title: Evolution of a passive scalar spectrum in the flow of random waves.
abstract: We consider a passive pollutant advected by the flow due to linear random waves with finite attenuation. We derive the equation that governs the evolution of the pair correlation function of pollutant concentration and show that it coincides with the equation for the case of a short-correlated velocity. Due to a finite wave attenuation, nontrivial evolution (particularly, the growth of inhomogeneities) appears already in the second order in wave amplitudes. We show that random potential waves lead to the growth of concentration inhomogeneities. We identify two stationary solutions for the spectral density of concentration, equipartition, and flux state. Which one is established depends on the relation between mean square velocity gradients due to potential and solenoidal parts of the flow, respectively. We also analyze transient regimes and show how periodic component in the concentration distribution appears and disappears.
authors.affiliation: Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Gregory
authors.initials: G
authors.lastname: Falkovich
authors.forename: Doron
authors.initials: D
authors.lastname: Shlomo