Effect of Fluid Viscoelasticity on Turbulence and Large-Scale Vortices behind Wall-Mounted Plates
Effect of Fluid Viscoelasticity on Turbulence and Large-Scale Vortices behind Wall-Mounted Plates
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DOI：
10.1155/2014/823138
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发表时间：
2014-03
影响因子：
2.1
通讯作者：
T. Tsukahara;Masaaki Tanabe;Y. Kawaguchi
中科院分区：
文献类型：
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作者：
T. Tsukahara;Masaaki Tanabe;Y. Kawaguchi
对壁挂板通道中的湍流粘弹性流体流动进行了直接数值模拟，以研究粘弹性对湍流结构和板周围平均流量的影响。本构方程遵循 Giesekus 模型，适用于聚合物或表面活性剂溶液，通常能够减少平滑通道中的湍流摩擦阻力。我们发现，粘弹性流体中板块后面的湍流涡旋的数量和强度都减少了，但它们的大小却增加了。在牛顿流体和粘弹性流体中，在板的下游观察到三对有组织的纵向涡流：两对涡流位于板后面，另一对长度最长的涡流位于无板区域。在粘弹性流体中，无板区的后一个涡对得以维持并到达下游肋，但其旋流强度减弱，涡附近的局部表面摩擦阻力比牛顿流中的小得多。平均流量和展向小涡受到粘弹性引起的附加流体力的影响，此外，流体弹力的展向分量也可能对板后流体涡运动起到抑制作用。
Direct numerical simulations of turbulent viscoelastic fluid flows in a channel with wall-mounted plates were performed to investigate the influence of viscoelasticity on turbulent structures and the mean flow around the plate. The constitutive equation follows the Giesekus model, valid for polymer or surfactant solutions, which are generally capable of reducing the turbulent frictional drag in a smooth channel. We found that turbulent eddies just behind the plates in viscoelastic fluid decreased in number and in magnitude, but their size increased. Three pairs of organized longitudinal vortices were observed downstream of the plates in both Newtonian and viscoelastic fluids: two vortex pairs were behind the plates and the other one with the longest length was in a plate-free area. In the viscoelastic fluid, the latter vortex pair in the plate-free area was maintained and reached the downstream rib, but its swirling strength was weakened and the local skin-friction drag near the vortex was much weaker than those in the Newtonian flow. The mean flow and small spanwise eddies were influenced by the additional fluid force due to the viscoelasticity and, moreover, the spanwise component of the fluid elastic force may also play a role in the suppression of fluid vortical motions behind the plates.