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The objective of the present research is to investigate the recent development of the vorticity confinement method. First, a new formulation of the vorticity confinement term is studied. Advantages of the new formulation over the original one include the ability to conserve the momentum, and the ability to preserve the centroid motion of some flow properties such as the vorticity magnitude. Next, new difference schemes, which are simpler and more efficient than the old schemes, are discussed. At last, two computational models based on the vorticity confinement method are investigated. One of the models is devised to simulate inviscid flows over bodies with surfaces not aligned with the grid. The other is a surface boundary layer model, which is intended for efficiently simulating viscous flows with separations from the body surfaces. To validate the computational models, numerical simulations of three-dimensional flows over 6:1 ellipsoid at incidence are performed. Comparisons have been made with exact solutions for inviscid simulations or experimental data for viscous simulations, and data obtained with conventional CFD methods. It is observed that both the inviscid and the viscous solutions with the new models exhibit good agreement with the exact solutions or the experiment data. The new models can have much higher efficiency than conventional CFD methods, and are able to obtain solutions with comparable accuracy.
The vortex intensification mechanism of heat transfer on the dimpled surfaces and crossed flow control of the bodies with additional construction elements like forward disks and vortex cells is analyzed by numerical methods. Self-organizing 3D vortex structures generating within dimple enhance the heat transfer from the wall and the effect on the boundary layer by bleeding-suction or rotating central body of the vortex cell results in diminishing of the separation effect influence accompanied by the reduction of the body drag and increasing of lift force. 3D vortex like toroid generated in the gap between forward disk and leading body edge is responsible for the pressure deficit at this region and as a sequence additional thrust that almost compensates the forward disk drag Vortex strain at the forward separation region at the angle of attack different from zero causes the effect of head stability for the cylinder with forward disc.
Vorticity Confinement (VC) is a numerical technique which enhances computation of fluid flows by acting as negative diffusion within the limit of vortical regions, preventing the inherent numerical dissipation present with conventional methods. VC shares similarities with large eddy simulation (LES), but its behavior is based on a stable negative dissipation of vortical structures controlled by the automatic balance between two parameters, [mu] and [epsilon]. In this thesis, three-dimensional, parallel-computing Navier-Stokes solvers with VC are developed using the OpenFOAM computational framework. OpenFOAM is an open-source collection of C++ libraries developed for computational fluid dynamics. Object-oriented programming concepts are used to develop the finite volume solvers, which introduce the VC source term into the governing equations as a body force. An immersed boundary method is implemented with the VC module to mitigate limitations of body-fitted grids. The developed solvers are examined using two-dimensional boundary layer simulations, which demonstrate that for a given range of confinement parameters the boundary layer can be relaxed to a desired height to approximate a turbulent boundary layer thickness. Unlike wall function models, however, the VC boundary layer can still separate in an adverse pressure gradient. The application of VC to a two-dimensional advecting compact vortex results in the propagation of the vortex without dissipation. Solutions for a three-dimensional backward-facing step are validated against experimental data. The VC simulations show excellent agreement with experimental data for a fixed value of [mu] and a given range of [epsilon]. Coarsening the mesh increases inherent numerical dissipation and requires using a smaller value of [mu] to show good agreement with experimental data. Turbulence kinetic energy spectra exhibit a -5/3 slope inertial wavenumber range indicating proper turbulence cascading using the VC model. Simulation of a Formula One racecar represented by an immersed surface demonstrates the suitability of VC for fast prototyping. A time-accurate VC analysis on a 3,400,000 cell coarse mesh appears more realistic in the wake region than a steady RANS simulation on a 30,000,000 cell mesh. The VC solution appears visually comparable to an LES solution but represents a fraction of the computational cost.
