016/j.applthermaleng.2015.09.073})], \textit{R. N. Roy} and the second author had coupled CMC code with FLUENT to model non-premixed turbulent combustion, but it was through manual two-way coupling method where CFD and CMC codes were sequentially solved one after the other until the steady state is reached. The extensible and flexible framework of OpenFOAM encouraged us to build a CFD-CMC solver called \texttt{cmcFoam}. This fully-coupled solver solves CMC equations internally in OpenFOAM along with flow-field equations. Major advantages of this solver are (1) it is built in the open-source framework, (2) it can predict the transient behavior of flames, and (3) one can benefit from all features of OpenFOAM. The validity of the proposed solver has been thoroughly demonstrated by accurately predicting experimental data published for the Sandia syngas (CO/H\(_{2}\)/N\(_{2}\)) flame. Two-dimensional axisymmetric simulations were performed with a modified \(k\)-\(\varepsilon\) turbulence model and using a chemical kinetic scheme having 21 species and 84 chemical reactions (DRM 19). Results predicted by the solver showed an excellent agreement with the published data, both in mixture fraction and physical space. This benchmarked coupled code may be useful to analyze fairly complex industrial problems.reactingfoam-SCI: an open source CFD platform for reacting flow simulationhttps://zbmath.org/1496.760132022-11-17T18:59:28.764376Z"Yang, Qi"https://zbmath.org/authors/?q=ai:yang.qi"Zhao, Peng"https://zbmath.org/authors/?q=ai:zhao.peng"Ge, Haiwen"https://zbmath.org/authors/?q=ai:ge.haiwenSummary: Computational fluid dynamics (CFD) has become a major tool in understanding and predicting the behavior of reacting flows, which intrinsically involve the complex interaction of chemical kinetics and fluid mechanics. Among various open source CFD packages, the widely used C++ finite volume simulation toolbox OpenFOAM has many advantages such as its object-orientated framework, convenience to add multiphysics module and free availability, however, many weaknesses have been identified regarding its application in chemically reacting flows, especially incomplete splitting schemes, poor ordinary differential equation (ODE) solvers for stiff chemistry and the oversimplified mixture transport models, etc. In this work, an OpenFOAM 5.0 based reacting flow CFD platform \texttt{reactingFoam-SCI} is constructed by further implementing a few state-of-the-art advances in computational combustion, including a robust midpoint operator splitting scheme, and an accurate stable stiff ODE solver with error control. An interface between OpenFOAM 5.0 and the open source package Cantera 2.3.0 is also developed, to allow the evaluation of multicomponent and mixture-averaged transport properties and the call of other Cantera subroutines. The effectiveness and robustness of this new platform have been systematically validated against the analytical solutions and literature reported direct numerical calculation results, including those from a diffusion-convection problem, homogeneous ignition delay, shock tube, one-dimensional spherical flame initiation and propagation, two-dimensional unsteady premixed flame subject to hydrodynamic and diffusional-thermal instabilities, one-dimensional non-premixed counterflow flame and two-dimensional non-premixed co-flow flame. The satisfactory agreement demonstrates the accuracy and robustness of the current platform.Shape optimisation of a heat source in a thermal convection field considering perimeter constraint conditionhttps://zbmath.org/1496.760502022-11-17T18:59:28.764376Z"Wada, Kaito"https://zbmath.org/authors/?q=ai:wada.kaito"Kurahashi, Takahiko"https://zbmath.org/authors/?q=ai:kurahashi.takahikoSummary: In this study, we present an investigation of shape optimisation analysis for a heat convection problem taking into account perimeter constraint condition. The incompressible Navier-Stokes equation using the Boussinesq approximation, the equation of continuity and the energy equation are employed for the governing equations in the heat convection field. The mixed interpolation method is applied to solve the flow field, and the quadratic and linear triangular elements are, respectively, employed for the velocity and the pressure. The quadratic triangular element is applied to interpolate the temperature. The purpose of this study is to find the optimal shape of a heat source so as to maximise the quantity of radiation on the outer boundary. The adjoint variable method is applied to obtain the optimal shape, and the perimeter constraint condition for the heat source is considered in this optimisation problem. The perimeter constraint condition is adapted in the traction method.Thermal instability and chaos in a hybrid nanofluid flowhttps://zbmath.org/1496.760522022-11-17T18:59:28.764376Z"Dèdèwanou, S. J."https://zbmath.org/authors/?q=ai:dedewanou.s-j"Monwanou, A. V."https://zbmath.org/authors/?q=ai:monwanou.a-v"Koukpémèdji, A. A."https://zbmath.org/authors/?q=ai:koukpemedji.a-a"Hinvi, L. A."https://zbmath.org/authors/?q=ai:hinvi.laurent-amoussou"Miwadinou, C. H."https://zbmath.org/authors/?q=ai:miwadinou.clement-hodevewan"Chabi Orou, J. B."https://zbmath.org/authors/?q=ai:chabi-orou.jean-bBuoyancy-driven instabilities of partially miscible fluids in inclined porous mediahttps://zbmath.org/1496.760532022-11-17T18:59:28.764376Z"Emami-Meybodi, Hamid"https://zbmath.org/authors/?q=ai:emami-meybodi.hamid"Zhang, Fengyuan"https://zbmath.org/authors/?q=ai:zhang.fengyuanSummary: This study presents a buoyancy-driven stability analysis in a three-dimensional inclined porous medium with a capillary transition zone that is formed between a non-wetting and an underlying wetting phase. In this two-phase, two-component, partially miscible system, a solute from a non-wetting phase diffuses into a porous layer saturated with a wetting-phase fluid, creating a dense diffusive boundary layer beneath an established capillary transition zone. Transient concentration and gravity-driven velocity fields are derived for the wetting phase while the saturation field remains fixed. Linear stability analysis with the quasi-steady-state approximation is employed to determine the onset of solutal convective instability for buoyancy-dominant, in-transition and capillary-dominant systems. The analysis of the problem leads to a differential eigenvalue problem composed of a system of three complex-valued equations that are numerically solved to determine the critical times, critical wavenumbers and neutral stability curves as a function of inclination angle for different Bond numbers. The layer inclination is shown to play an essential role in the stability of the problem, where the gravity-driven flow removes solute concentrations in the diffusive boundary layer. The results indicate that the horizontal porous layer exhibits the fastest onset of instability, and longitudinal rolls are always more unstable than oblique and transverse rolls. The