CFD-CSD Coupled Aeroelastic Analysis of Flexible Flapping Wings for MAV Applications: Methodology Validation

A coupled CFD-CSD solver is used to simulate the aerodynamics of a flexible flapping wing. The CFD solver is a compressible RANS solver. The free general-purpose multibody dynamics solver MBDyn is used as the structural solver after an extension to take into account non linear shell straining, making it possible to analyze plates with large deformations. Validation of the two codes for flapping wings/plates is carried out independently. The solvers are then coupled and validated against prior experiments and analysis on a spanwise flexible wing at Re = 30,000. It is observed that due to flexibility, the average chordwise propulsive force, CT increases by 47% as a result of increase in plunge amplitude, effective angle of attack and leading edge suction towards the outer sections as compared to for a rigid wing. Additionally, the flexible wing has higher 3D flow. Then, a chordwise flexible root flapping wing is analyzed using the solver at Re = 10,000. As a result of the flexibility, camber is induced in the wing as it flaps. Highly 3D flow was observed with the strength of the vortices increasing from root to tip. Due to camber in the wing, the resultant force is vectored more in the chordwise direction as compared to for rigid wings, which results in higher thrust. The average CT increased by 25% and average CL increased by 10%. The current work demonstrates the capability of an aeroelastic solver to characterize the flowfield of a flexible flapping wing MAV in 3D.

[1]  Marco Morandini,et al.  Tightly Coupled CFD/Multibody Analysis of Flapping-Wing Micro-Aerial Vehicles , 2011 .

[2]  Sam Heathcote,et al.  Effect of Spanwise Flexibility on Flapping Wing Propulsion , 2006 .

[3]  Chunyong Yin,et al.  Measuring wing kinematics, flight trajectory and body attitude during forward flight and turning maneuvers in dragonflies , 2003, Journal of Experimental Biology.

[4]  Carlos E. S. Cesnik,et al.  Computational Aeroelasticity Framework for Analyzing Flapping Wing Micro Air Vehicles , 2009 .

[5]  C. Farhat,et al.  Two efficient staggered algorithms for the serial and parallel solution of three-dimensional nonlinear transient aeroelastic problems , 2000 .

[6]  Adam Hart,et al.  Low Reynolds Number Unsteady Aerodynamic over a Pitching-Plunging Flat Plate , 2010 .

[7]  Thomas H. Pulliam,et al.  Implementation of Preconditioned Dual-Time Procedures in OVERFLOW , 2003 .

[8]  L. Carr.  Progress in analysis and prediction of dynamic stall , 1988 .

[9]  K. Isogai,et al.  Effects of Dynamic Stall on Propulsive Efficiency and Thrust of Flapping Airfoil , 1999 .

[10]  Benedict,et al.  Experimental Investigation of a Flapping Wing Concept in Hover and Forward Flight for Micro Air Vehicle Applications , 2010 .

[11]  Inderjit Chopra.  Hovering micro air vehicles: Challenges and opportunities , 2013 .

[12]  C. Merkle,et al.  A Preconditioned Dual-Time, Diagonalized ADI Scheme for Unsteady Computations , 1997 .

[13]  Beerinder Singh,et al.  Dynamics and Aeroelasticity of Hover-Capable Flapping Wings: Experiments and Analysis , 2006 .

[14]  P. Spalart.  A One-Equation Turbulence Model for Aerodynamic Flows , 1992 .

[15]  R Katzmayr,et al.  Effect of Periodic Changes of Angle of Attack on Behavior of Airfoils , 1922 .

[16]  James D. Baeder,et al.  Computational Investigation of Small Scale Coaxial Rotor Aerodynamics in Hover , 2009 .

[17]  Max F. Platzer,et al.  Thrust Generation due to Airfoil Flapping , 1996 .

[18]  P. Mantegazza,et al.  Multibody Implementation of Finite Volume C-0 Beams , 2000 .

[19]  Weixing Yuan,et al.  Numerical and Experimental Simulations of Flapping Wings , 2010 .

[20]  Ismail H. Tuncer,et al.  A computational study on the dynamic stall of a flapping airfoil , 1998 .

[21]  Vinod K. Lakshminarayan,et al.  Computational investigation of micro-scale coaxial rotor aerodynamics in hover , 2010 .

[22]  James D. Baeder,et al.  Computational Investigation of Micro Hovering Rotor Aerodynamics , 2006 .

[23]  Peter Ifju,et al.  Flapping Wing Structural Deformation and Thrust Correlation Study with Flexible Membrane Wings , 2010 .

[24]  Pierangelo Masarati,et al.  Coupled CFD/Multibody Analysis of NREL Unsteady Aerodynamic Experiment Phase VI Rotor , 2011 .

[25]  P. Mantegazza,et al.  A Conservative Mesh-Free Approach for Fluid Structure Interface Problems , 2005 .

[26]  T. Pulliam,et al.  A diagonal form of an implicit approximate-factorization algorithm , 1981 .

[27]  Danesh K. Tafti,et al.  Effect of Wing Flexibility on Lift and Thrust Production in Flapping Flight , 2010 .