Development of a Reduced Order Model to represent Leading Edge Vortex Formation constituting Insect Flapping Wing Aerodynamics using CFD

This thesis explores the application of numerical fluid dynamics computation methods to advance current understanding of insect wing flapping kinematics by developing a Reduced Order Model (ROM) of said kinematics. A method is proposed to identify the significant frequencies of wing flapping that lead to the production and maintenance of lift in flying insects. The Finite Volumes Method (FVM) is selected as the CFD method for simulating 2D steady flow and is interfaced with code written in the C programming language to simulate the wing kinematics moving across the simulated flow domain. A dynamic mesh system has been employed to remesh the flow domain for simulating wing movement through it. The model has then been validated against experimental data from literature.The kinematic model is proposed based on Quasi-Steady assumptions parameterizing wing geometry and kinematics representing pitching and flapping aerodynamics as simple harmonic motions (SHM) for translational and angular velocity and consequently the corresponding resulting inertial effects on the wing during stroke reversal. This effect has been evaluated in terms of how it increases with an increase in chord lengths (distance) travelled by the wing. These pitching and flapping assumptions are then modified using a coefficient with the SHM function, such that wing translation becomes constant during upstroke and downstroke, and angular rotation becomes near instantaneous as the coefficients are increased in magnitude. The use of these coefficients is part of the Quasi-Steady assumptions made in that the best flight condition in insects is when the flapping velocity is constant.Finally, a Fourier Fitting method is proposed for producing the ROM model based on decomposing the lift and drag forces from the simulation of wing kinematics in air. In the results, the observation is that the Leading Edge Vortex (LEV) generated from the separated boundary layer during wing translation leads to the augmentation of lift forces on the insect wing, and generally increases with an increase in stroke distance of the wing. Increasing the coefficient values modifying the SHM of the wing however caused some issues, in that the instantaneous pitching and rectangular flapping (constant velocity) profiles caused large spikes in the aerodynamic forces due to added mass (inertial effects) during stroke reversal. While this behaviour is expected, it meant that the Fourier decomposition of modes is unable to fully resolve the forces generated during instantaneous pitching for the largest value of the pitching coefficients. Thus, Fourier decomposition proved effective mainly for periodic sinusoidal flapping and pitching.