Numerical simulation of the air-water interface effects of an airboat

Abstract

This paper describes the Air-Water Interface (AWI) occurrence effects of the airboat at various speed, draught, and trim angle. This evaluates the dynamics of AWI with focus on the mechanisms involved in air displacement, the formation of air cushion, boundary layer turbulence, surface tension and wave generation. The analysis involves the change in speed, draught, and trim (0, 1, 1.5 and 2 degrees). The speed of 1.01 and 3.35m/s for displacement and planning regions of the airboat operation were examined. At the AWI, the thin layer of water molecules is affected by the airboat movement at the said trim, it is observed that the layer at the boundary will experience turbulence due to passing air over the layer and the interaction between the air and water at the interface causes mixing and creates waves or ripples at that trim. The wave generated at various trim angles will also create unique wave even at the same speed and draught with a change in trim. The difference in wave formation is seen not to be the same with the change in trim and these changes are observed at the bow and the aft of the vessel. This is also connected to the volume displacement of the boat, the resistance of the vessels, the angle of trim of the airboat and the hull form of the boat. This shows that displacement, resistance, angle of trim and hull form of the boat play critical and crucial roles in wave formation especially for the airboat.