Instability and rotating stall in cascades

Rotating stall is a fundamental hydrodynamic instability which is encounter ed in most hydraulic and aeraulic turbomachinery. It appears to exist only with cascades that considerably slow down the fluid flow and occurs in the form of rotating structures in which the flow rate may be negative. The pap er analyses this instability and its transitions in a simple two-dimensiona l configuration using a multi-domain numerical scheme and solver The space- time variation of the flow rates occurring for an angle of attack increasin g by steps shows first standing waves, then intermittent and permanent trav elling waves of limited amplitude, corresponding to blade stall. At higher angles of attack, a high amplitude wave propagates a single structure (cell ) with a negative flow rate, corresponding to stalling of the cascade. (C) 1999 Academie des sciences/Editions scientifiques et medicales Elsevier SAS .