Characteristics of Turbulent Boundary Layers along a Hypersonic Vehicle PDF Download
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Author: Nicholas J. DiGregorio
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Nicholas J. DiGregorio
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Antonio Ferri
Publisher:
ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 130
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Book Description
The main research effort has been concerned in trying to obtain a better understanding as well as to give some insight of the turbulent boundary layer characteristics such that exist on future hypersonic vehicles. The major portion of the experimental effort has been performed at the New York University high Reynolds number Mach 6 facility. In order to understand in detail the boundary layer characteristics, detailed flow field mapping has been performed in several of the research efforts. Several problems requiring semiviscous inviscid interaction problems have been solved by utilizing the vorticity techniques. In addition, research has been performed in a spectrum of related fields. (Author).
Author: PILBUM KIM
Publisher:
ISBN:
Category :
Languages : en
Pages : 112
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Understanding non-equilibrium effects of hypersonic turbulent boundary layers is essential in order to build cost efficient and reliable hypersonic vehicles. It is well known that non-equilibrium effects on the boundary layers are notable, but our understanding of the effects are limited. The overall goal of this study is to improve the understanding of non-equilibrium effects on hypersonic turbulent boundary layers. A new code has been developed for direct numerical simulations of spatially developing hypersonic turbulent boundary layers over a flat plate with finite-rate reactions. A fifth-order hybrid weighted essentially non-oscillatory scheme with a low dissipation finite-difference scheme is utilized in order to capture stiff gradients while resolving small motions in turbulent boundary layers. The code has been validated by qualitative and quantitative comparisons of two different simulations of a non-equilibrium flow and a spatially developing turbulent boundary layer. With the validated code, direct numerical simulations of four different hypersonic turbulent boundary layers, perfect gas and non-equilibrium flows of pure oxygen and nitrogen, have been performed. In order to rule out uncertainties in comparisons, the same inlet conditions are imposed for each species, and then mean and turbulence statistics as well as near-wall turbulence structures are compared at a downstream location. Based on those comparisons, it is shown that there is no direct energy exchanges between internal and turbulent kinetic energies due to thermal and chemical non-equilibrium processes in the flow field. Instead, these non-equilibria affect turbulent boundary layers by changing the temperature without changing the main characteristics of near-wall turbulence structures. This change in the temperature induces the changes in the density and viscosity and the mean flow fields are then adjusted to satisfy the conservation laws. The perturbation fields are modified according to the adjusted mean field and the conservation laws. From this, it can be concluded that Morkovin's hypothesis is still valid with thermal and chemical non-equilibrium, and the effects of non-equilibrium can be compensated by taking the variations of mean density and viscosity into account. In the present study, it is shown that a semi-local scale is a proper scale that can account for the non-equilibrium effects.
Author: William H. Dorrance
Publisher: Courier Dover Publications
ISBN: 048681288X
Category : Technology & Engineering
Languages : en
Pages : 353
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Designed for advanced undergraduate and graduate courses in modern boundary-layer theory, this frequently cited work offers a self-contained treatment of theories for treating laminar and turbulent boundary layers of reacting gas mixtures. 1962 edition.
Author: Michael S. Holden
Publisher:
ISBN:
Category :
Languages : en
Pages : 326
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This report describes a series of studies to investigate the underlying aero-thermodynamic phenomena which influence the accuracy and survivability of Ballistic Reentry Vehicles. The influence of transition on the aerodynamic characteristics of slender RV's is discussed first. Here the primary interest was in determining the influence of the angle of attack and bluntness ratio on the shape of the transition front and the properties of these regions. A detailed study was made of the influence of asymmetric nose bluntness on the pressure and heat transfer distribution over the cone frustum, and the contribution of the cone frustum to the forces and moments experienced by the total configuration. Particular emphasis was placed on determining the destabilizing effect of the NRV and RTE nose shapes recovered from flight tests. It was found that nose shaping can significantly change the pressure distribution over the conical frustum relative to a spherically-capped configuration; this effect must be accounted for if accurate predictions of cone stability at low altitude are required. Detailed heat transfer and pressure measurements made on a model of the NRV nose shape for test conditions indicated that regions of flow separation and shock wave boundary-layer interaction were induced over this configuration and produced heating rates in the reattachment regions on the ablated conical frustum of up to three times those recorded at the stagnation point on the spherical nose tip.
Author: D. K. Patel
Publisher:
ISBN:
Category : Aerodynamics, Supersonic
Languages : en
Pages : 68
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Author: Arnold Polak
Publisher:
ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 56
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Book Description
Results of a study of hypersonic-turbulent boundary-layer separation over axisymmetric bodies are presented. Pressure, heat-transfer and flow visualization data were obtained for a cone-cylinder-flare configuration. The experimental data were correlated with a theoretical prediction. (Author).
Author: Henry G. Lew
Publisher:
ISBN:
Category : Acoustic radiation pressure
Languages : en
Pages : 80
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Book Description
This investigation was conducted to determine the ability to predict acoustic loads on supersonic/hypersonic structures with attached and separated flows. These techniques, which are based on laws governing boundary layer flow and shock physics, provide scaling parameters to extrapolate ground test results to flight conditions and can be used for the design process. It was determined that efficient, thin aerodynamic control surfaces generally produce weak shock/ boundary layers interactions where the rms pressure levels are not significantly augmented over attached flow levels. The exception to these findings include: (1) corner flow (inlet and stabilizers); (2) bow shock interaction (inlet and stabilizer); and (3) shock on shock/boundary layer (cowl/inlet, bow shock/inlet, and bow/inlet/cowl). Other potential interactions that may cause problems have been identified as: (1) axial offset (non-common intersection of two planes); (2) shock interaction with laminar boundary layers; (3) angle of attack effects; and (4) viscous approach flow along ramp leading to the inlet. An experimental program is recommended to address these issues; in particular for M> 3 where acoustic data does not exist. These experiments should be conducted in a facility that allows for preliminary test runs to ensure desired results. The WRDC Mach 3 and Mach 12 facilities are recommended for a Phase II investigation. Results of the Phase I and II efforts will provide the ability to design structures subject to complex flow interactions such as the National AeroSpace Plane.
Author: Alexander J. Smits
Publisher: Springer Science & Business Media
ISBN: 0387263055
Category : Science
Languages : en
Pages : 418
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Book Description
A good understanding of turbulent compressible flows is essential to the design and operation of high-speed vehicles. Such flows occur, for example, in the external flow over the surfaces of supersonic aircraft, and in the internal flow through the engines. Our ability to predict the aerodynamic lift, drag, propulsion and maneuverability of high-speed vehicles is crucially dependent on our knowledge of turbulent shear layers, and our understanding of their behavior in the presence of shock waves and regions of changing pressure. Turbulent Shear Layers in Supersonic Flow provides a comprehensive introduction to the field, and helps provide a basis for future work in this area. Wherever possible we use the available experimental work, and the results from numerical simulations to illustrate and develop a physical understanding of turbulent compressible flows.
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.
