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  • Organic Chemistry  (1,807)
  • FLUID MECHANICS AND HEAT TRANSFER  (1,464)
  • 2010-2014
  • 1990-1994  (3,271)
  • 1992  (1,747)
  • 1990  (1,524)
Collection
Keywords
Publisher
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  • 2010-2014
  • 1990-1994  (3,271)
Year
  • 1
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    Finite difference solution for transient radiative cooling of a conducting semitransparent square region (1992)
    In:  Other Sources
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    Publication Date: 2011-12-09
    Description: Transient solutions were obtained for a square region of heat conducting semitransparent material cooling by thermal radiation. The region is in a vacuum environment, so energy is dissipated only by radiation from within the medium leaving through its boundaries. The effect of heat conduction during the transient is to partially equalize the internal temperature distribution. As the optical thickness of the region is increased, the temperature gradients increase near the boundaries and corners, unless heat conduction is large. The solution procedure must provide accurate temperature distributions in these regions to prevent error in the calculated radiation losses. Two-dimensional numerical Gaussian integration is used to obtain the local radiative source term. A finite difference procedure with variable space and time increments is used to solve the transient energy equation. Variable spacing was used to concentrate grid points in regions with large temperature gradients.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal of Heat and Mass Transfer (ISSN 0017-9310); 35; 10; p. 2579-2592.
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  • 2
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    Direct numerical simulations of a spatially developing plane wake (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: In the present paper, direct numerical methods by which to simulate the spatially developing free shear flows in the transitional region are described and the numerical results of a spatially developing plane wake are presented. The incompressible time-dependent Navier-Stokes equations were solved using Pade finite difference approximations in the streamwise direction, a mapped pseudospectral Fourier method in the cross-stream direction, and a third-order compact Runge-Kutta scheme for time advancement. The unstable modes of the Orr-Sommerfeld equations were used to perturb the inlet of the wake. Statistical analyses were performed and some numerical results were compared with experimental measurements. When only the fundamental mode is forced, the energy spectra show amplification of the fundamental and its higher harmonics. In this case, unperturbed alternate vortices develop in the saturation region of the wake. The phase jitter around the fundamental frequency plays a critical role in generating vortices of random shape and spacing. Large- and small-scale distortions of the fundamental structure are observed. Pairing of vortices of the same sign is observed, as well as vortex coupling of vortices of the opposite sign.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: JSME International Journal, Series II (ISSN 0914-8817); 35; 4; p. 543-548.
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  • 3
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    Thermal radiation heat transfer (3rd revised and enlarged edition) (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: This book first reviews the overall aspects and background information related to thermal radiation heat transfer and incorporates new general information, advances in analytical and computational techniques, and new reference material. Coverage focuses on radiation from opaque surfaces, radiation interchange between various types of surfaces enclosing a vacuum or transparent medium, and radiation including the effects of partially transmitting media, such as combustion gases, soot, or windows. Boundary conditions and multiple layers are discussed with information on radiation in materials with nonunity refractive indices.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ; 1090 p.
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  • 4
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    The development of a turbulent junction vortex system (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The growth and development of a horseshoe vortex system in an incompressible, three-dimensional turbulent junction flow were investigated experimentally. A streamlined cylinder mounted with its axis normal to a flat surface was used to generate the junction vortex flow. The flow environment was characterized by a body Reynolds number of 183,000, based on the leading edge diameter of the streamlined cylinder. The study included surface flow visualizations, surface pressure measurements, and mean flow measurements of total pressure, static pressure, and velocity distributions in three planes around the base of the streamlined cylinder, and in two planes in the wake flow. Some characterizations of vortex properties based on the measured mean cross-flow velocity components are presented. The results show the presence of a single large, dominant vortex, with strong evidence of a very small corner vortex in the junction between the cylinder and the flat surface. The center of the dominant vortex drifts away from both the body and the flat surface as the flow develops along and downstream of the body. The growth and development of the core of the large, dominant vortex are documented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME, Transactions, Journal of Fluids Engineering (ISSN 0098-2202); 114; 4; p. 559-565.
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  • 5
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    Fully coupled resonant-triad interaction in an adverse-pressure-gradient boundary layer (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The nonlinear resonant-triad interaction, proposed by Raetz (1959), Craik (1971), and others for a Blasius boundary layer, is analyzed here for an adverse-pressure-gradient boundary layer. We assume that the adverse pressure gradient is in some sense weak and, therefore, that the instability growth rate is small. This ensures that there is a well-defined critical layer located somewhere within the flow and that the nonlinear interaction is effectively confined to that layer. The initial interaction is of the parametric resonance type, even when the modal amplitudes are all of the same order. This means that the oblique instability waves exhibit faster than exponential growth and that the growth rate of the two-dimensional mode remains linear. However, the interaction and the resulting growth rates become fully coupled, once oblique-mode amplitudes become sufficiently large, but the coupling terms are now quartic, rather than quadratic as in the Craik (1971) analysis. More importantly, however, new nonlinear interactions, which were not present in the Craik-type analyses, now come into play. These interactions eventually have a dominant effect on the instability wave development.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); p. 523-551.
