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  • AERODYNAMICS  (11)
  • COMMUNICATIONS AND RADAR  (3)
  • 2020-2022
  • 1975-1979  (14)
  • 1
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    A generalized vortex lattice method for subsonic and supersonic flow applications (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: If the discrete vortex lattice is considered as an approximation to the surface-distributed vorticity, then the concept of the generalized principal part of an integral yields a residual term to the vorticity-induced velocity field. The proper incorporation of this term to the velocity field generated by the discrete vortex lines renders the present vortex lattice method valid for supersonic flow. Special techniques for simulating nonzero thickness lifting surfaces and fusiform bodies with vortex lattice elements are included. Thickness effects of wing-like components are simulated by a double (biplanar) vortex lattice layer, and fusiform bodies are represented by a vortex grid arranged on a series of concentrical cylindrical surfaces. The analysis of sideslip effects by the subject method is described. Numerical considerations peculiar to the application of these techniques are also discussed. The method has been implemented in a digital computer code. A users manual is included along with a complete FORTRAN compilation, an executed case, and conversion programs for transforming input for the NASA wave drag program.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2865 , LR-28112
    Format: application/pdf
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  • 2
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    The finite element method in low speed aerodynamics (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The finite element procedure is shown to be of significant impact in design of the 'computational wind tunnel' for low speed aerodynamics. The uniformity of the mathematical differential equation description, for viscous and/or inviscid, multi-dimensional subsonic flows about practical aerodynamic system configurations, is utilized to establish the general form of the finite element algorithm. Numerical results for inviscid flow analysis, as well as viscous boundary layer, parabolic, and full Navier Stokes flow descriptions verify the capabilities and overall versatility of the fundamental algorithm for aerodynamics. The proven mathematical basis, coupled with the distinct user-orientation features of the computer program embodiment, indicate near-term evolution of a highly useful analytical design tool to support computational configuration studies in low speed aerodynamics.
    Keywords: AERODYNAMICS
    Type: NASA-CR-143190 , TR-75-T5
    Format: application/pdf
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  • 3
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    Analytical study of mixing and reacting three-dimensional supersonic combustor flow fields (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analytical investigation is presented of mixing and reacting hydrogen jets injected from multiple orifices transverse and parallel to a supersonic airstream. The COMOC computer program, based upon a finite-element solution algorithm, was developed to solve the governing equations for three-dimensional, turbulent, reacting, boundary-region, and confined flow fields. The computational results provide a three-dimensional description of the velocity, temperature, and species-concentration fields downstream of hydrogen injection. Detailed comparisons between cold-flow data and results of the computational analysis have established validity of the turbulent-mixing model based on the elementary mixing-length hypothesis. A method is established to initiate computations for reacting flow fields based upon cold-flow correlations and the appropriate experimental parameters of Mach number, injector spacing, and pressure ratio. Key analytical observations on mixing and combustion efficiency for reacting flows are presented and discussed.
