×

The unsteady three-dimensional wake produced by a trapezoidal pitching panel. (English) Zbl 1241.76027

Summary: Particle image velocimetry (PIV) is used to investigate the three-dimensional wakes of rigid pitching panels with a trapezoidal geometry, chosen to model idealized fish caudal fins. Experiments are performed for Strouhal numbers from 0.17 to 0.56 for two different trailing edge pitching amplitudes. A Lagrangian coherent structure (LCS) analysis is employed to investigate the formation and evolution of the panel wake. A classic reverse von Kármán vortex street pattern is observed along the mid-span of the near wake, but the vortices realign and exhibit strong interactions near the spanwise edges of the wake. At higher Strouhal numbers, the complexity of the wake increases downstream of the trailing edge as the spanwise vortices spread transversely and lose coherence as the wake splits. This wake transition is shown to correspond to a qualitative change in the LCS pattern surrounding each vortex core, and can be identified as a quantitative event that is not dependent on arbitrary threshold levels. The location of this transition is observed to depend on both the pitching amplitude and free stream velocity, but is not constant for a fixed Strouhal number. On the panel surface, the trapezoidal planform geometry is observed to create additional vortices along the swept edges that retain coherence for low Strouhal numbers or high sweep angles. These additional swept-edge structures are conjectured to add to the complex three-dimensional flow near the tips of the panel.

MSC:

76-05 Experimental work for problems pertaining to fluid mechanics
76D25 Wakes and jets
76D17 Viscous vortex flows
PDF BibTeX XML Cite
Full Text: DOI Link

References:

[1] DOI: 10.1007/s00348-007-0412-1
[2] DOI: 10.1017/S0022112095000462 · Zbl 0847.76007
[3] DOI: 10.1016/S0167-2789(00)00142-1 · Zbl 0970.76043
[4] DOI: 10.1017/S0022112004002526 · Zbl 1065.76031
[5] DOI: 10.1063/1.857730
[6] DOI: 10.1063/1.1477449 · Zbl 1185.76161
[7] DOI: 10.1017/S0022112008000906 · Zbl 1151.76312
[8] DOI: 10.1017/S0022112008003583 · Zbl 1175.76012
[9] DOI: 10.1063/1.3270045 · Zbl 06437290
[10] DOI: 10.1063/1.3270044 · Zbl 1311.76102
[11] DOI: 10.1017/S0022112006003648 · Zbl 1111.76025
[12] DOI: 10.1242/jeb.025007
[13] DOI: 10.1017/S0022112005003757 · Zbl 1156.76315
[14] DOI: 10.1242/jeb.016279
[15] DOI: 10.1017/S0022112003005408 · Zbl 1063.76516
[16] DOI: 10.1063/1.3273036 · Zbl 06437289
[17] DOI: 10.1017/S002211209900467X · Zbl 0946.76030
[18] Dong, 43rd AIAA Aerospace Sciences Meeting and Exhibit (2005)
[19] DOI: 10.1146/annurev.fluid.010908.165232 · Zbl 1157.76062
[20] DOI: 10.1017/S0022112006001297 · Zbl 1157.76302
[21] DOI: 10.1016/S0889-9746(88)90058-8
[22] DOI: 10.1093/icb/icq057
[23] DOI: 10.1006/jfls.1993.1012
[24] DOI: 10.1063/1.3276061 · Zbl 1311.70034
[25] DOI: 10.1007/s10439-008-9502-3
[26] DOI: 10.1017/S0022112007008865 · Zbl 1151.76350
[27] DOI: 10.1063/1.3272780 · Zbl 06437292
[28] DOI: 10.1016/j.physd.2005.10.007 · Zbl 1161.76487
[29] DOI: 10.1063/1.2189885 · Zbl 1185.76700
[30] DOI: 10.1016/j.compfluid.2004.10.002 · Zbl 1134.76417
[31] DOI: 10.1063/1.3275499 · Zbl 06437293
[32] DOI: 10.1088/1751-8113/41/34/344011 · Zbl 1190.76143
[33] Lauder, Fish Biomechanics pp 425– (2006)
[34] DOI: 10.1063/1.1499395 · Zbl 1080.76526
[35] DOI: 10.2514/3.10246
[36] DOI: 10.1088/0957-0233/8/12/007
This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. It attempts to reflect the references listed in the original paper as accurately as possible without claiming the completeness or perfect precision of the matching.