Analysis, presentation, and understanding in experimental fluid flow studies: A colourful evolutionary story

The modelling of uncoupled fluid flow and heat transfer problems of a district heating network using the finite element method (FEM) is presented. Since the standard thermo-hydraulic pipe elements cannot be directly used for modelling insulation, the main attention was paid to discretisation of multilayered structure of pipes and surrounding by one-dimensional thermal elements. In addition, validity of the finite element method was verified numerically by solving fluid flow and heat transfer problems in district heating pipelines. Verification analysis involves standard single pipe problems and simulation of fragment of district heating in Vilnius. Pressure and temperature results obtained by finite element method are compared with those by other approaches.

Four problems of fluid flow and heat transfer were designed in which non‐orthogonal, boundary‐fitted grids were to be used. These are proposed to serve as test cases for testing new solution methods. This paper presents solutions of the test problems obtained by using a multigrid finite volume method with grids of up to 320 × 320 control volumes. Starting from zero fields, iterations were performed until the sum of the absolute residuals had fallen seven orders of magnitude, thus ensuring that the variable values did not change to six most significant digits. By comparing the solutions for successive grids at moderate Reynolds and Rayleigh numbers, the discretization errors were estimated to be lower than 0·1%. The results presented in this paper may thus serve for comparison purposes as bench‐mark solutions.

Understanding fluid flow in fractured porous media is of great importance in the fields of civil engineering in general or in soil science particular. This study is devoted to the development and validation of a numerical tool based on the use of the finite element method. To this aim, the problem of fluid flow in fractured porous media is considered as a problem of coupling free fluid and fluid flow in porous media or coupling of the Stokes and Darcy equations. The strong formulation of the problem is constructed, highlighting the condition at the free surface between the Stokes and Darcy regions, following by the variational formulation and numerical integration using the finite element method. Besides, the analytical solutions of the problem are constructed and compared with the numerical solutions given by the finite element approach. Both local properties and macroscopic responses of the two solutions are in excellent agreement, on condition that the porous media are sufficiently discretized by a certain level of finesse. The developed finite element tool of this study could pave the way to investigate many interesting flow problems in the field of soil science.

A primary goal of the Department of Energy’s Nuclear Energy Advanced Modeling and Simulation (NEAMS) program is to develop the next generation of simulations tools to support the design and deployment of commercial nuclear power. The mission of the NEAMS Center of Excellence for Thermal-fluids Applications in Nuclear Energy is to advance this goal by providing leadership, best practices, research, and support and training for computational thermal-fluids applications in nuclear energy. This is accomplished by leveraging expertise in the NEAMS tools to solve challenging problems in fluid flow and heat transfer. The NEAMS tools provide simulation capabilities covering a range of temporal and spatial scales and the Center connects stakeholders in industry with the expertise to use these tools to their fullest. This addresses a pressing need, facilitating advanced reactor development and commercialization.

The main goal of this paper is to demonstrate the general characteristics of the educational
user-friendly CFD Studio package for CFD teaching. The package was designed for
teaching 2D fluid mechanics and heat transfer process, including conduction, coupled
conduction/convection, natural and forced convection, external and internal flows, among
other phenomena. The finite volume methodology and its related topics can also be taught
using the software. Therefore, general aspects of the three main modules, pre-processor,
solver and post-processor are discussed aiming to show the generality of the tool. These
modules are integrated in the application by a so-called “numerical problem project”
which guide the student through the steps to obtain the solution. To approximate the
partial differential equations the finite volume approach is employed using a fully-implicit
formulation with the interpolation schemes CDS, UDS and WUDS. Mesh editing and nonorthogonal
boundary-fitted mesh generation, using algebraic interpolation and elliptic
equations, are important features of the package. Coupled heat transfer problems are
handled using the “solid-block” formulation and the pressure-velocity coupling uses the
SIMPLE and SIMPLEC methods with non-staggered grids. To demonstrate the
capabilities two fluid flow and heat transfer “problem projects” are presented.

Chapter IX - Elliptical Ducts

A Meshless Radial Basis Function Method for Fluid Flow with Heat Transfer K Nagamani Devi1, D.W. Pepper2 Summary Over the past few years, efforts have been made to solve fluid flow and heat transfer problems using radial basis functions. This approach is meshless, easy to understand, and simple to implement. Preliminary results indicate accuracies on the order of finely meshed conventional techniques, but with considerably less computational effort. In this study, a projection-based technique is used to solve the primitive equations of motion and energy using radial basis functions. Three benchmark test cases are examined: (1) lid-driven cavity flow, (2) natural convection in a square enclosure, and (3) flow with forced convection over backward facing step. Results are compared with COMSOL and FLUENT – two popular commercial CFD packages.

