Dissertations / Theses: 'Hypersonic wind tunnels'

1

Ajmani, Kumud. "Turbulence modeling in hypersonic inlets." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/101365.

Full text

Abstract:

A study is conducted to analyze the performance of different turbulence models when applied to flow through a Mach 7.4 hypersonic inlet. The analysis, which is two-dimensional, is done by comparing computational results from a Parabolized Navier Stokes code, with experimental data. The McDonald Camarata (MC) and Baldwin Lomax (BL) models were the two zero-equation models used in the study. The Turbulent Kinetic Energy (TKE) model was chosen as a representative higher order model. The MC model, when run with transition of flow, provides a solution which compares excellently with the data. Transition has a first order effect on the overall solution provided by the code. The BL model predicts separation of flow in the inlet, which contradicts experimental findings. The TKE model does not perform any better than the MC and BL models, despite the fact that it is a higher order turbulence model. The BL and TKE models predict transition in the inlet at a location which is much earlier than observed in the experiment. This may be attributed to the empirical constants used to determine the point of transition.
M.S.

APA, Harvard, Vancouver, ISO, and other styles

2

Goozee, Richard J. "Simulation of a complete shock tunnel using parallel computer codes /." St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17470.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Tirtey, Sandy C. "Characterization of a transitional hypersonic boundary layer in wind tunnel and flight conditions." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210367.

Full text

Abstract:

Laminar turbulent transition is known for a long time as a critical phenomenon influencing the thermal load encountered by hypersonic vehicle during their planetary re-entry trajectory. Despite the efforts made by several research laboratories all over the world, the prediction of transition remains inaccurate, leading to oversized thermal protection system and dramatic limitations of hypersonic vehicles performances. One of the reasons explaining the difficulties encountered in predicting transition is the wide variety of parameters playing a role in the phenomenon. Among these parameters, surface roughness is known to play a major role and has been investigated in the present thesis.

A wide bibliographic review describing the main parameters affecting transition and their coupling is proposed. The most popular roughness-induced transition predictions correlations are presented, insisting on the lack of physics included in these methods and the difficulties encountered in performing ground hypersonic transition experiments representative of real flight characteristics. This bibliographic review shows the importance of a better understanding of the physical phenomenon and of a wider experimental database, including real flight data, for the development of accurate prediction methods.

Based on the above conclusions, a hypersonic experimental test campaign is realized for the characterization of the flow field structure in the vicinity and in the wake of 3D roughness elements. This fundamental flat plate study is associated with numerical simulations for supporting the interpretation of experimental results and thus a better understanding of transition physics. Finally, a model is proposed in agreement with the wind tunnel observations and the bibliographic survey.

The second principal axis of the present study is the development of a hypersonic in-flight roughness-induced transition experiment in the frame of the European EXPERT program. These flight data, together with various wind tunnel measurements are very important for the development of a wide experimental database supporting the elaboration of future transition prediction methods.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

APA, Harvard, Vancouver, ISO, and other styles

4

Grossir, Guillaume. "Longshot hypersonic wind tunnel flow characterization and boundary layer stability investigations." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209044.

Full text

Abstract:

The hypersonic laminar to turbulent transition problem above Mach 10 is addressed experimentally in the short duration VKI Longshot gun tunnel. Reentry conditions are partially duplicated in terms of Mach and Reynolds numbers. Pure nitrogen is used as a test gas with flow enthalpies sufficiently low to avoid its dissociation, thus approaching a perfect gas behavior. The stabilizing effects of Mach number and nosetip bluntness on the development of natural boundary layer disturbances are evaluated over a 7 degrees half-angle conical geometry without angle of attack.

Emphasis is initially placed on the flow characterization of the Longshot wind tunnel where these experiments are performed. Free-stream static pressure diagnostics are implemented in order to complete existing stagnation point pressure and heat flux measurements on a hemispherical probe. An alternative method used to determine accurate free-stream flow conditions is then derived following a rigorous theoretical approach coupled to the VKI Mutation thermo-chemical library. Resulting sensitivities of free-stream quantities to the experimental inputs are determined and the corresponding uncertainties are quantified and discussed. The benefits of this different approach are underlined, revealing the severe weaknesses of traditional methods based on the measurement of reservoir conditions and the following assumptions of an isentropic and adiabatic flow through the nozzle. The operational map of the Longshot wind tunnel is redefined accordingly. The practical limits associated with the onset of nitrogen flow condensation under non-equilibrium conditions are also accounted for.

