Theoretical and Experimental Aerodynamics

Kaushik, Mrinal

doi:10.1007/978-981-13-1678-4

Cited by 20 publications

(23 citation statements)

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“…Essentially, a Reynolds number below 500 is troublesome for pressure measurement as the flow at that condition is dominated by the viscous effect. Hence, the Reynolds number below 500 is referred to as the troublesome number [23,24]. This study explores the efficacy of a plain and the corrugated tabs on the mixing behavior of a Mach 1.73 jet at overexpansion, near-correct-expansion, marginal-underexpansion, and high-underexpansion conditions corresponding to NPR 4, 5, 6, 7, and 8, respectively.…”

Section: Experimental Methodologymentioning

confidence: 99%

“…Essentially, a Reynolds number below 500 is troublesome for pressure measurement as the flow at that condition is dominated by the viscous effect. Hence, the Reynolds number below 500 is referred to as the troublesome number [23,24]. Pressure measurements were performed using a pitot probe, which is placed on a three-dimensional traverse system (Figure 5).…”

Section: Experimental Methodologymentioning

confidence: 99%

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Experimental Assessment of Corrugated Rectangular Actuators on Supersonic Jet Mixing

Jana

Kaushik

2020

Actuators

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To improve the stealth capability of a military aircraft, the reduction in core length is essential to reduce the heat signature and the noise characteristics of the engine exhaust. The efficacy of rectangular vortex generators in achieving these objectives has been demonstrated by several researchers, owing to their simplicity. One way of producing the mixed-size vortices is by providing corrugations on the edge of the tab (actuator). Therefore, in the current study, two tabs of aspect ratio 1.5, mounted diametrically opposite to each other at the outlet of a Mach 1.73 circular nozzle, are examined at varying levels of expansions, ranging from overexpanded to underexpanded jet states. In addition, to generate the mixed-size vortices, three corrugation geometries, i.e., rectangular, triangular, and semicircular, are configured along the tab edges. Both quantitative and qualitative investigations are carried out by using the pitot probe to measure the stagnation pressures and by utilizing a shadowgraph technique to visualize the flow field. The corrugated tabs generated a significant mixing, and among them, the tabs with triangular corrugations are found to be most effective. A maximum reduction of about 99.7% in the supersonic core is obtained with triangular corrugated tabs at near-correct-expansion, corresponding to nozzle pressure ratio (NPR) 5. Interestingly, the semicircular corrugated tab significantly reduces the asymmetry near the nozzle exit plane. The shadowgraph images confirm the efficacy of different corrugated tabs in reducing the strength of the waves, prevalent in the supersonic core.

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Section: Experimental Methodologymentioning

confidence: 99%

“…Essentially, a Reynolds number below 500 is troublesome for pressure measurement as the flow at that condition is dominated by the viscous effect. Hence, the Reynolds number below 500 is referred to as the troublesome number [23,24]. Pressure measurements were performed using a pitot probe, which is placed on a three-dimensional traverse system (Figure 5).…”

Section: Experimental Methodologymentioning

confidence: 99%

Experimental Assessment of Corrugated Rectangular Actuators on Supersonic Jet Mixing

Jana

Kaushik

2020

Actuators

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“…Instead, there are generations of shocks and expansion waves in the supersonic jet core region. Essentially, the supersonic jet core is defined as the extent of axial distance from the nozzle outlet to the location where characteristic decay starts or axial location up to which the waves prevail from the nozzle outlet [8]. According to the static pressure difference between the nozzle exit and the surrounding atmosphere where the jet is discharged, the expansion of the supersonic jet is classified into three categories: overexpansion, correct expansion, and underexpansion.…”

Section: Free Round Jetsmentioning

confidence: 99%

Survey on Vortex Shedding Tabs as Supersonic Jet Control

et al. 2022

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This study provides an overview of the tab-controlled jets to understand and predict the influence of mixing promoting vortices at speeds ranging from subsonic to supersonic. A detailed description of various features of the circular jets controlled by tab-like vortex generators is provided. Here, both the experimental and the numerical investigations on the impacts of tabs on the mixing enhancement and noise suppression are presented. Following a brief introduction about subsonic and supersonic circular jets, this study discusses the influences of certain key parameters on mixing characteristics, including the effect of tab geometry, tab number, tab orientation, tab size, and tab position relative to nozzle outlet. Subsequently, their effect on noise suppression is also reviewed. The detrimental effect of tabs in terms of thrust penalty is described. Finally, the future direction of research on the tab-controlled jets is outlined.

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“…An indirect approach that might be used to quantify jet mixing is to measure the extent of jet centerline decay. Faster descent implies rapid mixing and vice versa [2]. Usually, the decay of centerline pressure or velocity is observed to quantify jet decay.…”

Section: Introductionmentioning

confidence: 99%

“…Delta-tabs were used and it was found that two delta-tabs, spaced 180 • apart, absolutely dichotomized the jet. Kaushik andRathakrishnan (2013, 2015) clearly revealed that the magnitude and potency of vortices actuated from control tabs can be enhanced with geometrical alterations [8,9]. A recent work by Thillaikumar et al (2020) suggested that the introduction of vortex actuating tabs in the divergent section of the supersonic nozzle changes the structure of the shock cell, thereby reducing the jet core length [10].…”

Section: Introductionmentioning

confidence: 99%

Assessment of Short Rectangular-Tab Actuation of Supersonic Jet Mixing

et al. 2020

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This work explores the extent of jet mixing for a supersonic jet coming out of a Mach 1.8 convergent-divergent nozzle, controlled with two short rectangular vortex-generating actuators located diametrically opposite to each other with an emphasis on numerical methodology. The blockage ratio offered by the tabs is around 0.05. The numerical investigations were carried out by using a commercial computational fluid dynamics (CFD) package and all the simulations were performed by employing steady Reynolds-averaged Navier–Stokes equations and shear-stress transport k-ω turbulence model on a three-dimensional computational space for more accuracy. The numerical calculations are administered at nozzle pressure ratios (NPRs) of 4, 5, 6, 7 and 8, covering the overexpanded, the correctly expanded and the underexpanded conditions. The centerline pressure decay and the pressure profiles are plotted for both uncontrolled and the controlled jets. Numerical schlieren images are used to capture the barrel shock, the expansion fans and the Mach waves present in the flow field. Mach contours are also delineated at varying NPRs indicating the number of shock cells, their length and the variation of the shock cell structure and strength, to substantiate the prominent findings. The outcomes of this research are observed to be in sensible concurrence with the demonstrated exploratory findings. A reduction in the jet core length of 75% is attained with small vortex-generating actuators, compared to an uncontrolled jet, corresponding to nozzle pressure ratio 5. It was also seen that the controlled jet gets bifurcated downstream of the nozzle exit at a distance of about 5 D, where D is the nozzle exit diameter. Furthermore, it was fascinating to observe that the jet spread increases downstream of the nozzle exit for the controlled jet, as compared to the uncontrolled jet at any given NPR.

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Theoretical and Experimental Aerodynamics

Cited by 20 publications

References 0 publications

Experimental Assessment of Corrugated Rectangular Actuators on Supersonic Jet Mixing

Experimental Assessment of Corrugated Rectangular Actuators on Supersonic Jet Mixing

Survey on Vortex Shedding Tabs as Supersonic Jet Control

Assessment of Short Rectangular-Tab Actuation of Supersonic Jet Mixing

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