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Author: Stanford University. Thermosciences Division. Thermosciences Division
Publisher:
ISBN:
Category :
Languages : en
Pages : 64
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Book Description
Author: Stanford University. Thermosciences Division. Thermosciences Division
Publisher:
ISBN:
Category :
Languages : en
Pages : 64
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 59
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Book Description
For linear stability analysis of high speed boundary layers, we use a direct method for its ability to yield eigenvalues without a priori knowledge and to capture all modes. Temporal linear stability analysis is performed for the 2D boundary layer on a flat plate using the local parallel flow assumption. An estimate of all the eigenvalues is obtained by solving the generalized eigenvalue problem; a local eigenvalue search is used to improve the accuracy of the most unstable eigenvalue. A compact fourth order accurate method is to compute both the mean flow and the most unstable eigenfunction. This method is more efficient than lower order methods. Local grid refinement based on error estimates is useful in providing the accuracy needed for initial conditions for direct numerical simulation of transition. Grid adaptation based on refinement yields better than power law convergence in the mean flow error. (AN).
Author: Xiaolin Zhong
Publisher:
ISBN:
Category :
Languages : en
Pages : 31
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Book Description
The goal of this research project is to develop new advanced numerical methods and to perform direct numerical simulation (DNS) studies of transient hypersonic reacting flows over full 3-D maneuvering vehicles. The DNS tools and supporting theoretical approaches are used to gain new fundamental understanding of transition phenomena of 3-D chemically-reacting hypersonic boundary layers. Our research accomplishments in the report period can be classified into three areas. First, we have developed and validated new efficient and high-order accurate numerical methods for the DNS of 3-D hypersonic reacting boundary layers. The new methods include high-order semi-implicit Runge-Kutta schemes and new upwind high-order finite-difference shock-fitting schemes. These new methods were developed in order to overcome the difficulties associated with the DNS of hypersonic reacting flows with shock waves. Second, we have conducted extensive studies on the stability and receptivity phenomena of hypersonic boundary layers over blunt leading edges and elliptical cross-section blunt cones both by direct numerical simulation and by linear stability analyses. Third, the effects of using Burnett equations for rarefied hypersonic flow computations were investigated.
Author: Kenneth Joseph Franko
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The design of vehicles which travel at hypersonic speeds is strongly determined by drag characteristics and heat transfer. A portion of this drag and heating is due to the boundary layer where viscosity and thermal conductivity are most important. The level of drag and heating depends on whether the boundary layer is laminar or turbulent with the latter leading to higher levels of drag and heating. In addition, as high speed boundary layers transition from laminar to turbulent flow, an overshoot of the heat transfer beyond that of turbulent flow has been observed in experiments. In low disturbance environments, transition to turbulence follows the path of receptivity, linear growth, nonlinear interaction, and finally breakdown to turbulence. The linear growth of disturbances can be determined by linear stability theory. An analysis of the predicted growth rates and integrated growth of linear disturbances for hypersonic boundary layers including thermal and chemical non-equilibrium is undertaken. The sensitivity to different chemical assumptions, transport models and thermal boundary conditions is investigated. A disturbance energy norm is proposed and its corresponding balance equation is derived. This energy norm is then to determine the effect of different terms of the linear stability equations and to compute transient growth for hypersonic laminar boundary layers. DNS (Direct Numerical Simulation) is used to simulate the nonlinear breakdown to turbulence for a variety of transition scenarios for both zero pressure gradient and adverse pressure gradient high-speed flat plate boundary layers in order to investigate the mechanism for the overshoot of heat transfer in transitional hypersonic boundary layers. The initial disturbances are excited through suction and blowing at the wall and their frequencies are chosen based on linear stability theory. Different transition mechanisms are investigated including a pair of oblique waves and 2D and 3D instabilities at higher frequencies which are unique to high speed boundary layers. Oblique breakdown shows a clear overshoot in heat transfer and skin friction and leads to a fully turbulent boundary layer. The alternative scenarios also lead to transition but further downstream and without large overshoots in heat transfer. A detailed analysis of the transitional and turbulent regions is undertaken.
Author: Kenneth F. Stetson
Publisher:
ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 116
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Book Description
This is a survey paper on the subject of hypersonic boundary-layer transition. Part 1 discusses boundary-layer stability theory, hypersonic boundary-layer stability experiments, and a comparison between theory and experiment. Part 2 contains comments on how many configuration and flow parameters influence transition. Part 3 discusses some additional general aspects of transition. Part 4 discusses problems of predicting transition and comments on three prediction methods. Part 5 contains some general guidelines for prediction methodology. Keywords: Boundary layer transition, Boundary layer stability, Hypersonic boundary layers.
Author: Kursat Kara
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 334
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Author: Thorwald Herbert
Publisher:
ISBN:
Category : Aerodynamics, Supersonic
Languages : en
Pages : 24
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Book Description
Author: Hongwu Zhao
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 412
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Book Description
Author: Heath B. Johnson
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
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Book Description
Author: BALLMAN
Publisher: Springer Science & Business Media
ISBN: 1461203791
Category : Technology & Engineering
Languages : en
Pages : 448
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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.