Boundary layer transition experiments are then performed in this environment with free-stream Mach numbers ranging between 10-12. Instrumentation along the 800mm long conical model includes flush-mounted thermocouples and fast-response pressure sensors. Transition locations on sharp cones compare favorably with engineering correlations. A strong stabilizing effect of nosetip bluntness is reported and no transition reversal regime is observed for Re_RN<120000. Wavelet analysis of wall pressure traces denote the presence of inviscid instabilities belonging to Mack's second mode. An excellent agreement with Linear Stability Theory results is obtained from which the N-factor of the Longshot wind tunnel in these conditions is inferred. A novel Schlieren technique using a short duration laser light source is developed, allowing for high-quality flow visualization of the boundary layer disturbances. Comparisons of these measurement techniques between each other are finally reported, providing a detailed view of the transition process above Mach 10.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

APA, Harvard, Vancouver, ISO, and other styles

5

Edy, Jean-Luc. "Application de la photoluminescence pour la mesure des flux thermiques en soufflerie hypersonique à rafales." Valenciennes, 1995. https://ged.uphf.fr/nuxeo/site/esupversions/b8f44f3d-2475-494b-9670-b3b708b9c821.

Full text

Abstract:

Une étude a été entreprise à la direction de l'aérodynamique de l'onera concernant l'application en soufflerie hypersonique d'une nouvelle méthode thermographique utilisant les propriétés de la photoluminescence. Après avoir étudie la faisabilité de la technique en mesure ponctuelle, il a été décidé de développer un système cartographique basé sur l'utilisation d'une camera video 3-ccd et d'un système de traitement d'images et de vérifier son adéquation aux mesures des transferts de chaleur pariétaux dans les souffleries hypersoniques à rafales. Le système a été étalonné en laboratoire, puis évalué dans le cadre d'essais dans les installations de l'onera à Chalais-Meudon. Il apparait que la thermographie par photoluminescence (tph) fournit des résultats satisfaisants sur des maquettes en matériau isolant thermiquement. Quant aux corps d'étude en matériau conducteur, la comparaison soit avec une évaluation théorique, soit avec données acquises au moyen de capteurs ponctuels montre que l'accord est moins bon. Cette méthode, avec la configuration expérimentale choisie, ne peut concurrencer directement la thermographie infrarouge. Elle est plutôt d'une technique complémentaire applicable quand la thermographie infrarouge ne peut être mise en œuvre

APA, Harvard, Vancouver, ISO, and other styles

6

Jeyaratnam, Jonathan Jehan. "On the low speed longitudinal stability of hypersonic waveriders." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/22456.

Full text

Abstract:

The development of hypersonic civilian transport aircraft requires solutions to a number of challenging problems in the areas of aerothermodynamics, control, aeroelasticity, propulsion and others encountered at high Mach number flight. The desire for good aerodynamic performance at high Mach numbers results in slender vehicle designs called waveriders. The stability and handling of waverider shapes at the low speeds at the take-off and landing phases of flight is not well studied. This thesis covers static and dynamic CFD simulations of the Hexafly-Int glider which have been used to obtain longitudinal stability derivatives at low speeds. Complementary static and free-to-pitch dynamic wind tunnel testing, are used to validate the CFD computations. A final chapter on the optimisation of waverider designs including low speed longitudinal stability is presented to show the impacts of this additional requirement on the hypersonic design space. The static wind tunnel testing has identified stability issues relating to the location of the centre of gravity. The design centre of gravity which is suitable for the Hexafly-Int vehicle at Mach 7.2 is found to be too far aft which results in instability at low speeds. In addition, the dynamic testing in the wind tunnel shows that the pitch damping is inadequate at low speeds. The CFD simulations agree well with the wind tunnel test results validating the use of CFD tools for determining dynamic stability derivatives of this class of slender vehicle in the design process. To alleviate the low speed stability issue of hypersonic vehicles, a waverider shape optimisation study has been carried out to understand what shapes will produce better low speed stability behaviour. These shapes are found to produce lower aerodynamic efficiency at high speeds which suggests that a design compromise between low speed stability and high speed performance is required at the outset of hypersonic waverider design.

APA, Harvard, Vancouver, ISO, and other styles

7

Bensassi, Khalil. "Contribution to the Numerical Modeling of the VKI Longshot Hypersonic Wind Tunnel." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/229727.

