On Dynamic Characteristics of SES Seal Systems

Abstract

The Surface Effect Ship (SES) has been under Research & Development for over 20 years and many kind of commercial SES are now in service. Generally, cushion pressure of SES is kept by two side-hulls and two seals (or skirts) each located at fore and aft end of SES cushion chamber.The restoring forces and moments of these seals are considered to affect on craft's dynamics but we can find very few reports about seal dynamic characteristics up to the present.In this study, the two dimensional dynamic model test was carried out to inspect fundamental characteristics of 3 types seal configurations which are considered to be proper for high speed SES, namely, Bag finger seal, Planing seal and Lobe seal. The experimental equipment is consist of fan-duct system, plenum-chamber, load-cells, pressure-gages, oscillating plate, power units and controller to simulate SES airflow system. The propriety of the mathematical model which corresponds to the SES seal-airflow system was confirmed by these experimental results.The conclusion may be summarized as follows : 1) The mathematical model is composed of two equation groups, namely, equations of seal geometrical shapes for each configurations and equations of cushion airflow system. This mathematical model is confirmed to show a good agreement with model experimental results except of some high frequency region.2) The lobe seal has different characteristics, especially shows good responsibility to wave elevation (in this experiment replaced with flat plate oscillator).SES seal dynamics was fundamentally clear by this work but a further study including craft's motion in waves is necessary to discuss actual SES seal dynamic restoring forces and moments.