Experimental analysis of unsteady separated flows in a supersonic planar nozzle

Bourgoing, Alexis; Reijasse, Philippe

doi:10.1007/s00193-005-0269-2

Cited by 44 publications

(16 citation statements)

References 8 publications

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“…15 It is important to note that the spectra are broadband with no pronounced peaks or bumps such as the ones noticed in the experiments by Bourgoing and Reijasse. 16 This implies that for the conditions of this experiment, the unsteadiness is not governed by any resonant interactions, but rather by random fluctuations.…”

Section: A Statistics Of Shock Motionmentioning

confidence: 82%

Instability of shock-induced nozzle flow separation

Johnson

Papamoschou

2010

Physics of Fluids

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We investigate experimentally the causes of jet plume instability and enhanced mixing observed in the exhaust of shock-containing convergent-divergent nozzles. Key features of the internal flow are the separation shock, separation shear layers, and pattern of alternating expansion and compression waves downstream of the shock. We focus on two possible reasons for this instability-the motion of the separation shock and the wave pattern downstream of the shock. The nozzle flow was generated in a planar facility with variable area ratio and pressure ratio, and the motion of the shock was tracked using time-resolved wall pressure measurements. The isolated effect of the wave pattern was investigated in a separate facility wherein a sonic shear layer, simulating the nozzle separation shear layer, was disturbed with compression and expansion waves emanating from a wavy wall. In both instances, the instability of the shear layer was characterized by time-resolved measurements of the total pressure. In the nozzle flow, the amplitude of shock motion increases with shock strength. Correlation of shock motion with shear layer total pressure is virtually absent for weak shocks but becomes significant for strong shocks. However, impingement of stationary waves on the shear layer had no impact on its growth rate. We conclude that the enhanced shear layer instability is strongly coupled to shock motion, and that the wave pattern by itself is not a cause of enhanced mixing. The occurrence of asymmetric separation at large shock strengths is a further contributor to the enhancement of instability.

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Section: A Statistics Of Shock Motionmentioning

confidence: 82%

Instability of shock-induced nozzle flow separation

Johnson

Papamoschou

2010

Physics of Fluids

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“…The most commonly considered interactions concern those with a turbulent boundary layer, although laminar or transitional interactions have also been investigated in the literature. Cases under consideration cover a large range of geometric configurations, including normal shock interactions (Atkin & Squire 1992;Bruce & Babinsky 2008;Bur et al 2008), blunt fin interactions (Brusniak & Dolling 1994;Ünalmis & Dolling 1996;Bueno 2006), over-expanded nozzles (Frey & Hagemann 1998, 2000Bourgoing & Reijasse 2005), compression ramp interactions (Thomke & Roshko 1969;Spaid & The characteristic length L used in the Strouhal number represents the effects of the presence of the boundary layer in comparison to a purely inviscid flow (see the scheme in figure 1). It is defined as the observed upstream shift of the shock wave C S due to the thickening of the boundary layer, subject to the imposed pressure jump (or equivalently the angle of deviation of the flow).…”

Section: Introductionmentioning

confidence: 99%

A scaling analysis for turbulent shock-wave/boundary-layer interactions

Souverein¹,

Bakker²,

Dupont³

2013

J. Fluid Mech.

119

108

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A model based on mass conservation properties is developed for shock-wave/boundarylayer interactions (SWBLIs), aimed at reconciling the observed great diversity in flow organization documented in the literature, induced by variations in interaction geometry and aerodynamic conditions. It is the basis for a scaling approach for the interaction length that is valid independent of the geometry of the flow (considering compression corners and incident-reflecting shock interactions). As part of the analysis, a scaling argument is proposed for the imposed pressure jump that depends principally on the free-stream Mach number and the flow deflection angle. Its interpretation as a separation criterion leads to a successful classification of the separation states for turbulent SWBLIs (attached, incipient or separated). In addition, the dependence of the interaction length on the Reynolds number and the Mach numbers is accounted for. A large compilation of available data provides support for the validity of the model. Some general properties on the state of the flow are derived, independent of the geometry of the flow and for a wide range of Mach numbers and Reynolds numbers.

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“…In other words; when NPR increases (start-up process) or decreases (shut-down process), shock wave-boundary layer interaction structure has asymmetry accompanied by transition of RSS to FSS. This asymmetry of the flow could be the manifestation of a Coanda effect which is directly connected to side-loads according to previous work (11) . Consequently, we can confirm from the acquired images that the origin of side loads is in the asymmetric nature of shock wave-boundary layer interaction structure, when the separation pattern changes in the 2D supersonic nozzle.…”

Section: Resultsmentioning

confidence: 52%

Experimental and Computational Studies of FSS-RSS Phenomena in an Over-Expanded Nozzle

Lee¹,

Kim²

2010

Journal of the Korean Society of Visualization

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Abstract. The interaction patterns between shock wave and boundary layer in a rocket nozzle are mainly classified into two categories, FSS(Free Shock Separation) and RSS(Restricted Shock Separation), both of which are associated with the thrust characteristics as well as side loads of the engine. According to the previous investigations, strong side loads of the engine are produced during the period of transition from FSS to RSS or vice versa. The present work aims at investigating the unsteady behavior of the separation shock waves in a two-dimensional supersonic nozzle, using experimental method and CFD. Schlieren optical method was employed to visualize the time-mean and time-dependent shock motions in the nozzle. The unsteady, compressible N-S equations with SST K-ω turbulence closure were solved using a fully implicit finite volume scheme. The results obtained show the separation shock motions during the transition of the interaction pattern.

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Experimental analysis of unsteady separated flows in a supersonic planar nozzle

Cited by 44 publications

References 8 publications

Instability of shock-induced nozzle flow separation

Instability of shock-induced nozzle flow separation

A scaling analysis for turbulent shock-wave/boundary-layer interactions

Experimental and Computational Studies of FSS-RSS Phenomena in an Over-Expanded Nozzle

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