4. A supersonic wind tunnel uses air from a large plenum. The air passes through the test section and exhausts to a larg

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4 A Supersonic Wind Tunnel Uses Air From A Large Plenum The Air Passes Through The Test Section And Exhausts To A Larg 1 (457.5 KiB) Viewed 29 times

4. A supersonic wind tunnel uses air from a large plenum. The air passes through the test section and exhausts to a large vacuum chamber, Pa~ 0. Station 1 refers to the throat of the converging- diverging nozzle. A sphere is placed in the test section between stations 2 and 3 (downstream of throat). The tunnel and sphere are adiabatic. The effect of wall friction on the flow can be neglected compared to the effect of drag of the sphere. Relevant areas are A2/A1=5, A2= A3, and AclA1=3. A reasonable model for the stagnation pressure drop due to the sphere is: M3 Asphere 1- 2 Pt3 Pt2 Cd with Ca= 1 and Asphere. Atunnel = 0.04. Assume: y=1.4, R=287 J/kg/K. a) Supersonic flow is established in the test section. Determine, M2 and M3. b) Suppose Ae is decreased. At what value of Ael A1 does the wind tunnel un-start? c) Is there a normal shock between 1 and 2 after the tunnel un-starts? If so, estimate the Mach number of the normal shock. Hint: Assume the stagnation pressure change between 2 and 3 (found in part A) is now due to the shock wave. 14 points