LES of passive scalar with phase relaxation time in isotropic turbulence

We conduct LES of passive scalar with the phase relaxation time to obtain wider inertial ranges with two -5/3 power-law spectra at large Reynolds numbers. Supersaturation (SS) fluctuations in cloud turbulence are modeled as a passive scalar advected by an isotropic turbulence and found to have two -5/3 power-law ranges with different amplitudes. The condensation-evaporation rate is expressed as the product of the liquid water content and SS in a continuum approximation, which appears as a linear damping term with the phase relaxation time in the equation of the supersaturation. LES model for the present system is developed, and the spectrum and the probability density functions of SS are examined with the focus on the effects of the phase relaxation time.