DOI: 10.1615/TSFP10
DISSIPATIVE RANGE STATISTICS OF TURBULENT FLOWS WITH VARIABLE VISCOSITY
ABSTRACT
The decay of homogeneous isotropic turbulence in a variable viscosity fluid is analyzed by means of highly resolved direct numerical simulations. An important question that is addressed by the present work is how the dissipation mechanism is changed by fluctuations of the viscosity. From the budget equation of the turbulent energy it is shown that the mean dissipation is nearly unchanged by variable viscosity effects. This result is explained by a negative correlation between the local viscosity and the local velocity gradients. However, the dissipation is a highly fluctuating quantity with a strong level of intermittency. From a statistical analysis it is shown that turbulent flows with variable viscosity are characterized by an enhanced level of small-scale intermittency, which results in the presence of smaller length scales and a modified turbulent mixing. The effect of variable viscosity on the turbulent cascade is analyzed by two-point statistics.