Analysis of characteristic wake flow modes on a generic transonic backward-facing step configuration

Statnikov, V.; Bolgar, Istvan; Scharnowski, Sven; Meinke, Matthias; Kähler, Christian J.; Schröder, Wolfgang

doi:10.1016/j.euromechflu.2016.05.008

Cited by 53 publications

(12 citation statements)

References 33 publications

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“…Close to the separation at about x∕L r ∼ 0 , the measurement results for FOV2 are favored due to the higher spatial resolution. There, as in the previous citations (Statnikov 2016;Statnikov et al 2016;Brown and Roshko 1974), the vorticity-thickness evolution does not show a notable exponential growth; it appears linear instead.…”

Section: Vorticity Thicknesssupporting

confidence: 80%

“…In succession, a second segment with linear spreading rate is to be expected that reaches a plateau (third segment) at about x∕L r ∼ 0.6-0.7 if approaching obstructing elements such as a solid wall or a jet. In some studies, the initial exponential growth region is more pronounced (Deck and Thorigny 2007;Simon et al 2007) than in others where they are barely notable (Statnikov 2016;Statnikov et al 2016;Brown and Roshko 1974). Figure 21 shows the vorticity-thickness evolution in the streamwise direction for the investigated Mach numbers and for both field of views.…”

Section: Vorticity Thicknessmentioning

confidence: 94%

“…Measured loads on the actuator and accelerometers placed on the nozzle support the finding that the transonic flow regime is challenging with respect to the dynamics of the wake. Lately, a lot of attention has been put on revealing the governing instability mechanisms and the modes of the excitations (e.g., Weiss et al 2009;Meliga et al 2010;Schrijer et al 2014;Statnikov et al 2016;Statnikov 2016).…”

Section: Introductionmentioning

confidence: 99%

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On the subsonic near-wake of a space launcher configuration without jet

2019

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Wake flows have been extensively investigated in the past mainly with the objective to reduce drag. The failure of Ariane 5 Flight 157 though revealed that the understanding has not been sufficient, which triggered a new series of base-flow investigations. Most of them scrutinized the dynamics of the flow at one specific point along the flight path either in the subsonic, transonic, or supersonic range. However, no coherent image of the flow topology development in terms of a parametric study is available so far. The current work addresses the question of a near-wake scaling of a generic space launcher configuration. This question is tackled experimentally by means of particle image velocimetry measurements in the vertical test section Cologne in the range of Mach 0.5, 0.6, 0.7, 0.8, and 0.9 for Reynolds numbers between Re D = 0.8 × 10 6 and 1.7 × 10 6. Results show the mean, the turbulence intensity, and the Reynolds shear stress distribution in the wake in comparison with the literature. In addition, data to the incoming boundary layer are provided and to the evolving shear layer. In that regime, the results indicate that the velocity and Reynolds stresses might be independent from the Mach and Reynolds number if scaled with the reattachment length. If this hypothesis holds true, it might be useful for the validation of numerical codes and for the initial determination of the flow field of space launchers in the design phase.

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Section: Vorticity Thicknesssupporting

confidence: 80%

Section: Vorticity Thicknessmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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On the subsonic near-wake of a space launcher configuration without jet

2019

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“…The thickness of the forebody and the splitter plate is 25 mm and 15 mm, respectively. The forebody geometry is the same as that used in [8,35,47]. In the center of the splitter plate, a 2D dual-bell nozzle is integrated.…”

Section: Measurement Set-upmentioning

confidence: 99%

Investigation of the base flow of a generic space launcher with dual-bell nozzle

Scharnowski

Kähler

2020

CEAS Space J

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The typical afterbody flow of a space launcher is characterized by a strong interaction of the engine’s exhaust jet and the separated shear layer emerging from the main body. This interaction is further complicated by strong changes in the spatial and temporal behavior of the afterbody flow during the atmospheric ascent of a launcher. Theoretically, a dual-bell nozzle not only allows for a gain in payload compared to standard single-bell nozzles, but also it alters the wake flow topology due to the two nozzle modes. To predict the benefits as well as the additional risks, the afterbody flow of a generic space launcher model equipped with a cold-flow dual-bell nozzle is investigated in detail. The flow was analyzed for sub-, trans- and supersonic Mach numbers ranging from 0.3 to 2.9 for a variety of nozzle pressure ratios. Particle image velocimetry measurements and schlieren measurements with high repetition rate were performed to determine the dynamics of the separated shear layer, the nozzle jet and their interaction. It is shown that the reattachment length of the base flow decreases with increasing nozzle pressure ratio. Furthermore, the nozzle pressure ratio at which the dual-bell nozzle switches from sea-level mode to altitude mode is reduced by $$15\%$$ 15 % with high subsonic outer flow and by as much as $$65\%$$ 65 % for an outer flow at a Mach number of 1.6. Even for a constant nozzle pressure ratio, the nozzle flow topology depends on the Mach number of the outer flow.

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“…Zonal grid topology; supersonic (a) and transonic (b) configuration is determined by the reformulated synthetic turbulence generation (RSTG) method developed by Roidl et al[8]. For a comprehensive description of the flow solver see Statnikov et al[12,14].…”

mentioning

confidence: 99%

Numerical Analysis of the Turbulent Wake for a Generic Space Launcher with a Dual-Bell Nozzle

Loosen

Meinke

Schröder

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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The turbulent wake of an axisymmetric generic space launcher equipped with a dual-bell nozzle is simulated at transonic ($$Ma_\infty = 0.8$$ and $$Re_D = 4.3\cdot 10^5$$) and supersonic ($$Ma_\infty = 3$$ and $$Re_D = 1.2\cdot 10^6$$) freestream conditions, to investigate the influence of the dual-bell nozzle jet onto the wake flow and vice versa. In addition, flow control by means of four in circumferential direction equally distributed jets injecting air encountering the backflow in the recirculation region is utilized to determine if the coherence of the wake and consequently, the buffet loads can be reduced by flow control. The simulations are performed using a zonal RANS/LES approach. The time-resolved flow field data are analyzed by classical spectral analysis, two-point correlation analysis, and dynamic mode decomposition (DMD). At supersonic freestream conditions, the nozzle counter pressure is reduced by the expansion of the outer flow around the nozzle lip leading to a decreased transition nozzle pressure ratio. In the transonic configuration a spatio-temporal mode with an eigenvalue matching the characteristic buffet frequency of $$Sr_D=0.2$$ is extracted by the spectral and DMD analysis. The spatial shape of the detected mode describes an antisymmetric wave-like undulating motion of the shear layer inducing the low frequency dynamic buffet loads. By flow control this antisymmetric coherent motion is weakened leading to a reduction of the buffet loads on the nozzle fairing.

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Analysis of characteristic wake flow modes on a generic transonic backward-facing step configuration

Cited by 53 publications

References 33 publications

On the subsonic near-wake of a space launcher configuration without jet

On the subsonic near-wake of a space launcher configuration without jet

Investigation of the base flow of a generic space launcher with dual-bell nozzle

Numerical Analysis of the Turbulent Wake for a Generic Space Launcher with a Dual-Bell Nozzle

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