Experimental study of turbulent mixing of the cloud with unsaturated air under different humidity

This paper presents PIV results of turbulent mixing of the cloud and unsaturated air with different environmental humidity in a small cloud chamber (80 ×80 ×100cm3 ).Turbu-lence characteristics such as the variation,skewness and flatness factors of two-dimensional ve-locities are first calculated to demonstrate the anisotropy of such turbulent fields of several centi-meters scale.Experimental results further show that the departure of the probability density function(PDF)of the vertical velocity component from the standard Gaussian distribution be-comes more obvious at the tails with the increase of unsaturated environmental humidity.The anisotropy of the turbulence is further revealed by the difference between the second-order struc-ture functions of two velocity components.The isotropic ratio (the ratio of transverse structure functions to longitudinal structure functions)is far different from the theoretical value for homo-geneous and isotropic turbulence and its dependence on the environmental humidity is complicated and needs further investigation.