Full text

Abstract:

The numerical modelling of the VKI-Longshot facility remains a challeng-ing task as it requires multi-physical numerical methods in order to simulate all the components. In the current dissertation, numerical tools were developed in order to study each component of the facility separately and a deep investigations of each stage of the shot were performed. This helped to better understand the different processes involved in the flow development inside this hypersonic wind tunnel. However the numerical computation of different regions of the facility treated as independent from each others remains an approximation at best.The accuracy of the rebuilding code for determining the free stream conditions and the total enthalpy in the VKI-Longshot facility was investigated by using a series of unsteady numerical computations of axisymmetric hypersonic flow over a heat flux probe. Good agreement was obtained between the numerical results and the measured data for both the stagnation pressure and the heat flux dur- ing the useful test time.The driver-driven part of the Longshot facility was modelled using the quasi one-dimensional Lagrangian solver L1d2. The three main conditions used for the experiments —low, medium and high Reynolds number —were considered.The chambrage effect due to the junction between the driver and the driven tubes in the VKI-Longshot facility was investigated. The computation showed great ben- efit of the chambrage in increasing the speed of the piston and thus the final compression ratio of the test gas.Two dimensional simulations of the flow in the driver and the driven tube were performed using Arbitrary Lagrangian Eulerian (ALE) solver in COOLFLuiD. A parallel multi-domain strategy was developed in order to integrate the moving piston within the computational domain.The computed pressure in the reservoir is compared to the one provided by the experiment and good agreement was obtained for both con- editions.Finally, an attempt was made to compute the starting process of the flow in the contoured nozzle. The transient computation of the flow showed how the primary shock initiates the flow in the nozzle before reaching the exit plan at time of 1.5 [ms] after the diaphragm rupture. The complex interactions of the reflected shocks in the throat raise the temperature above 9500 [K] which was not expected. Chemical dissociation of Nitrogen was not taken into account during this transient investigation which may play a key role considering the range of temperature reached near the throat.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

APA, Harvard, Vancouver, ISO, and other styles

8

Bykerk, Tamas. "Low Speed Aerodynamics, Performance and Handling Qualities of a Hypersonic Waverider." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23111.

Full text

Abstract:

Interest in the development of high speed commercial aircraft capable of travelling in excess of Mach 5 is on the increase. This is mainly driven by the potential of these vehicles to significantly reduce long haul flight times, connecting antipodal city pairs such as Brussels and Sydney in less than three hours. The hypersonic waverider concept has received particular attention because of its ability to achieve comparatively high aerodynamic efficiency at hypersonic cruise, as the body shock is contained by the wing leading edges. As research into the extreme conditions at high Mach numbers takes priority, no full subsonic handling quality analysis of a waverider has ever been completed, nor has an understanding of the mechanisms behind both static and dynamic stability been developed. This gap in literature is addressed by this thesis, which presents a combination of results from computational fluid dynamics simulations and wind tunnel experiments, completing the first full subsonic handling quality analysis of a waverider.

APA, Harvard, Vancouver, ISO, and other styles

9

Comstock, Robert. "Hypersonic Heat Transfer Load Analysis in STAR-CCM+." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2226.

Full text

Abstract:

This thesis investigates the capabilities of STAR-CCM+, a Computational Fluid Dynamics (CFD) software owned by Siemens, in predicting hypersonic heat transfer loads on forward-facing surfaces. Results show that STAR-CCM+ predicted peak heat transfer loads within +/- 20% of experimental data on the leading edge of a delta wing design from the X-20 Dyna-Soar program with 73o of sweep. Steady-state laminar simulations were run as replications of wind tunnel tests documented in NASA CR-535, a NASA technical report that measured and studied the hypersonic pressure and heat transfer loads on preliminary X- 20 wing designs across a wide range of Reynolds numbers and Mach numbers in different wind tunnel and shock tunnel facilities. One of the Mach 8.08 test cases that was run at NASA Arnold Engineering Development Center Wind Tunnel B was selected as the case of comparison for this thesis, which was designated as test AD462M-1 in the original report. The CFD simulations assumed an ideal gas in laminar flow with temperature-dependent viscosity, thermal conductivity, and isobaric specific heat across an angle of attack range from 0o to 30o. A separate CFD study of heat transfer loads of a hemisphere-cylinder at Mach 6.74 was used as a simpler and less computationally-expensive validation case compared against wind tunnel data from NASA Langley Research Center to help select the appropriate CFD solver and mesh settings for this thesis. For the hemisphere-cylinder, the heat transfer load at the stagnation point was overpredicted in STAR-CCM+ by 21.8%. Peak heat transfer loads on the delta wing leading edge were all within +/- 20% of the wind tunnel data, which was published for angles of attack between 15o to 30o. A more adverse heat transfer gradient along the leading edge of the delta wing was also observed in the direction from the front of the wing to the outer wing tip when compared to wind tunnel data. The pressure loads on the delta wing leading edge in CFD were within +/-10% of wind tunnel measurements.

