Resistance of wing in ground effect craft model during take-off

Abstract

Wing In Ground craft (WIG) is relatively a new concept of transportation. It flies very close to underlying surface that increases lift drag ratio. It is more efficient than aircraft and faster than counterpart marine vessels but high power requirement during take-off is the biggest impediment of its growth. Estimating WIG drag during take-off is difficult as both aerodynamic and hydrodynamic force act together unlike planing hull where hydrodynamic force mainly carries the weight of the craft. The aerodynamic force acts at a specific WIG, depends on speed and characteristics of its wing. Planing hull has been preferred for the wing in ground effect craft to gain higher speed necessary for take-off. In this thesis first, a critical review of the WIG craft has been done after that the work concentrates on the problem of estimating take-off resistance. A mathematical model has been described by modifying Savitsky’s method through considering aerodynamic effect along with hydrodynamic effect to estimate the resistance of a classical WIG model during take-off in calm water. WIG and planing craft resistances at different speed are compared to understand the effect of aerodynamic force on resistance during take-off. Wind tunnel test has been performed at Universiti Teknologi Malaysia’s (UTM) aeronautic laboratory to investigate aerodynamic characteristics of the wing necessary for considering aerodynamic effect during take-off and free running test of the WIG model has been performed at UTM lake to estimate resistance at different velocities. WIG resistance characteristic curve and free running test results have been used to validate the mathematical model. Generally from the comparison between WIG and planing craft it can be seen that as the speed increases, wetted length ratio, trim, draft at transom, hydrodynamic lift coefficient of WIG craft reduce more drastically than that of planing hull, thus resistance reduces sharply during WIG take-off. It was found that the peak resistance to be 30% lower than that of planing hull. Finally it can be concluded from the results obtained, the proposed mathematical model can be useful to estimate WIG take-off drag and power requirement.