inclination angle has a more substantial impact on stabilizing the diffusive boundary layer in the buoyancy-dominant than in the capillary-dominant systems. Furthermore, for both buoyancy-dominant and capillary-dominant systems, the critical times and wavenumbers vary exponentially with inclination angle \(\leq 60\circ\) and follow the Stirling model.A linear stability analysis of two-layer moist convection with a saturation interfacehttps://zbmath.org/1496.760622022-11-17T18:59:28.764376Z"Fu, Hao"https://zbmath.org/authors/?q=ai:fu.haoSummary: The linear convective instability of a mixture of dry air, water vapour and liquid water, with a stable unsaturated layer residing on an unstable saturated layer, is studied. It may serve as a prototype model for understanding the instability that causes mixing at the top of stratocumulus cloud or fog. Such a cloud-clear air interface is modelled as an infinitely thin saturation interface where radiative and evaporative cooling take place. The interface position is determined by the Clausius-Clapeyron equation, and can undulate with the evolution of moisture and temperature. In the small-amplitude regime two physical mechanisms are revealed. First, the interface undulation leads to the undulation of the cooling source, which destabilizes the system by superposing a vertical dipole heating anomaly on the convective cell. Second, the evolution of the moisture field induces non-uniform evaporation at the interface, which stabilizes the system by introducing a stronger evaporative cooling in the ascending region and \textit{vice versa} in the descending region. These two mechanisms are competing, and their relative contribution to the instability is quantified by theoretically estimating their relative contribution to buoyancy flux tendency. When there is only evaporative cooling, the two mechanisms break even, and the marginal stability curve remains the same as the classic two-layer Rayleigh-Bénard convection with a fixed cooling source.Heat transport and temperature boundary-layer profiles in closed turbulent Rayleigh-Bénard convection with slippery conducting surfaceshttps://zbmath.org/1496.760752022-11-17T18:59:28.764376Z"Huang, Maojing"https://zbmath.org/authors/?q=ai:huang.maojing"Wang, Yin"https://zbmath.org/authors/?q=ai:wang.yin"Bao, Yun"https://zbmath.org/authors/?q=ai:bao.yun"He, Xiaozhou"https://zbmath.org/authors/?q=ai:he.xiaozhouSummary: We report direct numerical simulations (DNS) of the Nusselt number \(Nu\), the vertical profiles of mean temperature \(\varTheta(z)\) and temperature variance \(\varOmega(z)\) across the thermal boundary layer (BL) in closed turbulent Rayleigh-Bénard convection (RBC) with slippery conducting surfaces (\(z\) is the vertical distance from the bottom surface). The DNS study was conducted in three RBC samples: a three-dimensional cuboid with length \(L = H\) and width \(W = H/4\) (\(H\) is the sample height), and two-dimensional rectangles with aspect ratios \(\varGamma \equiv L/H = 1\) and 10. The slip length \(b\) for top and bottom plates varied from 0 to \(\infty\). The Rayleigh numbers \(Ra\) were in the range \(10^6 \leqslant Ra \leqslant 10^{10}\) and the Prandtl number \(Pr\) was fixed at 4.3. As \(b\) increases, the normalised \(Nu/Nu_0\) (\(Nu_0\) is the global heat transport for \(b = 0\)) from the three samples for different \(Ra\) and \(\varGamma\) can be well described by the same function \(Nu/Nu_0 = N_0 \tanh(b/\lambda_0) + 1\), with \(N_0 = 0.8 \pm 0.03\). Here \(\lambda_0 \equiv L/(2Nu_0)\) is the thermal boundary layer thickness for \(b = 0\). Considering the BL fluctuations for \(Pr>1\), one can derive solutions of temperature profiles \(\varTheta(z)\) and \(\varOmega(z)\) near the thermal BL for \(b \geqslant 0\). When \(b=0\), the solutions are equivalent to those reported by
\textit{O. Shishkina} et al. [``Thermal boundary layer equation for turbulent Rayleigh-Bénard convection'', Phys. Rev. Lett. 114, No. 11, Article ID 114302, No. 11, 5 p. (2015; \url{doi:10.1103/PhysRevLett.114.114302})] and
\textit{Y. Wang} et al. [``Boundary layer fluctuations and their effects on mean and variance temperature profiles in turbulent Rayleigh-Bénard convection'', Phys. Rev. Fluids 1, No. 8, Article ID 082301, 11 p. (2016; \url{doi:10.1103/PhysRevFluids.1.082301})], respectively, for no-slip plates. For \(b > 0\), the derived solutions are in excellent agreement with our DNS data for slippery plates.On numerical and analytical solutions for mixed convection Falkner-Skan flow of nanofluids with variable thermal conductivityhttps://zbmath.org/1496.761272022-11-17T18:59:28.764376Z"Boumaiza, Nawel"https://zbmath.org/authors/?q=ai:boumaiza.nawel"Kezzar, Mohamed"https://zbmath.org/authors/?q=ai:kezzar.mohamed"Eid, Mohamed R."https://zbmath.org/authors/?q=ai:eid.mohamed-r"Tabet, Ismail"https://zbmath.org/authors/?q=ai:tabet.ismail(no abstract)Buoyancy effects on film boiling heat transfer from a sphere at low velocitieshttps://zbmath.org/1496.761282022-11-17T18:59:28.764376Z"Singh, Rishabh"https://zbmath.org/authors/?q=ai:singh.rishabh"Pal, Anikesh"https://zbmath.org/authors/?q=ai:pal.anikesh"De, Santanu"https://zbmath.org/authors/?q=ai:de.santanuSummary: A theoretical model is developed for the forced convection film boiling phenomenon over a heated sphere moving vertically downwards in the water. Unprecedented compared with the previous analytical studies, this model accounts for the buoyancy effects while solving the momentum and energy equations in the vapour phase to obtain the velocity and the temperature distribution in terms of the vapour boundary layer thickness. To calculate the vapour boundary layer thickness, an energy balance is applied at the vapour-liquid interface. The flow of liquid around the sphere is considered to be governed by potential theory, and the energy equation in liquid is then solved for the known velocity distribution. We find that the vapour boundary layer thickness increases with an increase in the sphere temperature, the bulk water temperature and a decrease in the free stream velocity. This further results in a decrease in the film boiling heat transfer coefficient. The present study concludes that at low free stream velocities (\(<0.5\,\mathrm{m\, s}^{-1}\)) buoyancy becomes significant in delaying the separation, and when the velocity is further reduced the separation angle approaches \(180^\circ\).Numerical simulation of a steam-water-oil mixture during thermal-steam treatment of reservoirhttps://zbmath.org/1496.761552022-11-17T18:59:28.764376Z"Bublik, S. A."https://zbmath.org/authors/?q=ai:bublik.s-a"Semin, M. A."https://zbmath.org/authors/?q=ai:semin.m-aSummary: The article presents a mathematical model and algorithm of numerical modeling of three phase mixture of steam-water-oil in porous media under thermal-steam treatment. Two-dimension problem and convection-diffusion mechanism of heat and mass transfer of mixture are considered. Physical properties of porous media are assumed homogeneous