APA, Harvard, Vancouver, ISO, and other styles

10

Boyd, Robert Raymond. "An Experimental and Computational Investigation on the Effect of Transonic Flow in Hypersonic Wind Tunnel Nozzles, Including Filtered Rayleigh Scattering Measurements /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu148793364864785.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Perkins, Hugh Douglas. "Development and Demonstration of a Computational Tool for the Analysis of Particle Vitiation Effects in Hypersonic Propulsion Test Facilities." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1227553721.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Sheard, A. G. "Aerodynamic and mechanical performance of a high-pressure turbine stage in a transient wind tunnel." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:73ecb15e-efde-474d-ae30-3f8f7e1d6f4e.

Full text

Abstract:

Unsteady three-dimensional flow phenomena have major effects on the aerodynamic performance of, and heat transfer to, gas-turbine blading. Investigation of the mechanisms associated with these phenomena requires an experimental facility that is capable of simulating a gas turbine, but at lower levels of temperature and pressure to allow conventional measurement techniques. This thesis reports on the design, development and commissioning of a new experimental facility that models these unsteady three-dimensional flow phenomena. The new facility, which consists of a 62%-size, high-pressure gas-turbine stage mounted in a transient wind tunnel, simulates the turbine design point of a full-stage turbine. The thesis describes the aerodynamic and mechanical design of the new facility, a rigorous stress analysis of the facility’s rotating system and the three-stage commissioning of the facility. The thesis concludes with an assessment of the turbine stage performance.

APA, Harvard, Vancouver, ISO, and other styles

13

北村, 圭一, Keiichi KITAMURA, 啓伺小澤, Hiroshi OZAWA, 勝祥花井, Katsuhisa HANAI, 浩一森, Koichi MORI, 佳朗中村, and Yoshiaki NAKAMURA. "極超音速TSTOにおける衝撃波干渉・境界層剥離を伴う流れ場の解析." 日本航空宇宙学会, 2008. http://hdl.handle.net/2237/13872.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Di, Giovanni Antonio [Verfasser], Christian [Akademischer Betreuer] Stemmer, Wolfgang [Gutachter] Schröder, and Christian [Gutachter] Stemmer. "Roughness-Induced Transition in a Hypersonic Capsule Boundary Layer under Wind-Tunnel and Reentry Conditions / Antonio Di Giovanni ; Gutachter: Wolfgang Schröder, Christian Stemmer ; Betreuer: Christian Stemmer." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1211725227/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Retaureau, Ghislain J. "On recessed cavity flame-holders in supersonic cross-flows." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43703.

Full text

Abstract:

Flame-holding in a recessed cavity is investigated experimentally in a Mach 2.5 preheated cross-flow for both stable and unstable combustion, with a relatively low preheating. Self-sustained combustion is investigated for stagnation pressures and temperatures reaching 1.4 MPa and 750 K. In particular, cavity blowout is characterized with respect to cavity aspect ratio (L/D =2.84 - 3.84), injection strategy (floor - ramp), aft ramp angle (90 deg - 22.5 deg) and multi-fuel mixture (CH₄-H₂ or CH₄-C₂H₄ blends). The results show that small hydrogen addition to methane leads to significant increase in flame stability, whereas ethylene addition has a more gradual effect. Since the multi-fuels used here are composed of a slow and a fast chemistry fuel, the resulting blowout region has a slow (methane dominant) and a fast (hydrogen or ethylene dominant) branch. Regardless of the fuel composition, the pressure at blowout is close to the non-reacting pressure imposed by the cross-flow, suggesting that combustion becomes potentially unsustainable in the cavity at the sub-atmospheric pressures encountered in these supersonic studies. The effect of preheating is also investigated and results show that the stability domain broadens with increasing stagnation temperature. However, smaller cavities appear less sensitive to the cross-flow preheating, and stable combustion is achieved over a smaller range of fuel flow rate, which may be the result of limited residence and mixing time. The blowout data point obtained at lower fuel flow rate fairly matches the empirical model developed by Rasmussen et al. for floor injection phi = 0.0028 Da^-.8, where phi is the equivalence ratio and Da the Damkohler number. An alternate model is proposed here that takes into account the ignition to scale the blowout data. Since the mass of air entrained into the cavity cannot be accurately estimated and the cavity temperature is only approximated from the wall temperature, the proposed scaling has some uncertainty. Nevertheless the new phi-Da scaling is shown to preserve the subtleties of the blowout trends as seen in the current experimental data.

