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  • 1
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    Application of an unsteady Navier-Stokes solver to transonic turbine design (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 8; 5, Se; 1079-108
    Format: text
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  • 2
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    Computational analysis of rotor-stator interaction in turbomachinery using zonal techniques (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The development of CFD zonal techniques which allow more intensive computational treatment in some regions than in others, in conjunction with robust, high-accuracy algorithms for the numerical solution of the Navier-Stokes equations, is presently shown to have facilitated the investigation of rotor-stator interactions in turbomachinery. Attention is given to integration schemes with two and three spatial dimensions, the conservative 'patched' and the nonconservative zonal boundary schemes, and such natural boundary conditions as those of the endwall, the stator inlet, the airfoil surface, and the rotor exit. Illustrative three-dimensional rotor-stator interaction calculations are presented.
    Keywords: AERODYNAMICS
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  • 3
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    Supercomputer applications in gas turbine flowfield simulation (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The numerical simulation of the unsteady three-dimensional viscous flow in a gas turbine stage is considered. Results from a three-dimensional time-accurate Navier-Stokes simulation of rotor-stator interaction in an axial turbine stage are presented. The present study uses a fine grid in the spanwise direction to better resolve the complex three-dimensional flowfield, and complements earlier reported coarse-grid calculations. Several different features of the flowfield are analyzed and compared to earlier calculations and to experimental data whenever possible. Computer animation techniques are used to visualize various unsteady three-dimensional features of the flow. The results demonstrate the capabilities of current computing hardware in obtaining accurate simulations of unsteady flows in turbomachines.
    Keywords: AERODYNAMICS
    Type: International Journal of Supercomputer Applications (ISSN 0890-2720); 4; 81-95
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  • 4
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    Prediction of turbine rotor-stator interaction using Navier-Stokes methods (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Flows in turbomachinery are generally complex and do not easily lend themselves to numerical computation. The flows are three-dimensional and inherently unsteady. Complicated blade geometries and flow phenomena such as separation and periodic transition from laminar to turbulent flow add to the numerical complexity. Nevertheless, the accurate numerical analysis of such flows is a problem of considerable interest and practical importance to the turbomachinery community. Much of the early work in turbomachinery flow prediction focussed on airfoil cascades. While such analyses of flows in isolated airfoil rows have helped improve understanding of the flow phenomena and have gained widespread acceptance in the industrial community as a design tool, they do not yield any information regarding the unsteady effects arising out of rotor-stator aerodynamic interaction. These interaction effects become increasingly important as the distance between successive stator and rotor rows is decreased. Thus, the need exists for analytical tools that treat the rotor and stator airfoils as a system and provide information regarding the magnitude and the impact of the unsteady effects. The focus a three-dimensional, time-accurate, thin-layer Navier-Stokes code that was recently developed to study rotor-stator interaction problems. A system of patched and overlaid grids that move relative to each other is used to discretize the flow field and the governing equations are integrated using a third-order upwind scheme set in an iterative, implicit framework. The code was used to simulate subsonic flow through an axial turbine configuration for which considerable experimental data exists. Grid refinement studies were also conducted as part of the code validation process. The current status of the research, along with planned future directions, are also discussed.
