Unified Analysis of Grid Turbulence

Abstract

The deficiencies of the conventional power laws for the decay of grid turbulence, i.e., the discontinuous change from an initial to a final zone and the undefined range of validity, have been successfully overcome by analyzing grid flow as the plane-source counterpart of flows past point and line sources of turbulence energy. A comparison of the analytical results with experimental data on turbulence intensity, dissipation length, and integral scale for a great variety of grid geometries and Reynolds numbers reveals good agreement for all down-stream zones. The data used include those of Baines and Peterson, Batchelor and Townsend, Comte-Bellot and Corrsin, Dryden, Stewart and Townsend, Uberoi, van der Hegge-Zijnen, von Kármán, and Wyatt. Functional relationships between the constants of the resulting analytical expressions, including the position of the virtual origin, and the grid-flow parameters have been deduced to facilitate prediction of turbulence characteristics and their downstream development for any given grid flow.