A STUDY ON THE LEAKAGE-FLOW-INDUCED VIBRATIONS IN A TWO-DIMENSIONAL NARROW PASSAGE

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Severe self-excited vibrations occur frequently in mechanical structures with narrow leakage-flow passages. Based on the previous studies on one-dimensional leakage-flow-induced vibrations, the authors have applied the one-dimensional theory to the two-dimensional leakage-flow-passages and calculated numerically the pressure distributions in an eccentric annular passage to analyze the stability of leakage-flow-induced vibrations in two-dimensional narrow passages.In the calculations of pressure distributions in the eccentric annular passages a leakage-flow scheme was applied, where diffuser effects were neglected in the circumferential flow. The calculated pressure distributions were in fairly well agreement with those by experiments, which has proven the validity of the leakage-flow scheme proposed in calculations of pressure distributions in eccentric annular passages.As a result, it is found that, in parallel and convergent passages in the axial direction, fluid forces acting on the passage walls are positive restoring forces and in divergent passages they become negative restoring forces. The calculated critical velocities for the flutter-type instability were also in good agreement with experiments.