Higherorder derivative correlations and the alignment of smallscale structures in isotropic numerical turbulence
Abstract
In a three dimensional simulation higher order derivative correlations, including skewness and flatness factors, are calculated for velocity and passive scalar fields and are compared with structures in the flow. The equations are forced to maintain steady state turbulence and collect statistics. It is found that the scalar derivative flatness increases much faster with Reynolds number than the velocity derivative flatness, and the velocity and mixed derivative skewness do not increase with Reynolds number. Separate exponents are found for the various fourth order velocity derivative correlations, with the vorticity flatness exponent the largest. Three dimensional graphics show strong alignment between the vorticity, rate of strain, and scalargradient fields. The vorticity is concentrated in tubes with the scalar gradient and the largest principal rate of strain aligned perpendicular to the tubes. Velocity spectra, in Kolmogorov variables, collapse to a single curve and a short minus 5/3 spectral regime is observed.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 December 1983
 Bibcode:
 1983STIN...8414464K
 Keywords:

 Flow Velocity;
 Statistical Distributions;
 Steady State;
 Turbulence;
 Velocity Distribution;
 Flow Distribution;
 Kurtosis;
 Mathematical Models;
 Reynolds Number;
 Scalars;
 Tensor Analysis;
 Three Dimensional Models;
 Fluid Mechanics and Heat Transfer