Fluctuations and Massive Separation in Three-dimensional Shock-wave/boundary-layer Interactions PDF Download

Author: Marvin I. Kussoy
Publisher:
ISBN:
Category : Boundary layer (Meteorology)
Languages : en
Pages : 26

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Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781792619748
Category : Science
Languages : en
Pages : 30

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Book Description
Shock-wave unsteadiness was observed in rapidly compressed supersonic turbulent boundary layer flows with significant separation. A Mach 2.85 shock-wave/turbulent boundary layer flow was set up over a series of cylinder-flare bodies in the High Reynolds Number Channel 1. The transition from fully attached to fully separated flow was studied using axisymmetric flares with increasing compression angles. In the second phase, the 30 deg flare was inclined relative to the cylinder axis, so that the effect on a separated flow of increasing 3 dimensionality could be observed. Two 3-D separated cases are examined. A simple conditional sampling technique is applied to the data to group them according to an associated shock position. Mean velocities and turbulent kinetic energies, computed from the conditionally samples data, are compared to those from the unsorted data and to computed values. Three basic questions were addressed: can conditional sampling be used to provide snapshots of the flow; are averaged turbulence quantities dominated by the bimodal nature of the interaction; and is the shock unsteadiness really important to computational accuracy. Kussoy, M. I. and Brown, J. D. and Brown, J. L. and Lockman, W. K. and Horstman, C. C. Ames Research Center NASA-TM-89224, NAS 1.15:89224 NCC2-452...

Author: Holger Babinsky
Publisher: Cambridge University Press
ISBN: 1139498649
Category : Technology & Engineering
Languages : en
Pages : 481

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Shock wave-boundary-layer interaction (SBLI) is a fundamental phenomenon in gas dynamics that is observed in many practical situations, ranging from transonic aircraft wings to hypersonic vehicles and engines. SBLIs have the potential to pose serious problems in a flowfield; hence they often prove to be a critical - or even design limiting - issue for many aerospace applications. This is the first book devoted solely to a comprehensive, state-of-the-art explanation of this phenomenon. It includes a description of the basic fluid mechanics of SBLIs plus contributions from leading international experts who share their insight into their physics and the impact they have in practical flow situations. This book is for practitioners and graduate students in aerodynamics who wish to familiarize themselves with all aspects of SBLI flows. It is a valuable resource for specialists because it compiles experimental, computational and theoretical knowledge in one place.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 22

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Author: D. K. M. Tan
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: B. Oskam
Publisher:
ISBN:
Category :
Languages : en
Pages : 15

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An exploratory experimental investigation has been carried out on the three dimensional flow fields caused by the interaction of oblique shock waves and a planar turbulent boundary layer. The study was performed at a free stream Mach number of 2.95, a Reynolds number per inch of 1.6 million and near adiabatic wall conditions. The interaction was studied on two experimental configurations having different initial boundary layer thicknesses (delta = approx. 0.13 and 0.55 inches). Both surface measurements as well as complete flow field surveys were performed. The main contributions of the present investigation are two experimentally derived flow field models for shock generator angles of 4 deg and 10 deg. Based upon both static pressure and surface flow patterns, as well as heat transfer data, the interaction region can be characterized as quasi-two-dimensional along the shock direction in the region studied. A critical examination of the occurrence of 'ordinary' flow separation and its character, as applied to the present problem, was carried out. It was concluded that McCabe's criterion, as used by the previous investigators, is not a sufficient condition to determine the onset of flow separation.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 26

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A theoretical model consists of the Reynolds-averaged 3-D compressible Navier-Stokes equations, with turbulence incorporated using the algebraic turbulent eddy viscosity model of Baldwin and Lomax, This year research efforts focused on both 2-D and 3-D turbulent interactions. A theoretical model was examined for a series of separated 2-D compression corner flows at Mach 2 and 3. Calculations were performed for four separate compression corners using 2-D compressible Navier-Stodes conde with MacCormack's hybrid algorithm. Results were compared to earlier computations using the Beam-Warming algorithm, and recent experiment data for turbulent Reynolds stresses. Calculated Reynolds stresses were observed to differ significantly from experimental measurements due to the inability of the turbulence model to incorporate the multiple scale effects of the turbulence structure downstream of reattachment. Computed results using the MacCormack hybrid algorithm were observed to be insensitive to the Courant number. The 3-D turbulence interactions research concentrated on the 3-D sharp fin and on the 3-D swept compression corner. In the former case, the computed flowfield for the 20 deg sharp fin at Mach 3 and a Reynolds number of 930,000 was compared with the calculated results of Horstman (who used the Jones-Launder turbulence model) and experimental data of the Princeton Gas Dynamics Lab. Overall comparison with experiment was very good.

Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704

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Author: Lee J. Mears
Publisher:
ISBN:
Category : Aerospace engineering
Languages : en
Pages : 0

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Book Description
Research efforts in shock wave/boundary-layer interactions (SBLI) are motivated by the pursuit of faster, lighter, and more maneuverable aircraft. Flow separation, strong pressure fluctuations, and high aerodynamic heating are all detrimental phenomena associated with these interactions. With a deeper understanding of the physics that drive the inherent unsteady pressure and shear forces, engineers can apply control techniques that target important flow regions and frequencies instead of overdesigning vehicles to survive these adverse effects. However, the mechanisms that drive the unsteady behavior in SBLI have been difficult to isolate and accurate predictions of unsteady pressure are not currently achievable for simulations with realistic Reynolds numbers. In order to further the understanding of 3-D SBLI physics, an experimental investigation of controlled perturbations introduced to a fin-generated swept shock wave/boundary-layer interaction is conducted. The principal mean and unsteady flow features are studied with special emphasis on the difference between separation found in two-dimensional and three-dimensional interactions. Regions of high-amplitude pressure fluctuation on the surface beneath the interaction and coincident unsteady flow features above the surface are identified to support the development of physics-based models of interaction unsteadiness. Several techniques are employed to measure the flow response, including steady and unsteady surface pressure measurements using pressure-sensitive paint (PSP), shadowgraph to capture shock motion, particle image velocimetry (PIV) to quantify velocity fields in the flow, and high-bandwidth unsteady pressure sensors. Global measurement techniques, including steady and unsteady PSP, tomographic PIV, and multiple planes of high-speed stereo PIV permit uniquely illuminating analysis of the flow dynamics. Some of the experimental methods are novel for the facilities and types of flows, and validation and uncertainty quantification efforts are included. Controlled flow perturbations, which have been historically difficult to implement in supersonic flows due to strong momentum of the flow and limited bandwidth of available actuators, are introduced within the interaction to gauge flow response to frequency and location of the disturbance. The perturbations are generated from Resonance-Enhanced Microjets (REM) which produce pulsed supersonic jets at frequencies on the order of several kilohertz. An evolution in the design of surface-mounted, modular REM actuators produces an improved implementation with greater repeatability and bandwidth. The frequency range studied here (between 2 and 4 kHz) has been selected based on separation and reattachment dynamics measured by unsteady pressure on the surface beneath the interaction. Measurements combining the plate and heretofore-unstudied fin surface provide significantly more information about the response of this complex, highly three-dimensional interaction with details that are not easily obtained using traditional sensors. In general, the disturbances created by the actuators were found to excite convective mechanisms within the interactions and remained localized. Large-scale alterations in the flowfield due to microjet blowing are noted, including reduction of the size of separation and smaller shock traverse distances. The flow response to pulsed actuation reveals varying sensitivity of interaction key features, which offers promise for future efforts to design more effective flow control devices.

Author: David S. Dolling
Publisher:
ISBN:
Category :
Languages : en
Pages : 75

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An experimental study of three-dimensional (3-D) shock wave turbulent boundary layer interaction has been carried out. Interactions generated by fin models having sharp and hemi-cylindrically blunted leading edges have been studied. The emphasis in this particular study was twofold. First, the influence of incoming turbulent boundary layer thickness delta on the streamwise, spanwise and vertical scaling of the interaction was examined. Turbulent boundary layers varying in thickness from .127 cm (.05 in.) to 2.27 cm (0.89 in.) were used. In addition, a study has been conducted to examine the effects of the ratio D/delta (where D is the blunt fin leading edge diameter) on the interaction properties and scaling. Second, an investigation has been started to examine the unsteady shock wave-boundary layer structure and the resulting high frequency, large amplitude pressure fluctuations which occur ahead of and around the blunt fin leading edge. This is an area which in the past has been largely ignored, yet has important implications, since it is not clear that any mean surface property or flowfield measurements have any real physical significant. To date, measurement techniques and computer software have been developed and exploratory measurements made in the undisturbed turbulent boundary layer and also on the plane of symmetry ahead of the blunt fin.