    Keywords: AERODYNAMICS
    Type: Aerodynamic Analyses Requiring Advanced Computers, Pt. 1; p 251-315
    Format: application/pdf
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  • 4
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    Finite element analysis of low speed viscous and inviscid aerodynamic flows (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A weak interaction solution algorithm was established for aerodynamic flow about an isolated airfoil. Finite element numerical methodology was applied to solution of each of differential equations governing potential flow, and viscous and turbulent boundary layer and wake flow downstream of the sharp trailing edge. The algorithm accounts for computed viscous displacement effects on the potential flow. Closure for turbulence was accomplished using both first and second order models. The COMOC finite element fluid mechanics computer program was modified to solve the identified equation systems for two dimensional flows. A numerical program was completed to determine factors affecting solution accuracy, convergence and stability for the combined potential, boundary layer, and parabolic Navier-Stokes equation systems. Good accuracy and convergence are demonstrated. Each solution is obtained within the identical finite element framework of COMOC.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2908 , COMOC-77TR-2
    Format: application/pdf
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  • 5
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    An interaction solution algorithm for viscous aerodynamic performance prediction (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A weak-interaction solution algorithm is established for aerodynamic flow field prediction about an isolated airfoil. It requires numerical solution of differential equations governing potential flow, viscous and turbulent boundary layer flow, and the turbulent wake flow downstream of a trailing edge. The algorithm accounts for computed viscous displacement effects on the potential flow. These in turn alter the viscous flow through imposed pressure gradients. Closure for turbulence is accomplished using a second order model. Numerical evaluations assess factors affecting solution accuracy, convergence and stability for the combined potential, boundary layer, and parabolic Navier-Stokes equation systems as solved using a finite element algorithm.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 78-153 , Aerospace Sciences Meeting; Jan 16, 1978 - Jan 18, 1978; Huntsville, AL
    Format: text
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  • 6
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    A numerical solution algorithm for prediction of turbulent aerodynamic corner flows (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A numerical solution algorithm is established for prediction of subsonic turbulent three-dimensional flows in aerodynamic configuration juncture regions. In concert with a complete three-dimensional exterior potential flow solution, the developed parabolic algorithm yields prediction of the details of the corner region flowfield. Turbulence closure is established using the complete Reynolds stress. Pressure coupling is accomplished using the concepts of complementary and particular solutions to a Poisson equation. Numerical results for three-dimensional turbulent flow in the juncture of two intersecting parabolic arc airfoils are presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 79-0073 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 15, 1979 - Jan 17, 1979; New Orleans, LA
    Format: text
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  • 7
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    Concepts for 18/30 GHz satellite communication system study. Executive summary (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An examination of a multiplicity of interconnected parameters ranging from specific technology details to total system economic costs for satellite communication systems at the 18/30 GHz transmission bands are presented. It was determined that K sub A band systems can incur a small communications outage during very heavy rainfall periods and that reducing the outage to zero would lead to prohibitive system costs. On the other hand, the economics of scale, ie, one spacecraft accommodating 2.5 GHz of bandwidth coupled with multiple beam frequency reuse, leads to very low costs for those users who can tolerate the 5 to 50 hours per year of downtime. A multiple frequency band satellite network can provide the ultimate optimized match to the consumer performance/economics demands.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159680 , WDL-TR8457
    Format: application/pdf
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  • 8
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    Concepts for 18/30 GHz satellite communication system, volume 1 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Concepts for 18/30 GHz satellite communication systems are presented. Major terminal trunking as well as direct-to-user configurations were evaluated. Critical technologies in support of millimeter wave satellite communications were determined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159625-VOL-1 , WDL-TR8457-VOL-1
    Format: application/pdf
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  • 9
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    Concepts for 18/30 GHz satellite communication system, volume 1A: Appendix (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The following are appended: (1) Propagation phenomena and attenuation models; (2) Models and measurements of rainfall patterns in the U.S.; (3) Millimeter wave propagation experiments; (4) Comparison of the theory and Millimeter wave propagation experiments; (4) Comparison of theory and experiment; (5) A practical rain attenuation model for CONUS; (6) Space diversity; (7) Values of attenuation for selected U.S. cities; and (8) Additional considerations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159625-VOL-1A , WDL-TR8457-VOL-1A
    Format: application/pdf
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  • 10
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    Numerical prediction of three-dimensional juncture region flow using the parabolic Navier-Stokes equations (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A numerical solution algorithm is established for prediction of subsonic turbulent three-dimensional flows in aerodynamic configuration juncture regions. A turbulence closure model is established using the complete Reynolds stress. Pressure coupling is accomplished using the concepts of complementary and particular solutions to a Poisson equation. Specifications for data input juncture geometry modification are presented.
    Keywords: AERODYNAMICS
    Type: NASA-CR-159024 , COMOC-78TR-3
    Format: application/pdf
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