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  • FLUID MECHANICS AND HEAT TRANSFER
  • 1995-1999  (10)
  • 1950-1954  (1)
  • 1945-1949  (2)
  • 1
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    A study of the vortex flow over 76/40-deg double-delta wing (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A low-speed wind-tunnel study of the flow about a 76/40-deg double-delta wing is described for angles of attack ranging from -10 to 25 deg and Reynolds numbers ranging from 0.5 to 1.5 Million. The study was conducted to provide data for the purpose of understanding the vortical flow behavior and for validating Computational Fluid Dynamics methods. Flow visualization tests have provided insight into the effect of the angle of attack and Reynolds number of the vortex-dominated flow both on and off of the surface of the double-delta wing. Upper surface pressure recordings from pressure orifices and Pressure Sensitive Paint have provided data on the pressures induced by the vortices. Flowfield surveys were carried out at an angle of attack of 10 deg by using a thin 5-hole probe. Numerical solutions of the compressible thin-layer Navier-Stokes equations were conducted and compared to the experimental data.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-195032 , NAS 1.26:195032 , ICASE-95-5 , AIAA PAPER 95-0560
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  • 2
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    Block-structured grids for complex aerodynamic configurations: Current status (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The status of CFD methods based on the use of block-structured grids for analyzing viscous flows over complex configurations is examined. The objective of the present study is to make a realistic assessment of the usability of such grids for routine computations typically encountered in the aerospace industry. It is recognized at the very outset that the total turnaround time, from the moment the configuration is identified until the computational results have been obtained and postprocessed, is more important than just the computational time. Pertinent examples will be cited to demonstrate the feasibility of solving flow over practical configurations of current interest on block-structured grids.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 163-177
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  • 3
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    Extensional flow convecting a reactant undergoing a first order homogeneous reaction and diffusional mass transfer from a sphere at low to intermediate Peclet and Damkohler numbers (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Forced convective diffusion-reaction is considered for viscous axisymmetric extensional convecting velocity in the neighborhood of a sphere. For Peclet numbers in the range 0.1 less than or equal to Pe less than or equal to 500 and for Damkohler numbers increasing with increasing Pe but in the overall range 0.02 less than or equal to Da less than or equal to 10, average and local Sherwood numbers have been computed. By introducing the eigenfunction expansion c(r, Theta) = Sum of c(n)(r)P(n)(cos Theta) into the forced convective diffusion equation for the concentration of a chemical species undergoing a first order homogeneous reaction and by using properties of the Legendre functions Pn(cos Theta), the variable coefficient PDE can be reduced to a system of N + 1 second order ODEs for the radial functions c(sub n)(r), n = 0, 1, 2,..., N. The adaptive grid algorithm of Pereyra and Lentini can be used to solve the corresponding 2(N + 1) first order differential equations as a two-point boundary value problem on 1 less than or equal to r less than or equal to r(sub infinity). Convergence of the expansion for a specific value of N can thus be established and provides 'spectral' behavior as well as the full concentration field c(r, Theta).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, The Sixth Annual Thermal and Fluids Analysis Workshop; p 1-23
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  • 4
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    Volumetric imaging of supersonic boundary layers using filtered Rayleigh scattering background suppression (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: We demonstrate the use of Filtererd Rayleigh Scattering and a 3D reconstruction technique to interrogate the highly three dimensional flow field inside of a supersonic inlet model. A 3 inch by 3 inch by 2.5 inch volume is reconstructed yielding 3D visualizations of the crossing shock waves and of the boundary layer. In this paper we discuss the details of the techniques used, and present the reconstructured 3D images.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 94-0491 , Development of Filtered Rayleigh Scattering for Accurate Measurement of Gas Velocity; 8 p
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  • 5
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    Computational strategies for three-dimensional flow simulations on distributed computer systems (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This research effort is directed towards an examination of issues involved in porting large computational fluid dynamics codes in use within the industry to a distributed computing environment. This effort addresses strategies for implementing the distributed computing in a device independent fashion and load balancing. A flow solver called TEAM presently in use at Lockheed Aeronautical Systems Company was acquired to start this effort. The following tasks were completed: (1) The TEAM code was ported to a number of distributed computing platforms including a cluster of HP workstations located in the School of Aerospace Engineering at Georgia Tech; a cluster of DEC Alpha Workstations in the Graphics visualization lab located at Georgia Tech; a cluster of SGI workstations located at NASA Ames Research Center; and an IBM SP-2 system located at NASA ARC. (2) A number of communication strategies were implemented. Specifically, the manager-worker strategy and the worker-worker strategy were tested. (3) A variety of load balancing strategies were investigated. Specifically, the static load balancing, task queue balancing and the Crutchfield algorithm were coded and evaluated. (4) The classical explicit Runge-Kutta scheme in the TEAM solver was replaced with an LU implicit scheme. And (5) the implicit TEAM-PVM solver was extensively validated through studies of unsteady transonic flow over an F-5 wing, undergoing combined bending and torsional motion. These investigations are documented in extensive detail in the dissertation, 'Computational Strategies for Three-Dimensional Flow Simulations on Distributed Computing Systems', enclosed as an appendix.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NIPS-95-05591 , NASA-CR-199562 , NAS 1.26:199562
