弯曲槽道边壁振动情况下湍流特性的大涡模拟

LES of turbulent flow in a vibrating curved-wall channel

为了更好地理解透平机械流道内能量耗散的机理和湍流结构变化,利用大涡数值模拟方法,数值试验了时、空做正弦振动的壁面所围成的弯曲槽道内的湍流流动。研究了6种不同的振动参数下,槽道内压力分布、近壁涡量以及其它相关湍流统计量的分布特性。计算结果表明,受展向壁面振动的影响,近壁区速度梯度增加,粘性底层变薄,湍流强度增加,能量耗散加大。该研究还发现壁面展向振动而引起的能量耗散主要依赖于近壁区粘性底层的展向涡量大小。

To well understand the mechanism of energy dissipation in a turbine flow passage and explore the change of turbulence structures, a spatio-temporal sinusoidal oscillatory mode is numerieaUy tested in a turbulent curved-channel flow using large eddy simulation （LES）. Six computing eases incorporated with different vibrating parameters of the wall are dealt with, and the distributions of the pressure, vortices, and other turbulent statistical quantities in the near wall regions are studied. The results show that the turbulenee intensities increase largely in near wall regions, suggesting that the viseons sublayer is thinner as a result of the velocity graduate＇s rise due to the spanwise wall oscillation. Furthermore, the energy dissipation is increasing. The present study also shows that the mechanism of energy dissipation by spanwise-wall oscillation is strongly related to the spanwise-vortex generated at the edge of the viscous sublayer by the periodic Couette flow layer.