摘要
采用激光多普勒测速技术对光滑和粗糙槽道湍流特性进行了实验研究。粗糙元为二维横向V型沟槽,沟槽深度为0.8mm,沟槽间距为6.4mm,对应的槽道半高度与沟槽深度比为12.5。基于中线时均速度和槽道半高度的流动雷诺数范围为2740～17400。实验测量了包括时均速度、湍流强度、雷诺切应力和速度脉动偏斜因子和平坦因子在内的湍流统计量,结果表明沟槽型粗糙度对湍流的影响不仅局限于边界层内区,而是延伸到整个边界层范围。粗糙壁面上的粗糙度函数随雷诺数的增大而增大,时均亏损速度也较光滑壁面高。沟槽抑制了内区的流向湍流强度,同时增大了外区的湍流强度。粗糙壁面上的雷诺切应力高于光滑壁面,且与湍流强度一样表现出对雷诺数的依赖性。尽管沟槽型粗糙度对流向平坦因子影响不大,但对流向偏斜因子有显著影响。
The turbulent channel flows with smooth and rough walls are investigated using laser Doppler velocimeter（LDV）.The roughness element is two-dimensional spanwise V-shape groove,and the depth and pitch of groove is 0.8mm and 6.4mm respectively.The ratio of channel half height to groove depth is 12.5.The Reynolds number based on the centerline velocity and channel half height is varied from 2740 to 17400.The measurements involve mean velocity,turbulence intensity,Reynolds shear stress and the third and fourth order moments of velocity fluctuation.Results show that the effects of groove-shape roughness are not limited in the inner layer,but extend to the whole boundary layer.The roughness function on the rough wall increases with the Reynolds number,and the velocity defect profiles are slightly higher than those on the smooth wall.The streamwise turbulence intensity is attenuated significantly in the inner layer and meanwhile is intensified slightly in the outer layer by the grooves.The Reynolds shear stress on the rough wall is evidently larger than that on the smooth wall.Similar to the turbulence intensity,the Reynolds shear stress profiles on the smooth and rough walls both exhibit low-Reynolds-number dependence.The skewness of streamwise velocity fluctuation is increased by the groove-roughness,although the flatness is hardly affected by the wall conditions.
出处
《实验流体力学》
EI
CAS
CSCD
北大核心
2012年第2期17-22,共6页
Journal of Experiments in Fluid Mechanics
