Accession Number:

ADA239269

Title:

Oscillating Shock Impingement on Low-Angle Gas Injection into a Supersonic Flow

Descriptive Note:

Master's thesis,

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s):

Report Date:

1991-01-01

Pagination or Media Count:

192.0

Abstract:

Experiments were performed to determine effects of impinging oscillating shocks of different frequencies on a 15 deg downstream angled, underexpanded, sonic helium jet injected into a supersonic airflow. Information on mixing, penetration, total pressure loss and turbulence structure from these experiments was used to estimate mixing control achieved by adding an oscillating shock to the helium injection flow field. Tests were conducted at Mach 3.0, with a total pressure of 6.5 atm, total temperature of 290 K and a Reynolds number of 51.0 millionm. Oscillating shocks of 3 different frequencies were studied. Frequencies selected were designed to allow tuning of the shock frequency to the estimated frequency, about 100 - 150 kHz, of the largest eddies in the approach boundary layer. Visualization using nanoshadowgraph photography showed large turbulent structures in all cases. Changes in eddy size with changing shock frequency were clearly visible on the nanoshadowgraphs. The primary measurement made for the mixing studies was the molar concentration of helium. Concentration data, as well as mean flow data, was collected at 9 lateral positions at each of 3 axial stations downstream of the helium injector. The resulting data produced contours of helium concentration, total pressure, Mach number, velocity, mass flux and static flow properties. Additional tests were conducted to determine the shock oscillation frequency, correlation between the oscillating shock and turbulence in the shear layer and angle of large-scale structures in the flow.

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE