On the Nature of Stall

Abstract

The physical data available on the problem of stall are reviewed. The discussion is centered on the problem of flow in passages. The emphasis is placed on systematic visual data showing flow patterns as a function of geometrical parameters. These data lead to a view of stall as a spectrum including three or possibly four major types of flow patterns; these patterns involve both transient and steady elements. A qualitative parameter is formulated which provides a classification for the major types of stall. It is shown that this parameter and its underlying concepts are useful in rationalizing known but previously inexplicable results and in obtaining important qualitative predictions. Comparisons between the predictions of boundary-layer theory and the actual systematic stall data of passages are given.