Effects of dual jets distance on mixing characteristics and flow path within a cavity in supersonic crossflow

Abstract

Abstract:A rectangular open cavity with upstream dual injectors at a freestream Mach number of 1.9 was investigated experimentally. To evaluate the effect of the distance between the jets, the flow characteristics were investigated using the high-speed schlieren photography, particle image velocimetry, and surface oil flow techniques. The dual jet distances of 18 and 54 mm were used.Unstable flow occurs over the cavity in all cases and is not improved by changing the distance between the dual jets. Although the distance between the dual jets does not influence the flow stability, the flow field varies decidedly depending on the dual jets distance. The enhancement of air mixing depends on the distance between the jets. A long dual jets distance was found to yield better mixing characteristics within the cavity than a short one. When the jets are further apart, the mainstream between two counter-rotating vortex pairs behind the jets flows strongly into the cavity because of the increased blow-down occurring between the vortex pairs. Additionally, a counterflow with a low velocity magnitude occurs behind the jets. Hence, mixing is enhanced within the cavity by effects of the opposed flow. When the jet pairs are closer to each other, the counter-rotating vortex pairs are in contact; as a result, the blow-down effect does not occur between them. The flow drawn into the cavity from the mainstream is supplied from the sides of the test section into the cavity.

Static and Wind-on Performance of Polymer-Based Pressure-Sensitive Paints Using Platinum and Ruthenium as the Luminophore

“…The same wind tunnel was also employed in a wide range of supersonic flow related studies [15,23,24,25,27,28,29,30,31,32,33]. The test section of the wind tunnel has dimensions of 485.5 mm (length) × 150 mm (width) × 216.5 mm (height).…”

Active flow control over a backward-facing step using plasma actuation

“…Olive oil particles, with a diameter in the order of 1µm, 44 were used as seeders. The PIV system used for the experiments was a Litron Lasers -Nano L PIV, double oscillator laser system, providing a 532nm Nd:YAG pulsed laser beam.…”

Flow visualisation of a normal shock impinging over a rounded contour bump in a Mach 1.3 free-stream

“…The same wind tunnel was previously employed in a wide range of transonic and supersonic aerodynamic related studies. The details of this wind tunnel can be found in Lo ( 2014 ), Lo and Kontis ( 2015 , 2016 ), Lo et al ( 2013 , 2015 , 2016 ), Zare-behtash et al ( 2014 , 2015 , 2016 ), and Ukai et al ( 2014a , b ). Therefore, only a brief description on this wind tunnel facility is provided here.…”

“…All of these windows are made of quartz. The wind tunnel has a stable runtime of 6 s (Lo and Kontis 2016 ; Lo et al 2013 , 2015 , 2016 ; Zare-Behtash et al 2014 , 2015 , 2016 ; Ukai et al 2014a , b ). Under the same initial conditions, the variation of the free-stream Mach number ( M ∞ ) is about M ∞ = 1.3 ± 0.1.…”