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  • Articles
  • Other Sources  (11)
  • FLUID MECHANICS AND HEAT TRANSFER  (6)
  • AERODYNAMICS  (5)
  • 1995-1999
  • 1985-1989  (11)
  • 1980-1984
  • 1965-1969
  • 1989  (7)
  • 1985  (4)
Collection
  • Articles
  • Other Sources  (11)
Source
Keywords
Years
  • 1995-1999
  • 1985-1989  (11)
  • 1980-1984
  • 1965-1969
Year
  • 1
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    Dynamics of face and annular seals with two-phase flow (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A detailed study was made of face and annular seals under conditions where boiling, i.e., phase change of the leaking fluid, occurs within the seal. Many seals operate in this mode because of flashing due to pressure drop and/or heat input from frictional heating. High pressure, water pumps, industrial chemical pumps, and cryogenic pumps are mentioned as a few of many applications. The initial motivation was the LOX-GOX seals for the space shuttle main engine, but the study was expanded to include any face or annular seal where boiling occurs. Some of the distinctive behavior characteristics of two-phase seals were discussed, particularly their axial stability. While two-phase seals probably exhibit instability to disturbances of other degrees of freedom such as wobble, etc., under certain conditions, such analyses are too complex to be treated at present. Since an all liquid seal (with parallel faces) has a neutral axial stiffness curve, and is stabilized axially by convergent coning, other degrees of freedom stability analyses are necessary. However, the axial stability behavior of the two-phase seal is always a consideration no matter how well the seal is aligned and regardless of the speed. Hence, axial stability is thought of as the primary design consideration for two-phase seals and indeed the stability behavior under sub-cooling variations probably overshadows other concerns. The main thrust was the dynamic analysis of axial motion of two-phase face seals, principally the determination of axial stiffness, and the steady behavior of two-phase annular seals. The main conclusions are that seals with two-phase flow may be unstable if improperly balanced. Detailed theoretical analyses of low (laminar) and high (turbulent) leakage seals are presented along with computer codes, parametric studies, and in particular a simplified PC based code that allows for rapid performance prediction. A simplified combined computer code for the performance prediction over the laminar and turbulent ranges of a two-phase seal is described and documented. The analyses, results, and computer codes are summarized.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-4256 , E-4999 , NAS 1.26:4256
    Format: application/pdf
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  • 2
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    Low-speed wind tunnel performance of high-speed counterrotation propellers at angle-of-attack (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The low-speed aerodynamic performance characteristics of two advanced counterrotation pusher-propeller configurations with cruise design Mach numbers of 0.72 were investigated in the NASA Lewis 9- by 15-Foot Low-Speed Wind Tunnel. The tests were conducted at Mach number 0.20, which is representative of the aircraft take/off/landing flight regime. The investigation determined the effect of nonuniform inflow on the propeller performance characteristics for several blade angle settings and a range of rotational speeds. The inflow was varied by yawing the propeller mode to angle-of-attack by as much as plus or minus 16 degrees and by installing on the counterrotation propeller test rig near the propeller rotors a model simulator of an aircraft engine support pylon and fuselage. The results of the investigation indicated that the low-speed performance of the counterrotation propeller configurations near the take-off target operating points were reasonable and were fairly insensitive to changes in model angle-of-attack without the aircraft pylon/fuselage simulators installed on the propeller test rig. When the aircraft pylon/fuselage simulators were installed, small changes in propeller performance were seen at zero angle-of-attack, but fairly large changes in total power coefficient and very large changes of aft-to-forward-rotor torque ratio were produced when the propeller model was taken to angle-of-attack. The propeller net efficiency, though, was fairly insensitive to any changes in the propeller flowfield conditions near the take-off target operating points.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 89-2583
    Format: text
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  • 3
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    Analytical modeling of circuit aerodynamics in the new NASA Lewis Altitude Wind Tunnel (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Rehabilitation and extention of the capability of the altitude wind tunnel (AWT) was analyzed. The analytical modelling program involves the use of advanced axisymmetric and three dimensional viscous analyses to compute the flow through the various AWT components. Results for the analytical modelling of the high speed leg aerodynamics are presented; these include: an evaluation of the flow quality at the entrance to the test section, an investigation of the effects of test section bleed for different model blockages, and an examination of three dimensional effects in the diffuser due to reentry flow and due to the change in cross sectional shape of the exhaust scoop.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-0380
    Format: text
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  • 4
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    Analysis of some fully-discrete algorithms for the one-dimensional heat equation (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The present investigation is concerned with a fully discrete accuracy and stability analysis of the one-dimensional heat equation, taking into account the evaluation of two-pass explicit schemes which simultaneously employ lumped and coupled capacity matrices. Schemes of the considered characteristics are not amenable to uncoupled semidiscrete and ordinary differential equation analyses. The obtained results illustrate that superior behavior may be achieved by schemes of the employed type when compared with the performance of the standard one-pass explicit schemes. The key idea in the considered approach is related to the utilization of a reduced-quadrature capacity matrix in the evaluation of the right-hand-side residual.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 21; 163-168
    Format: text
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  • 5
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    Analytical modeling of circuit aerodynamics in the new NASA Lewis wind tunnel (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Rehabilitation and extention of the capability of the altitude wind tunnel (AWT) was analyzed. The analytical modeling program involves the use of advanced axisymmetric and three dimensional viscous analyses to compute the flow through the various AWT components. Results for the analytical modeling of the high speed leg aerodynamics are presented; these include: an evaluation of the flow quality at the entrance to the test section, an investigation of the effects of test section bleed for different model blockages, and an examination of three dimensional effects in the diffuser due to reentry flow and due to the change in cross sectional shape of the exhaust scoop.
