Vent Valve Thrust Force for Surface Effect Ships

Abstract

The Surface Effect Ship (SES) holds promise as a viable and appealing alternative for transferring crew to offshore wind farms and oil platforms due to its superior seakeeping capability, high comfort and speed. A SES is a marine craft with catamaran hull, with flexible stern- and bow rubber-seal system. The air cushion is defined as the enclosed volume between the hull, seals and water plane. Centrifugal lift fans blow air into the air cushion, pressurizing the air cushion that lifts up to 90 % of the vessel weight. Modern SES are also equipped with adjustable vent valves allowing out outflow air from the pressurized cushion. By mounting the vent valves on the hull sides, the thrust force coming from the air exiting the vent valves can be seen as an extra actuator on the ship. Using Vent valve to control the ship's position requires an accurate thrust force model. This paper develops two thrust force models and investigates their performance. Both models are compared to computational fluid dynamic (CFD) analysis and experimental tests. Results show that both models may be used to estimate the maximum thrust, However, one holds higher promise to be used for control design.