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  • 1
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    Effects of curvature and rotation on turbulence in the NASA low-speed centrifugal compressor impeller (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The flow in the NASA Low-Speed Impeller is affected by both curvature and rotation. The flow curves due to the following: (1) geometric curvature, e.g. the curvature of the hub and shroud profiles in the meridional plane and the curvature of the backswept impeller blades; and (2) secondary flow vortices, e.g. the tip leakage vortex. Changes in the turbulence and effective turbulent viscosity in the impeller are investigated. The effects of these changes on three-dimensional flow development are discussed. Two predictions of the flow in the impeller, one with, and one without modification to the turbulent viscosity due to rotation and curvature, are compared. Some experimental and theoretical background for the modified mixing length model of turbulent viscosity will also be presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Goddard Space Flight Center, Tenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, Part 1; p 315-338
    Format: text
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  • 2
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    Explicit finite-volume time-marching calculations of total temperature distributions in turbulent flow (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A method was developed which calculates two-dimensional, transonic, viscous flow in ducts. The finite volume, time-marching formulation is used to obtain steady flow solutions of the Reynolds-averaged form of the Navier-Stokes equations. The entire calculation is performed in the physical domain. This paper investigates the introduction of a new formulation of the energy equation which gives improved transient behavior as the calculation converges. The effect of variable Prandtl number on the temperature distribution through the boundary layer is also investigated. A turbulent boundary layer in an adverse pressure gradient (M = 0.55) is used to demonstrate the improved transient temperature distribution obtained when the new formulation of the energy equation is used. A flat plate turbulent boundary layer with a supersonic free-stream Mach number of 2.8 is used to investigate the effect of Prandtl number on the distribution of properties through the boundary layer. The computed total temperature distribution and recovery factor agree well with the measurements when a variable Prandtl number is used through the boundary layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Thermodynamic Evaluation of Transonic Compressor Rotors Using the Finite Volume Approach; p 71-82
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  • 3
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    An explicit finite-volume time-marching procedure for turbulent flow calculations (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A method was developed which calculates two-dimensional, transonic, viscous flow in ducts. The finite-volume, time-marching formulation is used to obtain steady flow solutions of the Reynolds-averaged form of the Navier-Stokes equations. The entire calculation is performed in the physical domain. Control volumes are chosen so that smoothing of flow properties, typically required for stability, is not required. Different time steps are used in the different governing equations. A new pressure interpolation scheme is introduced which improves the shock capturing ability of the method. A multi-volume method for pressure changes in the boundary layer allows calculations which use very long and thin control volumes (length/height - 1000). The method is compared with two test cases. Essentially incompressible turbulent boundary layer flow in an adverse pressure gradient is calculated and the computed distributions of mean velocity and shear are in good agreement with the measurements. Transonic viscous flow in a converging diverging nozzle is calculated; the Mach number upstream of the shock is approximately 1.25. The agreement between the calculated and measured shock strength and total pressure losses is good.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Thermodynamic Evaluation of Transonic Compressor Rotors Using the Finite Volume Approach; p 59-70
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  • 4
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    A prediction of 3-D viscous flow and performance of the NASA Low-Speed Centrifugal Compressor (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A prediction of the three-dimensional turbulent flow in the NASA Low-Speed Centrifugal Compressor Impeller has been made. The calculation was made for the compressor design conditions with the specified uniform tip clearance gap. The predicted performance is significantly worse than that predicted in the NASA design study. This is explained by the high tip leakage flow in the present calculation and by the different model adopted for tip leakage flow mixing. The calculation gives an accumulation of high losses in the shroud/pressure-side quadrant near the exit of the impeller. It also predicts a region of meridional backflow near the shroud wall. Both of these flow features should be extensive enough in the NASA impeller to allow detailed flow measurements, leading to improved flow modeling. Recommendations are made for future flow studies in the NASA impeller.