    Keywords: AERODYNAMICS
    Type: NASA-TM-86912 , E-2405 , NAS 1.15:86912 , AIAA PAPER 85-0380 , Aerospace Sci. Meeting; Jan 14, 1985 - Jan 17, 1985; Reno, NV; United States
    Format: application/pdf
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  • 6
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    Low-speed wind tunnel performance of high-speed counterrotation propellers at angle-of-attack (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The low-speed aerodynamic performance characteristics of two advanced counterrotation pusher-propeller configurations with cruise design Mach numbers of 0.72 were investigated in the NASA Lewis 9- by 15-Foot Low-Speed Wind Tunnel. The tests were conducted at Mach number 0.20, which is representative of the aircraft take-off/landing flight regime. The investigation determined the effect of nonuniform inflow on the propeller performance characteristics for several blade angle settings and a range of rotational speeds. The inflow was varied by yawing the propeller model to angle-of-attack by as much as plus or minus 16 degrees and by installing on the counterrotation propeller test rig near the propeller rotors a model simulator of an aircraft engine support pylon and fuselage. The results of the investigation indicated that the low-speed performance of the counterrotation propeller configurations near the take-off target operating points were reasonable and were fairly insensitive to changes in model angle-of-attack without the aircraft pylon/fuselage simulators installed on the propeller test rig. When the aircraft pylon/fuselage simulators were installed, small changes in propeller performance were seen at zero angle-of-attack, but fairly large changes in total power coefficient and very large changes of aft-to-forward-rotor torque ratio were produced when the propeller model was taken to angle-of-attack. The propeller net efficiency, though, was fairly insensitive to any changes in the propeller flowfield conditions near the take-off target operating points.
    Keywords: AERODYNAMICS
    Type: NASA-TM-102292 , E-4883 , NAS 1.15:102292 , AIAA PAPER 89-2583 , Joint Propulsion Conference; Jul 10, 1989 - Jul 12, 1989; Monterey, CA; United States
    Format: application/pdf
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  • 7
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    A new family of stable elements for the Stokes problem based on a mixed Galerkin/least-squares finite element formulation (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Adding to the classical Hellinger-Reissner formulation, a residual form of the equilibrium equation, a new Galerkin/least-squares finite element method is derived. It fits within the framework of a mixed finite element method and is stable for rather general combinations of stress and velocity interpolations, including equal-order discontinuous stress and continuous velocity interpolations which are unstable within the Galerkin approach. Error estimates are presented based on a generalization of the Babuska-Brezzi theory. Numerical results (not presented herein) have confirmed these estimates as well as the good accuracy and stability of the method.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Conference on Finite Element Methods in Flow Problems; Apr 03, 1989 - Apr 07, 1989; Huntsville, AL; United States
    Format: text
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  • 8
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    Compressible flow calculations employing the Galerkin/least-squares method (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A multielement group, domain decomposition algorithm is presented for solving linear nonsymmetric systems arising in the finite-element analysis of compressible flows employing the Galerkin/least-squares method. The iterative strategy employed is based on the generalized minimum residual (GMRES) procedure originally proposed by Saad and Shultz. Two levels of preconditioning are investigated. Applications to problems of high-speed compressible flow illustrate the effectiveness of the scheme.
    Keywords: AERODYNAMICS
    Type: International Conference on Finite Element Methods in Flow Problems; Apr 03, 1989 - Apr 07, 1989; Huntsville, AL; United States
    Format: text
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  • 9
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    The Stokes problem with various well-posed boundary conditions - Symmetric formulations that converge for all velocity/pressure spaces (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Symmetric finite-element formulations are presented for the primitive-variables form of the Stokes equations. These formulations are convergent for any combination of pressure and velocity interpolations. Various boundary conditions, such as pressure, are accommodated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Conference on Finite Element Methods in Flow Problems; Apr 03, 1989 - Apr 07, 1989; Huntsville, AL; United States
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  • 10
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    Galerkin/least-squares procedures in computational fluid dynamics (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The application of Galerkin/least-squares methodology to computational fluid dynamics is reviewed. Applications to advective-diffusive systems of equations and incompressible and compressible Euler and Navier-Stokes equations are described. Space-time finite-element methodology for time-dependent problems is emphasized and the status and role of so-called 'discontinuity-capturing operators' is reviewed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Conference on Finite Element Methods in Flow Problems; Apr 03, 1989 - Apr 07, 1989; Huntsville, AL; United States
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