Using nonequilibrium statistical mechanics closure method, it is shown that the skewness factor of the velocity derivative of isotropic turbulence ap- proaches a constant -0.515 when the Reynolds number is very high, ...Using nonequilibrium statistical mechanics closure method, it is shown that the skewness factor of the velocity derivative of isotropic turbulence ap- proaches a constant -0.515 when the Reynolds number is very high, which is in agree- ment with the DNS (direct numerical simulation) result of Vincent and Meneguzzi (1991).展开更多
Based on the analysis of the known quantitative observations and qualitative measurements in the near wall region of the flow over a smooth wall, the distribution of the skewness factor in the vertical direction has b...Based on the analysis of the known quantitative observations and qualitative measurements in the near wall region of the flow over a smooth wall, the distribution of the skewness factor in the vertical direction has been discussed for the openchannel flow over a fully roughened wall. It is found that when H/ks > 1. 0,S >0 is obtained in the range of y/H <0. 2, which means that there exist the low speed streaks, i. e. the turbulence of the now is produced by the phenomenon called 'burst'. For H/ks <1. 0, which belongs to the large-scale roughness case, the turbulence will be produced in another way. Moreover, the burst period is also discussed in this paper.展开更多
基金The project supported by the National Basic Research Program "Non-linear Science"
文摘Using nonequilibrium statistical mechanics closure method, it is shown that the skewness factor of the velocity derivative of isotropic turbulence ap- proaches a constant -0.515 when the Reynolds number is very high, which is in agree- ment with the DNS (direct numerical simulation) result of Vincent and Meneguzzi (1991).
文摘Based on the analysis of the known quantitative observations and qualitative measurements in the near wall region of the flow over a smooth wall, the distribution of the skewness factor in the vertical direction has been discussed for the openchannel flow over a fully roughened wall. It is found that when H/ks > 1. 0,S >0 is obtained in the range of y/H <0. 2, which means that there exist the low speed streaks, i. e. the turbulence of the now is produced by the phenomenon called 'burst'. For H/ks <1. 0, which belongs to the large-scale roughness case, the turbulence will be produced in another way. Moreover, the burst period is also discussed in this paper.
