Viscoelastic effect on steady wavy roll cells in wall-bounded shear flow
Viscoelastic effect on steady wavy roll cells in wall-bounded shear flow
复制标题
DOI：
10.1088/1873-7005/aac477
复制
发表时间：
2018-08
影响因子：
1.5
通讯作者：
Tomohiro Nimura;T. Kawata;T. Tsukahara
中科院分区：
文献类型：
--
作者：
Tomohiro Nimura;T. Kawata;T. Tsukahara
了解近壁减阻湍流流动的另一个步骤可以是检查具有层流背景的组织良好的流向涡流中的流动。在此，我们研究了吉塞库斯粘弹性流体在旋转平面库埃特流动系统中的流动行为，该系统伴随着稳定的滚动单元结构。通过将雷诺数和旋转数固定在提供稳定波状滚动单元（即一系列蜿蜒流向涡流）的值，魏森伯格数增加到 2000（其中弛豫时间通过壁速度和运动粘度标准化）。我们观察到，在粘弹性流中，二次流（壁法线和展向速度波动）被抑制，而流向分量保持不变，并且波状滚动单元被调制为与流向无关的直滚动单元。在非湍流背景下研究了平均剪切流、滚动单元引起的雷诺应力和粘弹性应力之间的动能传输。我们进一步讨论了调制机制及其与粘弹性壁湍流中减阻现象的相关性。
An alternative step in understanding the flows of near wall drag-reducing turbulence can be examining the flow in a well-organized streamwise vortex with a laminar background. Herein, we studied the flow behaviors of the Giesekus viscoelastic fluid in a rotating plane Couette flow system, which is accompanied by steady roll cell structures. By fixing the Reynolds and rotation numbers at values that provide as steady wavy roll cell, i.e., an array of meandering streamwise vortices, the Weissenberg number was increased up to 2000 (where the relaxation time was normalized by the wall speed and the kinematic viscosity). We observed that, in the viscoelastic flows, the secondary flow (wall-normal and spanwise velocity fluctuations) are suppressed while the streamwise component is maintained, and the wavy roll cells are modulated into streamwise-independent straight roll cells. The kinetic energy transports among the mean shear flow, Reynolds stresses due to the roll cell, and viscoelastic stress are investigated in the non-turbulent background. We further discussed the modulation mechanism and its relevance to the drag reduction phenomenon in the viscoelastic wall turbulence.