Experimental Study of a Telescopic Morphing Aspect Ratio Wing inside a Channel

Abstract

W ING-IN-GROUND (WIG) effect vehicles use the wellknown increase in the lift-to-drag ratio of a wing near the ground. Most WIG vehicles developed or under construction are water based or amphibious. Ollia [1] and Hooker [2] published historical reviews and technological knowledge of water-basedWIG vehicles. Rozhdestvensky [3] presented an extensive literature review on water-based WIG vehicle developments. Conceptual land-based WIG vehicles have also been proposed. These are designed to move faster and to consume less energy than current conventional ground transporters [4–9]. A novel form of high-speed ground transporter, called an aerolevitation electric vehicle (AEV), has been proposed in South Korea [8,9]. This is an over-the-ground-surface tracked WIG vehicle (TWIG) [4], which flies above or within the guideways of the track. It has the advantage of being able to fly faster and in close proximity to the rigid ground surface, as compared to the water-based WIG vehicles. The TWIG has a relatively small wing area (ormore precisely, a low aspect ratio) because of the large lift augmentation resulting from the ground effect. However, the small wing area optimized for a design cruise condition requires some special high-lift concepts for takeoff because of the limited capability of flaps [9]. The AEV also requires effective roll control assistance when it runs inside the winding channel-type guideway. The variable-spanmorphing (telescopic) wing can change itswing area symmetrically to obtain an optimally performing wing configuration at each given flight condition. It changes its wing area asymmetrically to swiftly control the roll motion of the vehicle. Tidwell et al. [10] compared various morphing strategies while demonstrating the impact of the morphing aircraft on aircraft performance. They showed that planform morphing improves the performance significantly more than that provided by airfoil morphing alone. Blondeau et al. [11] discussed the design and testing of a telescopic wing. They tested a small scale telescopic wingmodel within theReynolds number range of 182,000–454,000. It was found in their study that the telescoping wing at maximum deployment did incur a slightly larger drag penalty and a reduced lift-to-drag ratio. Neal [12] used the vortex-lattice method and performed the wind tunnel testing to model the aerodynamics on the morphing aircraft and to evaluate the performance and control of the morphing aircraft maneuvering. Neal et al. [13] designed and tested a fully adaptive aircraft configuration to investigate morphing for multimission unmanned aerial vehicles (UAVs). Wind tunnel tests of five independent planform changes along with independent twist control for each wing showed that different configurations produce minimum drag over a range of flight conditions. The present study is focused on applying the variable-span morphingwing concept [10–12] to the design of the land-basedWIG vehicles [6,9] with effective roll control. Thus, it is the aim of this paper to investigate the basic aerodynamic characteristics of a telescopic wing inside of a channel guideway. The effects of the ground and sidewall (GE and SE) on the steady aerodynamic characteristics of the telescopic wing are investigated by changing the ground height and the gap between wing tips and sidewalls.