The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Andrea Arnone - One of the best experts on this subject based on the ideXlab platform.
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rotor stator interaction analysis using the navier stokes equations and a multigrid method
Journal of Turbomachinery-transactions of The Asme, 1996Co-Authors: Andrea Arnone, Roberto PaccianiAbstract:A recently developed, time-accurate multigrid viscous solver has been extended to the analysis of unsteady rotor-stator interaction. In the proposed method, a fully implicit discretization is used to remove stability limitations. By means of a dual time-stepping approach, a four-stage Runge-Kutta scheme is used in conjunction with several accelerating techniques typical of steady-state solvers, instead of traditional time-expensive factorizations. The accelerating strategies include local time stepping, Residual Smoothing, and multigrid. Two-dimensional viscous calculations of unsteady rotor-stator interaction in the first stage of a modern gas turbine are presented. The stage analysis is based on the introduction of several blade passages to approximate the stator:rotor count ratio. Particular attention is dedicated to grid dependency in space and time as well as to the influence of the number of blades included in the calculations.
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Multigrid computations of unsteady rotor-stator interaction using the Navier-Stokes equations
Journal of Fluids Engineering, 1995Co-Authors: Andrea Arnone, Roberto Pacciani, Alessandra SestiniAbstract:A Navier-Stokes time-accurate solver has been extended to the analysis of unsteady rotor-stator interaction. In the proposed method, a fully-implicit time discretization is used to remove stability limitations. A four-stage Runge-Kutta scheme is used in conjunction with several accelerating techniques typical of steady-state solvers, instead of traditional time-expensive factorizations. Those accelerating strategies include local time stepping, Residual Smoothing, and multigrid. Direct interpolation of the conservative variables is used to handle the interfaces between blade rows. Two-dimensional viscous calculations of unsteady rotor-stator interaction in a modern gas turbine stage are presented to check for the capability of the procedure.
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viscous analysis of three dimensional rotor flow using a multigrid method
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 1993Co-Authors: Andrea ArnoneAbstract:A three-dimensional code for rotating blade-row flow analysis has been developed. The space discretization uses a cell-centered scheme with eigenvalues scaling for the artificial dissipation. The computational efficiency of a four-stage Runge-Kutta scheme is enhanced by using variable coefficients, implicit Residual Smoothing, and a full-multigrid method.An application is presented for the NASA rotor 67 transonic fan. Due to the blade stagger and twist, a zonal, non-periodic H-type grid is used to minimize the mesh skewness. The calculation is validated by comparing it with experiments in the range from the maximum flow rate to a near-stall condition. A detailed study of the flow structure near peak efficiency and near stall is presented by means of pressure distribution and particle traces inside boundary layers.Copyright © 1993 by ASME
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A Navier–Stokes Solver for Turbomachinery Applications
Journal of Turbomachinery, 1993Co-Authors: Andrea Arnone, R C SwansonAbstract:A computer code for solving the Reynolds-averaged full Navier-Stokes equations has been developed and applied using H- and C-type grids. The Baldwin-Lomax eddy-viscosity model is used for turbulence closure. The integration in time is based on an explicit four-stage Runge-Kutta scheme. Local time stepping, variable coefficient implicit Residual Smoothing, and a full multigrid method have been implemented to accelerate steady-state calculations. A grid independence analysis is presented for a transonic rotor blade. Comparisons with experimental data show that the code is an accurate viscous solver and can give very good blade-to-blade predictions for engineering applications.
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Multigrid time-accurate integration of Navier-Stokes equations
1993Co-Authors: Andrea Arnone, Meng-sing Liou, Louis A. PovinelliAbstract:Efficient acceleration techniques typical of explicit steady-state solvers are extended to time-accurate calculations. Stability restrictions are greatly reduced by means of a fully implicit time discretization. A four-stage Runge-Kutta scheme with local time stepping, Residual Smoothing, and multigridding is used instead of traditional time-expensive factorizations. Some applications to natural and forced unsteady viscous flows show the capability of the procedure.
Louis A. Povinelli - One of the best experts on this subject based on the ideXlab platform.
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Multigrid time-accurate integration of Navier-Stokes equations
1993Co-Authors: Andrea Arnone, Meng-sing Liou, Louis A. PovinelliAbstract:Efficient acceleration techniques typical of explicit steady-state solvers are extended to time-accurate calculations. Stability restrictions are greatly reduced by means of a fully implicit time discretization. A four-stage Runge-Kutta scheme with local time stepping, Residual Smoothing, and multigridding is used instead of traditional time-expensive factorizations. Some applications to natural and forced unsteady viscous flows show the capability of the procedure.