and isotropic. Explicit accounting of fracture structure is absent. Properties of steam and water are considered independent of thermodynamic parameters of the system. Physical properties of oil are also independent of thermodynamic parameters of system except for dynamic viscosity, which is depends on temperature. Description of variable steam saturation, water saturation and oil saturation is made using transient mass balance relations for each phase. From these relations and Darcy's law an equation to calculate unsteady pressure distribution is received. Temperature calculations is implemented by heat conductivity equation with hypotheses of a quasi-equilibrium thermal state of all phases and a single temperature. The presented model also considers phase transitions between steam and water by W. H. Lee model. Finite volume method is used for spatial discretization of received equations and the direct Euler scheme is used for temporal discretization. Since the mass balance equations is highly nonlinear, the Newton's method applied to solve them. Simulation of three-phase steam-water-oil mixture seepage through porous media under conditions of steam-gravity drainage was carried out using the constructed numerical scheme. During the analysis of the simulation results, the pecularities of proposed numerical method are shown.Self-turbulization in cellularly unstable laminar flameshttps://zbmath.org/1496.761642022-11-17T18:59:28.764376Z"Liu, Zirui"https://zbmath.org/authors/?q=ai:liu.zirui"Unni, Vishnu R."https://zbmath.org/authors/?q=ai:unni.vishnu-r"Chaudhuri, Swetaprovo"https://zbmath.org/authors/?q=ai:chaudhuri.swetaprovo"Sui, Ran"https://zbmath.org/authors/?q=ai:sui.ran"Law, Chung K."https://zbmath.org/authors/?q=ai:law.chung-k"Saha, Abhishek"https://zbmath.org/authors/?q=ai:saha.abhishek.1|saha.abhishekSummary: It has been suggested that a cellularly unstable laminar flame, which is freely propagating in unbounded space, can accelerate and evolve into a turbulent flame with the neighbouring flow exhibiting the basic characteristics of turbulence. Famously known as \textit{self-turbulization}, this conceptual transition in the flow regime, which arises from local interactions between the propagating wrinkled flamefront and the flow, is critical in extreme events such as the deflagration-to-detonation transition (DDT) leading to supernova explosions. Recognizing that such a transition in the flow regime has not been conclusively demonstrated through experiments, in this work, we present experimental measurements of flow characteristics of flame-generated `turbulence' for expanding cellular laminar flames. The energy spectra of such `turbulence' at different stages of cellular instability are analysed. A subsequent scaling analysis points out that the observed energy spectra are driven by the fractal topology of the cellularly unstable flamefront.Compressibility effect on Markstein number for a flame front in long-wavelength approximationhttps://zbmath.org/1496.761652022-11-17T18:59:28.764376Z"Wada, Keigo"https://zbmath.org/authors/?q=ai:wada.keigo"Fukumoto, Yasuhide"https://zbmath.org/authors/?q=ai:fukumoto.yasuhideSummary: The effect of compressibility on the Markstein number for a planar front of a premixed flame is examined, at small Mach numbers, in the form of \(M^2\)-expansions. The method of matched asymptotic expansions is used to analyze the solution in the preheat zone in a power series in two small parameters, the relative thickness of the preheat zone and the Mach number. We employ a specific form of perturbations, valid at long wavelengths, for the thermodynamic variables, which produces the correction term, to the Markstein number, of second order in the Mach number in drastically simple form. Our analysis accounts for the pressure variation as a source term in the heat-conduction equation and calls for the Navier-Stokes equation. The suppression effect of the front curvature on the Darrieus-Landau instability is enhanced by the viscous effect if \(Pr > 4/3\), but is weakened if otherwise.
For the entire collection see [Zbl 1459.37002].Non-linear boundary condition for non-ideal electrokinetic equations in porous mediahttps://zbmath.org/1496.780112022-11-17T18:59:28.764376Z"Allaire, Grégoire"https://zbmath.org/authors/?q=ai:allaire.gregoire"Brizzi, Robert"https://zbmath.org/authors/?q=ai:brizzi.robert"Labbez, Christophe"https://zbmath.org/authors/?q=ai:labbez.christophe"Mikelić, Andro"https://zbmath.org/authors/?q=ai:mikelic.androSummary: This paper studies the partial differential equation describing the charge distribution of an electrolyte in a porous medium. Realistic non-ideal effects are incorporated through the mean spherical approximation (MSA) model which takes into account finite size ions and screening effects. The main novelty is the consideration of a non-constant surface charge density on the pore walls. Indeed, a chemical equilibrium reaction is considered on the boundary to represent the dissociation of ionizable sites on the solid walls. The surface charge density is thus given as a non-linear function of the electrostatic potential. Even in the ideal case, the resulting system is a new variant of the famous Poisson-Boltzmann equation, which still has a monotone structure under quantitative assumptions on the physical parameters. In the non-ideal case, the MSA model brings in additional non-linearities which break down the monotone structure of the system. We prove existence, and sometimes uniqueness, of the solution. Some numerical experiments are performed in 2d to compare this model with that for a constant surface charge.Unification of optimization criteria and energetic analysis of a thermoelectric cooler and heaterhttps://zbmath.org/1496.800012022-11-17T18:59:28.764376Z"Gonzalez-Hernandez, S."https://zbmath.org/authors/?q=ai:gonzalez-hernandez.sSummary: The energetic analysis of a thermoelectric cooler (TEC) and a thermoelectric heater \(^1\) (TEH) is presented, with optimization criteria being unified through the ``x'' variable. A number of modes of operation are introduced that are different to those used by several authors for this type of energy converter; such modes of operation are commonly used and have been extensively studied in finite time thermodynamics (FTT) and successfully introduced into linear irreversible thermodynamics (LIT). In addition, new modes of operation are proposed for both cooler and heater. Introducing these modes of operation enables a fuller description of the energy of thermoelectric converters of this type. Finally, the loop-shaped curves concept is introduced and extended to thermoelectric cooler and heater converters in order to clarify the meaning of the dimensionless variables introduced.Heat flow calculation for a harmonic model of a one-dimensional crystalhttps://zbmath.org/1496.800022022-11-17T18:59:28.764376Z"Guzev, M. A."https://zbmath.org/authors/?q=ai:guzev.mickhail-a|guzev.mikhail-a"Dmitriev, A. A."https://zbmath.org/authors/?q=ai:dmitriev.aleksandr-a|dmitriev.a-aSummary: A one-dimensional non-dissipative harmonic chain of particles is considered, located between two thermal reservoirs. Using the fundamental solution of the one-dimensional harmonic model, an analytical representation is obtained for the discrete expression of the heat flux. Time averaging was performed, which allows taking into account the stationary characteristics of the heat transfer process. It is shown that the averaged heat flux includes two physically different components. The first one is proportional to the temperature difference between the reservoirs and characterizes the heat transfer along the chain. The second one determines the initial value of the flow when the temperatures of the tanks are equal.The calibration method for the thermal insulation functionalhttps://zbmath.org/1496.800032022-11-17T18:59:28.764376Z"Labourie, C."https://zbmath.org/authors/?q=ai:labourie.camille"Milakis, E."https://zbmath.org/authors/?q=ai:milakis.emmanouilSummary: We provide minimality criteria by construction of calibrations for functionals arising in the theory of thermal insulation.Thermal conductivity in a homogeneous strip with a linear change in thickness under boundary conditions of the first kindhttps://zbmath.org/1496.800042022-11-17T18:59:28.764376Z"Ryazhskikh, Aleksandr Viktorovich"https://zbmath.org/authors/?q=ai:ryazhskikh.aleksandr-viktorovichSummary: An accurate analytical solution has been obtained in quadratures of the initial boundary value problem for one-dimensional unsteady-state heat-transfer equation with boundary conditions of the first kind for an endless strip, while one of its boundaries is moving at a constant preset speed decreasing the strip thickness. Preliminarily, through the self-similar change of the spatial variable, the initial system of equations has been reduced to a fixed boundary system, to which the method of partitioning of dependent variables has been applied. The requirement that the coefficients before the first-order derivative must be equal to zero for the self-similar derivative and separately included function in a modified equation in partial derivative of parabolic type has allowed to determine the general structure of the solution containing an unknown function. This function is presented as a superposition of two potentials, which are proportionally connected using the self-similar derivative, what has made it possible to simplify the modified equation and to apply the classical Fourier sine integral transformation for its solution. The computation results has shown the dynamics of the local temperature profile along the changing strip thickness at a constant speed, while the kinetics of the average integral temperature shows (unlike with the case of absence of boundary movement) the presence of the maximum that shifts with the growth of the ratio of the boundary movement speed to the heat transfer speed by the conductivity to the fixed boundary. This is explained by the intensive heating up of the strip material in the conditions of the decreasing of its thickness; meanwhile, with the increase in the boundary movement speed (or with the use of material with reduced thermal conductivity), it approaches the fixed boundary. By assuming that the strip thickness is a parameter, the problem in the initial wording is solved using the method of the one-sided Laplace integral time transformation. This solution, when using the linear dependence of parameter on time, correlates with the obtained accurate solution, and therefore it can be used for the preliminary evaluation of the required characteristics of a process under consideration.Global three-dimensional solvability the axisimmetric Stefan problem for quasilinear equationhttps://zbmath.org/1496.800052022-11-17T18:59:28.764376Z"Podgaev, A. G."https://zbmath.org/authors/?q=ai:podgaev.aleksandr-grigorevich"Prudnikov, V. Ya."https://zbmath.org/authors/?q=ai:prudnikov.v-ya"Kulesh, T. D."https://zbmath.org/authors/?q=ai:kulesh.t-dSummary: We prove results related to the study of the solvability of a problem with an unknown boundary by compactness methods. Relative compactness theorems are used, which were obtained in previous publications, adapted to the study of problems like the Stefan problem with an unknown boundary.
In previous papers, for the equation considered here, we studied the initial-boundary problem in a non-cylindrical domain with a given curvilinear boundary of class \(W^1_2\) and the problem for which, under the condition on the unknown boundary, the coefficient latent specific heat of fusion (in contrast to the Stefan problem, considered given here) was an unknown quantity.
Therefore, in some places calculations will be omitted that almost completely coincide with those set out in the works listed below. The proposed technique can be applied in more general situations: more phase transition boundaries, or more complex nonlinearities.
As a result, global over time, the regular solvability of a single-phase axisymmetric Stefan problem for a quasilinear three-dimensional parabolic equation with unknown boundary from the class \(W^1_4\), is proved.Lagrangian simulation of three-dimensional macro-scale melting based on enthalpy methodhttps://zbmath.org/1496.800062022-11-17T18:59:28.764376Z"Xiong, Jinbiao"https://zbmath.org/authors/?q=ai:xiong.jinbiao"Zhu, Yingzi"https://zbmath.org/authors/?q=ai:zhu.yingzi"Zhang, Tengfei"https://zbmath.org/authors/?q=ai:zhang.tengfei"Cheng, Xu"https://zbmath.org/authors/?q=ai:cheng.xuSummary: Melting and solidification are encountered or utilized in industrial applications. Based on the moving particle semi-implicit (MPS) method a robust numerical approach is developed for simulation of macroscopic melting. In the approach, the passively moving solid model, which accounts for liquid-solid interaction force, is introduced to facilitate simultaneous solution in the liquid and solid part for all the governing equations. An enthalpy-based viscosity model is utilized to realize smooth transition of viscosity on the liquid-solid interface. The potential-force surface tension and contact angle model are also employed to ensure realistic simulation of free surface motion during melting. To suppress possible numerical instability and ensure robustness of numerical solution, the viscosity term in the momentum equation is solved implicitly. In the meanwhile, the blended source term is utilized in the pressure Poisson equation. Verification of the developed simulation approach is carried out with a one-dimensional conduction-induced melting problem. The liquid-solid interface can be sharply predicted in the simulation. And the interface position and temperature profile are accurately calculated. The approach is further validated with the three-dimensional cube melting. Pressure oscillation is observed in the simulation when the melt starts. The oscillation can be dampened when enough liquid exists under the solid cube. Comparison with experimental data shows that the simulation can properly capture the motion of solid cube and spreading of liquid film during melting.On uniqueness in the problems of determining point sources in mathematical models of heat and mass transferhttps://zbmath.org/1496.800072022-11-17T18:59:28.764376Z"Neustroeva, Lyubov' Vladimirovna"https://zbmath.org/authors/?q=ai:neustroeva.lyubov-vladimirovnaSummary: We consider the problem of determining point sources for mathematical models of heat and mass transfer. The values of a solution (concentrations) at some points lying inside the domain are taken as overdetermination conditions. A second-order parabolic equation is considered, on the right side of which there is a linear combination of the Dirac delta functions \(\delta(x-x_i)\) with coefficients that depend on time and characterize the intensities of sources. Several different problems are considered, including the problem of determining the intensities of sources if their locations are given. In this case, we present the theorem of uniqueness of solutions, the proof of which is based on the Phragmén-Lindelöf theorem. Next, in the model case, we consider the problem of simultaneous determining the intensities of sources and their locations. The conditions on the number of measurements (the ovedetermination conditions) are described which ensure that a solution is uniquely determined. Examples are given to show the accuracy of the results. This problem arises when solving environmental problems, first of all, the problems of determining the sources of pollution in a water basin or atmosphere. The results are important when developing numerical algorithms for solving the problem. In the literature, such problems are solved numerically by reducing the problem to an optimal control problem and minimizing the corresponding objective functional. The examples show that this method is not always correct since the objective functional can have a significant number of minima.A dynamic load balancing method for the evaluation of chemical reaction rates in parallel combustion simulationshttps://zbmath.org/1496.800082022-11-17T18:59:28.764376Z"Muela, J."https://zbmath.org/authors/?q=ai:muela.j"Borrell, R."https://zbmath.org/authors/?q=ai:borrell.ricard"Ventosa-Molina, J."https://zbmath.org/authors/?q=ai:ventosa-molina.j"Jofre, L."https://zbmath.org/authors/?q=ai:jofre.lluis"Lehmkuhl, O."https://zbmath.org/authors/?q=ai:lehmkuhl.oriol"Pérez-Segarra, C. D."https://zbmath.org/authors/?q=ai:perez-segarra.carlos-davidSummary: The development and assessment of an efficient parallelization method for the evaluation of reaction rates in combustion simulations is presented. Combustion simulations where the finite-rate chemistry model is employed are computationally expensive. In such simulations, a transport equation for each species in the chemical reaction mechanism has to be solved, and the resulting system of equations is typically stiff. As a result, advanced implicit methods must be applied to obtain accurate solutions using reasonable time-steps at expenses of higher computational resources than explicit or classical implicit methods. In the present work, a new algorithm aimed to enhance the numerical performance of the time integration of stiff systems of equations in parallel combustion simulations is presented. The algorithm is based on a runtime load balancing mechanism, increasing noteworthy the computational performance of the simulations, and consequently, reducing significantly the computer time required to perform the numerical combustion studies.The study of the influence of impurities on the formation of synthetic diamond in the zone of thermal influence of laser radiationhttps://zbmath.org/1496.800092022-11-17T18:59:28.764376Z"Emelyanov, V. A."https://zbmath.org/authors/?q=ai:emelyanov.viacheslav-a"Shershnev, E. B."https://zbmath.org/authors/?q=ai:shershnev.e-b"Kupo, A. N."https://zbmath.org/authors/?q=ai:kupo.a-n"Sokolov, S. I."https://zbmath.org/authors/?q=ai:sokolov.s-iSummary: The paper presents the results of mathematical modeling of the process of thermochemical treatment of diamond. The influence of thermal-physical properties of synthetic diamond, which depend on the temperature, on the dynamics of physical and chemical processes in the laser treatment zone is studied.The influence of environmental conditions on the biological availability and accumulation of \(^{137}Cs\) by wild-growing meadow grasses of the exclusion zonehttps://zbmath.org/1496.800102022-11-17T18:59:28.764376Z"Kalinichenko, S. A."https://zbmath.org/authors/?q=ai:kalinichenko.s-a"Nikitin, A. N."https://zbmath.org/authors/?q=ai:nikitin.a-n"Shurankova, O. A."https://zbmath.org/authors/?q=ai:shurankova.o-aSummary: The features of the influence of various environmental conditions on the biological availability and accumulation of \(^{137}Cs\) by meadow grasses of exclusion zone of the CNPP have been established. A decrease in the concentration of \(^{137}Cs\) in meadow grasses was found as the phytocenozes moved away from the epicenter of the accident, with a decrease in the quality indicators of the community (projective cover and physical condition of plants). The effect of soil agrochemical parameters, soil moisture content, and the ratio of radionuclide mobility forms in soil on the bioavailability of \(^{137}Cs\) was studied. The analysis of the soil-to-plant transfer factors \((C_f)\) and aggregated transfer factors \((T_{ag})\), the discrimination coefficient (DF) of \(^{137}Cs\) by a chemical analog element (potassium) was carried out. The species features of the plants associated with the transport of \(K^+-Cs^+\) cations make significant adjustments to the mechanisms of \(^{137}Cs\) accumulation.Slow migration of brine inclusions in first-year sea icehttps://zbmath.org/1496.800112022-11-17T18:59:28.764376Z"Kraitzman, Noa"https://zbmath.org/authors/?q=ai:kraitzman.noa"Promislow, Keith"https://zbmath.org/authors/?q=ai:promislow.keith"Wetton, Brian"https://zbmath.org/authors/?q=ai:wetton.brian-rThe authors propose a thermodynamically consistent system for a mixture of water, ice and salt in the 3D domain \(\Omega =[0,d_{0}]^{3}\) containing a brine inclusion. Introducing a gradient flow which conserves the internal energy, increases the entropy and conserves the total salt density, together with modifications of the entropy density, they end with the coupled system
\[
\begin{aligned}
\phi _{t}&=\frac{1}{H}\Delta \phi -HW_{0}^{\prime }(\phi )-W_{1}^{\prime }(\phi )(N+b(\widehat{\theta })/\widehat{\theta })+\frac{N}{\phi }, \\
u_{t}&=\sigma _{\theta }\Delta \widehat{\theta },\quad N_{t}=\sigma _{N}\nabla \cdot (N(W_{1}^{\prime }(\phi )-\frac{1}{\phi })\nabla \phi +\nabla N+\delta _{g}e_{3}N),
\end{aligned}
\]
