A Theoretical Investigation of Simulation in Expansion Tubes and Tunnels PDF Download

Author: Robert L. Trimpi
Publisher:
ISBN:
Category : Shock (Mechanics)
Languages : en
Pages : 68

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Book Description
A preliminary theoretical analysis was conducted of expansion-tube and expansion-tunnel simulation whereby the postnormal shock stagnation conditions of a model were matched to those of flight for both a perfect gas and equilibrium real air. The selected simulation mode permitted large variations from flight conditions for the test-section ambient temperature and pressure but only a small excursion for ambient velocity or density. A brief treatment of the perfect-gas expansion tunnel with simulation demonstrated both gains and penalties in driver performance, depending on the Mach number, nozzle area ratio, driver gas, and simulation temperature ratio. A more exhaustive analysis of an equilibrium real-air expansion tube employing simulation with ambient-gas temperatures of 1000° and 2000°K was completed for equivalent flight velocities from 20,000 to 50,000 feet per second (6.096 to 15.24 km/sec) and altitudes from 100,000 to 300,000 feet (30..48 to 91.44 km). The primary advantages of simulation were found to be large increases in testing time, initial test-gas slug length, and velocity-altitude performance. The primary disadvantages were a small degree of test-section dissociation and an increased peak cycle dissociation for the highest flow velocities and altitudes. For equilibrium flow the gas state behind a shock wave was found to be closely simulated by all strong shock waves and to be well simulated even by weak waves with flow deflections as low as 30°