Effects of vortex generators on unsteady unstarted flows of an axisymmetric inlet with nose bluntness

Shock tunnel tests and CFD simulations are conducted to study effects of vortex generators (VGs) on unsteady unstarted flows of an axisymmetric hypersonic inlet with nose blunt radii of 0.8 mm and 3.2 mm. The inlet exit is throttled with a preseted block to generate unstarted flows at a freestream Mach number of 5.9. Unstarted flows of no VGs, 0.5 mm and 1 mm-thick VGs are recorded through schlieren imaging and pressure measurements. Experimental results show that the unstarted flows are characterized with prominent shock oscillations and pressure fluctuations. VGs reduce scales of the external separations, enlarge angles of the separated shock waves, and increase time-averaged magnitudes of surface pressures. The oscillatory period can be shortened from 4 ms to 3.13 ms by 1 mm-thick VGs for the R0.8 mm configuration. The maximum increment of the time-averaged pressure magnitudes can reach 16.2 times the freestream static pressure (p(infinity)) for the R0.8 mm configuration with 1 mm-thick VGs. In addition, VGs generally increase pressure standard deviations of the measuring points upstream of the throat section within 4.0 p(infinity) and decrease those of the downstream measuring points up to 8.6p(infinity), despite the 0.5 mm-thick VGs condition of the R3.2 mm configuration. Flow mechanisms dominating the effects of VGs on the unsteady unstarted flows are analyzed with the aid of the CFD simulations. Feasibility of VGs on unstarted flow control is also evaluated. (c) 2020 Elsevier Masson SAS. All rights reserved.