Non-Gaussian probability distribution of a velocity field in uniform straining-flow turbulence

摘要

The non-Gaussian probability distribution of a velocity field itself is found in the numerical simulation of uniform straining-flow turbulence. The distribution does not decrease as fast as a Gaussian distribution. The moment method to determine a limiting probability distribution, proposed by Sinai and Yakhot [Phys. Rev. Lett. 63, 1962 (1989)] for the passive scalar field, is examined in detail for the present velocity field. It is found by the examination of the conditional probability distribution on vorticity magnitudes that the non-Gaussianity is caused in the tube like high vorticity region, two-dimensional structure, appeared in the turbulent flow. The results are also compared with those of a passive scalar field and a three-dimensional flow with two-dimensional structure, which makes the contribution from pressure term to such distribution more apparent. It follows that the non-Gaussian distribution is due to the superior dissipation effect to the pressure (nonlinear) effect.