Effect of flat wall length on decay and shock structure of a supersonic square wall jet

Abstract

Experiments were conducted to find the effect of wall length on the decay behaviour and shock structure of a supersonic wall jet issuing from c-d nozzle of the square-shaped exit. A straight flat wall of width same as the side length of the square was attached to the lip of the nozzle such that the leading edge of the wall and the side of the square aligned properly which allowed the supersonic jet to graze past the flat wall. Experiments were conducted with five different wall lengths, that is, [Formula: see text] = 0.5, 1, 2, 4 and 8. Wall pressure measurements were made from leading edge to the trailing edge of the wall along its centreline. Schlieren flow visualization of the jet flow over the wall for the different wall lengths revealed the shock pattern and the effect of the wall length on the shock structure. The shock structure and jet deflection were significantly affected due to the presence of the wall. There was an upward jet deflection for [Formula: see text] up to [Formula: see text] whereas a downward jet deflection was observed for [Formula: see text]. Noticeable changes in the shock structure were observed for the wall lengths up to 2 D h. The wall length also significantly affected the jet decay characteristics and supersonic core length. Maximum enhancement in jet decay and maximum reduction in supersonic core length resulted when the wall length was [Formula: see text]. However, when the wall length was increased to [Formula: see text], there was a significant reduction in jet decay and a recovery of [Formula: see text]. Presence of wall always resulted a reduction in Lsc irrespective of wall length. The wall effect was to induce a more precipitous pressure drop closer to the nozzle exit, and a more gradual drop farther from it for [Formula: see text] > [Formula: see text].

Effect of wall length on an interacting supersonic rectangular jet

“…Changes in wall length were found to have significant effect on decay characterizes of a square supersonic jet flowing past the wall in the study conducted by Manikanta et al (2022). The interaction effects between a rectangular jet and a flat wall at various wall lengths were found to have significant results in force and moment coefficients up to L w ¼ 4 D h at all nozzle pressure ratios (NPRs) (Manikanta and Sridhar, 2024).…”

“…To determine the wall effect on the supersonic jet decay behavior, the following parameters (ref. Manikanta et al, 2022) would be useful:…”

“…The wall-induced change in total pressure drop corresponding to 100s percent along the NECL in the jet flow field can be assessed from the following [equation ( 2)] parameter: The wall-induced change in the SCL (L sc ) of the rectangular jet can be characterized by the parameter, m w in percentage using equation (3) (ref. Manikanta et al, 2022):…”

An experimental study on the interaction effects between a rectangular supersonic jet and a flat wall at different wall lengths

“…Florian Baier et al [35] undertook the flow measurements at high temperature when a supersonic flow exhausted over a flat surface. Manikanta et al [36] studied the wall length effects on the shock structure and decay characteristics of a square wall-jet. It is well known that supersonic jets flowing past a wall are partially constrained on the wall bound side and free to expand on the other sides.…”

Numerical investigation of mixing performance for controlled supersonic jet

“…are used for jet control. 3,4 However, for the passive control, the controlling energy is extracted from the flow itself by providing some geometrical modification such as grooved nozzle, notches at the nozzle exit, and placing of tabs at the nozzle exit. [5][6][7][8] Small tabs and vortex generators have been found to be effective passive control techniques.…”