Linear Stability Analysis of Laminar Separation Bubble over NACA0012 airfoil at Low Reynolds Numbers

摘要

Low Reynolds number flows are important especially for MAV applications due to the presence of the LSB, which affects airfoil performance. The transition model of Fluentl2 is used to extract the local velocity profiles and their second derivatives for flow past NACA0012 airfoil at .Re=0.34×10~6. These form the input to a numerical linear stability code developed to understand the T-S wave characteristics in the LSB. The code solves the Orr- Sommerfeld equation locally for NACA0012 mean profiles at α=9° with parallel flow approach. The OSE is solved as a spatial stability problem where the temporal frequency is a real number and the eigen values are the spatial wave numbers. A complex Newton-Raphson technique is used for the Eigen value search and e~N method is used to predict transition. The growth of the most unstable 'wave is such that the amplification ratio reaches a predefined number e~9. Based on e~N method the T-S wave frequency and phase speed are predicted. The LSB is observed using the C_p and velocity vector plots from Fluent12.