成層乱流中のパッシブスカラとアクティブスカラの輸送に与える粘性・拡散性の効果(流体工学,流体機械)

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 viscosity and diffusion excite a 'showly' oscillating mode which doubles the oscillating period of the turbulent diffusion coefficient of the passive scalar. The slow mode becomes dominant with a small amount of initial potential energy. Even when the initial potential energy is negligibly small as in the grid turbulence, the slow mode still strenghens the counter-gradient passive-scalar flux especially at high wave number, in agreement with the previous laboratory experiments. The results illustrate the importance of unseady analysis of the unsteady turbulence, which has been often ignored in the previous studies.
2005-05-25