This series of volumes on the ?Frontiers of Computational Fluid Dynamics? was introduced to honor contributors who have made a major impact on the field. The first volume was published in 1994 and was dedicated to Prof Antony Jameson; the second was published in 1998 and was dedicated to Prof Earl Murman. The volume is dedicated to Prof Robert MacCormack.The twenty-six chapters in the current volume have been written by leading researchers from academia, government laboratories, and industry. They present up-to-date descriptions of recent developments in techniques for numerical analysis of fluid flow problems, and applications of these techniques to important problems in industry, as well as the classic paper that introduced the ?MacCormack scheme? to the world.
This book consists of 37 articles dealing with simulation of incompressible flows and applications in many areas. It covers numerical methods and algorithm developments as well as applications in aeronautics and other areas. It represents the state of the art in the field.
Bringing together the world's leading researchers and practitioners of computational mechanics, these new volumes meet and build on the eight key challenges for research and development in computational mechanics. Researchers have recently identified eight critical research tasks facing the field of computational mechanics. These tasks have come about because it appears possible to reach a new level of mathematical modelling and numerical solution that will lead to a much deeper understanding of nature and to great improvements in engineering design.The eight tasks are: The automatic solution of mathematical models Effective numerical schemes for fluid flows The development of an effective mesh-free numerical solution method The development of numerical procedures for multiphysics problems The development of numerical procedures for multiscale problems The modelling of uncertainties The analysis of complete life cycles of systems Education - teaching sound engineering and scientific judgement Readers of Computational Fluid and Solid Mechanics 2003 will be able to apply the combined experience of many of the world's leading researchers to their own research needs. Those in academic environments will gain a better insight into the needs and constraints of the industries they are involved with; those in industry will gain a competitive advantage by gaining insight into the cutting edge research being carried out by colleagues in academia. Features Bridges the gap between academic researchers and practitioners in industry Outlines the eight main challenges facing Research and Design in Computational mechanics and offers new insights into the shifting the research agenda Provides a vision of how strong, basic and exciting education at university can be harmonized with life-long learning to obtain maximum value from the new powerful tools of analysis
This series of volumes on the OC Frontiers of Computational Fluid DynamicsOCO was introduced to honor contributors who have made a major impact on the field. The first volume was published in 1994 and was dedicated to Prof Antony Jameson; the second was published in 1998 and was dedicated to Prof Earl Murman. The volume is dedicated to Prof Robert MacCormack. The twenty-six chapters in the current volume have been written by leading researchers from academia, government laboratories, and industry. They present up-to-date descriptions of recent developments in techniques for numerical analysis of fluid flow problems, and applications of these techniques to important problems in industry, as well as the classic paper that introduced the OC MacCormack schemeOCO to the world. Contents: The Effect of Viscosity in Hypervelocity Impact Cratering (R W MacCormack); The MacCormack Method OCo Historical Perspective (C M Hung et al.); Numerical Solutions of Cauchy-Riemann Equations for Two and Three Dimensional Flows (M M Hafez & J Houseman); Extension of Efficient Low Dissipation High Order Schemes for 3-D Curvilinear Moving Grids (M Vinokur & H C Yee); Scalable Parallel Implicit Multigrid Solution of Unsteady Incompressible Flows (R Pankajakshan et al.); Lattice Boltzmann Simulation of Incompressible Flows (N Satofuka & M Ishikura); Numerical Simulation of MHD Effects on Hypersonic Flow of a Weakly Ionized Gas in an Inlet (R K Agarwal & P Deb); Development of 3D DRAGON Grid Method for Complex Geometry (M-S Liou & Y Zheng); Advances in Algorithms for Computing Aerodynamic Flows (D W Zingg et al.); Selected CFD Capabilities at DLR (W Kordulla); CFD Applications to Space Transportation Systems (K Fujii); Information Science OCo A New Frontier of CFD (K Oshima & Y Oshima); Integration of CFD into Aerodynamics Education (E M Murman & A Rizzi); and other papers. Readership: Researchers and graduate students in numerical and computational mathematics."