Mean and turbulent velocity measurements of supersonic mixing layers

Abstract

Abstract. The behavior of supersonic mixing layers under three x conditions has been examined by schlieren photography and laser y Doppler velocimetry. In the schlieren photographs, some largeYo scale, repetitive patterns were observed within the mixing layer; ( however, these structures do not appear to dominate the mixing layer character under the present flow conditions. It was found that 7 higher levels of secondary freestream turbulence did not increase the b peak turbulence intensity observed within the mixing layer, but slightly increased the growth rate. Higher levels of freestream turbu-~/ lence also reduced the axial distance required for development of the 0 mean velocity. At higher convective Mach numbers, the mixing # layer growth rate was found to be smaller than that of an incompressible mixing layer at the same velocity and freestream density a ratio. The increase in convective Mach number also caused a de~b crease in the turbulence intensity (a./A U).

Early evolution of the compressible mixing layer issued from two turbulent streams

“…To visually appreciate the mixing layer evolution, in figure 3 we show the mixing layer mid-line (y 0 , marked as a thick white line), and the position of the lower and upper boundary of the mixing layer (y L , y U , thick black lines). These are defined by vertically scanning the mean velocity profiles as suggested by Goebel et al (1990), as follows. For those profiles for which a location where u < U 2 − 0.1 U does not exist (i.e.…”

“…In most analyses presented in the literature both boundary layers are laminar, or one is laminar and one is turbulent (Sandham & Sandberg 2009). A notable exception is the study of Goebel et al (1990), Goebel & Dutton (1991), who considered a wide range of flow conditions, in terms of speed and density ratios of the two streams, with two turbulent incoming boundary layers. Although the (alleged) asymptotic developed state of turbulent mixing layers has been extensively studied (Bradshaw 1966), much less information is available from experiments regarding the non-similar region just past the trailing edge of the splitter plate, mainly because of technical difficulties in obtaining the necessary resolution in experimental facilities.…”

Response of dispersed droplets to shock waves in supersonic mixing layers

“…The position of droplet is integrated by the third-order Adams scheme, for example, in the ith direction The grid-set is specified as 256 3 150 nodes after the verification of grid-independence. The flow parameters of air are chosen the same as those in Goebel et al, 8 as shown in Table 1. Figure 1 shows the sketch of the physical model and calculation domain.…”

“…1 Recently, the compressible mixing layer has been studied by the experiments and numerical simulations, which have shown that the growth rate of mixing layer thickness is determined by the evolution of vortices 2,3 and is decreased with an increasing convective Mach number. [4][5][6][7][8][9] In addition, turbulence intensity and Reynolds stress are also depressed due to the compressibility effects. 5,6 Therefore, the mixing enhancement is more problematic in supersonic flows with high convective Mach number and has attracted much attention.…”

Flow physics of a hypervelocity mixing wake with oxygen enrichment

“…For c M greater than 0.8 it was found that the spreading rate becomes asymptotic to a value approximately one quarter that of the incompressible rate. Dimotakis (1991) Early efforts to characterise the turbulence structures within a compressible mixing layer employed laser Doppler velocimetry (Goebel, et al, 1990;Goebel & Dutton, 1991;Elliott & Samimy, 1990).…”