Shallow-water zero-speed tests and modelling of power-augmented ram craft

Abstract

A study of the shallow-water static performance of an amphibious power-augmented ram vehicle model has been undertaken. The recovered thrust of the model and pressure under the model platform were measured for variable propulsor thrust, loading conditions, and water depths. When the model hulls do not touch the ground, the sensitivity of the model performance to the water depth is found to be small. In sufficiently shallow waters, when the hulls are in contact with the ground, the recovered thrust is zero at low propulsor thrust and approaches that in deep water at high propulsor thrust. The pressure under the platform saturates when the air leakage appears under the side hulls. A mathematical model is developed accounting for the water surface depression under the platform and for reaction and frictional forces between the hulls and ground. This theory provides reasonable estimates for the recovered thrust and the under-platform pressure.