Level-set modeling of the two-phase flow generated by a surface piercing body

The flow field around a ship is extremely complex, even for the simplest case of motion through calm water with constant forward speed. In particular, many vortical structures are originated by the ship motion. Some of them are directly related to ship breaking waves, e.g. [3]. In other cases, vorticity is created at the hull boundary and shed along and downstream the ship. Here, we present our investigations on some fluid dynamic processes connected with the motion of a blunt structure piercing the air-water interface. We consider a two-dimensional prototype problem consisting in a vertical flat plate, moving forward with known velocity (cf. figure 1). This rather simple problem is meant to be roughly representative of the fluid phenomena occurring around the bow of a blunt ship and near a transom stern. The problem is studied numerically by a Navier-Stokes solver with a Level-Set technique to capture the air-water interface. The problem has been studied from an experimental point of view as well. Figure 2 shows a first comparison between numerical and experimental results The experimental picture, in the background, is accompained by the interface location (the blue line) and the vorticity contours obtained numerically. Theflow is characterized by many complex features: vortex shedding from the immersed plate tip, wave breaking on the upstream side and (later on) breaking-induced air entrapment and wave breaking on the downstream side. Several plate velocities have been studied, with Froude number in the range 0 ?6-1 ?2. Different regimes of interaction between the vortical structures and the interface have been analysed, [6]. In the following, we focus on the computational method and details of the implementation are discussed through numerical results. Experimental measurements of the interface deformation, of the pressure on the plate and of the velocity field are under development and will be presented at the Workshop to complement the physical interpretation of the flow.