COMPUTATION OF FLOW ABOUT AIRFOILS – COMPARISON OF PANEL METHOD AND CFD METHOD

Abstract

The aerodynamic study of an airfoil is fundamental to analyze the behavior and define geometrical characteristics of a wing for prescribed flight conditions. Based on analyzes and simulations we are able to define the variables for aerodynamic design of an aircraft. The unmanned aerial vehicle (UAV) designed for SAE Aerodesign competition use high lift airfoils for low Reynolds number flow. The viscous or inviscid flow about airfoils can be computed using different methodologies, such as panel method or finite volume method. The main objective of this work is to compute and compare the lift and drag coefficients as well as pressure distributions in the contour of airfoils calculating the inviscid and viscous flow, using a panel method and a finite volume method. For the numerical analysis, high lift airfoils of families NACA 4, EPPLER, GOE, CH and SELIG were selected. These airfoils have very good aerodynamic efficiency with high ratio between the lift and drag coefficients.  These profiles are highlighted by its high mean-line curvature and are used at low speeds, being indicated for the SAE Aerodesign competition aircrafts. The criterion used to choose the airfoil was the highest lift coefficient generated in relation to its maximum stall angle, at a number of Reynolds of cruising flight speed, that is close to the transition from laminar boundary layer to turbulent boundary layer. The panel method analysis was performed using the XFRL5 software that uses XFOIL as source code. In the finite volume method, the Fluent code of ANSYS was used. Different types of meshes, structured and unstructured, are compared and quality parameters of mesh cells are analyzed and presented. The pressure distributions and the lift and drag coefficient curves, for the selected aerodynamic profile, calculated using panel method and finite volume method, are also presented and compared.