Large eddy simulation investigation on the effects of the forebody shape of a supercavitating torpedo

The forebody length of a supercavitating vehicle requires careful consideration during the design process. Variations in this dimension have the potential to profoundly influence the supercavitation characteristics. In this numerical study, we qualitatively and quantitatively explore the characteristics of natural and ventilated supercavitating flow under various forebody lengths. We use the multiphase volume-of-fluid method and the large-eddy simulation framework coupled with the Schnerr–Sauer cavitation model. Three forebody lengths (LF = 10dc, 15dc, and 20dc, where dc is the diameter of the cavitator) are applied to the test model. The numerical simulations effectively predict variations in supercavity geometry, hydrodynamic force, and supercavitating internal flow under the influence of the forebody length. The results indicate that the time required to generate a clear supercavity for the model with a 10dc forebody length is ∼6% and 9% less than for the 15dc and 20dc forebody length models, respectively. Additionally, the 10dc forebody length model experiences about 5% smaller total drag force compared to the longer models. The variations in forebody length significantly influence the supercavitating internal flow and pressure distribution inside the supercavity. Specifically, the ventilation air is distributed as an outer layer of the supercavity for the 10dc forebody length model, whereas it moves along the surface of the models with 15dc and 20dc forebody lengths. In terms of pressure distribution, the 10dc forebody length model exhibits the highest local pressure compared to the models with longer forebody lengths. These observations provide insights into the physical mechanisms underlying the effects of forebody length on supercavity characteristics.