APA, Harvard, Vancouver, ISO, and other styles

16

Naiman, Hadassah. "Analysis and design of quiet hypersonic wind tunnels." 2010. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000052138.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

(7399604), Phillip Portoni. "Using Suction for Laminar Flow Control in Hypersonic Quiet Wind Tunnels: A Feasibility Study." Thesis, 2019.

Find full text

Abstract:

To reduce the risk of using suction in a hypersonic quiet-tunnel nozzle design, this project tested micro-perforated suction sections to remove the boundary layer on an axisymmetric model in the Boeing/AFOSR Mach-6 Quiet Tunnel. The model was a cone-flare geometry tested at 0° angle of attack. The turn from the 7° half-angle cone to the flare was designed to prevent flow separation. The flare was designed to amplify the Görtler instability.

Five suction sections were designed with different perforation patterns and porosities. Four were successfully manufactured, but only the first of the four sections has been tested so far. The first suction section has pores drilled along straight lines with a nominal 5% porosity.

Measurements were made with temperature-sensitive paint and oil-flow visualization on a non-perforated blank to measure the baseline development of Görtler vortices on the flare. Although the signal-to-noise ratio of the measurement techniques were insufficient to measure the vortices, it was confirmed that the boundary layer is laminar for the entire model. Measurements with suction also did not show the Görtler vortices.

Surface pressure fluctuations were measured on the flare. Apparent second-mode waves were detected. The suction measurements showed a slight increase in second-mode peak frequency over the baseline results, as expected.

Concerns had been raised about acoustic noise that might be radiated from the suction section. Thus, fluctuations above the suction section were measured using a pitot probe and using focused-laser differential interferometry. The measurements during suction showed no noticeable increase in fluctuations compared to the baseline results.

APA, Harvard, Vancouver, ISO, and other styles

18

Thakur, Ruchi. "Experimental Analysis of Shock Stand off Distance over Spherical Bodies in Hypersonic Flows." Thesis, 2015. http://etd.iisc.ac.in/handle/2005/3848.

Full text

Abstract:

One of the characteristics of the high speed ows over blunt bodies is the detached shock formed in front of the body. The distance of the shock from the stagnation point measured along the stagnation streamline is termed as the shock stand o distance or the shock detachment distance. It is one of the most basic parameters in such ows. The need to know the shock stand o distance arises due to the high temperatures faced in these cases. The biggest challenge faced in high enthalpy ows is the high amounts of heat transfer to the body. The position of the shock is relevant in knowing the temperatures that the body being subjected to such ows will have to face and thus building an efficient system to reduce the heat transfer. Despite being a basic parameter, there is no theoretical means to determine the shock stand o distance which is accepted universally. Deduction of this quantity depends more or less on experimental or computational means until a successful theoretical model for its predictions is developed. The experimental data available in open literature for spherical bodies in high speed ows mostly lies beyond the 2 km/s regime. Experiments were conducted to determine the shock stand o distance in the velocity range of 1-2 km/s. Three different hemispherical bodies of radii 25, 40 and 50 mm were taken as test models. Since the shock stand o distance is known to depend on the density ratio across the shock and hence gamma (ratio of specific heats), two different test gases, air and carbon dioxide were used for the experiments here. Five different test cases were studied with air as the test gas; Mach 5.56 with Reynolds number of 5.71 million/m and enthalpy of 1.08 MJ/kg, Mach 5.39 with Reynolds number of 3.04 million/m and enthalpy of 1.42 MJ/kg Mach 8.42 with Reynolds number of 1.72 million/m and enthalpy of 1.21 MJ/kg, Mach 11.8 with Reynolds number of 1.09 million/m and enthalpy of 2.03 MJ/kg and Mach 11.25 with Reynolds number of 0.90 million/m and enthalpy of 2.88 MJ/kg. For the experiments conducted with carbon dioxide as test gas, typical freestream conditions were: Mach 6.66 with Reynolds number of 1.46 million/m and enthalpy of 1.23 MJ/kg. The shock stand o distance was determined from the images that were obtained through schlieren photography, the ow visualization technique employed here. The results obtained were found to follow the same trend as the existing experimental data in the higher velocity range. The experimental data obtained was compared with two different theoretical models given by Lobb and Olivier and was found to match. Simulations were carried out in HiFUN, an in-house CFD package for Euler and laminar own conditions for Mach 8 own over 50 mm body with air as the test gas. The computational data was found to match well with the experimental and theoretical data

APA, Harvard, Vancouver, ISO, and other styles

19

Thakur, Ruchi. "Experimental Analysis of Shock Stand off Distance over Spherical Bodies in Hypersonic Flows." Thesis, 2015. http://etd.iisc.ernet.in/2005/3848.

