## Unsteady RANS simulation of turbulent flow and heat transfer in ribbed coolant passages of different aspect ratios.(English)Zbl 1189.76276

Summary: The flow and heat transfer in ribbed coolant passages of aspect ratios (AR) 1:1, 4:1, and 1:4 are numerically studied through the solution of the unsteady Reynolds averaged Navier-Stokes (URANS) equations. The URANS procedure, which utilizes a two equation $$k-\varepsilon$$ model for the turbulent stresses, is shown to resolve large-scale bulk unsteadiness. The computations are carried out for a fixed Reynolds number of 25,000 and density ratio of 0.13, while the Rotation number is varied between 0.12 and 0.50.
At higher rotation numbers ($$\geqslant 0.5$$) at least three inter-rib modules are required to ensure periodicity in the streamwise direction. The flow exhibits unsteadiness in the Coriolis-driven secondary flow and in the separated shear layer. The average duct heat transfer is the highest for the 4:1 AR case. For this case, the secondary flow structures consist of multiple roll cells that direct flow both to the trailing and leading surfaces. The 1:4 AR duct shows flow reversal along the leading surface at high rotation numbers. For this AR, the potential for conduction-limited heat transfer along the leading surface is identified. The friction factor reveals an increase with the rotation number, and shows a significant increase at higher rotation numbers ($$\sim Ro = 0.5$$).

### MSC:

 76F25 Turbulent transport, mixing 76M20 Finite difference methods applied to problems in fluid mechanics 80A20 Heat and mass transfer, heat flow (MSC2010)
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