where \(\phi \) is the liquid phase function, \(\theta \) the temperature, \(u\) the internal energy, \(N\) the salt weight fraction, \(W_{0}\) the double-well potential \(W_{0}(\phi )=18\phi ^{2}(1-\phi )^{2}\), \(W_{1}\) the function \(W_{1}(\phi )=2\phi ^{2}(\phi -3/2)\), and \(H\) the ratio between the brine inclusion length and\ the liquid-ice water interface width. Zero-flux boundary conditions are imposed. The authors then introduce \(\rho >0\) as a spatial constant defining the salt density relative to liquid water density, they remove the fast variation from the salt variable, they consider the temperature as a dependent variable, and the potential modified as \(V(\phi ;\theta ,\rho )=W_{0}(\phi )+\frac{1}{H}V_{1}(\phi ;\theta ,\rho ) \), where \(V_{1}\) is some perturbation which involves \(W_{1}\).\ Considering the case \(H\gg 1\), they derive a Stefan-type problem for the evolution of the ice-liquid interface \(\Gamma (t)\) through its normal velocity \( V_{n}(p,t)=-H^{-1}\overset{.}{z}\), where \(\overset{.}{z}\) gives the rate of approach of the front to a point \(x=x(z,p)\) and has an expansion of the form \(\overset{.}{z}=\overset{.}{z}_{0}+H^{-1}\overset{.}{z}_{1}+O(H^{-2})\). The authors introduce similar asymptotic expansions for the variables \(\theta \), \(\phi \) and \(N\), in the outer region and for the variables \(\theta \), \(\phi \) and \(\rho \), in the inner region. They draw computations on the first-order terms distinguishing between outer and inner systems. In the last part of their paper, the authors build a Stefan-type problem for a brine inclusion in sea ice. Considering the slow evolution of the evolving boundary \(\Gamma (t)\), which divides the domain \(\Omega \) into subdomains \(\Omega _{s}\) and \( \Omega _{l}\), they derive the nonlinear parabolic equation for the temperature \((1+b(\Theta _{0})\chi _{l})\partial _{t}\Theta _{0}=\sigma \theta \Delta \Theta _{0}\), in \(\Omega \), where \(\chi _{l}\) is the characteristic function of the inclusion, with the boundary conditions \( \Theta _{0}=\Theta _{b}(x,t)\) on \(\partial \overline{\Omega }\cup \partial \underline{\Omega }\), \(\partial _{n}\Theta _{0}\)\ on \(\partial \Omega _{l}\), with \(\partial \overline{\Omega }=[0,d_{0}]^{2}\times \{d_{0}\}\), \(\partial \underline{\Omega }=[0,d_{0}]^{2}\times \{0\}\), and the parabolic equation for the salt in the brine inclusion \(\partial _{t}N_{0}=\sigma _{N}\nabla \cdot (\nabla N_{0}+\delta _{g}e_{3}N_{0})\), in \(\Omega _{l}\), with the boundary condition \(\partial _{n}N_{0}\)\ on \(\partial \Omega \cap \Omega _{l} \). They consider a particular case leading to a quasi-equilibrium Stefan-type problem. They numerically solve this problem for axisymmetric surfaces. They finally analyze the impact of thermal gradients on the behavior of the system.
Reviewer: Alain Brillard (Riedisheim)Homogenization of the time-dependent heat equation on planar one-dimensional periodic structureshttps://zbmath.org/1496.800122022-11-17T18:59:28.764376Z"Ljulj, Matko"https://zbmath.org/authors/?q=ai:ljulj.matko"Schmidt, Kersten"https://zbmath.org/authors/?q=ai:schmidt.kersten"Semin, Adrien"https://zbmath.org/authors/?q=ai:semin.adrien"Tambača, Josip"https://zbmath.org/authors/?q=ai:tambaca.josipSummary: In this paper we consider the homogenization of a time-dependent heat conduction problem on a planar one-dimensional periodic structure. On the edges of a graph the one-dimensional heat equation is posed, while the Kirchhoff junction condition is applied at all (inner) vertices. Using the two-scale convergence adapted to homogenization of lower-dimensional problems we obtain the limit homogenized problem defined on a two-dimensional domain that is occupied by the mesh when the mesh period \(\delta\) tends to 0. The homogenized model is given by the classical heat equation with the conductivity tensor depending on the unit cell graph only through the topology of the graph and lengthes of its edges. We show the well-posedness of the limit problem and give a purely algebraic formula for the computation of the homogenized conductivity tensor. The analysis is completed by numerical experiments showing a convergence to the limit problem where the convergence order in \(\delta\) depends on the unit cell pattern.Weak measurement effects on dynamics of quantum correlations in a two-atom system in thermal reservoirshttps://zbmath.org/1496.810342022-11-17T18:59:28.764376Z"Ananth, N."https://zbmath.org/authors/?q=ai:ananth.nandini"Muthuganesan, R."https://zbmath.org/authors/?q=ai:muthuganesan.r"Chandrasekar, V. K."https://zbmath.org/authors/?q=ai:chandrasekar.v-kSummary: The dynamical behaviour of quantum correlations captured by different forms of Measurement-Induced Nonlocality (MIN) between two atoms coupled with thermal reservoirs is investigated and compared with the entanglement. It is shown that the MIN quantities are more robust, while noise causes sudden death in entanglement. Further, we quantified the quantum correlation with weak measurement and the effect of measurement strength is observed. The role of mean photon number and weak measurements on quantum correlation is also highlighted.Bound state solutions and thermodynamic properties of modified exponential screened plus Yukawa potentialhttps://zbmath.org/1496.810482022-11-17T18:59:28.764376Z"Antia, Akaninyene D."https://zbmath.org/authors/?q=ai:antia.akaninyene-d"Okon, Ituen B."https://zbmath.org/authors/?q=ai:okon.ituen-b"Isonguyo, Cecilia N."https://zbmath.org/authors/?q=ai:isonguyo.cecilia-n"Akankpo, Akaninyene O."https://zbmath.org/authors/?q=ai:akankpo.akaninyene-o"Eyo, Nsemeke E."https://zbmath.org/authors/?q=ai:eyo.nsemeke-eSummary: In this research paper, the approximate bound state solutions and thermodynamic properties of Schrödinger equation with modified exponential screened plus Yukawa potential (MESPYP) were obtained with the help Greene-Aldrich approximation to evaluate the centrifugal term. The Nikiforov-Uvarov (NU) method was used to obtain the analytical solutions. The numerical bound state solutions of five selected diatomic molecules, namely mercury hydride (HgH), zinc hydride (ZnH), cadmium hydride (CdH), hydrogen bromide (HBr) and hydrogen fluoride (HF) molecules were also obtained. We obtained the energy eigenvalues for these molecules using the resulting energy eigenequation and total unnormalized wave function expressed in terms of associated Jacobi polynomial. The resulting energy eigenequation was presented in a closed form and applied to study partition function (Z) and other thermodynamic properties of the system such as vibrational mean energy (U), vibrational specific heat capacity (C), vibrational entropy (S) and vibrational free energy (F). The numerical bound state solutions were obtained from the resulting energy eigenequation for some orbital angular quantum number. The results obtained from the thermodynamic properties are in excellent agreement with the existing literature. All numerical computations were carried out using spectroscopic constants of the selected diatomic molecules with the help of MATLAB 10.0 version. The numerical bound state solutions obtained increases with an increase in quantum state.Wigner function as a detector of