Impact of tab location relative to the nozzle exit on the shock structure of a supersonic jet

Abstract

This paper presents an experimental study of a Mach 2.0 jet manipulated using rectangular tabs to understand the mixing enhancement at the overexpanded and perfectly expanded state of the jet. This paper also compares the mixing effectiveness of the tabs in comparison with the fluidic injection reported in our previous work [Kumar et al., “Empirical scaling analysis of supersonic jet control using steady fluidic injection,” Phys. Fluids 31(5), 056107 (2018)]. Tabs used in this investigation were rectangular strips of aspect ratio, AR, 2 (AR = length of the tab/width of the tab) and are positioned at 0De, 0.25De, 0.5De, and 0.95De (De is the nozzle exit diameter) downstream of the nozzle exit. Pitot pressure measurements were carried out along the jet centerline and in the radial directions to examine the supersonic core length (Lc*) and jet spread, respectively. The jet stream has been visualized using the shadowgraph technique in the orthogonal planes of the manipulated jet. The mixing capability of the manipulated jet quantified based on the reduction in supersonic core length ΔLc* strongly depends on the control technique and its location along the downstream direction. Three types of flow categories are identified, i.e., the “jet bifurcation,” “complex and strong shock-cell structure,” and “weak shock structure,” which depend on the tab location (xt*) and account for the jet mixing. The present study reveals that the tabs should be positioned downstream of the first shock crossover point which results in shorter core length and, hence, higher jet mixing. A conceptual model of the flow structure under control is proposed.

A Critical Review of Supersonic Flow Control for High-Speed Applications

“…Focusing the aspect ratio of the nozzle and nozzle pressure ratio (NPR) with the Mach number variation, the elliptic jet control with limiting tab [43] was investigated and showed that each parameter is important to control the jet flows, similar to the overexpanded plug nozzle jet [44] controlled by the passive method. Additionally, some researchers used ventilated triangular tabs to control the jet [45], control the supersonic elliptic jet with ventilated tabs [46], and to measure the impact of the tab location relative to the nozzle exit on the shock structure of a supersonic jet [47]. Khan et al [48] experimentally investigated the effect of the extended cowl on the flow field of planar plug nozzles for two different Mach number ranges (1.8 and 2.2) to observe the influence of the cowl length for the pressure distribution.…”

“…the jet flows, similar to the overexpanded plug nozzle jet [44] controlled by the passive method. Additionally, some researchers used ventilated triangular tabs to control the jet [45], control the supersonic elliptic jet with ventilated tabs [46], and to measure the impact of the tab location relative to the nozzle exit on the shock structure of a supersonic jet [47].…”

Investigation of slanted perforation diameter in tabs for supersonic jet control

“…Semicircular corrugations tab shows 90% reduction in core length in comparison with uncorrugated tabs for higher nozzle pressure ratio (NPR). All the above mentioned authors examined the profile modification, whereas Arun Kumar et al (2019) found that the correct position to place the tab against the nozzle exit is first shock crossover point. Subsequently, a paper by Quadros et al (2021) investigated the effect of shape modification on rectangular tabs.…”

Schlieren imaging investigation on azimuthally varying shock net from four-lobed corrugated nozzle

“…The stream is also affected by the azimuthal orientation of the vortex generator. The shock cell structure variation due to the positioning of the tab was studied by Arun Kumar et al (2019) and identified three flow categories according to the tab position. The categories of flow are “jet bifurcation”, “complex and strong shock structure” and “weak shock structure”.…”