A NUMERICAL STUDY OF PRESSURE-FLUCTUATIONS IN 3-DIMENSIONAL, INCOMPRESSIBLE, HOMOGENEOUS, ISOTROPIC TURBULENCE

Pressure fluctuations in incompressible turbulence are studied by direct numerical simulations of the three-dimensional (3-D) Navier-Stokes equations. The pressure probability distribution function (PDF) is shown to have an exponential tail on the negative side, and to be independent of the Reynolds number for Re(lambda) less than or similar to 60. At higher Reynolds numbers, the low pressure part of the pressure PDF becomes super exponential. The joint PDFs of strain, vorticity, and pressure (considered pairwise) show a strong dissymmetry between positive and negative pressure fluctuations. The results obtained from the numerical solutions of the Navier-Stokes equations are compared with a Gaussian velocity field. The two statistical ensembles are shown to lead to quantitatively different results.