entanglement in open two coupled Inas semiconductor quantum dotshttps://zbmath.org/1496.810632022-11-17T18:59:28.764376Z"Mansour, H. Ait"https://zbmath.org/authors/?q=ai:mansour.hicham-ait"Siyouri, F-Z."https://zbmath.org/authors/?q=ai:siyouri.f-zSummary: We tested the ability of Wigner function to reveal and capture the quantum entanglement presents in two coupled semiconductor InAs quantum dots that independently interact with dephasing reservoirs. In this respect, we analyze their evolution against the temperature parameter as well as against the dimensionless time in both Markovian and non-Markovian environments. Further, we compare their amounts and their behaviors under the Förster interaction effect. In particular, we show that for large values of dimensionless time and at higher temperature, unlike the full disappear of entanglement the positive part of Wigner function still survives. Moreover, we show that the Wigner function volume is influenced by the variation of the Förster interaction, the temperature and the non-Markovianity degree. Nevertheless, its ability to reveal the quantum entanglement presents inside two coupled semiconductor quantum dots is still kept.Quantum-memory-assisted entropic uncertainty relation in the Heisenberg XXZ spin chain model with external magnetic fields and Dzyaloshinski-Moriya interactionhttps://zbmath.org/1496.810702022-11-17T18:59:28.764376Z"Zhang, Yanliang"https://zbmath.org/authors/?q=ai:zhang.yanliang"Zhou, Qingping"https://zbmath.org/authors/?q=ai:zhou.qingping"Kang, Guodong"https://zbmath.org/authors/?q=ai:kang.guodong"Wen, Jiaxin"https://zbmath.org/authors/?q=ai:wen.jiaxin"Fang, Maofa"https://zbmath.org/authors/?q=ai:fang.maofaSummary: In this paper, we investigate the quantum-memory-assisted (QMA) entropic uncertainty relation in the two-qubit Heisenberg XXZ spin chain model. The contributions of relevant parameters of the model on the reducing of QMA entropic uncertainty concerning a pair of Pauli observables are studied in detail under the thermal equilibrium and intrinsic decoherence conditions, respectively. The results show that, in the case of thermal equilibrium, the lower of \(T\) and the stronger of spin coupling interaction \(J,J_z\) and Dzyaloshinskii-Moriya (DM) interaction \(D_z\) are more beneficial to the reducing of QMA entropic uncertainty. However, the stronger of external nonuniform magnetic field \(\mathfrak{B}\) hinders the reducing of the QMA entropic uncertainty. Meanwhile, there exists a critical phenomena with respect to \(\mathfrak{B}\) at the extremal low temperature. By taking into account the effect of intrinsic decoherence, it is found that the dynamical features of QMA entropic uncertainty are sensitive to the values of \(D_z\) and unnonuniform magnetic fields \(\mathfrak{b}\). In the weak DM interaction region, the strengthening of \(D_z\) can markedly reduce the entropic uncertainty \(U\) during the evolution process, but, in the strong DM interaction region, the strengthening of \(D_z\) makes the effect of intrinsic decoherence more pronounced. Furthermore, the large nonuniformity \(\mathfrak{b}\) dose not suppress the entropic uncertainty but makes the oscillation behaviours of \(U\) and \(U_b\) disappear. The large nonuniformity \(\mathfrak{b}\) also makes the effect of intrinsic decoherence more pronounced.Energy shift of a uniformly moving two-level atom through a thermal reservoirhttps://zbmath.org/1496.810722022-11-17T18:59:28.764376Z"Cai, Huabing"https://zbmath.org/authors/?q=ai:cai.huabing"Wang, Li-Gang"https://zbmath.org/authors/?q=ai:wang.ligangSummary: We investigate the implications of an atomic constant velocity in the energy shift of a two-level atom inside the thermal bath of a quantum scalar field, which is described by the Bose-Einstein distribution. The use of DDC formalism shows that the contribution of thermal fluctuations on the atomic level shifts depends on the atomic velocity and the temperature of the heat reservoir but the contribution of radiation reaction is totally insusceptible. The resulting energy shifts are analyzed and examined in detail under different circumstances. The atomic uniform linear motion always broadens the atomic level spacing in the limit of low temperature but narrows down it in the limit of high temperature. Our work clearly indicates that the moving heat reservoir shifts the atomic levels in a way quite different from that of the static one.Ground-state cooling of the mechanical resonator in an optomechanical cavity with two-level atomic ensemblehttps://zbmath.org/1496.811152022-11-17T18:59:28.764376Z"Liu, Ni"https://zbmath.org/authors/?q=ai:liu.ni"Chang, Rui"https://zbmath.org/authors/?q=ai:chang.rui"Zhang, Suying"https://zbmath.org/authors/?q=ai:zhang.suying"Liang, J.-Q."https://zbmath.org/authors/?q=ai:liang.jiuqingSummary: We first propose the ground-state cooling of a mechanical resonator (MR) via a electromagnetically-induced-transparency (EIT)-like cooling mechanism in an optomechanical cavity with two-level atomic ensemble. By tuning optimal parameters in stable region, we meet that the cooling process of the MR corresponds to the maximum value of the optical fluctuation spectrum, while the heating process of the MR corresponds to the minimum value of the optical fluctuation spectrum. Without the original resolved sideband condition, the MR could be cooled to its ground state by manipulating the atom-field coupling strength only satisfying the decay rate is smaller than the MR's frequency, which can be observed by the cooling rate and the mean phonon number. Meanwhile, the action of the atomic ensemble in the ground-state cooling of the MR is equal to the one of the auxiliary cavity in a double-cavity optomechanical system. In addition, the influence of other parameters on the cooling of the MR is also discussed. In the experiment and theory, the optomechanical cavity with two-level atomic ensemble is easier to implement and manipulate than the related double-cavity optomechanical system.Möbius mirrorshttps://zbmath.org/1496.830062022-11-17T18:59:28.764376Z"Good, Michael R. R."https://zbmath.org/authors/?q=ai:good.michael-r-r"Linder, Eric V."https://zbmath.org/authors/?q=ai:linder.eric-vNon-isothermal squeeze film damping in the test of gravitational inverse-square lawhttps://zbmath.org/1496.830122022-11-17T18:59:28.764376Z"Ke, Jun"https://zbmath.org/authors/?q=ai:ke.jun"Luo, Jie"https://zbmath.org/authors/?q=ai:luo.jie"Tan, Yu-Jie"https://zbmath.org/authors/?q=ai:tan.yujie"Liu, Zhe"https://zbmath.org/authors/?q=ai:liu.zhe"Shao, Cheng-Gang"https://zbmath.org/authors/?q=ai:shao.chenggang"Yang, Shan-Qing"https://zbmath.org/authors/?q=ai:yang.shan-qingOptical and thermodynamic behaviors of Ayón-Beato-García black holes for 4D Einstein Gauss-Bonnet gravityhttps://zbmath.org/1496.830232022-11-17T18:59:28.764376Z"Belhaj, Adil"https://zbmath.org/authors/?q=ai:belhaj.adil"Sekhmani, Yassine"https://zbmath.org/authors/?q=ai:sekhmani.yassineSummary: We investigate a family of