Deformation Measurement of a Birdlike Airfoil with Optical Flow and Numerical Simulation

A Lucas-Kanade optical flow technique was developed to measure the deformation of a flexible birdlike airfoil undergoing an increasing angle of attack at Reynolds number 100,000. A pyramidal scheme was used to allow large displacements; a nonlinear structure tensor diffusion was introduced to preserve image intensity discontinuities. The accuracy and convergence of this Lucas-Kanade method was studied. Then, this optical flow method was adapted for a wind-tunnel experimental setup to estimate the vertical deformation of a newly designed flexible, birdlike airfoil with an improved wing loading. At last, the proposed optical flow method was compared to image correlation and numerical simulation results that were carried out solving the fluid-structural interaction problem through a well-validated coupling environment with conservative load transfer and a partitioned coupling approach.