The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
James M. Luckring - One of the best experts on this subject based on the ideXlab platform.
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A Reduced-Complexity Investigation of Blunt Leading-Edge Separation Motivated by UCAV Aerodynamics
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: James M. Luckring, Okko J. BoelensAbstract:A reduced complexity investigation for blunt-leading-Edge vortical Separation has been undertaken. The overall approach is to design the fundamental work in such a way so that it relates to the aerodynamics of a more complex Uninhabited Combat Air Vehicle (UCAV) concept known as SACCON. Some of the challenges associated with both the vehicle-class aerodynamics and the fundamental vortical flows are reviewed, and principles from a hierarchical complexity approach are used to relate flow fundamentals to system-level interests. The work is part of roughly 6-year research program on blunt-leading-Edge Separation pertinent to UCAVs, and was conducted under the NATO Science and Technology Organization, Applied Vehicle Technology panel.
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A Unit-Problem Investigation of Blunt Leading-Edge Separation Motivated by AVT-161 SACCON Research
2011Co-Authors: James M. Luckring, Okko J. BoelensAbstract:A research effort has been initiated to examine in more detail some of the challenging flow fields discovered from analysis of the SACCON configuration aerodynamics. This particular effort is oriented toward a diamond wing investigation specifically designed to isolate blunt leading-Edge Separation phenomena relevant to the SACCON investigations of the present workshop. The approach taken to design this new effort is reviewed along with the current status of the program.
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A Survey of Factors Affecting Blunt Leading-Edge Separation for Swept and Semi-Slender Wings
28th AIAA Applied Aerodynamics Conference, 2010Co-Authors: James M. LuckringAbstract:A survey is presented of factors affecting blunt leading-Edge Separation for swept and semi-slender wings. This class of Separation often results in the onset and progression of Separation-induced vortical flow over a slender or semi-slender wing. The term semi-slender is used to distinguish wings with moderate sweeps and aspect ratios from the more traditional highly-swept, low-aspect-ratio slender wing. Emphasis is divided between a selection of results obtained through literature survey a section of results from some recent research projects primarily being coordinated through NATO s Research and Technology Organization (RTO). An aircraft context to these studies is included.
Sudhir L. Gai - One of the best experts on this subject based on the ideXlab platform.
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Laser-induced fluorescence velocimetry for a hypersonic leading-Edge Separation
Physics of Fluids, 2020Co-Authors: Laurent M. Le Page, Matthew Barrett, Sean O'byrne, Sudhir L. GaiAbstract:Two-dimensional mapping of the velocity distribution for a hypersonic leading-Edge Separation flowfield generated by a “tick” shaped geometry is presented for the first time. Discrete measurements of two velocity components were acquired at a flow condition having a total specific enthalpy of 3.8 MJ/kg by imaging nitric oxide fluorescence over numerous runs of the hypersonic tunnel at the Australian Defence Force Academy (T-ADFA). The measured freestream velocity distribution exhibited some non-uniformity, which is hypothesized to originate from images acquired using a set of ultraviolet specific mirrors mounted on the shock tunnel deflecting under load during a run of the facility, slightly changing the laser sheet orientation. The flow Separation point was measured to occur at 1.4 ± 0.2 mm from the model leading Edge, based on the origin of the free shear layer emanating from the expansion surface. Reattachment of this free shear layer on the compression surface occurred at 59.0 ± 0.2 mm from the model ...
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Direct simulation Monte Carlo computations and experiments on leading-Edge Separation in rarefied hypersonic flow
Journal of Fluid Mechanics, 2019Co-Authors: R. Prakash, Sudhir L. Gai, L. M. Le Page, Liam P. Mcquellin, Sean O'byrneAbstract:A comprehensive study of the fundamental characteristics of leading-Edge Separation in rarefied hypersonic flows is undertaken and its salient features are elucidated. Separation of a boundary layer undergoing strong expansion is typical in many practical hypersonic applications such as base flows of re-entry vehicles and flows over deflected control surfaces. Boundary layer growth under such conditions is influenced by effects of rarefaction and thermal non-equilibrium, thereby differing significantly from the conventional no-slip Blasius type. A leading-Edge Separation configuration presents a fundamental case for studying the characteristics of such a flow Separation but with minimal influence from a pre-existing boundary layer. In this work, direct simulation Monte Carlo computations have been performed to investigate flow Separation and reattachment in a low-density hypersonic flow over such a configuration. Distinct features of leading-Edge flow, limited boundary layer growth, Separation, shear layer, flow structure in the recirculation region and reattachment are all explained in detail. The fully numerical shear layer profile after Separation is compared against a semi-theoretical profile, which is obtained using the numerical Separation profile as the initial condition on existing theoretical concepts of shear layer analysis based on continuum flow Separation. Experimental studies have been carried out to determine the surface heat flux using thin-film gauges and computations showed good agreement with the experimental data. Flow visualisation experiments using the non-intrusive planar laser-induced fluorescence technique have been performed to image the fluorescence of nitric oxide, from which velocity and rotational temperature distributions of the separated flow region are determined.
