Empirical Correlations for Slightly Heated Decaying Passive-Grid Turbulence

摘要

For homogeneous isotropic turbulence approximated by grid turbulence, velocity and temperature fluctuations decay under the effects of viscosity and thermal diffusivity of the fluid. In the self-similar region of grid flow, there is no mean shear and no turbulence production, and the decay rate is well represented by a power law; this is supported by the present measurements in three different grid flows and by previously published data for passive-grid turbulence obtained over different ranges of streamwise distance and/or Reynolds number. The grid flow is slightly heated so that temperature acts as a passive scalar. From dimensional analysis and empirical power-law correlations, relations for basic flow parameters, such as the Kolmogorov, Taylor, and Corrsin microscales, and the Reynolds and Peclet numbers, are established as functions of the normalized streamwise distance downstream of the grid. With these relations, it is possible to determine the flow parameters for a specific passive-grid geometry or, more generally, a specific set of initial conditions.