Computation Fluid Dynamics

The speed of golf balls can be regarded as the fastest in all ball games. The flying distance of a golf ball is influenced not only by its material, but also by the aerodynamics of the dimple on its surface. By using Computational Fluid Dynamics method, the flow field and aerodynamics characteristics of golf balls can be studied and evaluated before the golf balls are actually manufactured. This work uses FLUENT as its solver and numerical simulations were carried out to estimate the aerodynamics parameters and noise levels for various kinds of golf balls having different dimple configurations. With the obtained aerodynamics parameters, the flying distance and trajectory for a golf ball were determined and visualized. The results showed that the lift coefficient of the golf ball increased if small dimples were added between the original dimples. When launched at small angles, golf balls with deep dimples were found to have greater lift effects than drag effects. Therefore, the golf balls would fly further. As far as noise generation was concerned, deep dimples produced lower noise levels.

The subject of study is the influence of sloshing liquid on the dynamics of spacecraft. A combined theoretical and experimental approach has been followed. On the one hand, CFD simulations have been carried out to predict the combined liquid/solid body motion. Basically a volume-of-fluid (VOF) approach is followed, however with improvements in the treatment of the free liquid surface: these cover the surface reconstruction and displacement and the calculation of surface tension effects by means of a local height function. Also attention has been paid to the stability of the numerical coupling between solid-body dynamics and liquid dynamics. On the other hand, in-orbit experiments have been carried out with the Sloshsat FLEVO satellite. The paper describes a first comparison between theoretical predictions and experimental findings.

This paper presents a framework of non-interactive algorithms for the mapping of blood flow information to vessels in 3D-RA images. With the presented method, mapping of flow information to 3D-RA images is done automatically without user interaction. So far, radiologists had to perform this task by extensive image comparisons and did not obtain visualizations of the results.

The results of comparative analysis of liquid and gas phase models for fuel droplets heating and evaporation, suitable for implementation into computational fluid dynamics (CFD) codes, are presented. Among liquid phase models, the analysis is focused on the model based on the assumption that the liquid thermal conductivity is infinitely large, and the so-called effective thermal conductivity model. Seven gas phase models are compared. These are six semi-theoretical models based on various assumptions and a model based merely on the approximation of experimental data. It is pointed out that the gas phase model, taking into account the finite thickness of the thermal boundary layer around the droplet, predicts the evaporation time closest to the one based on the approximation of experimental data. In most cases, the droplet evaporation time depends strongly on the choice of the gas phase model. The droplet surface temperature at the initial stage of heating and evaporation does not practically depend on the choice of the gas phase model, while the dependence of this temperature on the choice of the liquid phase model is strong. The direct comparison of the predictions of various gas models, with available experimental data referring to droplet heating and evaporation without break-up, leads to inconclusive results. The comparison of predictions of various liquid and gas phase models with the experimentally observed total ignition delay of n-heptane droplets without break-up, has shown that this delay depends strongly on the choice of the liquid phase model, but practically does not depend on the choice of the gas phase model. In the presence of droplet break-up processes, the evaporation time and the total ignition delay depend strongly on the choice of both gas and liquid phase models. q