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Numerical study of bluntness effects on laminar leading Edge Separation in hypersonic flow
Journal of Fluid Mechanics, 2019Co-Authors: Amna Khraibut, Sudhir L. Gai, Andrew J. NeelyAbstract:Bluntness effects on laminar hypersonic leading Edge Separation are investigated numerically at Mach number $M\approx 10$ , unit Reynolds number $Re=1.3\times 10^{6}~\text{m}^{-1}$ , specific enthalpy $h_{o}=3.1~\text{MJ}~\text{kg}^{-1}$ and wall-to-stagnation temperature ratio $T_{w}/T_{o}=0.1$ . Such effects are important from an experimental point of view and because bluntness can affect a separated flow favourably or adversely. In this study, two blunt leading Edge cases of small radius ( $15~\unicode[STIX]{x03BC}\text{m}$ ) and large radius ( $100~\unicode[STIX]{x03BC}\text{m}$ ) are investigated. A comparison with the idealised sharp leading Edge case is also given. General flow features and surface parameters such as the shear stress, pressure and heat flux are presented and analysed. The results have also been interpreted in terms of Cheng’s displacement-bluntness similitude parameter affecting the size of Separation. Previous experiments by Holden delineated small and large bluntness effects based on Cheng’s parameter and considering small to moderate separated regions. In this study, leading Edge Separation was found to suppress the favourable effect of bluntness in delaying Separation. Bluntness, furthermore, seemed to promote the appearance of secondary vortices within a main separated region. Analysis of reverse flow boundary layer profiles such as velocity, pressure and temperature is also given. It is shown that bluntness accentuates large transverse gradients. This in turn adversely effects the reverse flow boundary layer leading to the appearance of secondary vortices.
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Rotational temperature imaging of a leading-Edge Separation in hypervelocity flow
31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31, 2019Co-Authors: Laurent M. Le Page, Matthew Barrett, Sean O'byrne, Sudhir L. GaiAbstract:This paper presents a rotational temperature map of a leading-Edge Separation in a low-density hypersonic flow, obtained using imaged fluorescence of nitric oxide (NO). A flow condition with a total specific enthalpy of 3.8 MJ/kg, and for which the continuum assumption should hold, is generated using the T-ADFA free-piston shock tunnel. A leading-Edge separated flow, known as the ‘tick’ model configuration and first suggested by Chapman et al. [1] for the study of laminar flow Separation, is placed in this facility’s test section to produce the leading-Edge Separation. This model geometry is chosen for the study because it produces a near zero-thickness boundary layer prior to Separation. The planar laser-induced fluorescence (PLIF) thermometry technique was chosen to generate a spatially resolved rotational temperature map using multi-line fluorescence images [2]. This technique involves making multiple fluorescence measurements using different rotational lines across the γ(0, 0) vibrational band of NO and fitting the signals to a Boltzmann plot. Using five isolated transitions, the measured freestream temperature of 155±7 K was in good agreement with a one-dimensional nonequilibrium inviscid nozzle code calculation of 156 ± 8 K. The recirculating region was found to have a peak temperature of 2000 ± 500 K across the imaged flowfield and the wake neck formed at the flow reattachment exhibited a cooling effect to an almost uniform temperature of 450 ± 70 K.This paper presents a rotational temperature map of a leading-Edge Separation in a low-density hypersonic flow, obtained using imaged fluorescence of nitric oxide (NO). A flow condition with a total specific enthalpy of 3.8 MJ/kg, and for which the continuum assumption should hold, is generated using the T-ADFA free-piston shock tunnel. A leading-Edge separated flow, known as the ‘tick’ model configuration and first suggested by Chapman et al. [1] for the study of laminar flow Separation, is placed in this facility’s test section to produce the leading-Edge Separation. This model geometry is chosen for the study because it produces a near zero-thickness boundary layer prior to Separation. The planar laser-induced fluorescence (PLIF) thermometry technique was chosen to generate a spatially resolved rotational temperature map using multi-line fluorescence images [2]. This technique involves making multiple fluorescence measurements using different rotational lines across the γ(0, 0) vibrational band of NO a...
