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Unformatted text preview: Year 2010 Month 10 Day 4 Determination of Mach number In a Supersonic Wind Tunnel Mae 309 Aerospace Engineering Laboratory II Name : Martin Suhartono Student ID : 20106182 Martin Suhartono - 20106182 Page 2 1. Objective To observe the oblique shockwave generated at a wedge shaped body inside a wind tunnel using Schlieren Technique, as well as, measuring the shock wave Mach number 2. Introduction When the air flow velocity exceeds that of the speed of sound, a supersonic flow takes place. A shock wave is then generated inside this supersonic flow when the air is compressed in an extremely short interval of time due to external force. The sudden pressure change actually renders the compression part of the wave to change slowly and the expansion part to change rapidly as the waveforms are crushed. This in turn makes the pressure, density and velocity of the air flow to increase suddenly downstream of the shockwave. Oblique shockwave specifically occurs when the supersonic flow passes through a ramp or wedge shaped body, and consequently, the angle of shockwave is determined by the ramp or wedge inclination. Characteristic of an oblique shockwave can actually be derived easily from that of a normal shockwave. The flow is firstly, divided into its vertical and horizontal components relative to the oblique shockwave front just as shown in the diagram. The relationship between V 1vertical , V 2vertical , and the oblique shockwave is similar to that of the normal shockwave and thus all the normal shockwave formulas can be used to calculate the properties of the flow before and after the shockwave. As V 1 is related to V 1vertical with the trigonometry identity of sin β i.e. V 1vertical = V 1 x sin β, we can replace the term V 1 in the normal shockwave formula with V 1 sin β. Consequently, we can replace V 2 as V 2 sin (β – δ), M 1 with M 1 sin β and M 2 with M 2 sin (β – δ). Here, β (or θ for our experiment) is the shockwave angle and δ as the change in the flow direction due to the shockwave....
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