B132 成層乱流中のパッシブスカラーのフラックス

概要

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Passive and active scalar fluxes in unsteady stratified turbulence are analyzed using the rapid distortion theory (RDT). Analytical solutions of the RDT equations show that the initial conditions, i.e., the initial correlation between passive scalar and active scalar (density) and the initial potential energy, make difference between the passive and active scalar flux, giving difference between the turbulent diffusion coefficients for passive and active scalars. In other words the initial 'zero' correlation gives the 'complete' correlation in the long time development, in contrast to the previous discussions based on the 'steady' turbulence equations. It is also found that the correlation coefficient between passive and active scalars is not a good measure of identifying the agreement/disagreement of the turbulent diffusion coefficients, since the initially large variance of passive scalar leads to a final small correlation coefficient. These results show the importance of 'unsteady' analysis of the initial value problem in the diffusion problem in stratified turbulence.
2002-07-23