Use of Diamond Shaped Strut for a Large Test Section Subsonic Wind Tunnel

摘要

Wind Tunnel measurements on scaled down models of aerospace as well as for automotive systems are embedded in struts, so that the forces on supporting system are already excluded in the measurements. Most of the struts used in testing are cylindrical in shape with pitch rod for alpha mechanism and have issues for model attachment due to more thickness and frontal area. Diamond shaped strut is one of the prospective solution with additional benefits of less contribution towards lift and tapered profile for model attachment. In the present study, attention was drawn on the contribution to support interference that rose due to these two different types of struts. First, the entire main cylindrical strut was shrouded by a streamlined metal fairing and its influence on the actual force and moments were measured through a series of blow downs in IIUM-LSWT at different velocities and side slip angles. Later, the tests were conducted with pitch rod as well which is also mounted on the turn table at a certain distance from the main strut. The aerodynamic forces and moments obtained from the cylindrical strut (without fairing) were found to be of considerable magnitude. The developed databank for different struts will be highly beneficial for the future design of experiments in wind tunnels of similar dimensions. Moreover, it was found that the impact of the large flow disturbance due to the pitch rod is perhaps responsible for the asymmetric pattern in wind tunnel data for ±β, specially the drag and pitching moment coefficient.