Analytical Calculation of Drag Force on Hovercrafts in Calm and Wavy Water Conditions for the Design of Aerial Propellers in Propulsion Systems

A hovercraft is a dual-purpose vessel capable of traversing both water and land surfaces with minimal thrust, operating by generating a cushion of compressed air. This type of vessel comprises numerous components, many of which are unique and not utilized in other crafts. Consequently, accurately estimating the drag force on hovercraft presents a greater challenge compared to conventional vessels. In this research, first identifies and describes the various types of drag forces acting on a hovercraft. These include wave-making drag from the air cushion, aerodynamic profile drag, aerodynamic momentum drag, skirt drag, and the momentum drag force associated with air escaping from the front and rear skirts in calm water. In wavy conditions, additional forces such as wave-making drag, momentum drag, aerodynamic drag, residual drag, and wave motion drag are also considered. For each scenario, the relevant analytical relationships were presented. Subsequently, the total drag force acting on the hovercraft under specific conditions for both calm water and sea state 3 are calculated. The results indicate that the hump drag force at a speed of approximately 10 knots is approximately 30 kN in calm water and 36.2 kN in sea state 3. Furthermore, an appropriate propeller for the hovercraft is designed that can generate sufficient propulsion force to overcome the drag. The study also includes calculations of the propeller’s propulsion force in relation to the vehicle’s speed.