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B W Van Oudheusden - One of the best experts on this subject based on the ideXlab platform.
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three dimensional instantaneous structure of a shock wave turbulent boundary Layer Interaction
Journal of Fluid Mechanics, 2009Co-Authors: R A Humble, F Scarano, G E Elsinga, B W Van OudheusdenAbstract:An experimental study is carried out to investigate the three-dimensional instantaneous structure of an incident shock wave/turbulent boundary Layer Interaction at Mach 2.1 using tomographic particle image velocimetry. Large-scale coherent motions within the incoming boundary Layer are observed, in the form of three-dimensional streamwise-elongated regions of relatively low- and high-speed fluid, similar to what has been reported in other supersonic boundary Layers. Three-dimensional vortical structures are found to be associated with the low-speed regions, in a way that can be explained by the hairpin packet model. The instantaneous reflected shock wave pattern is observed to conform to the low- and high-speed regions as they enter the Interaction, and its organization may be qualitatively decomposed into streamwise translation and spanwise rippling patterns, in agreement with what has been observed in direct numerical simulations. The results are used to construct a conceptual model of the three-dimensional unsteady flow organization of the Interaction.
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effects of micro ramps on a shock wave turbulent boundary Layer Interaction
Shock Waves, 2009Co-Authors: Paul Blinde, R A Humble, B W Van Oudheusden, F ScaranoAbstract:Stereoscopic particle image velocimetry is used to investigate the effects of micro-ramp sub-boundary Layer vortex generators, on an incident shock wave/boundary Layer Interaction at Mach 1.84. Single- and double-row arrangements of micro-ramps are considered. The micro-ramps have a height of 20% of the unperturbed boundary Layer thickness and the measurement planes are located 0.1 and 0.6 boundary Layer thicknesses from the wall. The micro-ramps generate packets of individual vortex pairs downstream of their vertices, which produce counter-rotating longitudinal streamwise vortex pairs in a time-averaged view. These structures induce a pronounced spanwise variation of the flow properties, namely the mixing across the boundary Layer interface. The probability of reversed-flow occurrence is decreased by 20 and 30% for the single- and double-row configurations, respectively. Both configurations of micro-ramps stabilize the shock motion by reducing the length of its motion by about 20% in the lower measurement plane. The results are summarized by a conceptual model describing the boundary Layer’s and Interaction’s flow pattern under the effect of the micro-ramps.
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unsteady aspects of an incident shock wave turbulent boundary Layer Interaction
Journal of Fluid Mechanics, 2009Co-Authors: R A Humble, F Scarano, B W Van OudheusdenAbstract:An incident shock wave/turbulent boundary Layer Interaction at Mach 2.1 is investigated using particle image velocimetry in combination with data processing using the proper orthogonal decomposition, to obtain an instantaneous and statistical description of the unsteady flow organization. The global structure of the Interaction is observed to vary considerably in time. Although reversed flow is often measured instantaneously, on average no reversed flow is observed. On an instantaneous basis, the Interaction exhibits a multi-Layered structure, characterized by a relatively highvelocity outer region and low-velocity inner region. Discrete vortical structures are prevalent along their interface, which create an intermittent fluid exchange as they propagate downstream. A statistical analysis suggests that the instantaneous fullness of the incoming boundary Layer velocity profile is (weakly) correlated with the size of the separation bubble and position of the reflected shock wave. The eigenmodes show an energetic association between velocity fluctuations within the incoming boundary Layer, separated flow region and across the reflected shock wave, and portray subspace features that represent the phenomenology observed within the instantaneous realizations.
R A Humble - One of the best experts on this subject based on the ideXlab platform.
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three dimensional instantaneous structure of a shock wave turbulent boundary Layer Interaction
Journal of Fluid Mechanics, 2009Co-Authors: R A Humble, F Scarano, G E Elsinga, B W Van OudheusdenAbstract:An experimental study is carried out to investigate the three-dimensional instantaneous structure of an incident shock wave/turbulent boundary Layer Interaction at Mach 2.1 using tomographic particle image velocimetry. Large-scale coherent motions within the incoming boundary Layer are observed, in the form of three-dimensional streamwise-elongated regions of relatively low- and high-speed fluid, similar to what has been reported in other supersonic boundary Layers. Three-dimensional vortical structures are found to be associated with the low-speed regions, in a way that can be explained by the hairpin packet model. The instantaneous reflected shock wave pattern is observed to conform to the low- and high-speed regions as they enter the Interaction, and its organization may be qualitatively decomposed into streamwise translation and spanwise rippling patterns, in agreement with what has been observed in direct numerical simulations. The results are used to construct a conceptual model of the three-dimensional unsteady flow organization of the Interaction.