Full text

Abstract:

One of the characteristics of the high speed ows over blunt bodies is the detached shock formed in front of the body. The distance of the shock from the stagnation point measured along the stagnation streamline is termed as the shock stand o distance or the shock detachment distance. It is one of the most basic parameters in such ows. The need to know the shock stand o distance arises due to the high temperatures faced in these cases. The biggest challenge faced in high enthalpy ows is the high amounts of heat transfer to the body. The position of the shock is relevant in knowing the temperatures that the body being subjected to such ows will have to face and thus building an efficient system to reduce the heat transfer. Despite being a basic parameter, there is no theoretical means to determine the shock stand o distance which is accepted universally. Deduction of this quantity depends more or less on experimental or computational means until a successful theoretical model for its predictions is developed. The experimental data available in open literature for spherical bodies in high speed ows mostly lies beyond the 2 km/s regime. Experiments were conducted to determine the shock stand o distance in the velocity range of 1-2 km/s. Three different hemispherical bodies of radii 25, 40 and 50 mm were taken as test models. Since the shock stand o distance is known to depend on the density ratio across the shock and hence gamma (ratio of specific heats), two different test gases, air and carbon dioxide were used for the experiments here. Five different test cases were studied with air as the test gas; Mach 5.56 with Reynolds number of 5.71 million/m and enthalpy of 1.08 MJ/kg, Mach 5.39 with Reynolds number of 3.04 million/m and enthalpy of 1.42 MJ/kg Mach 8.42 with Reynolds number of 1.72 million/m and enthalpy of 1.21 MJ/kg, Mach 11.8 with Reynolds number of 1.09 million/m and enthalpy of 2.03 MJ/kg and Mach 11.25 with Reynolds number of 0.90 million/m and enthalpy of 2.88 MJ/kg. For the experiments conducted with carbon dioxide as test gas, typical freestream conditions were: Mach 6.66 with Reynolds number of 1.46 million/m and enthalpy of 1.23 MJ/kg. The shock stand o distance was determined from the images that were obtained through schlieren photography, the ow visualization technique employed here. The results obtained were found to follow the same trend as the existing experimental data in the higher velocity range. The experimental data obtained was compared with two different theoretical models given by Lobb and Olivier and was found to match. Simulations were carried out in HiFUN, an in-house CFD package for Euler and laminar own conditions for Mach 8 own over 50 mm body with air as the test gas. The computational data was found to match well with the experimental and theoretical data

APA, Harvard, Vancouver, ISO, and other styles

20

(10721112), Joshua Craig Ownbey. "Preliminary Design of a High-Enthalpy Hypersonic Wind Tunnel Facility and Analysis of Flow Interactions in a High-Speed Missile Configuration." Thesis, 2021.

Find full text

Abstract:

An approach for designing a high-enthalpy wind tunnel driven by exothermic chemical reactions was developed. Nozzle contours were designed using CONTUR, a program implementing the method of characteristics, to design nozzle contours at various flow conditions. A reacting mixture including nitrous oxide has been identified as the best candidate for providing clean air at high temperatures. The nitrous oxide has a few performance factors that were considered, specifically the combustion of the gas. Initial CFD simulations were performed on the nozzle and test region to validate flow characteristics and possible issues. Initial results show a fairly uniform exit velocity and ability to perform testing. In a second phase of the work, two generic, high-speed missile configurations were explored using numerical simulation. The mean flow was computed on both geometries at 0 and 45 roll and 0, 1, and 10 angle of attack. The computations identified complex flow structures, including three-dimensional shock/boundary-layer interactions, that varied considerably with angle of attack.

APA, Harvard, Vancouver, ISO, and other styles

21

Shun-Yu, Huang, and 黃順裕. "Modeling and Implementation a Hypersonic Wind Tunnel Controller." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/55543492087228514227.

