ON THE SCALING OF SEPARATION-BUBBLES

A simple analysis, based on the scaling of the Navier-Stokes equations , is presented for general flow situations involving separation bubble s. Three possible functional relations between the separation bubble l ength L and Reynolds number Re are derived: (i) L proportional to Re, (ii) L proportional to 1/Re, and (iii) L=constant. These relations are shown to correspond to the experimentally observed behavior of lamina r, transitional and turbulent separation bubbles, respectively. The re sults of the analysis are discussed in the context of several internal and external separated flows in various geometries, and the correspon ding empirical constants are evaluated from available experimental and numerical data.