Investigations of the aerodynamic interactions between wind tunnel models and their support systems at the GALCIT ten foot wind tunnel

Abstract

This work is divided into two parts. Part I describes the GALCIT image system tare procedure as it is used at the present time, the techniques of operation, and the assumptions used. The tare procedure is an experimental method for obtaining the aerodynamic interference forces and moments produced on a wind tunnel model by the supporting structure which holds it fixed in the windstream. The present technique has been in use at GALCIT for over five years, during which time many small inconstancies kept recurring, indicating the need for refinement of the procedures. Part II is a report on the first phase of the investigations planned for the attack on these problems. In Part II are given the measurements of the interactions on a simple, rectangular wing, and of the air loads on the suspension system without a model present. An attempt is made to give a physical picture of the rather elaborate flow patterns around the windshields, and of what happens to the aerodynamic characteristics of a wing when it is immersed in such a flow field. Some of the inadequacies of the present techniques are isolated and their magnitudes determined. A first try is made at measuring the tares for a yawed wing, with encouraging results. The need for further experimental work is clearly indicated, as well as for a theoretical study of the flow patterns in the tunnel throat.