Numerical Simulation And Experimental Study On Supercavity Characteristic Induced By Cavitators

Supercavitation technology is a new theory and approach which realizes high speed navigation of water vehicles. The main principle of its reduction drag is using a layer gas on body wall make the moving body isolated from water to avoid considerable viscous forces. The theoretical studies of cavitation primarily utilize the potential flow theory. Studies dealing with cavitation modeling through the computation of the N–S equations have emerged in the last decade. The current cavitation models can reasonably model natural cavity, but there are some limitation for modeling ventilated cavity due to ignoring considering condensability of the gas, which results in the bigger difference between simulated and experimental results. In this paper, state equation of complete gas is imported into cavitation model and the ventilated cavitation model with condensability effect is deduced. Based on the model, the main characteristics of supercavity initiated at cavitator are numerically simulated. Experimental apparatus applied for cavitation study may be divided into two great groups: hydrodynamic tunnels or flumes and projectiles, which have separately advantage and shortage. In this paper, water tunnel and projectile experiments are also carried out to study main characteristics of cavitator supercavity. The main works are as follows:The main works of numerical model are that the developed rules of ventilated supercavity are numerically simulated based on the ventilation cavitation model with condensability effect. The flow field of ventilated supercavity is analyzed, and flow parameters effecting on the developed rules of ventilated supercavity is studied. The fitted formulae between supercavity size and ventilation coefficient or cavitation number are obtained and using ventilated cavitation model also simulates the effect of cavitator parameters on ventilated supercavity shape and reduction drag. Those research results provide some reference for the design of ventilation system of underwater vehicles.Simultaneity, using natural caivtation model simulates natural supercavity shape and drag characteristics for cone cavitators. The main studies are the relations of cavitation number and the angle of cone effecting on supercavity size and drag coefficient, and zero cavitation number is analyzed. The speciality of movable cone cavitators is numereically simulated. The free-close and non-free-close supercavities are numerically simulated and compared. Using three-dimension numerical simulation obtaines the effect rules of disk cavitator attack angle on supercavity shape and drag reduction.Experimental works mainly include water tunnel and projectile experiments. Through water tunnel experiments, the formulation and development of ventilated supercavity have been analyzed and cavitator parameters effectting on the critical ventilation coefficient and supercavity size has been studied. The relations between cavitator diameter and reduction drag of ventilated supercavity are given. Influence of cavitator neck length on ventilated supercavity shape has been discussed. Influence rule of flow parameters (natural cavitation number and Froude number) on ventilated supercavity formation and size has been obtained. Using the experimental results of slender pole model analyzes free-close ventilated supercavity and validates the validity of numerical simulated results.Using projectile experiments studies the formulation and development of natural supercavity. The empirical formulae of natural supercavity shape have been presented. The typical formulae of supercavity size in literatures are been compared with experimental results. The experimental results are also been compared with numerical simulated results. The contour of partial natural and ventilated supercavities are measured and studied. Their contours are compared with experiential formulae and confirm its validity.