ESTIMATION OF DYNAMIC STABILITY DERIVATIVES OF BIO-INSPIRED AIRFOILS USING CFD

Abstract

Micro-Aerial vehicle (MAV) is a smaller size unmanned aerial vehicle (UAV) that has found wider commercial, military and industrial applications. Beside intelligence, reconnaissance and surveillance (ISR) missions, MAVs can be utilized in search and rescue missions in confined urban places like tunnels or in urban environments. Stability and control consideration of an aircraft is a major design element that is needed to be inspected at every design level to ensure safe and smooth flight flying vehicle. Dynamic stability derivatives measures the degree of damping provided to the disturbed aircraft and is an important parameter in determining the aircrafts’ attitude under disturbance, and for control designing. During the last few years, computational fluid dynamics has demonstrated its importance in the understanding of fluid dynamics by providing detailed insights of fluid flow to such an extent that was not possible before with experimental and analytical methods. Improvements in numerical methods and meticulous mathematical modeling has resulted in the development of high-fidelity CFD software that offers a mean of predicting complex flows with great accuracy. Currently, CFD is widely used to estimate damping coefficient of aircraft, missiles, UAVs etc. with adequate accuracy and lesser computational cost. This main aim of this research is to evaluate longitudinal dynamic stability derivatives of corrugated airfoils at low Reynolds number using CFD. CFD model is validated with experimental results and further the optimal turbulence model is selected by comparing with the endorsed results. Dynamic stability derivatives of flat plate and corrugated airfoils are calculated by simulating forced pitching sinusoidal oscillations specified at different mean angles of attack while studying the effect of amplitude, frequency, time step size and hysteresis VIII on the derivatives. Further, it has been observed that at Reynolds number of 100,000 and low angles of attack, damping coefficients of flat plate, corrugated and smoothened airfoils are similar and vary slightly with the angles of attack. This suggests that there is no significant effect of corrugations on the dynamic stability derivatives. However, large variation is seen at negative and near stall angles of attack which is related with the flow physics as flow separation and stall is observed at those angles