Generation of a wall jet to control unsteady cavitation over a 2D hydrofoil: visualization and hydroacoustic signal analysis

In the paper, the possibility of active manipulation of unsteady cavitating flow over a 2D hydrofoil, a scaled-down model of Francis turbine guide vane (GV), was tested. The flow manipulation was implemented by generating of a wall jet at various flow rates through a spanwise slot nozzle in the foil surface. The experiments were carried out at two attack angles of 3 and 9. Different cavitation conditions were reached by varying the cavitation number and injection velocity. Temporal and spatial cavity characteristics were studied by means of a high speed visualization. Hydroacoustic measurements were performed in order to investigate pressure pulsations spectral characteristics. It was found that the wall jet generation technique appears to be effective in suppressing cavity unsteady behavior or at least to reduce the corresponding pressure pulsations at low inclination angle and less efficient at high angles of attack, allowing only minor decrease of pressure pulsations.