SCALING LAWS OF THE DISSIPATION RATE OF TURBULENT SUBGRID-SCALE KINETIC-ENERGY

The energy dissipation term appearing in the transport equation for turbulent subgrid-scale kinetic energy k is studied experimentally. Special attention is directed at the scaling properties of its moments, which are described using the multifractal formalism. In large-eddy simulations, the dissipation is usually modeled in terms of k. Therefore, the scaling of moments of k is studied as well. It is found that the latter variable displays a slightly more pronounced level of intermittency than that of the dissipation, a discrepancy whose impact on simulations is difficult to assess a priori. However, it is shown that the scaling of the expected value of dissipation conditioned upon the local kinetic energy differs markedly from the model prediction. The equation for the probability density function is used to illustrate the importance of correctly predicting this conditional expected value. An alternative model is proposed that employs the inverse strain-rate magnitude as a time scale.