On the Calculation of Length Scales for Turbulent Heat Transfer Correlation

Abstract

Turbulence length scale calculation methods were critically reviewed for their usefulness in boundary layer heat transfer correlations. Using the variance of the streamwise velocity and the dissipation spectrum, a rigorous method for calculating an energy-based integral scale was introduced. A principal advantage of the new method is the capability to calculate length scales in a low-Reynolds-number turbulent boundary layer. The method was validated with data from grid-generated, free-shear-layer, and wall-bounded turbulence. Length scales were calculated in turbulent boundary layers with momentum thickness Reynolds numbers from 400 to 2100 and in flows with turbulent Reynolds numbers as low as 90.