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A direct simulation Monte Carlo study of hypersonic leading-Edge Separation with rarefaction effects
Physics of Fluids, 2018Co-Authors: R. Prakash, Sudhir L. Gai, Sean O'byrneAbstract:Hypersonic laminar flow Separation preceded by a strong expansion can occur in practical situations such as the base flow of re-entry vehicles and flow over deflected control surfaces. A leading-Edge Separation configuration provides a case for studying fundamental aspects of such flow Separation and reattachment in the absence of a pre-existing boundary layer. In hypersonic low-density flows, the onset of Separation is complicated by the presence of rarefaction and thermal non-equilibrium. The reattachment process is also characterized by high compressibility. A computational study of the characteristics of flow Separation and reattachment over such a configuration has been carried out using the direct simulation Monte Carlo code SPARTA. The salient features of Separation are explained from a fluid dynamic perspective, and distinct characteristics in surface parameters are identified and discussed in detail. The physical mechanisms behind the formation as well as co-existence of primary and secondary vortices are described. The region close to the leading-Edge is analyzed in detail, and the prevailing non-equilibrium aspects are presented. Various theoretical concepts, developed based on continuum flow Separation, are applied to the present configuration to explore its applicability in the presence of slip, and the resulting relative variations are highlighted. The temporal evolution of flow structures at various wall temperatures is studied, and its strong dependence on the wall-to-stagnation temperature ratio is elucidated.Hypersonic laminar flow Separation preceded by a strong expansion can occur in practical situations such as the base flow of re-entry vehicles and flow over deflected control surfaces. A leading-Edge Separation configuration provides a case for studying fundamental aspects of such flow Separation and reattachment in the absence of a pre-existing boundary layer. In hypersonic low-density flows, the onset of Separation is complicated by the presence of rarefaction and thermal non-equilibrium. The reattachment process is also characterized by high compressibility. A computational study of the characteristics of flow Separation and reattachment over such a configuration has been carried out using the direct simulation Monte Carlo code SPARTA. The salient features of Separation are explained from a fluid dynamic perspective, and distinct characteristics in surface parameters are identified and discussed in detail. The physical mechanisms behind the formation as well as co-existence of primary and secondary vor...
Andrew J. Neely - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of bluntness effects on laminar leading Edge Separation in hypersonic flow
Journal of Fluid Mechanics, 2019Co-Authors: Amna Khraibut, Sudhir L. Gai, Andrew J. NeelyAbstract:Bluntness effects on laminar hypersonic leading Edge Separation are investigated numerically at Mach number $M\approx 10$ , unit Reynolds number $Re=1.3\times 10^{6}~\text{m}^{-1}$ , specific enthalpy $h_{o}=3.1~\text{MJ}~\text{kg}^{-1}$ and wall-to-stagnation temperature ratio $T_{w}/T_{o}=0.1$ . Such effects are important from an experimental point of view and because bluntness can affect a separated flow favourably or adversely. In this study, two blunt leading Edge cases of small radius ( $15~\unicode[STIX]{x03BC}\text{m}$ ) and large radius ( $100~\unicode[STIX]{x03BC}\text{m}$ ) are investigated. A comparison with the idealised sharp leading Edge case is also given. General flow features and surface parameters such as the shear stress, pressure and heat flux are presented and analysed. The results have also been interpreted in terms of Cheng’s displacement-bluntness similitude parameter affecting the size of Separation. Previous experiments by Holden delineated small and large bluntness effects based on Cheng’s parameter and considering small to moderate separated regions. In this study, leading Edge Separation was found to suppress the favourable effect of bluntness in delaying Separation. Bluntness, furthermore, seemed to promote the appearance of secondary vortices within a main separated region. Analysis of reverse flow boundary layer profiles such as velocity, pressure and temperature is also given. It is shown that bluntness accentuates large transverse gradients. This in turn adversely effects the reverse flow boundary layer leading to the appearance of secondary vortices.
