Computing Wake-Capture effect on aerodynamic forces by varying Reynolds number for an insect

This paper attempts to utilize computational fluid dynamics and simulate a solution to the basic flow and Navier Stokes equations for a specific geometry and motion pattern to compute the wake capture for analyzing the lift enhancement phenomenon in an insect. The estimation of instantaneous flight forces around the flapping wings of an insect requires quantifying its temporal and spatial resolution. A fast-flapping wing moves in its wake, while the fluid around no longer remains stagnant and gets the energy in the form of momentum and heat transfer. The insect improves its flight performance by recovering some of the lost energy through the flapping wing while passing through the wake. The proposed approach considers a flat plat to mimic the insect motion in normal hovering flight through a series of unsteady motions. The Vorticity structures and aerodynamic forces are obtained from velocity and pressure fields. The wake-capture effect is computed for three different phases of the flapping motions, the pitching-down rotation and translational acceleration, translation at a constant speed and constant angle of attack, and the pitching-up rotation and translational deceleration at the end of the stroke. The kinematic parameters including the Reynolds number and the duration of pitch rotation are varied to compare these phases for symmetric, delayed, and advanced modes. The results demonstrate that the mean lift coefficient for the flapping wing of an insect is the largest for the advanced pitch mode for varying Reynolds numbers. However, the mean drag coefficient is the smallest for the same advanced pitch mode. It is also found that the fast pitch rotation provides the best demonstration of wake capture as the lift enhancement mechanism in symmetric mode while varying the duration of pitch rotation.