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Corresponding Author

Mostafa, Nabil

Subject Area

Mechanical Power Engineering

Article Type

Original Study

Abstract

Supercavitation has a great effect on the design of high-speed underwater vehicles. The transit flow around either partially cavitating or supercavitating body affects the trajectory of high-speed underwater vehicles. To improve the understanding of the unsteady behavior of supercavitating flows, the author used a three-dimensional Navier-Stokes code (CFDRC, 2000) to model the two phase flow field around a hemisphere cylinder. The governing equations are discretized on a structured grid using an upwind difference scheme. For different body shapes and cavitation numbers, the cavity shape was determined over the body and around the wake Also, the two-dimensional flowfield around the cavitating body was determined. This hemisphere cylinder body has a diameter about 0.2L to 0.4L; So, it has a strong wake effect. The maeroscopic behaviour of the formation and transport of vapor bubbles are discussed with the effect of the pressure, velocities and turbulent distribution. The results show that there are five stages for the cavities formation. First, a cavity starts to grow at the wake of the body only due its low pressure. At the second stage, another cavity grows beside the nose while growing the cavity at the body wake. The cavity beside the nose grows enough to affect the pressure at the body wake, so, the cavity at the body wake stans to collapse at the third stage. In the fourth stage, the cavity beside the nose grows enough to merge with the cavity at the body wake forming a large one. Finally, that cavity starts to have a fluctuation around the final shape. The results were compared with the experimental results obtained with Particle Image Velocimetry (PIV) by the author (2001). The results show great detailed views and analysis of different fields of transit cavitating flow. It illustrates clearly the mechanism of stabilization of the cavitation behaviour provided by high-speed underwater vehicles.

Keywords

supercavitation; Hydrofoils; CFD and Two-Phase Flows

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