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Viscous Analysis of ThreeDimensional Rotor Flows Using a Multigrid Method
, 1993
"... The Society shall not be responsible for statements or opinions advanced in papers or discussion at meetings of the Society or of its Divisions or Sections, or printed in its publications. Discussion is printed only if the paper is published in an ASME Journal. Papers are available from ASME for 15 ..."
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Cited by 28 (2 self)
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The Society shall not be responsible for statements or opinions advanced in papers or discussion at meetings of the Society or of its Divisions or Sections, or printed in its publications. Discussion is printed only if the paper is published in an ASME Journal. Papers are available from ASME for 15 months after the meeting.
An adaptive grid method and its application to steady Euler flow calculations
 SIAM J. Sci. Comput
, 1998
"... Abstract. An adaptive remeshing procedure based on a cell volume deformation method is presented. Starting with an initial grid, this method offers direct cell volume control through the specification of the transformation Jacobian. Grid points are moved with appropriate grid velocities so that the ..."
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Abstract. An adaptive remeshing procedure based on a cell volume deformation method is presented. Starting with an initial grid, this method offers direct cell volume control through the specification of the transformation Jacobian. Grid points are moved with appropriate grid velocities so that the specified cell volume distribution can be achieved at the end of the grid movement without adding or removing grid points. The grid velocities are determined by solving a scalar Poisson equation. This method is applied to solving the compressible Euler equations. Computational test cases of transonic flow over an airfoil are presented and demonstrate the desired control of grid sizes across shock waves. Key words. Euler flows, adaptive grid, deformation methods, shocks
Direct and LargeEddy Simulation of the Compressible Turbulent Mixing Layer
, 1995
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Preconditioning Compressible Flow Calculations on Stretched Meshes
 AIAA Paper 960889, 34th Aerospace Sciences Meeting and Exhibit
, 1996
"... High aspect ratio cells in a computational mesh compound the inherent stiffness in the Euler and Navier Stokes equations which arises from a disparity in the propagative speeds of convective and acoustic modes. A meshaligned preconditioning strategy is examined which improves full coarsening mult ..."
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Cited by 12 (5 self)
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High aspect ratio cells in a computational mesh compound the inherent stiffness in the Euler and Navier Stokes equations which arises from a disparity in the propagative speeds of convective and acoustic modes. A meshaligned preconditioning strategy is examined which improves full coarsening multigrid performance by clustering high frequency components of the spatial Fourier footprint away from the origin for effective damping by a RungeKutta time stepping scheme. For viscous computations on highly stretched meshes, a Jcoarsening multigrid algorithm is adopted that provides adequate clustering of all modes inside the boundary layer. In contrast to previous approaches, the methods presented are robust when used in conjunction with high resolution schemes on fine meshes and with multigrid. Substantial speedups are demonstrated for a variety of Euler and laminar and turbulent NavierStokes test cases. 1 Introduction Explicit Euler and NavierStokes solvers based on multigrid remai...
Transonic AxialFlow Blade Shape Optimization Using Evolutionary Algorithm and
 ThreeDimensional NavierStokes Solver, 9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization
, 2002
"... A reliable and efficient aerodynamic design optimization tool using evolutionary algorithm has been developed for transonic compressor blades. A realcoded adaptiverange genetic algorithm is used to improve efficiency and robustness in design optimization. To represent flow fields accurately and pr ..."
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Cited by 10 (1 self)
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A reliable and efficient aerodynamic design optimization tool using evolutionary algorithm has been developed for transonic compressor blades. A realcoded adaptiverange genetic algorithm is used to improve efficiency and robustness in design optimization. To represent flow fields accurately and produce reliable designs, threedimensional NavierStokes computation is used for aerodynamic analysis. To ensure feasibility of the present method, aerodynamic redesign of NASA rotor67 is demonstrated. Entropy production is considered as the objective function to be minimized. The computation is parallelized on the SGI ORIGIN2000
Leray and LANS−α modelling of turbulent mixing
, 2005
"... Mathematical regularisation of the nonlinear terms in the NavierStokes equations provides a systematic approach to deriving subgrid closures for numerical simulations of turbulent flow. By construction, these subgrid closures imply existence and uniqueness of strong solutions to the corresponding m ..."
