Steady and Time Dependent Study of Laminar Separation Bubble (LSB) behavior along UAV Airfoil RG-15

Abstract

The flow around the Unmanned Arial Vehicle (UAV) operating at a low Reynolds number regime of the O(10 5 ) is predominantly laminar and it leads to the formation of Laminar Separation Bubble (LSB). The pressure, shear stress, and heat flux distribution are considerably affected by LSB, which affects lift, drag, and pitching moment values. Most existing RANS (Reynolds-Averaged Navier-Stokes) turbulence models are built on the assumption of fully turbulent flow. Therefore, these models require additional transport equations or reformulations or specific transition information to predict the LSB observed in low Reynolds number transition flows. Steady and transient computational fluid dynamics simulations were done using the RANS based transition turbulence model to study the behavior of LSB on UAV airfoil RG-15. The transition turbulence model can predict the LSB with considerable accuracy. The steady state and time averaged simulation results are matching in the pre stall region but deviates after stalling. High amplitude velocity fluctuations were observed near regions of transition and separation.