Experimental Study on Morphological Characteristics of Ventilated Supercavity of Double Disc Cavitator Projectile

Based on the principle of independence of cavity sections expansion, a double disc cavitator for underwater projectiles is proposed in this paper.The high-speed water tunnel experiment is carried out to study the generation and morphological characteristics of the ventilated supercavity which generated by this series of double disc cavitator.The experiment observed the ventilated supercavity morphology under the different cone angles by changing the ventilation flow coefficient.The experimental results show that there are two kinds of cavitation states:the front disc preferential cavitation and the rear disc preferential cavitation. The transition between these two states occur at a cone angle about 55°.The value of the critical ventilation flow coefficient when generating stable ventilation supercavity has a positive correlation with the cone angle.The front disc and the rear disc of the cavitator have mutual inhibitory effect on the production of ventilated supercavities.And the morphological characteristics of ventilated supercavity do not increase with the increasing of ventilation flow coefficient, but there is an upper limit value of ventilation flow coefficient.

Flow Mechanism and Hydrodymanic Characteristics of 3D Cavity on the Surface of the Underwater Vehicle

The flow past 3D cavity is a common structure, which is located on the surface of the underwater vehicle. The flow mechanism and hydrodynamic characteristics of the cavity have great significance for the design of the underwater vehicle. In this paper, large eddy simulation (LES) is presented to investigate the flow mechanism and hydrodynamic characteristics of the 3D cavity in terms of flow mechanisms, drag and fluctuating pressure. It is found that the motion law of the large vortex inside the cavity, and the drag and fluctuating pressure of the trailing edge is the largest. By the water tunnel experiment, the calculation result agrees with the experiment well, and LES method is verified feasibly.

Hybrid RANS–LES Modeling for Unsteady Cavitating Flow Simulation

A typical hybrid RANS-LES approach, DES (Detached Eddy Simulation), was introduced into cavitating flow simulation in this paper. The applicability of two DES models, including one equation DES model and SST k-ω DES model, and standard k-ε model was analyzed through experimental data of a water tunnel experiment. Validation results illustrate that the precision of DES method depends on the RANS model used and the length scale used to distinguish LES zone and RANS zone. The SST k-ω DES method can well predict cavitating flow. The averaged results gained through this model are better than those of standard k-ε or one equation DES model. By comparison, the one equation DES model shows little advantage than standard k-ε model to simulate cavitating flow.

Drag of Bodies of Revolution in Supercavitating Flow

The drag of bodies of revolution at zero degree angle of attack in supercavitating flow has been calculated. The potential flow about the body and cavity is calculated using an axial distribution of source/sink elements and is coupled with laminar and turbulent boundary-layer solutions for the body. Excellent agreement for drag coefficient is demonstrated between theory and a water-tunnel experiment, also between theory and a high-speed water-entry experiment. Results show skin-friction drag is the dominant drag component for high-speed water entry or high-speed underwater travel.