S0506-3-5 一様な平均勾配のもとでのパッシヴスカラー乱流の統計([0506-3]乱流における運動量,熱,物質の輸送現象(3))

抄録

Statistics of transfer flux of a passive scalar under the mean uniform scalar gradient convected by homogeneous isotropic steady turbulence are examined by using the high resolution direct numerical simulation. It is found that the Nusselt number is expressed by the time integral of the Lagrangian velocity autocorrelation in the direction of the mean scalar gradient and increases as ScR^2_λ which agrees well with the results of the direct numerical simulation, where Sc and R_λ are the Schmidt and Reynolds numbers, respectively. The one point probability density function (PDF) of the scalar flux is also examined and found to be negatively skewed exponential but insensitive to the variation of the Reynolds and Schmidt numbers. The PDF of the scalar flux is also theoretically examined and found to be in good agreement with the numerical results.