SELF-EXCITATION OF FLUCTUATIONS OF INERTIAL PARTICLE CONCENTRATION INTURBULENT FLUID-FLOW

A mechanism for intermittency in spatial distribution of small inertia l particles advected by a turbulent incompressible fluid flow is discu ssed. The mechanism is related to self-excitation (i.e., exponential g rowth without an external source) of fluctuations of concentration of small particles in a turbulent fluid how. The effect is caused by the inertia of particles which results in a divergent velocity field of pa rticles. An equation for the high-order correlation functions of conce ntration of small inertial particles is derived. It is shown that the growth rates of the higher moments of particle concentration are highe r than those of the lower moments, i.e., particle spatial distribution is intermittent. Similar phenomena occur for noninertial admixtures a dvected by divergent turbulent velocity field.