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  • 6
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    Thermocapillary motion of bubbles and drops (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An account is given of interface-driven motions of drops and bubbles. It is shown that even in the simplest cases, theory predicts exotic flow topologies. Attention is given to several unsolved problems that must be addressed both theoretically and experimentally.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: In: Microgravity fluid mechanics; Proceedings of the IUTAM Symposium, Bremen, Germany, Sept. 2-6, 1991 (A93-41676 17-34); p. 393-403.
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  • 7
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    Mixing and chemical reaction in sheared and nonsheared homogeneous turbulence (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Direct numerical simulations were made to examine the local structure of the reaction zone for a moderately fast reaction between unmixed species in decaying, homogeneous turbulence and in a homogeneous turbulent shear flow. Pseudospectral techniques were used in domains of 64 exp 3 and higher wavenumbers. A finite-rate, single step reaction between non-premixed reactants was considered, and in one case temperature-dependent Arrhenius kinetics was assumed. Locally intense reaction rates that tend to persist throughout the simulations occur in locations where the reactant concentration gradients are large and are amplified by the local rate of strain. The reaction zones are more organized in the case of a uniform mean shear than in isotropic turbulence, and regions of intense reaction rate appear to be associated with vortex structures such as horseshoe vortices and fingers seen in mixing layers. Concentration gradients tend to align with the direction of the most compressive principal strain rate, more so in the isotropic case.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Fluid Dynamics Research (ISSN 0169-5983); 10; 4-6; p. 273-297.
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  • 8
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    Convective effects during the physical vapor transport process. I - Thermal convection (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The effects of convection on diffusive-convective physical vapor transport process are examined computationally. We analyze conditions ranging from typical laboratory conditions to conditions achievable only in a low gravity environment. This corresponds to thermal Rayleigh numbers Ra(T) ranging from 1.80 to 1.92 x 10 exp 6. Our results indicate that the effect of the sublimation and condensation fluxes at the boundaries is 10 increase the threshold of instability. For typical ground based conditions time dependent oscillatory convection can occur. This results in nonuniform temperature and concentration gradients at the crystal interface. Spectral analysis of the flow field shows regions of both periodic and quasi-periodic states. Low gravity conditions can effectively reduce convective effects, thus resulting in uniform temperature and concentration gradients at the interface, a desirable condition for crystal growth.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Materials Processing & Manufacturing Science (ISSN 1061-0656); p. 83-104.
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  • 9
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    Point-implicit relaxation strategies for viscous, hypersonic flows (1992)
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    Publication Date: 2011-08-24
    Description: An upwind-biased, point-implicit relaxation algorithm for obtaining the numerical solution to the governing equations for 3D, viscous, hypersonic flows in chemical and thermal nonequilibrium is described. The algorithm is derived using a finite-volume formulation in which the inviscid components of flux across cell walls are described with a modified Roe's averaging and Harten's entropy fix with second-order corrections based on Yee's symmetric total variation diminishing scheme. Newton relaxation of the fully coupled equation set is employed on a cell-to-cell basis. Under-relaxation of the inviscid and over-relaxation of the viscous contributions to the residual are implemented. Computational work is easily partitioned among many processors in an asynchronous, dynamic mode for convergence acceleration. An overview of the physical models employed herein for thermochemical nonequilibrium is included. Several test cases and comparisons with experimental data are presented involving hypersonic flow over blunt bodies which illustrate the qualitative and quantitative capabilities of this approach.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: In: Computational methods in hypersonic aerodynamics (A93-49521 21-02); p. 115-151.
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  • 10
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    Transition of oscillatory flow in tubes - An empirical model for application to Stirling engines (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Attention is given to an empirical model for transition to turbulence in oscillatory flows in straight tubes. Designed after a correlation for transition of a boundary layer on a flat plate, the model yields the laminar flow momentum thickness Reynolds number that must be met before transition to turbulence will occur. The transition point is located by comparing this to the actual momentum thickness Reynolds number. A scheme is proposed for estimating the momentum thickness Reynolds number in terms of the position within the cycle, the maximum value of the diameter Reynolds within the cycle, Re(max), and the dimensionless frequency, Valensi number. Results from an experimental study of oscillatory flow in a tube are employed to develop the model. When the flow is determined to be turbulent, it is proposed that a fully-developed, steady flow friction coefficient be applied. When the flow is laminar, the assumption of fully developed flow cannot be made; thus, a method is suggested for estimating the friction factor.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 5 (A93-25851 09-44); p. 5.495-5.502.
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