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effects of micro ramps on a shock wave turbulent boundary Layer Interaction
Shock Waves, 2009Co-Authors: Paul Blinde, R A Humble, B W Van Oudheusden, F ScaranoAbstract:Stereoscopic particle image velocimetry is used to investigate the effects of micro-ramp sub-boundary Layer vortex generators, on an incident shock wave/boundary Layer Interaction at Mach 1.84. Single- and double-row arrangements of micro-ramps are considered. The micro-ramps have a height of 20% of the unperturbed boundary Layer thickness and the measurement planes are located 0.1 and 0.6 boundary Layer thicknesses from the wall. The micro-ramps generate packets of individual vortex pairs downstream of their vertices, which produce counter-rotating longitudinal streamwise vortex pairs in a time-averaged view. These structures induce a pronounced spanwise variation of the flow properties, namely the mixing across the boundary Layer interface. The probability of reversed-flow occurrence is decreased by 20 and 30% for the single- and double-row configurations, respectively. Both configurations of micro-ramps stabilize the shock motion by reducing the length of its motion by about 20% in the lower measurement plane. The results are summarized by a conceptual model describing the boundary Layer’s and Interaction’s flow pattern under the effect of the micro-ramps.
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unsteady aspects of an incident shock wave turbulent boundary Layer Interaction
Journal of Fluid Mechanics, 2009Co-Authors: R A Humble, F Scarano, B W Van OudheusdenAbstract:An incident shock wave/turbulent boundary Layer Interaction at Mach 2.1 is investigated using particle image velocimetry in combination with data processing using the proper orthogonal decomposition, to obtain an instantaneous and statistical description of the unsteady flow organization. The global structure of the Interaction is observed to vary considerably in time. Although reversed flow is often measured instantaneously, on average no reversed flow is observed. On an instantaneous basis, the Interaction exhibits a multi-Layered structure, characterized by a relatively highvelocity outer region and low-velocity inner region. Discrete vortical structures are prevalent along their interface, which create an intermittent fluid exchange as they propagate downstream. A statistical analysis suggests that the instantaneous fullness of the incoming boundary Layer velocity profile is (weakly) correlated with the size of the separation bubble and position of the reflected shock wave. The eigenmodes show an energetic association between velocity fluctuations within the incoming boundary Layer, separated flow region and across the reflected shock wave, and portray subspace features that represent the phenomenology observed within the instantaneous realizations.
N A Adams - One of the best experts on this subject based on the ideXlab platform.
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analysis of unsteady behaviour in shockwave turbulent boundary Layer Interaction
Journal of Fluid Mechanics, 2012Co-Authors: Muzio Grilli, Peter J Schmid, S Hickel, N A AdamsAbstract:The unsteady behavior in shockwave turbulent boundary Layer Interaction is investi- gated by analyzing results from a LES of a supersonic turbulent boundary Layer over a compression-expansion ramp. The Interaction leads to a very-low-frequency motion near the foot of the shock, with a characteristic frequency that is three orders of magnitude lower than the typical frequency of the incoming boundary Layer. Wall pressure data are first analyzed by means of Fourier analysis, highlighting the low-frequency phenomenon in the Interaction region. Furthermore, the flow dynamics are analyzed by a dynamic mode decomposition which shows the presence of a low-frequency mode associated with the pulsation of the separation bubble and accompanied by a forward-backward motion of the shock.
