Numerical investigation on the effect of stroke plane inclination on the aerodynamic performance of dragonfly take-off flight

Abstract

A numerical investigation is carried out to study the role of inclined stroke plane on the aerodynamic performance of a dragonfly during a take-off flight. A two-dimensional numerical simulation of tandem foils oscillating in-phase along an inclined stroke plane at Re = 160 is performed using ANSYS Fluent. The stroke plane angle is varied from 10° ≤ β ≤ 80° to determine its effect on aerodynamic force coefficients of forefoil and hindfoil. The result shows that the presence of forefoil reduces the hindfoil Cv for low stroke plane angle cases. The cycle-average vertical force coefficient Cv of both foils increases with β up to 50° and then decreases. A vortex pair is present in the wake of the foils during each cycle, which induces a downward dipole jet. The dipole jet characteristics such as jet width, location and maximum velocity components are measured for each stroke plane angle. It is observed that the cause of variation in Cv and CH with stroke plane angle can be explained with the help of dipole jet characteristics.