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Author:
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Languages : en
Pages : 7
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Book Description
This paper presents computational results obtained with the direct simulation Monte Carlo (DSMC) method for several biconic test cases in which shock interactions and flow separation-reattachment are key features of the flow. Recent ground-based experiments have been performed for several biconic configurations and surface heating rate and pressure measurements have been proposed for code validation studies. The present focus is to expand on the current validating activities for a relatively new DSMC code called DS2V that Bird (second author) has developed. Comparisons with experiments and other computations help clarify the agreement currently being achieved between computations and experiments and to identify the range of measurement variability of the proposed validation data when benchmarked with respect to the current computations. For the test cases with significant vibrational nonequilibrium, the effect of the vibrational energy surface accommodation on heating and other quantities is demonstrated.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 7
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Book Description
This paper presents computational results obtained with the direct simulation Monte Carlo (DSMC) method for several biconic test cases in which shock interactions and flow separation-reattachment are key features of the flow. Recent ground-based experiments have been performed for several biconic configurations and surface heating rate and pressure measurements have been proposed for code validation studies. The present focus is to expand on the current validating activities for a relatively new DSMC code called DS2V that Bird (second author) has developed. Comparisons with experiments and other computations help clarify the agreement currently being achieved between computations and experiments and to identify the range of measurement variability of the proposed validation data when benchmarked with respect to the current computations. For the test cases with significant vibrational nonequilibrium, the effect of the vibrational energy surface accommodation on heating and other quantities is demonstrated.
Author: James N. Moss
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ISBN:
Category :
Languages : en
Pages :
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Author: James N. Moss
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ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 30
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This paper describes the results of a numerical study of interacting hypersonic flows at conditions that can be produced in ground-based test facilities. The computations are made with the direct simulation Monte Carlo (DSMC) method of Bird. The focus is on Mach 10 flows about flared axisymmetric configurations, both hollow cylinder flares and double cones. The flow conditions are those for which experiments have been or will be performed in the ONERA R5Ch low-density wind tunnel and the Calspan-University of Buffalo Research Center (CUBRC) Large Energy National Shock (LENS) tunnel. The range of flow conditions, model configurations, and model sizes provides a significant range of shock/shock and shock/boundary layer interactions at low Reynolds number conditions. Results presented will highlight the sensitivity of the calculations to grid resolution, contrast the difference in flow structure for hypersonic cold flows and those of more energetic but still low enthalpy flows, and compare the present results with experimental measurements for surface heating, pressure, and extent of separation.
Author: Kyle J. Higdon
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ISBN:
Category :
Languages : en
Pages : 692
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This work focuses on the development and sensitivity analyses of a direct simulation Monte Carlo (DSMC) code to understand the complex physical processes that occur during hypersonic entry into a rarefied atmosphere. Simulations are performed on 1-dimensional hypersonic shock scenarios that mimic the conditions of high altitude atmospheric entry to Earth and Saturn with the Computation of Hypersonic Ionizing Particles in Shocks (CHIPS) code. To model hypersonic entry problems accurately, the CHIPS code must resolve nonequilibrium flows and account for a number of complex gas dynamics processes at the molecular level. In this thesis, several high temperature models are added to the CHIPS code including charged particle models and electronic excitation. These models are refined using preliminary sensitivity analyses resulting in improved electronic excitation models and a new backward chemical reaction model. The CHIPS simulations completed in this work reproduce rarefied hypersonic shock tube experiments performed in the Electric Arc Shock Tube (EAST) at NASA Ames Research Center. The CHIPS results are post-processed by the NEQAIR line-by-line radiative solver to compare directly to spectra measured experimentally in EAST. The DSMC techniques used to model hypersonic phenomena require numerous experimentally calibrated parameters. Many of these parameters are inferred from lower temperature experiments, resulting in an unknown amount of uncertainty in the simulated results at the extreme conditions of hypersonic flow. A global Monte Carlo sensitivity analysis is performed by simultaneously varying the CHIPS input parameter values to understand the sensitivity of experimentally measured quantities simulated by the CHIPS and NEQAIR codes. The sensitivity of several of these output quantities is used to rank the input parameters, identifying the most important parameters for the simulation of the hypersonic scenario. It was concluded that experimentally measured radiation intensity is most sensitive to the following key processes: N+e−⇌N++e−+e−, NO+N+⇌N+NO+, N2+N⇌N+N+N, N+O⇌NO++e−, N+N⇌N2++e−, and Z [subscript elec] for N, O, and N2+. In the future, this ranking can be used to identify which input parameters should be experimentally investigated, where model improvements could be beneficial, and aid in reducing the parameter space for DSMC calibrations to experimental data.
