Simulation of water entry of a two-dimension finite wedge with flow detachment

Abstract

a b s t r a c tA two-dimensional finite wedge entering water obliquely at a prescribed speed is considered through the velocity potential theory for the incompressible liquid. The gravity is also included. The problem is solved by using the boundary element method in the time domain. The method of the stretched coordinate system is adopted at the initial stage. A condition is imposed at the intersection of the free surface and the body surface after flow detachment to allow the liquid to leave the body surface smoothly. A new methodology is developed to treat free jet with free surface on both sides. The auxiliary function method is used to calculate the pressure on the body surface. Detailed results for the free surface shape and pressure distribution are provided, and the effect of physical parameters on water entry is discussed.

Simulation of freefall water entry of a finite wedge with flow detachment

“…Tassin et al [7] used an analytical model based on the Logvinovich model for a finite wedge. Bao et al [8] simulated oblique water entry for an asymmetrical wedge. The gravity effect was included.…”

“…The moment may remain in the same direction and the body may continue to rotate in the same direction. Furthermore, after flow detachment, free jets may be formed [8]. Its accuracy should be ensured as the body motion can be very much affected by numerical error.…”

Free fall motion of a floating body: Bubble formation and its effect

“…Since the flow is assumed to leave the body tangentially, the continuity condition of velocity in the tangential direction can be imposed at the intersection point. Thus we have [7]…”

“…The first requirement for an air bubble to be formed behind a body during water entry is that the liquid has to detach from the body. A typical example is well illustrated in the work of Bao et al [7,8]. They considered the problem of a finite wedge entering into water vertically or obliquely.…”

“…To account all these collisions, we shall adopt and refine the various methods developed previously. In particular, the numerical condition for flow detachment [7] will be used for initial stage of water entry. The dual system method [20] based on the stretched system method [6] will be used for cavity surface collision and inner jet collision with the body surface.…”