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Laminar hypersonic leading Edge Separation - a numerical study
Journal of Fluid Mechanics, 2017Co-Authors: Amna Khraibut, Sudhir L. Gai, L. M. Brown, Andrew J. NeelyAbstract:This paper describes laminar hypersonic leading Edge Separation. Such a configuration of separated flow was originally studied by Chapman et al. ( NACA Tech. Rep. 1356, 1958) at supersonic Mach numbers as it is particularly amenable to theoretical analysis and assumes no pre-existing boundary layer. It can be considered as a limiting case of much studied generic configurations such as Separation at a compression corner and separated flow behind a base. A numerical investigation is described using a compressible Navier–Stokes solver assuming perfect gas air, no slip boundary condition and a non-catalytic surface. A moderate enthalpy flow of $3.1\times 10^{6}~\text{J}~\text{kg}^{-1}$ with a unit Reynolds number of $1.34\times 10^{6}~\text{ m}^{-1}$ and a Mach number of 9.66 was considered. The resulting separated flow is analysed in the context of viscous–inviscid interaction and interpreted in terms of ‘triple-deck’ concepts. Particular emphasis is given to wall temperature effects. The effects of strong to moderate wall cooling on flow in the separated region as well as on processes of Separation, reattachment and Separation length, are highlighted. The numerical simulations have also shown the existence of a secondary eddy embedded within the primary recirculation region, with its size, shape and position, being strongly affected by the wall temperature.
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Numerical Investigation of Bluntness Effects on Hypersonic Leading Edge Separation
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Amna Khraibut, Sudhir L. Gai, Andrew J. NeelyAbstract:In this paper, bluntness effects on hypersonic leading Edge Separation have been considered for a numerical investigation at M = 9.66, ho = 3.1 MJ/kg, and Re = 1.3x10 6 m -1 . The importance of this study arises from the fact that any leading Edge in practice has a finite bluntness, which can affect Separation. To simplify the problem, a two-dimensional leading Edge Separation configuration has been chosen for the study. Specifically, a semicircular shaped bluntness of radius r = 100 m has been used to carry out the numerical simulations. The flow conditions have been selected so that the flow remains a continuum, and a Navier–Stokes solver can still be used with confidence. The results have been compared with a previous study on a sharp leading Edge case with the same flow conditions. The comparison has shown that the small bluntness considered in the study increased the adverse pressure, which prompted an earlier Separation. The comparison has also shown an overall reduction in heat flux over the surface and peak heating. The increased size of Separation has necessitated the increase of compression length to account for flow physics beyond reattachment. An additional comparison of flow structure has shown that the detached bow shockwave in front of the blunt leading Edge forms an entropy layer just behind the shock. Most importantly, the results have shown a secondary vortex, which sits just below the main vortex. The effects of bluntness on Separation and reattachment angles have been investigated here as well. The angles have been evaluated using two methods: 1) direct measurement from the dividing streamline, and 2) Oswatitsch’ formula, which relates the angles to the local shear stress and pressure gradients. The results have shown that directly measured angles were higher than in theory; the reasons for this are still under investigation. In short, a reduction of streamline angles and curvature, especially, at Separation, has been observed.
