Comparative Study of Two Dimensional Boundary Layer over NACA 23012 and NACA 23021 Airfoils by Using Keller’s Box Method

Abstract

This paper begins with general description onvarious methods for solving boundary layer equation. In particular, Prandtl's boundary layer equation is a simplified version of Navier-Stokes equation thatis solved integrally. Order of magnitudeanalysiscan be used to solve laminar and turbulent flow problems along the boundary layer.A more complex technique based onKeller’sbox method isalso discussed.This study aims atutilising a developed computercode which allows one to predict the development of boundary layer characteristics along airfoils’ surface, andhavea comparative understanding on flow behavioursbetween NACA 23012 and NACA 23021 airfoils, as well as 0⁰ and 5⁰angles of attack. The ability of Keller’s box method to solve the boundary layer equation prevails through correctskin friction,momentum thickness, and shape factor distributions over the surfaces. It was found that skin frictionin boundary layer over NACA23021 is higher than that over NACA23012 for about 10% of the chord length from the leading edge. However, momentum thickness of the boundary layer over NACA23021is lessthan the boundary layer momentum thickness over NACA23012for the whole chord length. Similarly, the shape factor Hfor the boundary layer over the formeris smallerin comparison to the latterfor about 30% of the chord length.