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large eddy simulation of shock wave turbulent boundary Layer Interaction
Journal of Fluid Mechanics, 2006Co-Authors: Maxim S Loginov, N A Adams, Alexander A ZheltovodovAbstract:Well-resolved Large-Eddy Simulations (LES) are performed in order to investigate flow phenomena and turbulence structure of the turbulent boundary Layer along a supersonic compression-decompression ramp. For the first time it was possible to reproduce directly a reference experiment with a free-stream Mach number of M = 2.95 and a Reynolds number based on the incoming boundary-Layer thickness of Re = 63560. The effect of subgrid-scales is modeled by the approximate deconvolution model. An analysis of the results shows a good agreement with reference experiment in terms of mean quantities and turbulence structure. The computational data confirm theoretical and experimental results on fluctuation-amplification across the Interaction region. In the wake of the main shock a shedding of shocklets is observed. The temporal behavior of the coupled shock-separation system agrees well with experimental data. The simulation data provide indications for a large-scale shock motion. Also the existence of three-dimensional large-scale streamwise structures, commonly referred to as Gortler-like vortices, is confirmed. The LES provide a reliable and detailed flow information, which helped to improve the understanding of shock-boundary-Layer Interaction considerably.
Noel T Clemens - One of the best experts on this subject based on the ideXlab platform.
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control of mean separation in shock boundary Layer Interaction using pulsed plasma jets
Shock Waves, 2015Co-Authors: Benton R Greene, Noel T Clemens, Patrick Magari, Daniel MickaAbstract:The current study investigates the use of pulsed plasma jets (spark jets) to reduce the separation induced by shock wave-boundary Layer Interaction generated by a \(20^{\circ }\) compression ramp in a Mach 3 flow with a Reynolds number of 5,400, based on the undisturbed boundary Layer momentum thickness. Surface oil streak visualization is used in a parametric study to determine the optimum pulsing frequency of the jet, the optimum distance of the jet from the compression corner, and the optimum configuration of the jets. Several 3-jet actuator configurations are tested, including those where the jets are pitched, and pitched and skewed. The jet pulsing frequency is varied between 2 and 4 kHz, corresponding to a Strouhal number based on separation length of 0.012 and 0.023. Particle image velocimetry is used to characterize the effect that the actuators have on the reattached boundary Layer profile on the ramp surface. Results show that plasma jets pitched at \(20^{\circ }\) from the wall, and pulsed at a Strouhal number of 0.018, can reduce the distance between the separation line and the compression ramp corner by up to 40 % and increase the integrated momentum in the downstream reattached boundary Layer, albeit with a concomitant increase in the shape factor.
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control of unsteadiness of a shock wave turbulent boundary Layer Interaction by using a pulsed plasma jet actuator
Physics of Fluids, 2012Co-Authors: Venkateswaran Narayanaswamy, Laxminarayan L Raja, Noel T ClemensAbstract:A pulsed-plasma jet actuator is used to control the unsteady motion of the separation shock of a shock wave/boundary Layer Interaction formed by a compression ramp in a Mach 3 flow. The actuator is based on a plasma-generated synthetic jet and is configured as an array of three jets that can be injected normal to the cross-flow, pitched, or pitched and skewed. The typical peak jet exit velocity of the actuators is about 300 m/s and the pulsing frequencies are a few kilohertz. A study of the Interaction between the pulsed-plasma jets and the shock/boundary Layer Interaction was performed in a time-resolved manner using 10 kHz schlieren imaging. When the actuator, pulsed at StL ≈ 0.04 (f = 2 kHz), was injected into the upstream boundary Layer, the separation shock responded to the plasma jet by executing a rapid upstream motion followed by a gradual downstream recovery motion. Schlieren movies of the Interaction showed that the separation shock unsteadiness was locked to the pulsing frequency of the actuator, with amplitude of about one boundary Layer thickness. Wall-pressure measurements made under the intermittent region showed about a 30% decrease in the overall magnitude of the pressure fluctuations in the low-frequency band associated with unsteady large-scale motion of the separated flow. Furthermore, by increasing the pulsing frequency to 3.3 kHz, the amplitude of the separation shock oscillation was reduced to less than half the boundary Layer thickness. Investigation into the effect of the actuator location on the shock wave/boundary Layer Interaction (SWBLI) showed qualitatively and quantitatively that the actuator placed upstream of the separation shock caused significant modification to the SWBLI unsteadiness, whereas injection from inside the separation bubble did not cause a noticeable effect.A pulsed-plasma jet actuator is used to control the unsteady motion of the separation shock of a shock wave/boundary Layer Interaction formed by a compression ramp in a Mach 3 flow. The actuator is based on a plasma-generated synthetic jet and is configured as an array of three jets that can be injected normal to the cross-flow, pitched, or pitched and skewed. The typical peak jet exit velocity of the actuators is about 300 m/s and the pulsing frequencies are a few kilohertz. A study of the Interaction between the pulsed-plasma jets and the shock/boundary Layer Interaction was performed in a time-resolved manner using 10 kHz schlieren imaging. When the actuator, pulsed at StL ≈ 0.04 (f = 2 kHz), was injected into the upstream boundary Layer, the separation shock responded to the plasma jet by executing a rapid upstream motion followed by a gradual downstream recovery motion. Schlieren movies of the Interaction showed that the separation shock unsteadiness was locked to the pulsing frequency of the actuato...
