AN INVESTIGATION OF THE THEORETICAL AND EXPERIMENTAL AERODYNAMIC CHARACTERISTICS OF A LOW-CORRECTION WIND TUNNEL WALL CONFIGURATION FOR AIRFOIL TESTING.

摘要

This thesis deals with a new approach to reduce wall corrections in high-lift airfoil testing, by employing two similar non-uniform transversely slotted walls. The solid elements of the slotted wall are symmetrical airfoils at zero incidence, and the spaces between the slats are non-uniform, increasing linearly towards the rear.;Also, the performance of this new wall configuration was examined experimentally. Two different sizes of NACA-0015 airfoil were tested in the existing low speed wind tunnel after modifying both the configuration of the side walls and the test section to accommodate the new test. Pressure distributions about the test airfoils were measured using pressure taps around their contours. Also the lifts and the pitching moments were obtained by integrating the measured surface pressures. The experimental results show that the use of the new wall configuration with AOAR = 59% would produce wind tunnel test data very close to the free air values.;This wall configuration provides the flow conditions close to the free air test environment which lead to negligible or small wall corrections. The theory uses the potential flow surface vortex-element method, with "Full Load" Kutta Conditions satisfied on the test airfoil and wall slats. This method is very well supported by physical evidence and it is simple to use. The surface velocities can be calculated directly and the aerodynamic lift and pitching moment are determined by numerical integration of the calculated pressure distributions around the airfoil contour. This method can be developed to include a simulation of the flow in the plenum chambers in the analysis.