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  • 1
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    Nonlinear effects for the Taylor column for a hemisphere (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: When a flow is forced past an obstacle in a rapidly rotating fluid, a Taylor column forms. This is defined by a set of vertical detached shear layers circumscribing the obstacle which provide the smooth transition from an external inviscid potential flow to a stagnant core above the obstacle. For a hemispherical object, the main adjustment takes place in an external E to the 1/4 power layer and an internal E to the 2/7 power layer; here, the nonlinear flow in these layers is investigated. The problem in the E to the 1/4 power layer is identical to a problem occurring in magnetohydrodynamic flow; in addition, some features of the magnetohydrodynamic problem have been resolved. Numerical solutions are obtained for the steady nonlinear external E to the 1/4 power layer flow up to the point where unsteady flow separation from the Taylor column is imminent. The response of the internal E to the 2/7 power layer to the flow in the E to the 1/4 power layer is calculated, and the results suggest that the internal shear layer is unlikely to play any significant role in the separation process
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids; 19; Nov. 197
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  • 2
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    On the application of algebraic turbulence models to high Mach number flows (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In this paper the implementation of embedded-function algorithms for conventional algebraic turbulence models is described; using this methodology it is shown that the entire wall layer may be removed from the calculation algorithm (as well as near-wall mixing-length models) with no degradation in the accuracy of predicted results for skin friction. Various difficulties that are associated with the application of conventional algebraic models in high-speed flows are discussed. Alternative algebraic models are proposed which are cast in terms of the Howarth-Dorodnitsyn variable and which lead to a simple 'law of the wall' for both velocity and total enthalpy.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 91-0616
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  • 3
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    Wall layer models for the calculation of velocity and heat transfer in turbulent boundary layers (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In the computation of turbulent boundary-layer flows and internal flows, a substantial amount of mesh points and computational effort is required to adequately resolve the intense temperature and velocity profile variations in the near wall region. In this study, analytical profile approximations are obtained for the mean velocity and temperature distribution in the wall layer; these profiles are based upon consideration of the observed coherent structure of the time-dependent wall-layer flow. The profile approximations are relatively simple analytical formulae which satisfy all the required compatibility conditions at the wall and the logarithmic behavior at the edge of the wall layer. The Reynolds analogy for heat transfer is not used in the present theory. A general method for utilizing the present wall-layer profile models in a prediction method is indicated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 86-0213
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  • 4
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    Computation of three-dimensional turbulent boundary layers with heat transfer in a plane of symmetry using embedded wall-layer functions (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In the calculation of turbulent boundary layers, a large number of mesh points are required to adequately resolve the intense variation in the velocity and enthalpy in the near-wall region. A substantial reduction in computational effort may be realized by representing the velocity and enthalpy profiles in the wall layer by analytical embedded functions. The effectively inviscid flow in the outer part of the boundary layer may then be resolved by employing a relatively coarser mesh. To obtain complete profiles, the outer numerical solution is matched asymptotically to the inner wall-layer analytical solution. To date, this approach has been restricted to two-dimensional flows; in the present study, a method which may be utilized for turbulent boundary layers with heat transfer in a plane of symmetry is developed as a first step in the application of the embedded-function method to full three-dimensional flows. The present method uses only about half as many mesh points as that required in a conventional procedure, which calculates the flow all the way to the wall, but there is no degradation in accuracy of the computed results.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-0307
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  • 5
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    Embedded function methods for compressible high speed turbulent flow (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This is the final report on the work performed on the grant 'Embedded Function Methods for Compressible High Speed Turbulent Flow' carried out at Lehigh University during the contract period from September, 1987, to October of 1991. Work has continued at Lehigh on this project on an unfunded basis to the present. The original proposed work had two separate thrusts which were associated with developing embedded function methods in order to obviate the need to expend computational resources on turbulent wall layers in Navier Stokes and boundary-layer calculations. Previous work on the incompressible problem had indicated that this could be done successfully for two-dimensional and three-dimensional incompressible flows. The central objective here was to extend the basic approach to the high speed compressible problem.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-196936 , NAS 1.26:196936
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  • 6
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    Asymptotic structure and similarity solutions for three-dimensional turbulent boundary layers (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The asymptotic structure of the three-dimensional turbulent boundary layer is investigated in the limit of large Reynolds numbers. A self-consistent, but relatively complex, two-layer structure exists and the simplest situation, corresponding to a plane of symmetry, is considered in this paper as a first step. The adjustment of the streamwise velocity to relative rest, through an outer defect layer and then an inner wall layer, is similar to that in two-dimensional flow. The adjustment of the cross-streamwise velocity is more complicated and it is shown that two terms in the expansion are required to obtain useful results, and in particular to obtain the velocity skew angle at the wall near the symmetry plane. The conditions under which self-similarity is achieved near a plane of symmetry are investigated. A set of ordinary differential equations is developed which describe the streamwise and cross-streamwise velocities near a plane of symmetry in a self-similar flow through two orders of magnitude. Calculated numerical solutions of these equations yield trends which are consistent with experimental observations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 89-1863
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  • 7
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    An embedded function approach for turbulent flow prediction (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In conventional prediction methods for turbulent flow influence on surface properties, very small mesh sizes and considerable computational effort is required to adequately resolve the intense velocity and temperature profile variations that occur in the wall-layer region. In this study, an approach is described wherein an outer region numerical solution is smoothly matched to a set of embedded analytic profile functions in the near-wall region; these wall-layer profile functions having been derived through consideration of the coherent structure of the time-dependent near-wall flow provide analytic expressions for the mean velocity and enthalpy profiles in the wall layer. The concept is demonstrated through example applications to turbulent boundary-layer flows in two dimensions. The technique is shown to be very efficient and it is demonstrated that a reduction of approximately half the mesh points across the 2-D layer may be realized (as compared to conventional methods) with no degradation in accuracy.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 87-1464
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  • 8
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    Wall-layer eruptions in turbulent flows (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The near-wall region of a turbulent flow is investigated in the limit of large Reynolds numbers. When low-speed streaks are present, the governing equations are shown to be of the boundary-layer type. Physical processes leading to local breakdown and a strong interaction with the outer region are considered. It is argued that convected vortices, predominantly of the hairpin type, will provoke eruptions and regenerative interactions with the outer region.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-102362 , E-5078 , ICOMP-89-26 , NAS 1.15:102362
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  • 9
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    Embedded function methods for compressible high speed turbulent flow (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Fundamental issues relating to compressible turbulent flow are addressed. The focus has been on developing methods and testing concepts for attached flows rather than trying to force a conventional law of the wall into a zone of backflow. Although the dynamics of the near-wall flow in an attached turbulent boundary layer are relatively well documented, the dynamical features of a zone of reversed turbulent flow are not, nor are they well understood. Incompressibility introduces effects and issues that have been dealt with only marginally in the literature, therefore, the present work has been focussed on attached high-speed flows. The wall function method has been extended up through the supersonic to hypersonic speeds. Algorithms have been successfully introduced into the code that calculates the flow all the way to the wall, and testing is being carried out for progressively more complex flow situations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-186131 , NAS 1.26:186131
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  • 10
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    Aerodynamic characteristics of GD B-15B booster during cruise and landing M equals 0.2 (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Aerodynamic characteristics of scale model of space shuttle booster at cruise and landing speed of Mach 0.2
    Keywords: SPACE VEHICLES
    Type: NASA-CR-119974 , DMS-DR-1109
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