EFFECT OF WING TWIST IN GROUND PROXIMITY O. K. KINACI, Yildiz Technical University, Turkey SUMMARY WIG vehicles have gained ground in the last decade due to bureaucratic and technological barriers lifted thanks to the developments in the control engineering. These crafts can offer an economical transportation over the sea with their natural ability to use air like a cushion but there is still some enhancement to be made in terms of their efficiency. This paper deals with an efficiency augmenting method and proposes a twisted wing in ground proximity to improve lift-drag ratio. The analyses executed via CFD look promising to enhance the efficiency of these crafts’ wings. NOMENCLATURE h Clearance from the ground (m) c Chord length of the wing (m) AoA Angle of attack Cl Lift coefficient Cd Drag coefficient 1. INTRODUCTION WIG crafts offer a modern way of fast transportation over sea. These crafts are even faster than high speed marine vehicles which suffer from the limit set by cavitation. According to Sinitsyn and Maskalik; hydrofoils cannot exceed the 53knots barrier, of which cause vessels suffer from cavitation [1]. WIG crafts start from the water but achieve high speed after they are detached from the sea making them immune to cavitation occurrence. There are many recorded vehicles that could even achieve 250knots of speed, please see reference [2] for more details. Not only these crafts are faster, but also they are more efficient than airplanes. Making use of the free water surface (or land instead) and clustering the air between the craft and the surface, they are able to provide low fuel consumption. Future transportation vessels are expected to be more environment-friendly; compared to airplanes, WIG crafts could be considered as a greener technology when looked from this perspective. Besides; the ground below the craft enhances lift generation, allowing these vessels to carry more weight. WIG crafts do not need any airfields to be built; instead, they use the natural landing field the seawater makes. This decreases the capital cost of the investment; WIG crafts could operate after they have just been built. There are also methods to improve the efficiency of these crafts to reduce the operational costs by optimizing their wing structure. Other than changing the wing itself, these methods may be the addition of endplates to the tips of the wings to reduce vortex formation or adding PAR (power augmented ram) to help the craft during take-off. WIG vehicles were first built by Soviet Russians during the cold war. However; after a tragic disaster when all the crew died inside an ekranoplane, the production of these vessels have slowed down. The control of these crafts is complex and regarding the technological progress of the time, continuation of the construction of these vehicles seemed risky. Besides, these crafts could not be identified; whether they were ships or aircrafts. Now both of these problems have been resolved. Computer technology have paved the way for control engineering to facilitate the stability and control; and these crafts were classed as ships to be engaged to IMO rules. This study is part of a currently running project whose subject is to construct a prototype model WIG craft. Due to economical limitations of the project, the lift – drag ratio of the wing should be maximized to optimize the efficiency of the craft. The very first CAD model of the model is given in figure 1. The aim of this study is to investigate a twisted wing structure aerodynamically to evaluate any changes in the efficiency. The calculations are made by a commercial CFD software. Figure 1. An early CAD model of the WIG craft.