Experimental investigation on the cavitation performance in a venturi reactor with special emphasis on the choking flow

•The cavitation region of choking flow in venturi reactor is divided into various parts.•Cavitation performance resulted from different collapse mechanisms is distinguished by a transition pressure ratio.•Wall pressure variations at different positions are systematically discussed.•The variations of pressure pulsation intensity influenced by various factors are considered.•The pulse frequency of choking cavitation flow at different pressure ratios is illustrated. Experiments were conducted to investigate the performance of choked cavitating flow in a transparent venturi reactor at different pressure ratios by high speed camera technique. Cavitation images of various flow conditions and corresponding pressure variations were analyzed to study the development performance of the cavitating flow. This work provides a thorough understanding of the evolution of cavitation regions, collapse mechanism, averaged wall pressure and pressure pulsation at different pressure ratios. The cavitation regions in venturi under choking flow condition can be divided into inception and developing region, fusion region and collapse region. Further analyses on the processed images reveal that cavitation performance can be approximately divided into two sections by a transition pressure ratio of 0.71. At smaller pressure ratios (pr 0.71), cavitation dynamics is governed by the shock wave. And the core position of collapse region moves upstream slowly with the increase of pressure ratio. The spectrum distribution of cavitation cloud in collapse region is concentrated and the peak frequency increases slowly at small pressure ratios. However, the spectrum distribution of cavitation cloud is relatively decentralized at large pressure ratios. The measured pressure data indicates that averaged pressure in diffuser goes through three stages at different slopes with the increase of pressure ratio under choking flow condition. In addition, the variations of pressure pulsation intensity (PPI) influenced by cavitation regions, collapse mechanisms, back pressure and collapse distance are exhibited in the present work.