DESIGN OF SUPERSONIC WIND TUNNEL USING METHOD OF CHARACTERISTICS

The future of aerospace is supersonic and a supersonic wind tunnel is the fundamental requirement of the day. This design will help build small scale and large scale supersonic wind tunnels for testing objects such as the spikes used in the fore section of supersonic aircrafts, and shock absorbing objects etc. Shocks are evident in a supersonic flow and when air passes through a shock, the velocity reduces and thus not allowing the speed to be maintained constant throughout the section and also reducing the efficiency of the wind tunnel. By using the Method of characteristics, we assume characteristic points and see to it that the shocks, if formed will be in contact with the surface and does not affect the uniformity of the flow through the duct and the velocity of the flow. A thorough understanding of the method of characteristics and its application to the design of supersonic wind tunnel nozzle is required. We make use of the Area-Mach relation, Prandtl Mayer spread sheet solver and other tools to define 64 coordinates in the supersonic section of the nozzle, including the internal points. The Wind Tunnel has been designed in CATIA v5 and the coordinates of the supersonic section of the wind tunnel have been obtained from MS Excel by doing the calculations and using its Goal Seek feature to simplify very complicated equation. The contour of the supersonic section of the wind tunnel is so designed that the shocks cancel each other, the shocks do not affect the velocity of the flow in order to obtain supersonic flow.