Author: BERTIN
Publisher: Springer Science & Business Media
ISBN: 1461203759
Category : Technology & Engineering
Languages : en
Pages : 438
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Book Description
These three volumes entitled Advances in Hypersonics contain the Proceedings of the Second and Third Joint US/Europe Short Course in Hypersonics which took place in Colorado Springs and Aachen. The Second Course was organized at the US Air Force Academy, USA in January 1989 and the Third Course at Aachen, Germany in October 1990. The main idea of these Courses was to present to chemists, com puter scientists, engineers, experimentalists, mathematicians, and physicists state of the art lectures in scientific and technical dis ciplines including mathematical modeling, computational methods, and experimental measurements necessary to define the aerothermo dynamic environments for space vehicles such as the US Orbiter or the European Hermes flying at hypersonic speeds. The subjects can be grouped into the following areas: Phys ical environments, configuration requirements, propulsion systems (including airbreathing systems), experimental methods for external and internal flow, theoretical and numerical methods. Since hyper sonic flight requires highly integrated systems, the Short Courses not only aimed to give in-depth analysis of hypersonic research and technology but also tried to broaden the view of attendees to give them the ability to understand the complex problem of hypersonic flight. Most of the participants in the Short Courses prepared a docu ment based on their presentation for reproduction in the three vol umes. Some authors spent considerable time and energy going well beyond their oral presentation to provide a quality assessment of the state of the art in their area of expertise as of 1989 and 1991.
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ISBN:
Category :
Languages : en
Pages : 0
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The combined Direct Simulation Monte Carlo (DSMC) and Monotonic Lagrangian Grid (MLG) methodologies are used on the massively parallel Connection Machines CM-5 to solve for the properties of a low density hypersonic flow through a channel containing a wedge. Numerical issues related to grid generation around the obstacle, the effects of resolution in terms of the simulated to actual particle ratio, and the use of time-averaging to obtain a statistically converged solution are discussed. A method is presented for quantifying the effects of the grid on the solution. The flow field shows many important aerodynamic features, such as shock waves, boundary layers, expansion fan, and their interactions. Since the flow is so rarefied, these structures are diffuse compared to what is expected in a continuum flow. For example, the reattachment shock behind the trailing edge of the wedge degenerates into a diffuse viscous layer. Other low density effects include the velocity slip, which peaks near the leading edges where the density is low, and temperature jump of the gas adjacent to the solid surfaces, which is highest at the entrance of the channel and decreases further downstream. The calculated skin friction and heat transfer agree well with the Reynolds analogy for boundary layer flow. The computed pressure distributions along the wall are consistent with hypersonic viscous theory and other DSMC calculations.
Author: Takashi Ozawa
Publisher:
ISBN:
Category :
Languages : en
Pages : 432
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Author: Bertin
Publisher: Springer Science & Business Media
ISBN: 1461203716
Category : Science
Languages : en
Pages : 280
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Book Description
These three volumes entitled Advances in Hypersonics contain the Proceedings of the Second and Third Joint US/Europe Short Course in Hypersonics which took place in Colorado Springs and Aachen. The Second Course was organized at the US Air Force Academy, USA in January 1989 and the Third Course at Aachen, Germany in October 1990. The main idea of these Courses was to present to chemists, com puter scientists, engineers, experimentalists, mathematicians, and physicists state of the art lectures in scientific and technical dis ciplines including mathematical modeling, computational methods, and experimental measurements necessary to define the aerothermo dynamic environments for space vehicles such as the US Orbiter or the European Hermes flying at hypersonic speeds. The subjects can be grouped into the following areas: Phys ical environments, configuration requirements, propulsion systems (including airbreathing systems), experimental methods for external and internal flow, theoretical and numerical methods. Since hyper sonic flight requires highly integrated systems, the Short Courses not only aimed to give in-depth analysis of hypersonic research and technology but also tried to broaden the view of attendees to give them the ability to understand the complex problem of hypersonic flight. Most of the participants in the Short Courses prepared a docu ment based on their presentation for reproduction in the three vol umes. Some authors spent considerable time and energy going well beyond their oral presentation to provide a quality assessment of the state of the art in their area of expertise as of 1989 and 1991.
Author: Wen-Lan Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721288014
Category :
Languages : en
Pages : 36
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Book Description
This paper presents the results of a numerical study that examines the surface heating discrepancies observed between computed and measured values along a sharp cone. With Mach numbers of an order of 10 and the freestream length Reynolds number of an order of 10 000, the present computations have been made with the direct simulation Monte Carlo (DSMC) method by using the G2 code of Bird. The flow conditions are those specified for two experiments conducted in the Veridian 48-inch Hypersonic Shock Tunnel. Axisymmetric simulations are made since the test model was assumed to be at zero incidence. Details of the current calculations are presented, along with comparisons between the experimental data, for surface heating and pressure distributions. Results of the comparisons show major differences in measured and calculated results for heating distributions, with differences in excess of 25 percent for the two cases examined. Moss, James N. Langley Research Center NASA/TM-2001-211253, NAS 1.15:211253, L-18122