A hybrid grid system that combines the Chimera overset grid scheme and an unstructured grid method is developed to study fluid flow and heat transfer problems. With the proposed method, the solid structural region, in which only the heat conduction is considered, can be easily represented using an unstructured grid method. As for the fluid flow region external to the solid material, the Chimera overset grid scheme has been shown to be very flexible and efficient in resolving complex configurations. The numerical analyses require the flow field solution and material thermal response to be obtained simultaneously. A continuous transfer of temperature and heat flux is specified at the interface, which connects the solid structure and the fluid flow as an integral system. Numerical results are compared with analytical and experimental data for a flat plate and a C3X cooled turbine cascade. A simplified drum-disk system is also simulated to show the effectiveness of this hybrid grid system.

Preface. Solving heat transfer problems by the dual reciprocity BEM. Transient problems using time-dependent fundamental solutions. Solving linear heat conduction problems by the multiple reciprocity method. Solving nonlinear heat transfer problems using the boundary element method. Coupled conduction-convection problems. Solving coupled problems involving conduction, convection and thermal radiation. Advanced thermoelastic analysis. Integral equation analyses of natural convection problems in fluid flow. Improperly posed problems in heat transfer. Acknowledgments. References.

Natural convection in a square cavity containing a nanofluid and an adiabatic square block at the center

The thermal, fluid flow, and tritium release problems represent a major part of the research and development issues for liquid-metal and solid breeder blankets. The issues are characterized, and recent progress in model development and experiments is described. The issues for liquid-metal blankets are dominated by magnetohydrodynamic (MHD) effects on fluid flow and heat transfer. New design solutions have been proposed, new facilities have been constructed, and models are being developed to address MHD effects. The problems of solid breeder blankets are dominated by tritium release, containment, and inventory. There has been remarkable progress in understanding tritium transport in solid breeders because of successful irradiation experiments of solid breeders in fusion reactors. New models on tritium transport have provided key tools for the analysis and interpretation of the experimental results, A new issue related to thermal control in solid breeder is the subject of active experimental and mod...

The velocity field of a strongly swirling flow has been examined using an LDA and PIV in combination. The PIV revealed an asymmetric component of the flowfield, in particular a movement of the swirl center away from the geometric center of the rotating cylinder. A statistical description of this asymmetric component has been developed, from which the apparent turbulence measured with an LDA has been estimated. These results are compared to the actual LDA measurements. The conclusion is that a large portion of the measured turbulence using a one point technique (LDA) can be attributed to this effect and can also explain the previously observed discrepancy between experiment and numerical simulation.

Continual technology development for fusion has come to rely on the principle of “design by analysis” where advanced finite element analysis (FEA) or finite volume analysis provides insight on the performance of engineered systems. Extensive three-dimensional (3D) computations in fluid dynamics, heat transfer, neutronics, magneto-hydrodynamics and electro-magnetics are involved in an iterative design process for magnets, vacuum vessels and in-vessel components. Many difficulties arose in the integration of computer-assisted design (CAD) packages and the numeric models and results from different FEA codes. Over the last decade, engineers developed a vast array of specialized translators and interpolation programs to deal with geometry, mesh and load transfers between single-discipline codes, often with mixed outcomes. Now, several multiphysics codes that allow calculations on the same mesh and easy transfer of loads and other boundary conditions are emerging in the commercial market. These codes often have a robust library of physics models and solvers that address both steady state and transient phenomena and provide simultaneous solutions to heat transfer, fluid flow and structural mechanics problems. This article reviews three existing design tools, provides some examples of how the multiphysics codes are impacting practical engineering design, and identifies some important gaps that still exist today.

Mobility changes from region to region can occur in a reservoir due to inhomogeneities in permeability and due to change in saturating fluid. In either case interfaces are present across which mobility changes abruptly. The problem of fluid flow in porous media in the presence of such interfaces is solved in this paper by using complex velocity potentials. On the interface tangential component of efflux vector is discontinuous. A vortex sheet appears on the interface and it affects the flow. Complex velocity potential in such a case can be expressed as a linear superposition of the potentials due to sources (injection wells), sinks (production wells) and due to vortex sheets along the interfaces of mobility discontinuity. Vorticity distribution on interfaces and the velocity field are inter-related. Therefore we get an integral equation for the vorticity distribution. The solution of the integral equation enables us to define the complex velocity potential completely and hence the velocity field in the flow region. It is shown that in the general case of several wells and interfaces the integral equation has a unique solution and leads to a unique flow pattern. An exact solution of the integral equation for a circular interface is obtained. An impervious no-flow boundary is an extreme case of mobility discontinuity. It is shown that its effect on the flow can be considered by an appropriate vortex sheet along it. Thus a formal solution in the form of an integral equation is obtained for instantaneous velocity distribution for arbitrary well pattern and mobility distribution.

Numerical evaluation of the latent heat thermal energy storage performance enhancement by installing longitudinal fins