Cong-Tu Ha

MULTIPHASE FLOW SIMULATION OF WATER-ENTRY AND -EXIT OF AXISYMMETRIC BODIES

A fully-compressible, multiphase, homogeneous mixture model, based on unsteady Reynolds-averaged Navier-Stokes equations is presented in this study. Dual-time preconditioning method was employed to improve the computational efficiency of the solution. The multiphase flow solver has been applied to computations of: (1) cavitating flows over underwater projectiles; (2) transonic flow past an underwater projectile; (3) water impact of a circular cylinder entering the water; (4) water-entry of a hemisphere with one degree of freedom; and (5) supercavitating flows over an axisymmetric projectile during water-entry and water-exit. The surface pressure coefficients, water impact forces, vertical accelerations, and impact velocities are compared with available experiments and other published results. Good agreements with those results are obtained. Aspects of water-entry and water-exit flow physics of a projectile with and without gaseous exhaust plume including cavity shape, phase topography and drag coefficients are presented.Copyright

Numerical Analysis of Ventilated Cavitation Using Non-Condensable Gas Injection on Underwater Vehicle

Supercavitating torpedo uses the supercavitation technology that can reduce dramatically the skin friction drag. The present work focuses on the numerical analysis of the condensable/non-condensable cavitating flow around the supercavitating torpedo. The governing equations are the Navier-Stokes equations based on the homogeneous mixture model. The cavitation model uses a new cavitation model which was developed by Merkle (2006). The multiphase flow solver uses an implicit preconditioning scheme in curvilinear coordinates. The ventilated cavitation is implemented by non-condensable gas injection on backward of cavitator cone and the base of the torpedo.Copyright