You are here:
QUESTIONING THE MACH NUMBER CRITERION OR WHY TURBULENT FLOW IS COMPRESSIBLE FLOW
Citation:
Frick, W E. AND J.M H. Keyes. QUESTIONING THE MACH NUMBER CRITERION OR WHY TURBULENT FLOW IS COMPRESSIBLE FLOW. Presented at 19th Annual American Geophysical Union Hydrology Days, Fort Collins, CO, August 16-20, 1999.
Description:
According to Frick and Sigleo (1999) turbulence is a distinct and observable physical process in which flow, which is initially one-dimensional (the stem), is converted into two-dimensional radial flow (the cap) by shear. In the stem the incompressible equations of mass and momentum can be simultaneously satisfied. However, in the cap the flow is necessarily expansionary, causing a reduction in density and pressure. Since turbulence is therefore intrinsically compressible flow and since turbulent flow typically exists below the Mach number criterion for compressible flow, it is proposed that the commonly accepted Mach number criterion of 0.3 is much too high and that, in fact, the Reynolds number criterion for the onset of turbulent flow represents a better, if not the best, Mach number criterion. This work shows that compressible effects cannot be ignored in turbulent flow, i.e., for Mach number at least as low as 0.05.