    Keywords: AERODYNAMICS
    Type: ASME PAPER 90-GT-234
    Format: text
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  • 5
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    A prediction of 3-D viscous flow and performance of the NASA low-speed centrifugal compressor (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A prediction of the 3-D turbulent flow in the NASA Low-Speed Centrifugal Compressor Impeller has been made. The calculation was made for the compressor design conditions with the specified uniform tip clearance gap. The predicted performance is significantly worse than that predicted in the NASA design study. This is explained by the high tip leakage flow in the present calculation and by the different model adopted for tip leakage flow mixing. The calculation gives an accumulation for high losses in the shroud/pressure-side quadrant near the exit of the impeller. It also predicts a region of meridional backflow near the shroud wall. Both of these flow features should be extensive enough in the NASA impeller to allow detailed flow measurements, leading to improved flow modelling. Recommendations are made for future flow studies in the NASA impeller.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-184765 , NAS 1.26:184765 , TRG-JM/89-1
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  • 6
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    Thermodynamic evaluation of transonic compressor rotors using the finite volume approach (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The development of a computational capability to handle viscous flow with an explicit time-marching method based on the finite volume approach is summarized. Emphasis is placed on the extensions to the computational procedure which allow the handling of shock induced separation and large regions of strong backflow. Appendices contain abstracts of papers and whole reports generated during the contract period.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-180587 , NAS 1.26:180587 , JM/87-4
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  • 7
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    An explicit finite-volume time-marching procedure for turbulent flow calculations (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A method was developed which calculates two-dimensional, transonic, viscous flow in ducts. The finite-volume, time-marching formulation is used to obtain steady flow solutions of the Reynolds-averaged form of the Navier-Stokes equations. The entire calculation is performed in the physical domain. Control volumes are chosen so that smoothing of flow properties, typically required for stability, is not required. Different time steps are used in the different governing equations. A new pressure interpolation scheme is introduced which improves the shock capturing ability of the method. A multi-volume method for pressure changes in the boundary layer allows calculations which use very long and thin control volumes (length/height - 1000). The method is compared with two test cases. Essentially incompressible turbulent boundary layer flow in an adverse pressure gradient is calculated and the computed distributions of mean velocity and shear are in good agreement with the measurements. Transonic viscous flow in a converging diverging nozzle is calculated; the Mach number upstream of the shock is approximately 1.25. The agreement between the calculated and measured shock strength and total pressure losses is good.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Numerical methods in laminar and turbulent flow; Jul 06, 1987 - Jul 10, 1987; Montreal; Canada
    Format: text
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  • 8
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    Explicit finite-volume time-marching calculations of total temperature distributions in turbulent flow (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A method was developed which calculates two-dimensional, transonic, viscous flow in ducts. The finite volume, time-marching formulation is used to obtain steady flow solutions of the Reynolds-averaged form of the Navier-Stokes equations. The entire calculation is performed in the physical domain. This paper investigates the introduction of a new formulation of the energy equation which gives improved transient behavior as the calculation converges. The effect of variable Prandtl number on the temperature distribution through the boundary layer is also investigated. A turbulent boundary layer in an adverse pressure gradient (M = 0.55) is used to demonstrate the improved transient temperature distribution obtained when the new formulation of the energy equation is used. A flat plate turbulent boundary layer with a supersonic free-stream Mach number of 2.8 is used to investigate the effect of Prandtl number on the distribution of properties through the boundary layer. The computed total temperature distribution and recovery factor agree well with the measurements when a variable Prandtl number is used through the boundary layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Numerical methods in laminar and turbulent flow; Jul 06, 1987 - Jul 10, 1987; Montreal; Canada
    Format: text
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  • 9
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    Use of Blade Lean in Turbomachinery Redesign (1993)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: Blade lean is used to improve the uniformity of exit flow distributions from turbomachinery blading. In turbines, it has been used to control secondary flows by tailoring blade turning to reduce flow overturning and underturning and to create more uniform loss distributions from hub to shroud. In the present study, the Pump Consortium centrifugal impeller has been redesigned using blade lean. The flow at the exit of the baseline impeller had large blade-to-blade variations, creating a highly unsteady flow for the downstream diffuser. Blade lean is used to redesign the flow to move the high loss fluid from the suction side to the hub, significantly reducing blade-toblade variations at the exit.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Marshall Space Flight Center, Eleventh Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, Part 1; p 251-269
    Format: application/pdf
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