N. A. Cumpsty - One of the best experts on this subject based on the ideXlab platform.
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Leading Edge Separation Bubbles on Turbomachine Blades
Journal of Turbomachinery, 1995Co-Authors: R. E. Walraevens, N. A. CumpstyAbstract:Results are presented for Separation bubbles of the type that can form near the leading Edges of thin compressor or turbine blades. These often occur when the incidence is such that the stagnation point is not on the nose of the aerofoil. Tests were carried out at low speed on a single aerofoil to simulate the range of conditions found on compressor blades. Both circular and elliptic shapes of leading Edge were tested. Results are presented for a range of incidence, Reynolds number, and turbulence intensity and scale. The principal quantitative measurements presented are the pressure distributions in the leading Edge and bubble region, as well as the boundary layer properties at a fixed distance downstream, where most of the flows had reattached. Reynolds number was found to have a comparatively small influence, but a raised level of free-stream turbulence has a striking effect, shortening or eliminating the bubble and increasing the magnitude of the suction spike. Increased free-stream turbulence also reduces the boundary layer thickness and shape parameter after the bubble. Some explanations of the processes are outlined
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Leading Edge Separation Bubbles on Turbomachine Blades
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 1993Co-Authors: R. E. Walraevens, N. A. CumpstyAbstract:Results are presented for Separation bubbles of the type which can form near the leading Edges of thin compressor or turbine blades. These often occur when the incidence is such that the stagnation point is not on the nose of the aerofoil. Tests were carried out at low speed on a single aerofoil to simulate the range of conditions found on compressor blades. Both circular and elliptic shapes of leading Edge were tested. Results are presented for a range of incidence, Reynolds number and turbulence intensity and scale.The principal quantitative measurements presented are the pressure distributions in the leading Edge and bubble region, as well as the boundary layer properties at a fixed distance downstream where most of the flows had reattached. Reynolds number was found to have a comparatively small influence, but a raised level of freestream turbulence has a striking effect, shortening or eliminating the bubble and increasing the magnitude of the suction spike. Increased freestream turbulence also reduces the boundary layer thickness and shape parameter after the bubble. Some explanations of the processes are outlined.© 1993 ASME
Sean O'byrne - One of the best experts on this subject based on the ideXlab platform.
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Laser-induced fluorescence velocimetry for a hypersonic leading-Edge Separation
Physics of Fluids, 2020Co-Authors: Laurent M. Le Page, Matthew Barrett, Sean O'byrne, Sudhir L. GaiAbstract:Two-dimensional mapping of the velocity distribution for a hypersonic leading-Edge Separation flowfield generated by a “tick” shaped geometry is presented for the first time. Discrete measurements of two velocity components were acquired at a flow condition having a total specific enthalpy of 3.8 MJ/kg by imaging nitric oxide fluorescence over numerous runs of the hypersonic tunnel at the Australian Defence Force Academy (T-ADFA). The measured freestream velocity distribution exhibited some non-uniformity, which is hypothesized to originate from images acquired using a set of ultraviolet specific mirrors mounted on the shock tunnel deflecting under load during a run of the facility, slightly changing the laser sheet orientation. The flow Separation point was measured to occur at 1.4 ± 0.2 mm from the model leading Edge, based on the origin of the free shear layer emanating from the expansion surface. Reattachment of this free shear layer on the compression surface occurred at 59.0 ± 0.2 mm from the model ...
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Direct simulation Monte Carlo computations and experiments on leading-Edge Separation in rarefied hypersonic flow
Journal of Fluid Mechanics, 2019Co-Authors: R. Prakash, Sudhir L. Gai, L. M. Le Page, Liam P. Mcquellin, Sean O'byrneAbstract:A comprehensive study of the fundamental characteristics of leading-Edge Separation in rarefied hypersonic flows is undertaken and its salient features are elucidated. Separation of a boundary layer undergoing strong expansion is typical in many practical hypersonic applications such as base flows of re-entry vehicles and flows over deflected control surfaces. Boundary layer growth under such conditions is influenced by effects of rarefaction and thermal non-equilibrium, thereby differing significantly from the conventional no-slip Blasius type. A leading-Edge Separation configuration presents a fundamental case for studying the characteristics of such a flow Separation but with minimal influence from a pre-existing boundary layer. In this work, direct simulation Monte Carlo computations have been performed to investigate flow Separation and reattachment in a low-density hypersonic flow over such a configuration. Distinct features of leading-Edge flow, limited boundary layer growth, Separation, shear layer, flow structure in the recirculation region and reattachment are all explained in detail. The fully numerical shear layer profile after Separation is compared against a semi-theoretical profile, which is obtained using the numerical Separation profile as the initial condition on existing theoretical concepts of shear layer analysis based on continuum flow Separation. Experimental studies have been carried out to determine the surface heat flux using thin-film gauges and computations showed good agreement with the experimental data. Flow visualisation experiments using the non-intrusive planar laser-induced fluorescence technique have been performed to image the fluorescence of nitric oxide, from which velocity and rotational temperature distributions of the separated flow region are determined.
