Transition Delay via Vortex Generators in a Hypersonic Boundary Layer at Flight Conditions

Paredes, Pedro; Choudhari, Meelan M.

doi:10.2514/6.2018-3217

Cited by 12 publications

(4 citation statements)

References 38 publications

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“…There have been many attempts over the years to develop control strategies in order to attenuate flow disturbances and sustain the laminar state of the boundary layer (see e.g. Schneider 1999;Zuccher, Luchini & Bottaro 2004;Leyva et al 2009;Fong et al 2015;Paredes, Choudhari & Li 2018;Xiao & Papadakis 2019). When instability waves are the target of the transition-delay strategy, linear theory is often used either directly or indirectly; and in some of the strategies ad hoc assumptions are at times invoked in particular regarding the form of the actuation.…”

Section: Introductionmentioning

confidence: 99%

Optimal heat flux for delaying transition to turbulence in a high-speed boundary layer

Jahanbakhshi

Zaki

2021

J. Fluid Mech.

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Section: Introductionmentioning

confidence: 99%

Optimal heat flux for delaying transition to turbulence in a high-speed boundary layer

Jahanbakhshi

Zaki

2021

J. Fluid Mech.

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“…In the case of swept wings, stationary crossflow vortices can be attenuated with discrete roughness elements [44,45]. In hypersonic flow, appropriately tuned streamwise streaks can stabilize Mack-modes (Mode-2 instabilities) both on flat plates [46] and cones [47]; a control technique that can be achieved by suitable vortex generators [48,49]. The PSE method could be used to improve the Technology Readiness Level of any of the above methods, with sufficient improvements in the computational cost.…”

Section: Introductionmentioning

confidence: 99%

Reused LU factorization as a preconditioner for efficient solution of the Parabolized Stability Equations

Szabó

Paál

2023

Preprint

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The parabolized stability equation (PSE) is a widely used, efficient method to calculate the evolution of streamwise traveling instabilities in spatially developing, weakly nonparallel flows. Although the PSE method is very economical, computational time can be significant due to the repeated solution of linear systems of equations in each marching step. The linear systems of equations are typically solved by LU factorization due to the moderate size and the sparsity of the coefficient matrices. In this paper, instead of repeated calculation of the LU factorization, a single LU factorization is calculated in each marching step, and used as a preconditioner for an iterative solver. Numerical experiments are conducted on the incompressible PSE, nonlinear PSE (NLPSE) with explicit discretization of the nonlinear terms, and NLPSE with implicit treatment of the nonlinearities. It is shown that the time spent on the solution of the linear systems of equations was reduced by a factor of 2.5, 4.5-7.5, and 20-60 for the three cases, respectively. The methodology can be generalized to the compressible PSE equations, and extended to similar boundary layer stability problems, or slowly varying parabolic partial differential equations.

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“…Common passive transition control methods include vortex generation [11,12], roughness [13][14][15][16][17], wavy wall [17], flexible coating [18], and porous coating [19,20]. The vortex generator has been successfully applied to the air inlet of high supersonic aircraft such as X-43.…”

Section: Introductionmentioning

confidence: 99%

“…The vortex generator has been successfully applied to the air inlet of high supersonic aircraft such as X-43. Paredes [11] studied a vortex generator that delayed transition in a hypersonic boundary dominated by Mack-mode instabilities by inducing streaks. Schneider's [13] paper outlines three or more modes of transition affected by roughness and indicates that at high hypersonic edge Mach numbers, a very large roughness height is required to influence transition.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Hypersonic Flat-Plate Boundary Layer Transition Subjected to Bi-Frequency Synthetic Jet

Liu,

Luo,

Liu

et al. 2023

Aerospace

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Transition delaying is of great importance for the drag and heat flux reduction of hypersonic flight vehicles. The first mode, with low frequency, and the second mode, with high frequency, exist simultaneously during the transition through the hypersonic boundary layer. This paper proposes a novel bi-frequency synthetic jet to suppress low- and high-frequency disturbances at the same time. Orthogonal table and variance analyses were used to compare the control effects of jets with different positions (USJ or DSJ), low frequencies (f1), high frequencies (f2), and amplitudes (a). Linear stability analysis results show that, in terms of the growth rate varying with the frequency of disturbance, an upstream synthetic jet (USJ) with a specific frequency and amplitude can hinder the growth of both the first and second modes, thereby delaying the transition. On the other hand, a downstream synthetic jet (DSJ), regardless of other parameters, increases flow instability and accelerates the transition, with higher frequencies and amplitudes resulting in greater growth rates for both modes. Low frequencies had a significant effect on the first mode, but a weak effect on the second mode, whereas high frequencies demonstrated a favorable impact on both the first and second modes. In terms of the growth rate varying with the spanwise wave number, the control rule of the same parameter under different spanwise wave numbers was different, resulting in a complex pattern. In order to obtain the optimal delay effect upon transition and improve the stability of the flow, the parameters of the bi-synthetic jet should be selected as follows: position it upstream, with f1 = 3.56 kHz, f2 = 89.9 kHz, a = 0.009, so that the maximum growth rate of the first mode is reduced by 9.06% and that of the second mode is reduced by 1.28% compared with the uncontrolled state, where flow field analysis revealed a weakening of the twin lattice structure of pressure pulsation.

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Transition Delay via Vortex Generators in a Hypersonic Boundary Layer at Flight Conditions

Cited by 12 publications

References 38 publications

Optimal heat flux for delaying transition to turbulence in a high-speed boundary layer

Optimal heat flux for delaying transition to turbulence in a high-speed boundary layer

Reused LU factorization as a preconditioner for efficient solution of the Parabolized Stability Equations

Numerical Investigation of Hypersonic Flat-Plate Boundary Layer Transition Subjected to Bi-Frequency Synthetic Jet

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