沟槽壁面对泰勒涡流稳定性影响的数值模拟

Numerical simulation of slit wall effect on Taylor-Couette flow stability

利用CFD数值模拟方法对光滑壁面与沟槽数量为18的2种同心圆柱模型内的泰勒-库艾特流动进行计算,在对比光壁模型的PIV试验与CFD数值计算结果后,发现两者吻合良好,验证了文中采用数值计算方法的准确性;针对泰勒涡流流态,定量分析了光壁模型R-Z平面上径向速度以及轴向速度的周期波动性,讨论了环隙中不同径向位置的径向以及轴向速度分布规律,获得了泰勒涡胞尺寸随着Re数增大而减小的变化规律;在相同的Re数下,沟槽数量为18的模型内也出现了泰勒涡流,通过比较2种不同结构模型内流场以及涡量场,发现沟槽的存在显著改变了流场分布,增大了环隙内涡量的大小及泰勒涡胞的尺寸,环隙中部指向外圆柱方向的径向速度也较光壁模型增大了20%,同时,计算获得R-θ平面内沟槽区域的流场分布表明该区域存在着明显的旋涡运动.

The Taylor- Couette flows in the gap between two concentric cylinders with smooth and 18-slit walls were studied using CFD method. The CFD method was validated with PIV experiments on the flow between two concentric cylinders with smooth walls and a very good agreement has been achieved. In the simulations,the periodic fluctuation properties in axial and radial velocities were quantized,and their profiles across the radius were discussed too. Importantly,a rule that the Taylor vortex size decreases with increasing Reynolds number was indentified. Interestingly,a Taylor vortex flow was also found in the gap with 18-slit walls at the same Reynolds number as the smooth walls. By comparing velocity and vorticity distributions across in the gap for two different wall profiles,it was found out the slit walls could alter the flow structure and strengthened vorticity significantly,and amplified the Taylor vortex size. As a result,the radial velocity in the mid-gap with slit walls was 20% larger than that with smooth walls. In addition,it was shown that there was an obvious vortex motion in the slit regions based on the predicted flow field in the circumferential plane in those regions.