Full text

Abstract:

碩士
國防大學中正理工學院
兵器系統工程研究所
92
Stagnation Pressure Control is a controller which is used to regulate the mass flow rate of air by an electrically controlled valve to set up a steady flow field in the settling chamber. Basically, a hypersonic wind tunnel experiment is performance in a high-rate flow field, and a high flow velocity makes relative shot response time of the control system, it is more difficult for the precise pressure control of the wind tunnel and the safe supervision of the test facilities. An ideal Wind Tunnel Controller, in addition to control the required amount of fluid flow to keep stable stagnation pressure in the settling chamber, it is also necessarily to have a sensitive control apparatus for safe monitoring. The aim of this thesis is to construct a hypersonic wind tunnel control system to compatible with the hypersonic wind tunnel at CCIT. Because of the nozzle configuration of the wind tunnel, the stability of the fixed geometry of the test section totally depends on the stagnation pressure in the settling chamber. Based On the rules mentioned above, the aim of this research will be in followings: 1. The model construction and the system analysis of the wind tunnel 2. The stagnation pressure control system simulation of the wind tunnel 3. The interface integration of data acquisition system

APA, Harvard, Vancouver, ISO, and other styles

22

LI, QING-PEI, and 李清培. "High speed wind tunnel nozzle design and numerical simulation of hypersonic flow." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/89846444013587741262.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

(7038167), Claire S. Diffey. "Characterization of The Flow Quality in the Boeing Subsonic Wind Tunnel." Thesis, 2019.

Find full text

Abstract:

Good wind-tunnel flow quality characteristics are vital to using test data in the aerodynamic design process. Spatially uniform velocity profiles are required to avoid yaw and roll moments that would not be present in real flight conditions. Low turbulence intensity levels are also important as several aerodynamic properties are functions of turbulence intensity. When measuring mean flow and turbulence properties, hot-wire anemometry offers good spatial resolution and high-frequency response with a fairly simple operation, and the ability to make near-wall measurements. Using hot-wire anemometry, flow quality experiments were conducted

in a closed-circuit wind tunnel with a test section that has a cross section area of 1.2 m x 1.8 m (4 ft. x 6 ft.). The experiments included measurements of flow velocity and turbulence intensity variation over the test section cross-section, spatial and temporal temperature variation, and

boundary layer measurements. The centerline velocity and turbulence intensity were also measured for flow speeds ranging from 13 to 43 m/s.

APA, Harvard, Vancouver, ISO, and other styles

24

Ashley, Jonathan Michael. "Closed-loop control of shock location to prevent hypersonic inlet unstart." Thesis, 2014. http://hdl.handle.net/2152/25782.

Full text

Abstract:

Hypersonic inlet unstart remains a major technical obstacle in the successful implementation of hypersonic air-breathing propulsion systems such as ramjets and scramjets. Unstart occurs when combustor-induced pressure fluctuations lead to rapid expulsion of the shock system from the isolator, and is associated with loss of thrust. The research presented here attempts to mitigate this behavior through the design and implementation of a closed-loop control scheme that regulates shock location within a Mach 1.8 wind tunnel isolator test section. To localize the position of the shock within the isolator, a set of high frequency Kulite pressure transducers are used to measure the static pressure at various points along the wind tunnel test section. A novel Kalman filter based approach is utilized, which fuses the estimates from two distinct shock localization algorithms running at 250 Hz to determine the location of the shock in real time. The primary shock localization algorithm is a geometrical shock detection scheme that can estimate the position of the shock system even when it is located between pressure transducers. The second algorithm utilizes a sum-of-pressures technique that can be calibrated by the geometrical algorithm in real time. The closed-loop controller generates commands every 100 ms to actuate a motorized flap downstream of the test section in an effort to regulate the shock to the desired location. The closed-loop control implementation utilized a simple logic-based controller as well as a Proportional-Integral (PI) and a Proportional-Derivative (PD) Controller. In addition to the implementation of control algorithms, the importance of various design criteria necessary to achieve satisfactory control performance is explored including parameters such as pressure transducer spacing, shock localization speed, flap-motor actuation speed and actuator resolution. Experimental results are presented for various test scenarios such as regulation of the shock location in the presence of stagnation pressure disturbances as well as tracking of time-varying step inputs. Performance and robustness properties of the tested control implementations are discussed. Further areas of improvement for the closed-loop control system in both hardware and software are discussed, and the need for reduced-order dynamics-based controllers is presented.
text

APA, Harvard, Vancouver, ISO, and other styles

25

(9515840), Jordan Matthew Fisher. "Advancements and Practical Applications of Molecular Tagging Velocimetry in Hypersonic Flows." Thesis, 2020.

