Professor Gordon Holloway and his student, Jason Bettle, of the University of New Brunswick obtained the following tabulated data for blow-dow n airflow through a converging- diverging nozzle similar in shape to Fig. P3.22. The supply tank pressure and temperature were 29 psig and 74°F, respectively. Atmospheric pressure was 14.7 psia. Wall pressures and centerline stagnation pressures were measured in the expansion section, which was a frustrum of a cone The nozzle throat is at v = 0.
item) | 0 | 1.5 | 3 | 4.5 | 6 | 7.5 | 9 |
Diameter (cm) | 1.00 | 1.098 | 1.195 | 1.293 | 1.390 | 1.488 | 1.585 |
PwaiKpsig) | 7.7 | -2.6 | -4.9 | -7.3 | -6.5 | -10.4 | -7.4 |
PsMglMIKHI (psig) | 29 | 26.5 | 22.5 | 18 | 16.5 | 14 | 10 |
Use the stagnation pressure data to estimate the local Mach number. Compare the measured Mach numbers and wall pressures with the predictions of one-dimensional theory. For.v > 9 cm. the stagnation pressure data was not thought by Holloway and Bettle to be a valid measure of Mach number. What is the probable reason?
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Fluid Mechanics
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