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Computer simulations of the laminar flow past three-dimensional bluff bodies are presented. The focus is on the time-dependent wake flow behind linearly tapered circular cylinders and downstream of a circular cylinder with an abrupt change in diameter. In both cases the intricate vortex shedding phenomena observed in earlier laboratory experiments are convincingly reproduced by the computer experiments...
Bubble-driven flows, which belong to the large group of bubbly multiphase flows, are important in many industrial processes. Relevant examples are metal refining operations such as tapping of steel furnaces, gas-stirred lades, and aluminum electrolysis. Over the last 15 years, numerical solutions of mathematical models for bubble-driven flows have contributed to a better understanding of the governing...
Computational Fluid Dynamics (CFD) has increased in usage within many areas of industry. In a large number of cases CFD is seen as an extension of CAD or FEM modelling and a long term vision is the integration of CFD with CAD and FEM structural analysis. Because of this it is now commonplace to import CAD based solid models into CFD packages for the use of studies. This is in principle a very practical...
Multipath ultrasonic transit time flow meters (USM) represent an alternative to conventional meters for fiscal gas flow measurement. When the meter is installed close to bend(s), the flow profile can be quite complex, with asymmetric axial and transversal flow profiles. To investigate the accuracy of the measurement in such situations, computational fluid dynamic (CFD) simulations of 3D flow in various...
A methodology for computing vortex-induced vibrations (VIV) on risers is presented. It is based on computation of the flow by a Computational Fluid Dynamics (CFD) program, structural dynamics by a nonlinear Computational Structural Dynamics (CSD) code and a coupling between them. Herein, we discuss in particular procedures for computing the mesh movement in staggered FSl-simulations. A two-level mesh...
Nitric-oxide formation from fuel-bound nitrogen in turbulent non-premixed flames was investigated. The calculations were performed using the k - e model for turbulence and the Eddy Dissipation Concept for turbulent combustion in conjunction with detailed chemistry of the chemical reaction mechanism GRI-Mech 2.11. Comparison with experimental data from the literature showed that the discrepancies for...
Lifetime prediction of thermal barrier coatings on gas turbine hot components is described. Existing modelling strategies are discussed. A more fundamental strategy, based on micromechanical analyses of the coating system is finally presented.
Small sensors and actuators made from materials like silicon, quartz or plastic are already parts of our everyday life. In cars there are often silicon sensors measuring acceleration, tyre pressure and car roll-over. There may be microfabricated mechanical components inside your light projector or in your ink-jet printer. In the future, microsystems are believed to be widespread, being used for environment...
The performance of a reversible pump turbine close to runaway is important for the stability of a pumped storage plant. In this study CFD is used to predict the turbine characteristics. Good correspondence between the experimental and computational results is found when a simplified loss model is used to account for the components not present in the CFD model. Despite the promising results, more work...
The demands from the extrusion market are constantly evolving towards tighter geometrical tolerances. Simulation models that with sufficient accuracy describe the flow in the container and die, as well as the deflection after exit will therefore become important tools to understand how to avoid geometrical deflection and shape variations. From a simulation point of view the extrusion process is very...
In this paper, we investigate the simulation of aluminum extrusion processes by means of a newly developed coupled heat- and flow solver. The extrusion problem is here formulated as two sub-problems which are solved separately in a staggered solution strategy: 1) A non-Newtonian Navier-Stokes flow problem where the viscosity depends both on the effective strain rate and the temperature, and 2) a linear...
We discuss structural response analysis of vessels subjected to hydrodynamic loads. The response analyses are performed in order to assess vessel strength either through quasi-static ultimate strength analyses (ULS) or stochastic fatigue analyses (FLS). We focus on consistency in modeling with emphasis on accurate load transfer between the fluid- and structure domains. In wave analysis the dynamic...
The line spring finite element is a versatile numerical tool for performing engineering fracture mechanics analysis of surface cracked shells. An accurate yield surface of plane strain single-cracked (SEC) specimens having shallow, as well as deep, cracks is presented here. The meaning of the J-integral when crack growth occurs is discussed. The J-integral is regarded as a sort of accumulated measure...
The present paper deals with masonry subjected to combined compression and shear. The purpose of the study was to demonstrate the capability of numerical simulations to reproduce the essential mechanical behaviour, as observed by experiments. A coarse 3-dimensional element mesh was used to study the mechanical behaviour of the Fixed Smeared Crack model, in combination with various shear retention...
We present a fully nonlinear method for numerical simulation of the inundation of an arbitrary solid body in large waves. The method is based on potential flow and is therefore expected to break down when wave breaking sets in. The method is expected to be useful to predict the initial phase of inundation and can thus give the flow field as initial condition to some other method more appropriate for...
Stretch bending is an important method for plastic forming of aluminium extrusions to some desired curvature. The industrial application of the process is, however, not always straightforward. Tolerance demands to the final product and production efficiency require proper control of possible difficulties such as cross sectional deformations and unloading springback. Traditionally, trial-and-error...
In this paper, we discuss some critical aspects of standard numerical models for tsunami simulation. We evaluate the importance of dispersion in open sea and demonstrate that the Boussinesq equations offer a surprisingly good balance between accuracy and mathematical simplicity for tsunami problems. Numerical artifacts of wave propagation in discrete media, with emphasis on effects of staircase boundaries...
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