This study demonstrates the usefulness of instantaneous and mean density ρ, standard deviation σ, relative standard deviation σ/ρ, and product standard deviation σ*ρ acquired using a low-sampling-rate instantaneous (10 ns) laser-based method to study effects of high-frequency phenomena on offbody freestream, bow-shock wave, and gas-cap unsteadiness. Spatial correlations of relative flow unsteadiness are acquired using laser Rayleigh scattering performed along a 38.7 mm line containing 200 pixels spanning the freestream, gas cap, near-normal, and oblique shocks created by a multipurpose crew vehicle model in the NASA Langley 31-in. Mach 10 air wind tunnel. A total of 371 instantaneous images are acquired at a fixed stagnation temperature of 990±11 K and five stagnation pressures spanning 2.41–10.0 MPa (350–1454 psi). Maximum σ occurs at the bow-shock-wave spatial density profile first-derivative maximum for a near-normal and oblique shock. Maximum σ/ρ and σ*ρ occur at the bow-shock-wave spatial density profile second-derivative maximum and minimum, respectively, for both the near-normal and oblique shocks. At P0=1454 psi, maximum σ (normal shock) >5/2σ (gas cap), and σ (gas cap) is >2σ (freestream). Additional spatially averaged unsteadiness correlations with flowfield conditions are presented.
Mach 10 Bow Shock and Gas-Cap Unsteadiness Measurements Using Rayleigh Scattering
AIAA journal ; 54 , 10 ; 3062-3074
2016
Article (Journal)
English
Mach 10 Bow Shock and Gas-Cap Unsteadiness Measurements Using Rayleigh Scattering
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