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Rotational temperature imaging of a leading-Edge Separation in hypervelocity flow
31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31, 2019Co-Authors: Laurent M. Le Page, Matthew Barrett, Sean O'byrne, Sudhir L. GaiAbstract:This paper presents a rotational temperature map of a leading-Edge Separation in a low-density hypersonic flow, obtained using imaged fluorescence of nitric oxide (NO). A flow condition with a total specific enthalpy of 3.8 MJ/kg, and for which the continuum assumption should hold, is generated using the T-ADFA free-piston shock tunnel. A leading-Edge separated flow, known as the ‘tick’ model configuration and first suggested by Chapman et al. [1] for the study of laminar flow Separation, is placed in this facility’s test section to produce the leading-Edge Separation. This model geometry is chosen for the study because it produces a near zero-thickness boundary layer prior to Separation. The planar laser-induced fluorescence (PLIF) thermometry technique was chosen to generate a spatially resolved rotational temperature map using multi-line fluorescence images [2]. This technique involves making multiple fluorescence measurements using different rotational lines across the γ(0, 0) vibrational band of NO and fitting the signals to a Boltzmann plot. Using five isolated transitions, the measured freestream temperature of 155±7 K was in good agreement with a one-dimensional nonequilibrium inviscid nozzle code calculation of 156 ± 8 K. The recirculating region was found to have a peak temperature of 2000 ± 500 K across the imaged flowfield and the wake neck formed at the flow reattachment exhibited a cooling effect to an almost uniform temperature of 450 ± 70 K.This paper presents a rotational temperature map of a leading-Edge Separation in a low-density hypersonic flow, obtained using imaged fluorescence of nitric oxide (NO). A flow condition with a total specific enthalpy of 3.8 MJ/kg, and for which the continuum assumption should hold, is generated using the T-ADFA free-piston shock tunnel. A leading-Edge separated flow, known as the ‘tick’ model configuration and first suggested by Chapman et al. [1] for the study of laminar flow Separation, is placed in this facility’s test section to produce the leading-Edge Separation. This model geometry is chosen for the study because it produces a near zero-thickness boundary layer prior to Separation. The planar laser-induced fluorescence (PLIF) thermometry technique was chosen to generate a spatially resolved rotational temperature map using multi-line fluorescence images [2]. This technique involves making multiple fluorescence measurements using different rotational lines across the γ(0, 0) vibrational band of NO a...
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A direct simulation Monte Carlo study of hypersonic leading-Edge Separation with rarefaction effects
Physics of Fluids, 2018Co-Authors: R. Prakash, Sudhir L. Gai, Sean O'byrneAbstract:Hypersonic laminar flow Separation preceded by a strong expansion can occur in practical situations such as the base flow of re-entry vehicles and flow over deflected control surfaces. A leading-Edge Separation configuration provides a case for studying fundamental aspects of such flow Separation and reattachment in the absence of a pre-existing boundary layer. In hypersonic low-density flows, the onset of Separation is complicated by the presence of rarefaction and thermal non-equilibrium. The reattachment process is also characterized by high compressibility. A computational study of the characteristics of flow Separation and reattachment over such a configuration has been carried out using the direct simulation Monte Carlo code SPARTA. The salient features of Separation are explained from a fluid dynamic perspective, and distinct characteristics in surface parameters are identified and discussed in detail. The physical mechanisms behind the formation as well as co-existence of primary and secondary vortices are described. The region close to the leading-Edge is analyzed in detail, and the prevailing non-equilibrium aspects are presented. Various theoretical concepts, developed based on continuum flow Separation, are applied to the present configuration to explore its applicability in the presence of slip, and the resulting relative variations are highlighted. The temporal evolution of flow structures at various wall temperatures is studied, and its strong dependence on the wall-to-stagnation temperature ratio is elucidated.Hypersonic laminar flow Separation preceded by a strong expansion can occur in practical situations such as the base flow of re-entry vehicles and flow over deflected control surfaces. A leading-Edge Separation configuration provides a case for studying fundamental aspects of such flow Separation and reattachment in the absence of a pre-existing boundary layer. In hypersonic low-density flows, the onset of Separation is complicated by the presence of rarefaction and thermal non-equilibrium. The reattachment process is also characterized by high compressibility. A computational study of the characteristics of flow Separation and reattachment over such a configuration has been carried out using the direct simulation Monte Carlo code SPARTA. The salient features of Separation are explained from a fluid dynamic perspective, and distinct characteristics in surface parameters are identified and discussed in detail. The physical mechanisms behind the formation as well as co-existence of primary and secondary vor...