    Keywords: AERODYNAMICS
    Type: NASA Computational Fluid Dynamics Conference. Volume 2: Sessions 7-12; p 205-216
    Format: application/pdf
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  • 5
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    Direct Numerical Simulation of Transitional and Turbulent Flow Over a Heated Flat Plate Using Finite-Difference Schemes (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The work in this report was conducted at NASA Ames Research Center during the period from August 1993 to January 1995 deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux were shown to compare well with experiment. The numerical method used here can be applied to complex geometries in a straightforward manner.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA-CR-200759 , NAS 1.26:200759 , Rept-95-16
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  • 6
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    Multi-airfoil Navier-Stokes simulations of turbine rotor-stator interaction (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An accurate numerical analysis of the flows associated with rotor-stator configurations in turbomachinery can be extremely helpful in optimizing the performance of turbomachinery. In this study the unsteady, thin-layer, Navier-Stokes equations in two spatial dimensions are solved on a system of patched and overlaid grids for a rotor-stator configuration from an axial turbine. The governing equations are solved using a finite-difference, upwind algorithm that is set in an iterative, implicit framework. Results in the form of pressure contours, time-averaged pressures, unsteady pressure amplitudes and phase are presented. The numerical results are compared with experimental data and the agreement is found to be good. The results are also compared with those of an earlier study which used only one rotor and one stator. The current study uses multiple rotors and stators and a pitch ratio that is much closer to the experimental ratio. Consequently the results of this study are found to be closer to the experimental data.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0361
    Format: text
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  • 7
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    Application of an unsteady Navier-Stokes solver to transonic turbine design (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This study presents a numerical evaluation of the performance of the first stage of a new-generation turbine design. The numerical method solves the two-dimensional Navier-Stokes equations using a system of patched grids. Three-dimensional effects of stream-tube contraction are also modeled. The study focuses on the effects of axial gap variation on the unsteady rotor-stator interactions and on stage performance. Results are presented for three different axial gaps. The results indicate that the unsteady interactions can be very large in this design. These interactions affect not only the stage efficiency but also substantially alter the time-averaged features of the flow. In particular, for the case of the smallest axial gap, it was found that there was an unsteady shock on the stator suction surface which spanned the gap region and impinged upon the moving rotor airfoils.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-2468
    Format: text
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  • 8
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    Unsteady analysis of hot streak migration in a turbine stage (1990)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Two- and three-dimensional Navier-Stokes analyses are used to predict unsteady viscous rotor-stator interacting flow in the presence of a combustor hot streak. Predicted results are presented for a two-dimensional three-stator/four-rotor, a two-dimensional one-stator/one-rotor, and a three-dimensional one-stator/one-rotor simulation of hot streak migration through a turbine stage. Comparison of these results with experimental data demonstrates the capability of the three-dimensional procedure to capture most of the flow physics associated with hot streak migration including the effects of combustor hot streaks on turbine rotor surface temperatures. It is noted that blade count ratio has little effect on predicted time-averaged surface pressure and temperature distributions, but a substantial effect on the unsteady flow characteristics. It is shown that high-temperature hot streak fluid accumulates on the pressure surface of the rotor blades, resulting in a high time-averaged surface temperature 'hot spots'.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-2354
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  • 9
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    Direct numerical simulation of transitional and turbulent flow over a heated flat plate using finite-difference schemes (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This report deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux, were shown to compare well with experiment. The results indicate that the essential features of the transition process have been captured. The numerical method used here can be applied to complex geometries in a straightforward manner.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-197753 , NAS 1.26:197753 , MCAT-95-16
    Format: application/pdf
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  • 10
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    Aerodynamic Shape Optimization Using Hybridized Differential Evolution (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An aerodynamic shape optimization method that uses an evolutionary algorithm known at Differential Evolution (DE) in conjunction with various hybridization strategies is described. DE is a simple and robust evolutionary strategy that has been proven effective in determining the global optimum for several difficult optimization problems. Various hybridization strategies for DE are explored, including the use of neural networks as well as traditional local search methods. A Navier-Stokes solver is used to evaluate the various intermediate designs and provide inputs to the hybrid DE optimizer. The method is implemented on distributed parallel computers so that new designs can be obtained within reasonable turnaround times. Results are presented for the inverse design of a turbine airfoil from a modern jet engine. (The final paper will include at least one other aerodynamic design application). The capability of the method to search large design spaces and obtain the optimal airfoils in an automatic fashion is demonstrated.
    Keywords: Aerodynamics
    Type: AIAA 21st Applied Aerodynamics Conference; Jun 23, 2003 - Jun 26, 2003; Orlando, FL; United States
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