F Scarano - One of the best experts on this subject based on the ideXlab platform.
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three dimensional instantaneous structure of a shock wave turbulent boundary Layer Interaction
Journal of Fluid Mechanics, 2009Co-Authors: R A Humble, F Scarano, G E Elsinga, B W Van OudheusdenAbstract:An experimental study is carried out to investigate the three-dimensional instantaneous structure of an incident shock wave/turbulent boundary Layer Interaction at Mach 2.1 using tomographic particle image velocimetry. Large-scale coherent motions within the incoming boundary Layer are observed, in the form of three-dimensional streamwise-elongated regions of relatively low- and high-speed fluid, similar to what has been reported in other supersonic boundary Layers. Three-dimensional vortical structures are found to be associated with the low-speed regions, in a way that can be explained by the hairpin packet model. The instantaneous reflected shock wave pattern is observed to conform to the low- and high-speed regions as they enter the Interaction, and its organization may be qualitatively decomposed into streamwise translation and spanwise rippling patterns, in agreement with what has been observed in direct numerical simulations. The results are used to construct a conceptual model of the three-dimensional unsteady flow organization of the Interaction.
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effects of micro ramps on a shock wave turbulent boundary Layer Interaction
Shock Waves, 2009Co-Authors: Paul Blinde, R A Humble, B W Van Oudheusden, F ScaranoAbstract:Stereoscopic particle image velocimetry is used to investigate the effects of micro-ramp sub-boundary Layer vortex generators, on an incident shock wave/boundary Layer Interaction at Mach 1.84. Single- and double-row arrangements of micro-ramps are considered. The micro-ramps have a height of 20% of the unperturbed boundary Layer thickness and the measurement planes are located 0.1 and 0.6 boundary Layer thicknesses from the wall. The micro-ramps generate packets of individual vortex pairs downstream of their vertices, which produce counter-rotating longitudinal streamwise vortex pairs in a time-averaged view. These structures induce a pronounced spanwise variation of the flow properties, namely the mixing across the boundary Layer interface. The probability of reversed-flow occurrence is decreased by 20 and 30% for the single- and double-row configurations, respectively. Both configurations of micro-ramps stabilize the shock motion by reducing the length of its motion by about 20% in the lower measurement plane. The results are summarized by a conceptual model describing the boundary Layer’s and Interaction’s flow pattern under the effect of the micro-ramps.
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unsteady aspects of an incident shock wave turbulent boundary Layer Interaction
Journal of Fluid Mechanics, 2009Co-Authors: R A Humble, F Scarano, B W Van OudheusdenAbstract:An incident shock wave/turbulent boundary Layer Interaction at Mach 2.1 is investigated using particle image velocimetry in combination with data processing using the proper orthogonal decomposition, to obtain an instantaneous and statistical description of the unsteady flow organization. The global structure of the Interaction is observed to vary considerably in time. Although reversed flow is often measured instantaneously, on average no reversed flow is observed. On an instantaneous basis, the Interaction exhibits a multi-Layered structure, characterized by a relatively highvelocity outer region and low-velocity inner region. Discrete vortical structures are prevalent along their interface, which create an intermittent fluid exchange as they propagate downstream. A statistical analysis suggests that the instantaneous fullness of the incoming boundary Layer velocity profile is (weakly) correlated with the size of the separation bubble and position of the reflected shock wave. The eigenmodes show an energetic association between velocity fluctuations within the incoming boundary Layer, separated flow region and across the reflected shock wave, and portray subspace features that represent the phenomenology observed within the instantaneous realizations.