Find full text

Abstract:

Hypersonic flows consist of harsh environments where chemistry effects are relevant and low speed assumptions such as the ideal gas law and the continuum hypothesis

begin to break down. Because of these processes, computer models do a poor job of predicting behavior of vehicles in hypersonic flight. High fi?delity ground test

measurements are necessary to anchor and extrapolate CFD simulations so that flight vehicle designs can continue to improve. Due to the harsh conditions and complexities

of test facilities, implementing experimental measurements can prove challenging. Molecular tagging methods such as Femtosecond Laser Electronic Excitation Tagging

(FLEET) are attractive for use in hypersonic ground test facilities for many reasons. They are generally considered non-intrusive, since they require no physical probes or seed particles to be placed in the flow. This both keeps the facility safe from damage and minimizes the disturbance imparted on the flowfi?eld by the measurement. Since the tracer is comprised of molecules already present in the flow, the measurement is reliable and can track velocities over a wide dynamic range. The optical arrangement for FLEET is rather simple, requiring only a focused laser beam and a camera to capture the signal. The method can even be applied as a one-sided measurement requiring only one direction of optical access. The current state-of-the-art for the FLEET method is point-wise measurements made at 1 kHz with a

commercially available laser system. The basis for this thesis is to identify and address current limitations in the implementation of FLEET to relevant flow facilities in terms of the useful aerodynamic information that can be extracted. Fundamental advances to the spatial extent and temporal resolution of FLEET are investigated, and novel applied measurements in high speed flow facilities are presented. Considerations of the precision, spatial resolution and ability to implement fundamental advances to harsh and more complex environments are discussed. A custom-built burst-mode femtosecond laser system is used to enable FLEET measurements at 1 MHz, an improvement of three orders

of magnitude in measurement rate. New optical arrangements including microlens arrays and holographic beamsplitters are developed to allow multi-dimensional grids

to be tracked to instantaneously measure velocity gradients. Shock wave and shear measurements in a supersonic bladeless turbine and boundary layer measurements

on a Mach 6 cone-cylinder-flare are demonstrated. Additionally, an adapted method, Femtosecond Laser Activation and Sensing of Hydroxyl (FLASH) is developed and applied to measure velocity in reacting environments such as a Rotating Detonation Engine (RDE). These innovations provide a path forward for improving the spatiotemproal fi?delity of velocity measurements and extending the capability for investigation high-speed reacting and non-reacting flows in hypersonic ground test facilities.

APA, Harvard, Vancouver, ISO, and other styles

26

Hofferth, Jerrod William. "Boundary-Layer Stability and Transition on a Flared Cone in a Mach 6 Quiet Wind Tunnel." Thesis, 2013. http://hdl.handle.net/1969.1/150990.

Full text

Abstract:

A key remaining challenge in the design of hypersonic vehicles is the incomplete understanding of the process of boundary-layer transition. Turbulent heating rates are substantially higher than those for a laminar boundary layer, and large uncertainties in transition prediction therefore demand conservative, inefficient designs for thermal protection systems. It is only through close collaboration between theory, experiment, and computation that the state of the art can be advanced, but experiments relevant to flight require ground-test facilities with very low disturbance levels. To enable this work, a unique Mach 6 low-disturbance wind tunnel, previously of NASA Langley Research Center, is established within a new pressure-vacuum blow-down infrastructure at Texas A&M. A 40-second run time at constant conditions enables detailed measurements for comparison with computation. The freestream environment is extensively characterized, with a large region of low-disturbance flow found to be reliably present for unit Reynolds numbers Re < 11×10^6 m-1. Experiments are performed on a 5º half-angle flared cone model at Re = 10×10^6 m-1 and zero angle of attack. For the study of the second-mode instability, well-resolved boundary-layer profiles of mean and fluctuating mass flux are acquired at several axial locations using hot-wire probes with a bandwidth of 330 kHz. The second mode instability is observed to undergo significant growth between 250 and 310 kHz. Mode shapes of the disturbance agree well with those predicted from linear parabolized stability equation (LPSE) computations. A 17% (40 kHz) disagreement is observed in the frequency for most-amplified growth between experiment and LPSE. Possible sources of the disagreement are discussed, and the effect of small misalignments of the model is quantified experimentally. A focused schlieren deflectometer with high bandwidth (1 MHz) and high signal-to-noise ratio is employed to complement the hot-wire work. The second-mode fundamental at 250 kHz is observed, as well as additional harmonic content not discernible in the hot-wire measurements at two and three times the fundamental. A bispectral analysis shows that after sufficient amplification of the second mode, several nonlinear mechanisms become significant, including ones involving the third harmonic, which have not hitherto been reported in the literature.

APA, Harvard, Vancouver, ISO, and other styles

27

Risius, Steffen. "Development of a time-resolved quantitative surface-temperature measurement technique and its application in short-duration wind tunnel testing." Thesis, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E44D-A.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Hypersonic wind tunnels'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles