Passive Flow Control for Reduced Load Dynamics Aft of a Backward-Facing Step

Bolgar, Istvan; Scharnowski, Sven; Kähler, Christian J.

doi:10.2514/1.j057274

Cited by 11 publications

(11 citation statements)

References 35 publications

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“…The lobe configuration shows a minor influence and the full-square lobes lead to lower fluctuations at the base and higher fluctuations at x/D = 0.31 compared to the half-circular lobes. This is in contrast to findings at subsonic Mach numbers by Bolgar et al [6]. Lobes seem not to be useful for suppressing dynamical loads at supersonic flow conditions on axisymmetric geometries.…”

Section: Passive Flow Control On Tic Configurationcontrasting

confidence: 98%

“…1. Full-square lobes are chosen since they showed to be most effective in previous studies on a backward facing step [6]. Half-circular lobes are additionally investigated since they produce less wave drag.…”

Section: Geometry and Test Casesmentioning

confidence: 99%

“…This can be accomplished by passive flow control devices. Bolgar et al [6] conducted experimental measurements on a backward facing step equipped with 7 different passive flow control devices. They showed a reduction of the cross-pumping motion of the shear-layer by the lobes.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Interaction of Wake and Propulsive Jet Flow of a Generic Space Launcher

Barklage

Radespiel

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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This work investigates the interaction of the afterbody flow with the propulsive jet flow on a generic space launcher equipped with two alternative nozzle concepts and different afterbody geometries. The flow phenomena are characterized by experimental measurements and numerical URANS and LES simulations. Investigations concern a configuration with a conventional truncated ideal contour nozzle and a configuration with an unconventional dual-bell nozzle. In order to attenuate the dynamic loads on the nozzle fairing, passive flow control devices at the base of the launcher main body are investigated on the configuration with TIC nozzle. The nozzle Reynolds number and the afterbody geometry are varied for the configuration with dual-bell nozzle. The results for integrated nozzles show a shift of the nozzle pressure ratio for transition from sea-level to altitude mode to significant lower levels. The afterbody geometry is varied including a reattaching and non-reattaching outer flow on the nozzle fairing. Investigations are performed at supersonic outer flow conditions with a Mach number of $$Ma_\infty =3$$. It turns out, that a reattachment of the outer flow on the nozzle fairing leads to an unstable nozzle operation.

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Section: Passive Flow Control On Tic Configurationcontrasting

confidence: 98%

Section: Geometry and Test Casesmentioning

confidence: 99%

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Interaction of Wake and Propulsive Jet Flow of a Generic Space Launcher

Barklage

Radespiel

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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“…However, a long nozzle increases the lever arm and, thus, the effect of buffeting, which is of course an additional risk. To overcome this issue, passive flow control devices at the end of the main body could be used to enhance shear layer mixing and to reduce pressure fluctuations at reattachment [7,36].…”

Section: Introductionmentioning

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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“…On a planar BFS the authors showed that the so-called 'step' and 'cross-pumping' modes are the main driving factors for the pressure fluctuations which excite buffeting [2]. With the application of passive flow control, the root mean square (RMS) of the pressure fluctuations was reduced by 35% [3]. This load reduction is achieved through the imprinting of strong streamwise vorticity aft of the BFS with so-called 'lobes' on the step.…”

Section: Introductionmentioning

confidence: 99%

Effects of a Launcher’s External Flow on a Dual-Bell Nozzle Flow

Bolgar

Scharnowski

Kähler

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Previous research on Dual-Bell nozzle flow always neglected the influence of the outer flow on the nozzle flow and its transition from sea level to altitude mode. Therefore, experimental measurements on a Dual-Bell nozzle with trans- and supersonic external flows about a launcher-like forebody were carried out in the Trisonic Wind Tunnel Munich with particle image velocimetry, static pressure measurements and the schlieren technique. A strongly correlated interaction exists between a transonic external flow with the nozzle flow in its sea level mode. At supersonic external flow conditions, a Prandtl–Meyer expansion about the nozzle’s lip decreases the pressure in the vicinity of the nozzle exit by about 55%. Therefore a new definition for the important design criterion of the nozzle pressure ratio was suggested, which considers this drastic pressure drop. Experiments during transitioning of the nozzle from sea level to altitude mode show that an interaction about the nozzle’s lip causes an inherently unstable nozzle state at supersonic free-stream conditions. This instability causes the nozzle to transition and retransition, or flip-flop, between its two modes. This instability can be eliminated by designing a Dual-Bell nozzle to transition during sub-/transonic external flow conditions.

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Passive Flow Control for Reduced Load Dynamics Aft of a Backward-Facing Step

Cited by 11 publications

References 35 publications

Interaction of Wake and Propulsive Jet Flow of a Generic Space Launcher

Interaction of Wake and Propulsive Jet Flow of a Generic Space Launcher

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

Effects of a Launcher’s External Flow on a Dual-Bell Nozzle Flow

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