Dynamic transfer characteristics of partially cavitated hydrofoil cascade.

The unsteady perturbed flow field is expressed by pressure doublet and source distributions for the partially cavitated hydrofoil cascade in uniformly varying gust of axial velocity and, in order to take the time variations of cavity area and cavity termination thickness into account, the unsteady cavity flow model is determined explicitly by applications of conservation law of mass and momentum to control surface taken within the passage in cascade. Thus the numerical method is presented for determining the above two singularity distributions from simultaneous integral equations derived from the boundary conditions and then the unsteady cavity characteristics, frequency responses of unsteady pressure rise and flow rate, and also cavitation compliance and mass flow gain factor inherent to dynamic transfer characteristics are obtained. Numerical calculations are made to show some notable effects of cavity length and gust frequency on the above quantities in typical partially cavitated hydrofoil cascade and also to compare with former analysis. (A)