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  • 6
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    DSMC calculations for 70-deg blunted cone at 3.2 km/s in nitrogen (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Numerical results obtained with the direct simulation Monte Carlo (DSMC) method are presented for Mach 15.6 nitrogen flow about a 70-deg spherically blunted cone at zero incidence. This flow condition is one of several generated in the Large Energy National Shock (LENS) tunnel during tests of a 15.24 cm diameter model with an afterbody sting. The freestream Knudsen number, based on model diameter, is 0.0023. The focus of the DSMC calculations is to characterize the near wake flow under conditions where rarefaction effects may influence afterbody aerothermal loads. This report provides information concerning computational details along with flowfield and surface quantities. Calculations show that the flow enveloping the test model is in thermal nonequilibrium and a sizable vortex develops in the near wake. Along the model baseplane the heating rates are about 0.6 percent of the forebody stagnation value while the maximum heating along the sting is about 4.2 percent of the forebody stagnation value. Comparison of a Navier-Stokes solution with the present calculations show good agreement for surface heating, pressure, and skin friction results.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-109181 , NAS 1.15:109181
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  • 7
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    A method for numerically calculating the area and distribution of water impingement on the leading edge of an airfoil in a cloud (1947)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NACA-TN-1397
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  • 8
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    The calculation of the heat required for wing thermal ice prevention in specified icing conditions (1947)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NACA-TN-1472
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  • 9
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    An Empirical Method Permitting Rapid Determination of the Area, Rate and Distribution of Water-Drop Impingement on an Airfoil of Arbitrary Section at Subsonic Speeds (1951)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An empirical method for the determination of the area, rate, and distribution of water-drop impingement on airfoils of arbitrary section is presented. The procedure represents an initial step toward the development of a method which is generally applicable in the design of thermal ice-prevention equipment for airplane wing and tail surfaces. Results given by the proposed empirical method are expected to be sufficiently accurate for the purpose of heated-wing design, and can be obtained from a few numerical computations once the velocity distribution over the airfoil has been determined. The empirical method presented for incompressible flow is based on results of extensive water-drop. trajectory computations for five airfoil cases which consisted of 15-percent-thick airfoils encompassing a moderate lift-coefficient range. The differential equations pertaining to the paths of the drops were solved by a differential analyzer. The method developed for incompressible flow is extended to the calculation of area and rate of impingement on straight wings in subsonic compressible flow to indicate the probable effects of compressibility for airfoils at low subsonic Mach numbers.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NACA-TN-2476
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  • 10
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    Parallel Navier-Stokes computations on shared and distributed memory architectures (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We study a high order finite difference scheme to solve the time accurate flow field of a jet using the compressible Navier-Stokes equations. As part of our ongoing efforts, we have implemented our numerical model on three parallel computing platforms to study the computational, communication, and scalability characteristics. The platforms chosen for this study are a cluster of workstations connected through fast networks (the LACE experimental testbed at NASA Lewis), a shared memory multiprocessor (the Cray YMP), and a distributed memory multiprocessor (the IBM SPI). Our focus in this study is on the LACE testbed. We present some results for the Cray YMP and the IBM SP1 mainly for comparison purposes. On the LACE testbed, we study: (1) the communication characteristics of Ethernet, FDDI, and the ALLNODE networks and (2) the overheads induced by the PVM message passing library used for parallelizing the application. We demonstrate that clustering of workstations is effective and has the potential to be computationally competitive with supercomputers at a fraction of the cost.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-106823 , ICOMP-94-32 , E-9369 , NAS 1.15:106823 , AIAA PAPER 95-0577 , Aerospace Sciences Meeting and Exhibit; Jan 09, 1995 - Jan 12, 1995; Reno, NV; United States
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