Experimental investigation on interaction modes and geometric features of two ventilated cavities

In this study, the interaction modes and geometric features of two cavities are explored in a closed-loop water tunnel at Harbin Institute of Technology. Firstly, it was observed that there are four interaction modes under different cavitator diameter d_n, Froude number Fr and distance between two cavitators d, namely, two basically independent cavities (TIC), two coupled-deformed cavities (TCDC), two partially fused cavities (TPFC) and two fully fused cavities (TFFC) respectively. In addition, an expression to describe the effect of different parameters on the interaction modes was established and obtained the critical value between the mode transitions. Subsequently, compared with the formulas of unbounded flows in the literature, it was found that the average value of the maximum diameters of the two cavities are close to those of the single cavitator at the same cavitation number. Moreover, a method used to quickly estimate the blockage ratio for two cavitators configuration was obtained, namely, the equivalent blockage ratio of the two cavities can be calculated from the equivalent diameter of the d_n × 2d_n rectangle. Finally, the estimation method was validated by Brennen's prediction.