four dimensional \((4D)\) Ayón-Beato-García (ABG) black holes in Einstein Gauss-Bonnet (EGB) gravity. We approach and examine the associated thermodynamic and the optical aspects by varying the involved parameters. We first compute and analyze the corresponding thermodynamic quantities. Among others, we inspect the global and the local stability behaviors. Then, we study the optical behaviors. Using Hamilton-Jacobi method, we study the shadow geometrical configurations in terms of one dimensional real closed curves. Using Gauss-Bonnet theorem, we calculate and examine the deflection angle of light rays by such black holes. In specific regions of a reduced moduli space obtained by fixing the mass and varying the remaining parameters, the present work recovers certain previous findings. Finally, we provide a possible speculative connection with observations from Event Horizon Telescope by imposing certain constraints on the involved b parameters in the light of the M\(87^\ast\) image.Topological confinement in Skyrme holographyhttps://zbmath.org/1496.830262022-11-17T18:59:28.764376Z"Cartwright, Casey"https://zbmath.org/authors/?q=ai:cartwright.casey"Harms, Benjamin"https://zbmath.org/authors/?q=ai:harms.benjamin-c"Kaminski, Matthias"https://zbmath.org/authors/?q=ai:kaminski.matthias"Thomale, Ronny"https://zbmath.org/authors/?q=ai:thomale.ronnyUniformly accelerated Brownian oscillator in (2+1)D: temperature-dependent dissipation and frequency shifthttps://zbmath.org/1496.830352022-11-17T18:59:28.764376Z"Moustos, Dimitris"https://zbmath.org/authors/?q=ai:moustos.dimitrisSummary: We consider an Unruh-DeWitt detector modeled as a harmonic oscillator that is coupled to a massless quantum scalar field in the (2+1)-dimensional Minkowski spacetime. We treat the detector as an open quantum system and employ a quantum Langevin equation to describe its time evolution, with the field, which is characterized by a frequency-independent spectral density, acting as a stochastic force. We investigate a point-like detector moving with constant acceleration through the Minkowski vacuum and an inertial one immersed in a thermal reservoir at the Unruh temperature, exploring the implications of the well-known non-equivalence between the two cases on their dynamics. We find that both the accelerated detector's dissipation rate and the shift of its frequency caused by the coupling to the field bath depend on the acceleration temperature. Interestingly enough this is not only in contrast to the case of inertial motion in a heat bath but also to any analogous quantum Brownian motion model in open systems, where dissipation and frequency shifts are not known to exhibit temperature dependencies. Nonetheless, we show that the fluctuating-dissipation theorem still holds for the detector-field system and in the weak-coupling limit an accelerated detector is driven at late times to a thermal equilibrium state at the Unruh temperature.Cosmological viability of a double field unified model from warm inflationhttps://zbmath.org/1496.830472022-11-17T18:59:28.764376Z"D'Agostino, Rocco"https://zbmath.org/authors/?q=ai:dagostino.rocco"Luongo, Orlando"https://zbmath.org/authors/?q=ai:luongo.orlandoSummary: In this paper, we investigate the cosmological viability of a double scalar field model motivated by warm inflation. To this end, we first set up the theoretical framework in which dark energy, dark matter and inflation are accounted for in a triple unification scheme. We then compute the overall dynamics of the model, analyzing the physical role of coupling parameters. Focussing on the late-time evolution, we test the model against current data. Specifically, using the low-redshift Pantheon Supernovae Ia and Hubble cosmic chronometers measurements, we perform a Bayesian analysis through the Monte Carlo Markov Chains method of integration on the free parameters of the model. We find that the mean values of the free parameters constrained by observations lie within suitable theoretical ranges, and the evolution of the scalar fields provides a good resemblance to the features of the dark sector of the universe. Such behaviour is confirmed by the outcomes of widely adopted selection criteria, suggesting a statistical evidence comparable to that of the standard \(\Lambda\)CDM cosmology. We finally discuss the presence of large uncertainties over the free parameters of the model and we debate about fine-tuning issues related to the coupling constants.Regions without invariant tori of given class for the planar circular restricted three-body problemhttps://zbmath.org/1496.850022022-11-17T18:59:28.764376Z"Kallinikos, N."https://zbmath.org/authors/?q=ai:kallinikos.n"MacKay, R. S."https://zbmath.org/authors/?q=ai:mackay.robert-s"Syndercombe, T."https://zbmath.org/authors/?q=ai:syndercombe.tSummary: A method to establish regions of phase space through which pass no invariant tori transverse to a given direction field is applied to the planar circular restricted three-body problem. Implications for the location of stable orbits for planets around a binary star are deduced. It is expected that lessons learnt from this problem will be useful for applications of the method to other contexts such as flux surfaces for magnetic fields, guiding centre motion in magnetic fields, and classical models of chemical reaction dynamics.Structure of magnetized strange quark star in perturbative QCDhttps://zbmath.org/1496.850042022-11-17T18:59:28.764376Z"Sedaghat, J."https://zbmath.org/authors/?q=ai:sedaghat.j"Zebarjad, S. M."https://zbmath.org/authors/?q=ai:zebarjad.s-mohammad|zebarjad.seyed-mostafa"Bordbar, G. H."https://zbmath.org/authors/?q=ai:bordbar.g-h"Eslam Panah, B."https://zbmath.org/authors/?q=ai:eslam-panah.bSummary: We have performed the leading order perturbative calculation to obtain the equation of state (EoS) of the strange quark matter (SQM) at zero temperature under the magnetic field \(B = 10^{18}G\). The SQM comprises two massless quark flavors (up and down) and one massive quark flavor (strange). Consequently, we have used the obtained EoS to calculate the maximum gravitational mass and the corresponding radius of the magnetized strange quark star (SQS). We have employed two approaches, including the regular perturbation theory (\textbf{RPT}) and the background perturbation theory (\textbf{BPT}). In \textbf{RPT} the infrared (IR) freezing effect of the coupling constant has not been accounted for, while this effect has been included in \textbf{BPT}. We have obtained the value of the maximum gravitational mass to be more than three times the solar mass. The validity of isotropic structure calculations for SQS has also been investigated. Our results show that the threshold magnetic field from which an anisotropic approach begins to be significant lies in the interval \(2 \times 10^{18}G < B < 3 \times 10^{18}G\). Furthermore, we have computed the redshift, compactness and Buchdahl-Bondi bound of the SQS to show that this compact object cannot be a black hole.