摘要
为抑制壁湍流减少表面摩擦阻力,利用Fourier-Chebyshev谱方法,通过直接数值模拟,对槽道湍流壁面展向周期振动抑制壁湍流、实现减阻的内在机理进行了研究,建立了槽道湍流数据库。通过改变振幅大小和振动周期,壁面展向周期振动可以使壁面摩擦阻力明显减少。随着平均减阻率的增加,壁面阻力随时间的变化也更加稳定并且周期逐渐变大。将1个典型的阻力变化周期分成3个特征时段进行讨论。结果表明,不同时段近壁湍流结构呈现出不同的变化规律,两种减阻机理交替出现:一是振动引起的涡与条带的倾斜,这导致负展向涡的产生;二是振动引起的涡与条带间的滑移,这导致条带的加宽以及流向涡的减弱。
In order to suppress near-wall turbulence and reduce skin-friction drag,the mechanisms of turbulence suppression and drag reduction due to spanwise wall oscillation in turbulent channel flow are investigated by direct numerical simulation（DNS） based on standard Fourier-Chebyshev spectral method.The database of turbulent channel flow is produced by DNS.The friction drag can be reduced significantly by changing the amplitude and the period of the spanwise wall oscillation.With the increase of the mean drag reduction rate,time evolution of skin-friction drag becomes steadier and shows longer periodicity.A typical drag reduction periodicity is divided to three phases for analyzing the mechanism of drag reduction.The results show： the structures of near-wall turbulence take on different states in the three typical phases;two kinds of mechanisms of turbulence suppression and drag reduction due to spanwise wall oscillation work by turns,one of which is the incline of streamwise vorticity and streaks,leading to creation of a negative spanwise vorticity,and the other of which is the relative displacement of the streamwise vorticity and streaks,making the streaks broad and the streamwise vorticity weak.
出处
《南京理工大学学报》
EI
CAS
CSCD
北大核心
2010年第3期361-366,共6页
Journal of Nanjing University of Science and Technology
关键词
槽道流
壁湍流
壁面展向周期振动
减阻
谱方法
直接数值模拟
channel flow
near-wall turbulence
spanwise wall oscillation
drag reduction
spectral method
direct numerical simulation
