Natural convection within an enclosed circular annular cavity formed by two concentric vertical cylinders is of fundamental interest and practical importance. Generally, the assumption of axisymmetric thermal flow is ...
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Natural convection within an enclosed circular annular cavity formed by two concentric vertical cylinders is of fundamental interest and practical importance. Generally, the assumption of axisymmetric thermal flow is adopted for simulating such natural convections and the validity of the assumption of axisymmetric thermal flow is still held even for some turbulent convection. Usually the Rayleigh numbers (Ra) of realistic flows are very high. However, the work to design suitable and efficient lattice Boltzmann (LB) models on such flows is quite rare. To bridge the gap, in this paper a simple LB subgrid-scale (SGS) model, which is based on our recent work [S. Chen, J. Tölke, and M. Krafczyk, Phys. Rev. E 79, 016704 (2009); S. Chen, J. Tölke, S. Geller, and M. Krafczyk, Phys. Rev. E 78, 046703 (2008)], is proposed for simulating convectional flow with high Ra within an enclosed circular annular cavity. The key parameter for the SGS model can be quite easily and efficiently evaluated by the present model. The numerical experiments demonstrate that the present model works well for a large range of Ra and Prandtl number (Pr). Though in the present study a popularly used static Smagorinsky turbulence model is adopted to demonstrate how to develop a LB SGS model for simulating axisymmetric thermal flows with high Ra, other state-of-the-art turbulence models can be incorporated into the present model in the same way. In addition, the present model can be extended straightforwardly to simulate other axisymmetric convectional flows with high Ra, for example, turbulent convection with internal volumetric heat generation in a vertical cylinder, which is an important simplified representation of a nuclear reactor.
A simple lattice Boltzmann model for numerical simulation of fluid flow and heat transfer inside a rotating disk-cylinder configuration, which is of fundamental interest and practical importance in science as well as ...
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A simple lattice Boltzmann model for numerical simulation of fluid flow and heat transfer inside a rotating disk-cylinder configuration, which is of fundamental interest and practical importance in science as well as in engineering, is proposed in this paper. Unlike existing lattice Boltzmann models for such flows, which were based on “primitive-variable” Navier-Stokes equations, the target macroscopic equations of the present model for the flow field are vorticity–stream function equations, inspired by our recent work designed for nonrotating flows [S. Chen, J. Tölke, and M. Krafczyk, Phys. Rev. E 79, 016704 (2009); S. Chen, J. Tölke, S. Geller, and M. Krafczyk, Phys. Rev. E 78, 046703 (2008)]. The flow field and the temperature field both are solved by the D2Q5 model. Compared with the previous models, the present model is more efficient, more stable, and much simpler. It was found that, even though with a relatively low grid resolution, the present model can still work well when the Grashof number is very high. The advantages of the present model are validated by numerical experiments.
A lattice Boltzmann model for incompressible axisymmetric flow is proposed in this paper. Unlike previous axisymmetric lattice Boltzmann models, which were based on “primitive-variables” Navier-Stokes equations, the...
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A lattice Boltzmann model for incompressible axisymmetric flow is proposed in this paper. Unlike previous axisymmetric lattice Boltzmann models, which were based on “primitive-variables” Navier-Stokes equations, the target macroscopic equations of the present model are vorticity-stream-function formulations. Due to the intrinsic features of vorticity-stream-function formulations, the present model is more efficient, more stable, and much simpler than the existing models. The advantages of the present model are validated by numerical experiments.
In this article we present an educational simulation tool, FlowSim 2007 CUDA edition, a computational steering application for interactive 2D flow simulation based on the Lattice Boltzmann Method. The application comb...
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In this article we present an educational simulation tool, FlowSim 2007 CUDA edition, a computational steering application for interactive 2D flow simulation based on the Lattice Boltzmann Method. The application combines a comfortable user interface as well as a convenient development platform on the one hand and a high performance flow solver on the other hand. The user interface is implemented using the Microsoft .NET Framework whereas the Lattice Boltzmann kernel is based on the Compute Unified Device Architecture (CUDA) by nVIDIA running on GeForce 8 series featuring G8X GPUs [2]. The gap between the managed intermediate language (IL) code and the hardware specific native code is filled using the recently introduced C++/CLI programming language [1]. We demonstrate that this integrated desktop approach can deliver a performance that exceeds that of a high end PC by at least an order of magnitude. In our conclusion we will focus on extensions to three dimensions and clusters of GPUs.
The basic physics of air flow through saturated porous media are reviewed and implications are drawn for the practical application of air sparging. A conceptual model of the detailed behavior of an air sparging system...
The basic physics of air flow through saturated porous media are reviewed and implications are drawn for the practical application of air sparging. A conceptual model of the detailed behavior of an air sparging system is constructed using elements of multiphase flow theory and the results of recent experimental work. Implications of the conceptual model on air sparging topics are discussed. The meaning of radius of influence in the context of air sparging is found to be ambiguous. The hydrodynamic effects of air sparging such as mounding of ground water and flow impedance are explored. Limitations on rates of remediation and operational strategies for improving sparging effectiveness are examined.
作者：
DEGIORGI, VMATIC, PVirginia Gensheimer DeGiorgiis a member of the Mechanics of Materials Branch at the Naval Research Laboratory in Washington
D.C. She received a B.S. and MEng in civil engineering from the University of Louisville. She received her Ph.D. in engineering mechanics from Southern Methodist University. Prior to joining NRL she was associated with the Nuclear Components Division and Breeder Reactor Component Project of Westinghouse Electric Corporation in Tampa and Pensacola Florida. Her research interests include nonlinear computational modeling large strain response and fracture of materials material-structural response to combined loading environmental effects and structural integrity evaluation. Peter Maticis a member of the Mechanics of Materials Branch at the Naval Research Laboratory in Washington
D.C. He received a B.S. in mechanical engineering from the Illinois Institute of Technology and a Ph.D. in applied mechanics from Lehigh University. Prior to joining NRL he was associated with the Electric Boat Division of General Dynamics Corporation in Groton Conn. His research interests include material constitutive behavior its measurement using computational techniques in conjunction with experimental data the mechanics of fracture structural integrity and the use of complex systems theory to analyze and model material deformation. In 1989 he received an NRL Alan Berman Publication Award and the ASNE “Jimmie” Hamilton Award.
As nonlinear computational methods become integrated into the structural design and analysis process, the effects of large deformation material response on large deflection structural response can, in principle, be pr...
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As nonlinear computational methods become integrated into the structural design and analysis process, the effects of large deformation material response on large deflection structural response can, in principle, be predicted. The accuracy of structural predictions ultimately depends on an accurate assessment of the material responses which are encountered in the structure. This is particularly true if information on locally severe plastic deformation or fracture initiation and flaw tolerance is desired. Previously determined parameters for the elastic-plastic response of HY-80, HY-100, HSLA-80 and HSLA-100 steels, accurate through large strains terminating at the point of fracture, were applied in finite element simulations to predict the performance of a bulkhead test panel geometry. Significant differences in panel performance under hydrostatic loading conditions were predicted for the materials considered. The plastic deflections were found to be strongly influenced by the relative local or diffuse nature of intense plastic deformation across the panel. These results suggest that the comparative nonlinearity of these materials was as important as the strength and ductility in affecting performance. Further analyses, aimed at assessing flaw tolerance, were considered by conducting small scale analyses of local details where severe deformation conditions were predicted by the larger scale panel model.
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