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Multigrid calculation of three-dimensional viscous cascade flows
Journal of Propulsion and Power, 1993Co-Authors: Andrea Arnone, Meng-sing Liou, Louis A. PovinelliAbstract:A three-dimensional code for viscous cascade flow prediction has been developed. The space discretization uses a cell-centered scheme with eigenvalue scaling to weigh the artificial dissipation terms. Computational efficiency of a four-stage Runge-Kutta scheme is enhanced by using variable coefficients, implicit Residual Smoothing, and a full-multigrid method. The Baldwin-Lomax eddy-viscosity model is used for turbulence closure. A zonal, nonperiodic grid is used to minimize mesh distortion in and downstream of the throat region. Applications are presented for an annular vane with and without end wall contouring, and for a large-scale linear cascade. The calculation is validated by comparing with experiments and by studying grid dependency.
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Navier-Stokes solution of transonic cascade flows using nonperiodic C-type grids
Journal of Propulsion and Power, 1992Co-Authors: Andrea Arnone, Meng-sing Liou, Louis A. PovinelliAbstract:A new kind of C-type grid is proposed for turbomachinery flow calculations. This grid is nonperiodic on the wake and results in minimum skewness for cascades with high turning and large camber. The Reynoldsaveraged Navier-Stokes equations are discretized on this type of grid using a finite volume approach. The Baldwin-Lomax eddy-viscosity model is used for turbulence closure. Jameson's explicit Runge-Kutta scheme is adopted for the integration in time, and computational efficiency is achieved through accelerating strategies such as multigriding and Residual Smoothing. A detailed numerical study has been carried out for a turbine rotor and for a vane. A grid dependence analysis is presented and the effect of the artificial dissipation is also investigated. Comparison of calculations with experiments clearly demonstrate the advantage of the proposed grid.
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Transonic cascade flow calculations using non-periodic C-type grids
1991Co-Authors: Andrea Arnone, Meng-sing Liou, Louis A. PovinelliAbstract:A new kind of C-type grid is proposed for turbomachinery flow calculations. This grid is nonperiodic on the wake and results in minimum skewness for cascades with high turning and large camber. Euler and Reynolds averaged Navier-Stokes equations are discretized on this type of grid using a finite volume approach. The Baldwin-Lomax eddy-viscosity model is used for turbulence closure. Jameson's explicit Runge-Kutta scheme is adopted for the integration in time, and computational efficiency is achieved through accelerating strategies such as multigriding and Residual Smoothing. A detailed numerical study was performed for a turbine rotor and for a vane. A grid dependence analysis is presented and the effect of artificial dissipation is also investigated. Comparison of calculations with experiments clearly demonstrates the advantage of the proposed grid.
R C Swanson - One of the best experts on this subject based on the ideXlab platform.
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A Navier–Stokes Solver for Turbomachinery Applications
Journal of Turbomachinery, 1993Co-Authors: Andrea Arnone, R C SwansonAbstract:A computer code for solving the Reynolds-averaged full Navier-Stokes equations has been developed and applied using H- and C-type grids. The Baldwin-Lomax eddy-viscosity model is used for turbulence closure. The integration in time is based on an explicit four-stage Runge-Kutta scheme. Local time stepping, variable coefficient implicit Residual Smoothing, and a full multigrid method have been implemented to accelerate steady-state calculations. A grid independence analysis is presented for a transonic rotor blade. Comparisons with experimental data show that the code is an accurate viscous solver and can give very good blade-to-blade predictions for engineering applications.
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An effective multigrid method for high-speed flows
Communications in Applied Numerical Methods, 1992Co-Authors: R C Swanson, E. Turkel, J. A. WhiteAbstract:The use is considered of a multigrid method with central differencing to solve the Navier-Stokes equations for high speed flows. The time dependent form of the equations is integrated with a Runge-Kutta scheme accelerated by local time stepping and variable coefficient implicit Residual Smoothing. Of particular importance are the details of the numerical dissipation formulation, especially the switch between the second and fourth difference terms. Solutions are given for 2-D laminar flow over a circular cylinder and a 15 deg compression ramp.
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Multigrid for hypersonic viscous two- and three-dimensional flows
10th Computational Fluid Dynamics Conference, 1991Co-Authors: E. Turkel, R C Swanson, V. N. Vatsa, J. A. WhiteAbstract:Abstract : We consider the use of a multigrid method with central differencing to solve the Navier Stokes equation for hypersonic flows. The time-dependent form of the equations is integrated with an explicit Runge-Kutta scheme accelerated by local time stepping and implicit Residual Smoothing. Variable coefficients are developed for the implicit process that remove the diffusion limit on the time step, producing significant improvement in convergence. A numerical dissipation formulation that provides good shock-capturing capability for hypersonic flow is presented. This formulation is shown to be a crucial aspect of the multigrid method. Solutions are given for two-dimensional viscous flow over a NACA 0012 airfoil and three-dimensional viscous flow over a blunt biconic.
