Boundary Layer Tripping in Supersonic Flow

Arnal, D.; Vignau, F.; Juillen, J. C.

doi:10.1007/978-3-642-84103-3_62

Cited by 6 publications

(8 citation statements)

References 2 publications

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“…This assumption can be confirmed by computing an intermittency function, which represents the probability of being in a turbulent spot at a given location (see the work of Narashima [48] for more details). The intermittency is computed based on pressure spectrograms following an idea of Arnal [49]. The intermittency distribution is displayed in figure 22 (b) for the three simulations.…”

Section: Impact Of the Large Scale Dynamics On Transitionmentioning

confidence: 99%

Multi-scale study of the transitional shock-wave boundary layer interaction in hypersonic flow

Lugrin

Beneddine

Garnier

et al. 2021

Theor. Comput. Fluid Dyn.

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A high-fidelity simulation of the massively separated shock/ transitional boundary layer interaction caused by a 15-degrees axisymmetrical compression ramp is performed at a free stream Mach number of 6 and a transitional Reynolds number. The chosen configuration yields a strongly multiscale dynamics of the flow as the separated region oscillates at low-frequency, and high-frequency transitional instabilities are triggered by the injection of a generic noise at the inlet of the simulation. The simulation is post-processed using Proper Orthogonal Decomposition to extract the large scale low-frequency dynamics of the recirculation region. The bubble dynamics from the simulation is then compared to the results of a global linear stability analysis about the mean flow. A critical interpretation of the eigenspectrum of the linearized Navier-Stokes operator is presented. The recirculation region dynamics is found to be dominated by two coexisting modes, a quasi-steady one that expresses itself mainly in the reattachment region and that is caused by the interaction of two self-sustained instabilities, and an unsteady one linked with the separation shock-wave and the mixing layer. The unsteady mode is driven by a feedback loop in the recirculation region, which may also be relevant for other unsteady shock-motion already documented for shock-wave/turbulent boundary layer interaction. The impact of the large-scale dynamics on the transitional one is then assessed through the numerical filtering of those low wavenumber modes; they are found to have no impact on the transitional dynamics.

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Section: Impact Of the Large Scale Dynamics On Transitionmentioning

confidence: 99%

Multi-scale study of the transitional shock-wave boundary layer interaction in hypersonic flow

Lugrin

Beneddine

Garnier

et al. 2021

Theor. Comput. Fluid Dyn.

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“…Thus, the results are consistent, and the N-factor of 6-7 means that no bypass transition occurs. (The limit to bypass transition is often defined as N = 0; see Arnal 1994.) Disturbances are amplified according to the linear stability theory.…”

Section: Transition Scenariomentioning

confidence: 99%

Dynamics of laminar separation bubbles at low-Reynolds-number aerofoils

2009

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The laminar separation bubble on an SD7003 aerofoil at a Reynolds numberRe= 66000 was investigated to determine the dominant frequencies of the transition process and the flapping of the bubble. The measurements were performed with a high-resolution time-resolved particle image velocimetry (TR-PIV) system. Contrary to typical measurements performed through conventional PIV, the different modes can be identified by applying TR-PIV. The interaction between the shed vortices is analysed, and their significance for the production of turbulence is presented. In the shear layer above the bubble the generation and amplification of vortices due to Kelvin–Helmholtz instabilities is observed. It is found that these instabilities have a weak coherence in the spanwise direction. In a later stage of transition these vortices lead to a three-dimensional breakdown to turbulence.

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“…In classic spatial LST analysis, the wavenumber vector is used typically to characterise the perturbation propagation direction (Mack 1984; Arnal 1993). The wavenumber vector is normal to the wavefronts, hence the results of figure 19 show graphical evidence that the trajectory of the wavefronts and the projected base-flow streamlines gradually diverge upstream of the step.…”

Section: Evolution Of the Perturbation Field At The Stepmentioning

confidence: 99%

“…Considering a low-disturbance background, representative of free-flight conditions, laminar–turbulent transition is initiated typically by modal instability growth. In this scenario, the early stage of transition can be analysed based on the evolution of small-amplitude perturbations superimposed on the laminar base flow (Mack 1984; Arnal 1993; Reed & Saric 1996; Schmid & Henningson 2001; Theofilis 2003). The vector of state variables representing the flow field is decomposed as where is a steady laminar solution of the Navier–Stokes equations, the so-called base flow, and is the perturbation field.…”

Section: Introductionmentioning

confidence: 99%

“…The scope of this paper is restricted to crossflow-dominated boundary layers. Strong crossflow instability growth is expected in regions of large favourable pressure gradient, as for instance near the leading edge (Arnal 1993). In a swept-wing boundary layer, the crossflow instability arises due to the combined effect of pressure gradient and sweep angle.…”

Section: Introductionmentioning

confidence: 99%

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Direct numerical simulation of interaction between a stationary crossflow instability and forward-facing steps

et al. 2022

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The interaction between forward-facing steps of several heights and a pre-existing critical stationary crossflow instability of a swept-wing boundary layer is analysed. Direct numerical simulations (DNS) are performed of the incompressible three-dimensional laminar base flow and the stationary distorted flow that arise from the interaction between an imposed primary stationary crossflow perturbation and the steps. These DNS are complemented with solutions of the linear and the nonlinear parabolised stability equations, used towards identifying the influence of linearity and non-parallelism near the step. A fully stationary solution of the Navier–Stokes equations is enforced numerically, in order to isolate the mechanisms pertaining to the interaction of the stationary disturbance with the step. Results provide insight into the salient modifications of the base laminar boundary layer due to the step, and the response of the incoming crossflow instability to these changes. The fundamental spanwise Fourier mode of the disturbance field gradually lifts up as it approaches the step and passes over it. The flow environment around the step is characterised by a sudden spanwise modulation of the base-flow streamlines. Additional stationary perturbation structures are induced at the step, which manifest in the form of spanwise-aligned velocity streaks near the wall. Shortly downstream of the step, the fundamental component of the crossflow perturbation maintains a rather constant amplification for the smallest steps studied. For the largest step, however, the fundamental crossflow perturbation is stabilised significantly shortly downstream of the largest step. This surprising result is ascribed to a modulation of the kinetic energy transfer between the base flow and the fundamental perturbation field, which is brought forward as a new step interaction mechanism. Possible non-modal growth effects at the step are discussed. Furthermore, the results from DNS indicate significant amplification of the high-order harmonic crossflow components downstream of the step.

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Boundary Layer Tripping in Supersonic Flow

Cited by 6 publications

References 2 publications

Multi-scale study of the transitional shock-wave boundary layer interaction in hypersonic flow

Multi-scale study of the transitional shock-wave boundary layer interaction in hypersonic flow

Dynamics of laminar separation bubbles at low-Reynolds-number aerofoils

Direct numerical simulation of interaction between a stationary crossflow instability and forward-facing steps

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