Scale effect research on cavity evolution and impact load characteristics during high-speed water entry

To investigate cavitation and load scale effects during high-speed water entry of large projectiles, a multiphase coupled numerical model based on detached eddy simulation (DES) is developed. The similarity between scaled models and the prototype in terms of cavity evolution and impact load characteristics is analyzed under a single similarity criterion, composite similarity criteria, and a zero-pressure gradient condition. The results indicate that when only the initial cavitation number or the Froude number is similar, the maximum cavity diameter differs from that of the prototype by approximately 8.7% and 56.7%, respectively. Under composite similarity conditions, the cavity morphology and evolution process can reproduce the prototype characteristics with discrepancies in the maximum cavity diameter and cavity length reduced to within 2.2%. Under the zero-pressure gradient condition, the cavity characteristics of models with different scale ratios show a high degree of consistency, with deviations in the maximum cavity diameter below 1.89%. The results provide important references for designing scaled experiments and selecting similarity criteria during high-speed water entry.