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A comparison of several implicit Residual Smoothing methods in combination with multigrid
Thirteenth International Conference on Numerical Methods in Fluid Dynamics, 1Co-Authors: J. Blazek, C C Rossow, N. Kroll, R C SwansonAbstract:Today, it is a standard technique to accelerate the convergence of explicit multistage time-stepping schemes to steady state using implicit Residual Smoothing (IRS) together with multigrid. In the past, various IRS methods have been developed. They all artificially extend the stability region of the basic explicit time-stepping scheme and thus they permit higher CFL-numbers. Additionally, Residual Smoothing strongly effects the damping properties of a scheme which are essential for the robustness and fast convergence of multigrid. The different IRS methods can be divided mainly into two categories. The first one contains smoothers with a centrally weighted form of the implicit operator [1, 31. The second category includes smoothers with an upwind biased form of the operator as developed in [2, 3]. The objective of this paper is to explore the capabilities of different IRS methods in combination with both central [1] as well as upwind [4] spatial discretizations and to compare their efficiency for various 2-D inviscid and viscous flow problems.
Rickard Enander - One of the best experts on this subject based on the ideXlab platform.
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Implicit Explicit Residual Smoothing for the Multidimensional Euler and Navier--Stokes Equations
SIAM Journal on Scientific Computing, 1997Co-Authors: Rickard EnanderAbstract:In this paper an implicit explicit version of the concept of Residual Smoothing in several space dimensions will be introduced. This version will improve damping properties and robustness considerably. Numerical examples are presented showing reduction of the CPU time needed to compute steady state solutions for inviscid and viscid cases as well as for subsonic and transonic cases.
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Improved Residual Smoothing
Nonlinear Hyperbolic Problems: Theoretical Applied and Computational Aspects, 1993Co-Authors: Rickard EnanderAbstract:In this paper we will discuss how to compute steady state solutions of first order hyperbolic systems in an efficient way. The basic numerical scheme is based on the time dependent equations with centered differences in space and explicit Runge-Kutta iteration in time. To accelerate the process of computing a steady state solution we will use Implicit Residual Smoothing (1RS) and propose a new version which has far better properties. The general idea is to use difference operators on the explicit side of the IRS. We will denote this new Residual smoother the Implicit Explicit Residual Smoother (IERS).
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Improved implicit Residual Smoothing for steady state computations of first-order hyperbolic systems
Journal of Computational Physics, 1993Co-Authors: Rickard EnanderAbstract:Improved implicit Residual Smoothing for steady state computations of first-order hyperbolic systems
Roberto Pacciani - One of the best experts on this subject based on the ideXlab platform.
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rotor stator interaction analysis using the navier stokes equations and a multigrid method
Journal of Turbomachinery-transactions of The Asme, 1996Co-Authors: Andrea Arnone, Roberto PaccianiAbstract:A recently developed, time-accurate multigrid viscous solver has been extended to the analysis of unsteady rotor-stator interaction. In the proposed method, a fully implicit discretization is used to remove stability limitations. By means of a dual time-stepping approach, a four-stage Runge-Kutta scheme is used in conjunction with several accelerating techniques typical of steady-state solvers, instead of traditional time-expensive factorizations. The accelerating strategies include local time stepping, Residual Smoothing, and multigrid. Two-dimensional viscous calculations of unsteady rotor-stator interaction in the first stage of a modern gas turbine are presented. The stage analysis is based on the introduction of several blade passages to approximate the stator:rotor count ratio. Particular attention is dedicated to grid dependency in space and time as well as to the influence of the number of blades included in the calculations.
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Multigrid computations of unsteady rotor-stator interaction using the Navier-Stokes equations
Journal of Fluids Engineering, 1995Co-Authors: Andrea Arnone, Roberto Pacciani, Alessandra SestiniAbstract:A Navier-Stokes time-accurate solver has been extended to the analysis of unsteady rotor-stator interaction. In the proposed method, a fully-implicit time discretization is used to remove stability limitations. A four-stage Runge-Kutta scheme is used in conjunction with several accelerating techniques typical of steady-state solvers, instead of traditional time-expensive factorizations. Those accelerating strategies include local time stepping, Residual Smoothing, and multigrid. Direct interpolation of the conservative variables is used to handle the interfaces between blade rows. Two-dimensional viscous calculations of unsteady rotor-stator interaction in a modern gas turbine stage are presented to check for the capability of the procedure.