Computational fluid dynamics study of unconventional air vehicle configurations

Abstract

that claps down atop the rear fixed surface on each stroke; and a vehicle with tandem pairs of biplane configured flapping wings, in which each pair moves in opposition so as to alternately clap together and separate. This latter vehicle, which does not employ fixed lifting surfaces, has the advantage of being dynamically balanced in flight so that its center of mass is not forced to oscillate vertically by the flapping action. In addition, development is underway on a stop-rotor hybrid vehicle. This employs a pair of single-blade, rotary/fixed wing panels, attached at their roots to separate coaxial shafts. For low-speed flight the wing panels are driven as contra-rotating rotor blades for lift. A pusher propeller provides primary thrust, and control surfaces in the propeller wash provide pitch, yaw, and roll control. In fixed wing flight the wing panels are stopped opposite each other to become a conventional wing. This configuration eliminates the airflow reversal over the wing that occurs upon conversion in other stop-rotor designs. Developmental models of this vehicle have flown successfully in both fixed and rotary wing modes. Computational fluid dynamics (CFD) studies of these vehicles are performed using an unstructured grid based finite element incompressible flow solver called, feflo, to optimise propulsion efficiency and flight control techniques. In this paper, description of the flow solver and adaptive remeshing, descriptions of the flying models, CFD simulation results of two novel unmanned air vehicles will be presented. ABSTRACTTwo unconventional micro air vehicles developed by the Naval Research Laboratory are described. One of the vehicles employs flapping wings which is inspired by the flight of birds or insects but does not copy it directly. The second vehicle is a stop-rotor hybrid vehicle employing a pair of single blade, rotary/fixed wing panels, attached at their roots to separate coaxial shafts. An unstructured grid based incompressible flow solver, called feflo, is used to simulate the flow past these novel configurations in order to determine the flight characteristics of these vehicles.

A computational investigation of the three-dimensional unsteady aerodynamics ofDrosophilahovering and maneuvering

“…Kellogg et al (Kellogg et al, 2001;Kellogg et al, 2003) and Jones and Platzer (Jones and Platzer, 2003) have experimentally investigated the use of tandem flapping foils for micro-air vehicle propulsion and were successful. Ramamurti et al (Ramamurti et al, 2005) computationally studied the unsteady thrust and lift generation of tandem multiple flapping wing vehicles as well as rotary-wing vehicles to support MicroAirVehicle (MAV) design efforts. For these types of vehicles, it is important to accurately quantify the performance of flapping wings in order to provide the controllability needed during a maneuver.…”

Computational Fluid Dynamics Studies of a Flapping Wing Nano Air Vehicle (NAV)

“…For reversing camber, an approach similar to our earlier study of the BITE vehicle [7] is used. The mean camber line would be NACA airfoil camber.…”

Ardışık çırpan kanatlı enerji üretecinin performansını artırmada ön kanat hareketinin etkisi

“…[33], Tuncer ve Kaya [34], Ramamurti vd. [35] ile Windte ve Radespiel [36]), Warkentin ve DeLaurier'in [37] simetrik olarak çırpma hareketi yapan kanatlar ile yapmış oldukları rüzgâr tüneli testlerine ait sonuçlar, ardışık olarak yerleştirilmiş kanatla ile belirli faz açısı ve kanatlar arası mesafe değerleri için tekil çırpan kanatlara oranla daha fazla itki verimliliği elde edilebileceğini göstermiştir. Dong ve Liang [38] Kanadın akıma dik yönde ötelenme hareketi süresi mümkün olduğunca uzun tutulup yunuslama açısının aniden ters yöne çevrilmesi ile oluşturulan periyodik ancak sinüzoidal olmayan hareketin, çırpan kanatlı enerji üreteçleri için daha verimli olduğu Platzer vd.…”