LES investigation into the generation of momentum deficits in the supersonic wake of a micro-ramp

Wang, Xiao; Yan, Ya; Sun, Zhengzhong; Liu, Chaoqun

doi:10.1007/s12206-013-1164-x

Cited by 7 publications

(4 citation statements)

References 21 publications

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“…This partially disagrees with conclusions drawn in Ref. [17], inasmuch as it is claimed that the mechanism of the micro-ramp is position alternation of high-and low-momentum fluid triggered by the primary vortices at the micro-ramp rather than downstream of it.…”

Section: Transport Of Momentum Streakscontrasting

confidence: 99%

“…Some authors have nonetheless recently questioned the micro-ramp working principle. For example, Wang et al [17] claim that the primary vortices are not capable of entraining a sufficient amount of high-momentum fluid from the free-stream to the wall downstream of the micro-ramp. Instead, it is proposed that the mechanism which makes the boundary layer fuller relies on the exchange of high-and low-momentum fluid of the boundary layer directly at the micro-ramp location.…”

Section: Introductionmentioning

confidence: 99%

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Transitional Flow Dynamics Behind a Micro-Ramp

Casacuberta

Groot

et al. 2019

Flow Turbulence Combust

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Micro-ramps are popular passive flow control devices which can delay flow separation by re-energising the lower portion of the boundary layer. We compute the laminar base flow, the instantaneous transitional flow, and the mean flow around a micro-ramp immersed in a quasi-incompressible boundary layer at supercritical roughness Reynolds number. Results of our Direct Numerical Simulations (DNS) are compared with results of BiLocal stability analysis on the DNS base flow and independent tomographic Particle Image Velocimetry (tomo-PIV) experiments. We analyse relevant flow structures developing in the micro-ramp wake and assess their role in the micro-ramp functionality, i.e., in increasing the near-wall momentum. The main flow feature of the base flow is a pair of streamwise counter-rotating vortices induced by the micro-ramp, the so-called primary vortex pair. In the instantaneous transitional flow, the primary vortex pair breaks up into large-scale hairpin vortices, which arise due to linear varicose instability of the base flow, and unsteady secondary vortices develop. Instantaneous vortical structures obtained by DNS and experiments are in good agreement. Matching linear disturbance growth rates from DNS and linear stability analysis are obtained until eight micro-ramp heights downstream of the micro-ramp. For the setup considered in this article, we show that the working principle of the micro-ramp is different from that of classical vortex generators; we find that transitional perturbations are more efficient in increasing the near-wall momentum in the mean flow than the laminar primary vortices in the base flow.

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Section: Transport Of Momentum Streakscontrasting

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transitional Flow Dynamics Behind a Micro-Ramp

Casacuberta

Groot

et al. 2019

Flow Turbulence Combust

View full text Add to dashboard Cite

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“…In our previous paper 5, [18][19][20][21] , the flow properties were also checked. It provides a shape factor H as about 1.35, which shows the flow before the MVG is fully developed turbulence flow.…”

Section: Numerical Methods Grid Generation and Turbulent Inflowmentioning

confidence: 99%

Optimization of MVG Position for Control of Shock Boundary Layer Interaction

Liu

Yang

Yan

2015

53rd AIAA Aerospace Sciences Meeting

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Based on the new theory of MVG to reduce separation caused by shock boundary layer interaction (SBLI), a new optimization method is presented in this paper, mainly to optimize the location of the MVG in front of the shock. The key issue is to generate a proper momentum deficit zone, which can generate a strong shear layer and further strong vortex rings frequently, in front of shock. Several artificial momentum deficit zones (low speed streaks) are tested by LES and the efficiency of reduction of SBLI induced separation is assessed. NomenclatureMVG = micro ramp vortex generator M = Mach number Re θ = Reynolds number based on momentum thickness h = micro ramp height δ = incompressible boundary-layer nominal thickness x, y, z = spanwise, normal and streamwise coordinate axes u,v,w = spanwise, normal and streamwise velocity LES = large eddy simulation Subscript 0 = inlet w = wall ∞ = free stream

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“…To generate the true turbulent inlet, twenty thousand turbulent profiles are obtained from previous DNS simulation and used as the time dependent inflow 9 . In our previous paper [10][11][12][13] , the flow properties were also checked. The inflow boundary layer velocity profile agrees with the analytical profile as well.…”

mentioning

confidence: 99%

LES Analysis on Shock-Vortex Ring Interaction

Yang

Tang

Liu

2016

54th AIAA Aerospace Sciences Meeting

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The mechanism why MVG can reduce flow separation is widely accepted as that the MVG can generate streamwise vortex which strongly mix the boundary layer and make the velocity profile fuller at the bottom. Therefore, the boundary layer becomes more capable to resistant the strong adverse pressure gradient caused by shocks to keep attached. However, this is not the case. The mechanism of reduction of shock induced flow separation by MVG is that the shock wave breaks down and disappears when the ring-like vortices generated by MVG are passing through the shock and the vortex structures never break down which is influenced very little when they pass the shock wave. In this paper, the interaction between supersonic boundary layer and the shock wave in a ramp flow at M=2.5 and Re=1440 is investigated by using a high order large eddy simulation code (LESUTA) with the 5th order Bandwidth-optimized WENO scheme developed in UTA. A quantitative investigation on the interaction between ring-like vortices and shock wave by tracking one ring-like vortex in three time steps is carried out. Details are reported in this paper.

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LES investigation into the generation of momentum deficits in the supersonic wake of a micro-ramp

Cited by 7 publications

References 21 publications

Transitional Flow Dynamics Behind a Micro-Ramp

Transitional Flow Dynamics Behind a Micro-Ramp

Optimization of MVG Position for Control of Shock Boundary Layer Interaction

LES Analysis on Shock-Vortex Ring Interaction

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