ABSTRACT

Flow Separation over the surface of the airfoil affect the aerodynamic performance of airfoil, flow separation increases drag force and decreases lift force. Aerodynamic efficiency of an airfoil can be improved by delaying separation, which increases the lift force and reduces the drag force. Flow separation can be controlled by altering boundary layer behavior such as reducing boundary layer thickness and increases maximum velocity over surface of an airfoil; these can be done by different techniques such as placing dielectric barrier discharge, Plasma actuator and modifying the geometry of airfoil. All of these techniques categorized into active and passive flow separation control techniques. In this research, E398 airfoil was selected for study. Experimental and numerical study has been carried out on standard E398 airfoil having chord length 0.15 m and airfoil modified with triangular roughness at 0.05 of Chord (with maximum height of roughness are O.Olof chord and 0.015 of chord) and 0.75 of chord from leading edge. After the modification of profiles, 2D structured mesh was generated using Gridgen VIS.
2D CFD based simulation of Smooth and modified E398 airfoil has been carried out, at low Reynolds Number ranging from Re 16000 to Re 29000 and Angle of Attack from o0 to 15o K-£ turbulent model is considered for numerical simulation.
Numerical Results shows that the aerodynamic efficiency of modified airfoil with roughness at O.75 of chord it increases co-efficient of lift by 13.7% at Re 16000, 16.3% at Re 22000% and 11.8% at Re 29000 than smooth airfoil, drag force decreases by 43% 12.3% and 27.6% respectively. It is observed that as roughness near trailing edge of airfoil improves significantly performance of airfoil, the suitable location of roughness is
0.75 of chord from leading edge.

Keywords: Airfoil, Low Reynolds Number, Flow Separation,
Triangular roughness