Numerical study on the vertical motion of underwater vehicle with air bubbles attached in a gravity field

摘要

Air bubbles may be injected and attached on the surface of a moving underwater vehicle to enhance its speed. Thus the nonlinear interactions between the moving body at a variable speed and the deformable bubble attached are of importance. In this paper, a body with an air bubble attached at a variable speed is simulated using the boundary-element method together with the potential theory. The motion of the body and deformation of the bubble under the action of gravity are considered in a moving coordinate system fixed on the body. Bernoulli equation and auxiliary function method in this moving coordinate system are adopted to calculate the pressure and fluid force on the body. Convergence study with mesh and time step has been undertaken with good convergence obtained. Simulated results have also been compared with other published numerical results and good agreement achieves. On this basis, the influences of different parameters have been further studied, such as Froude number, cavitation number and body acceleration. It is found that bubble shape and jet direction are influenced by the gravity a lot in the range of parameters considered and various jet patterns may generate such as inward jet, oblique jet or upward jet. (C) 2016 Elsevier Ltd. All rights reserved.