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Cited by 8 (1 self)
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Mathematical regularisation of the nonlinear terms in the NavierStokes equations provides a systematic approach to deriving subgrid closures for numerical simulations of turbulent flow. By construction, these subgrid closures imply existence and uniqueness of strong solutions to the corresponding modelled system of equations. We will consider the large eddy interpretation of two such mathematical regularisation principles, i.e., Leray and LANS−α regularisation. The Leray principle introduces a smoothed transport velocity as part of the regularised convective nonlinearity. The LANS−α principle extends the Leray formulation in a natural way in which a filtered Kelvin circulation theorem, incorporating the smoothed transport velocity, is explicitly satisfied. These regularisation principles give rise to implied subgrid closures which will be applied in large eddy simulation of turbulent mixing. Comparison with filtered direct numerical simulation data, and with predictions obtained from popular dynamic eddyviscosity modelling, shows that these mathematical regularisation models are considerably more accurate, at a lower computational cost. Particularly, the capturing of flow features characteristic of the smaller resolved scales improves significantly. Variations in spatial resolution and Reynolds number establish that the Leray model is more robust but also slightly less accurate than the LANS−α model. The LANS−α model retains
A continuous adjoint method for unstructured grids
 16th AIAA Computational Fluid Dynamic Conference
, 2008
"... Adjointbased shape optimization methods have proven to be computationally efficient for aerodynamic problems. The majority of the studies on adjoint methods have used structured grids to discretize the computational domain. Because of the potential advantages of unstructured grids for complex confi ..."
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Cited by 7 (3 self)
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Adjointbased shape optimization methods have proven to be computationally efficient for aerodynamic problems. The majority of the studies on adjoint methods have used structured grids to discretize the computational domain. Because of the potential advantages of unstructured grids for complex configurations, in this study we have developed and validated a continuous adjoint formulation for unstructured grids. The hurdles posed in the computation of the gradient for unstructured grids are resolved by using a reduced gradient formulation. The methods to impose thickness constraints on unstructured grids are also discussed. The results for two and threedimensional simulations of airfoils and wings in inviscid transonic flow are used to validate the design procedure. Finally, the design procedure is applied to redesign the shape of a transonic business jet configuration; we were able to reduce the inviscid drag of the aircraft from 235 to 216 counts resulting in a shockfree wing. Although the Euler equations are the focus of the study in this paper of the adjointbased approach, the solution of the adjoint system and gradient formulation can be conceptually extended to viscous flows. The approach presented in this study has been successfully used by the first and third authors for viscous flows using structured grids. However, particular aspects of the design process, such as the robustness of the mesh deformation process for unstructured grids, need more attention for viscous flows and are therefore the subject of ongoing research. Nomenclature
Remarks on the Calculation of Transonic Potential Flow by a Finite Volume Method
 Proc. IMA Conference on Numerical Methods in Fluid Dynamics
, 1978
"... The purpose of this paper is to review the development of a finite volume method for the numerical calculation of transonic flow, under the assumption that the flow is irrotational, so that the velocity can be represented as the gradient of the potential. Essentially this limits the application of t ..."
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Cited by 5 (4 self)
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The purpose of this paper is to review the development of a finite volume method for the numerical calculation of transonic flow, under the assumption that the flow is irrotational, so that the velocity can be represented as the gradient of the potential. Essentially this limits the application of the method to flows containing fairly week
Adiabatic Effectiveness and Heat Transfer Coefficient on a FilmCooled Rotating
 Blade, blamer. Heat Transfer, Pan A
, 1997
"... ABSTRACT A threedimensional NavierStokes code has been used to compute the adiabatic effectiveness and heat transfer coefficient on a rotating filmcooled turbine blade. The blade chosen is the UTRC rotor with five filmcooling rows containing 83 holes, including three rows on the shower head wit ..."
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Cited by 3 (2 self)
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ABSTRACT A threedimensional NavierStokes code has been used to compute the adiabatic effectiveness and heat transfer coefficient on a rotating filmcooled turbine blade. The blade chosen is the UTRC rotor with five filmcooling rows containing 83 holes, including three rows on the shower head with 49 holes, covering about 86% of the blade span. The mainstream is akin to that under real engine conditions with stagnation temperature = 1900 K and stagnation pressure = 3 MPa. The blade speed is taken to be 5200 rpm. The adiabatic effectiveness is higher for a rotating blade as compared to that for a stationary blade. Also, the direction of coolant injection from the showerhead holes affects considerably the effectiveness and heat transfer coefficient values on both the pressure and suction surfaces. In all cases, the heat transfer coefficient and adiabatic effectiveness are highly threedimensional in the vicinity of holes but tend to become twodimensional far downstream.