In the current age of space exploration, the push to reach further to deep space presents a greater need for analysis and verification and validation of rocketry components in the space environment. Due to the nature of space, firings of rocket thrusters in space is a multi-regime problem. With the low density, pressure, and temperature of the environment, the resultant plume structure, seeded with unburnt fuel droplets, extends up to multiple orders of magnitude in distance as compared to a plume structure in the Earth’s atmosphere. The frozen droplets, or particles, create concerns including surface contamination and erosion, calling a cause for study and model development to understand particle behavior in this multi-regime environment. This work intends to develop a model to analyze and understand multiphase flow and particle behavior in this environment utilizing the lower fidelity, but more computationally efficient, RANS turbulence modeling. Particle properties are compared against a regime-defining parameter to understand the trends in behavior. Finally, the work closes out on a preliminary look into implementing fully reacting flow chemistry for the multiphase flow. These results and progress are promising in developing an efficient model that may be integrated into a hybrid model to better predict particle behavior and dispersion in this multi-regime environment.

In multibody systems, mechanical components (bodies) can be assumed rigid (non-deformable), if their deformation is negligible. For components with non-negligible deformations several methods were developed to represent their deformation. The most widely used method is the floating frame of reference. In this formulation the deformable body is represented by a finite element model whose deformation is described with respect to a local body-fixed frame. Unfortunately, finite element models can include many degrees-of-freedom, which stand in contradiction to the requirements of multibody dynamics. System truncation is therefore inevitable to support computational efficiency. The use of modal data in representing a deformable body is well understood in the multibody community. By truncating modes associated with higher frequencies, the total degrees-of-freedom of the deformable body can be reduced while preserving its dynamic eigen-properties. However, since the finite element model may be in contact with other moving bodies, the reduction technique needs to address the issue of moving boundary conditions. The component mode synthesis reduction methods are such techniques that describe the deflection of all the nodes as a superposition of different types of modes. However, it is limited in the fact that the nodes in contact need to remain in contact throughout a simulation. In some applications these nodes may change, i.e. a node that is in contact with another body or the ground at one instant may become free at the next instant. The present methodologies in multibody modeling of a deformable body with modal data have not yet addressed the issue of changing contact nodes. This research highlights the usefulness of orientation invariant characteristics of some deformable bodies. It proposes to define orientation invariant degrees-of-freedom of the reduced model in Eulerian space, while the remaining degrees-of-freedom are defined in Lagrangian space. In some circumstances, this approach can resolve the issue of changing contact nodes. The combination of Eulerian and Lagrangian formulation for component mode synthesis reduced finite element models is a new concept in deformable multibody dynamics.

Ce travail porte sur le couplage des déformations d'une bulle avec son sillage et sa trajectoire dans plusieurs configurations. Un formalisme de type eulérien-lagrangien permet d'écrire le problème sur un domaine mouvant faiblement déformé par rapport à la configuration de référence. Grâce à cette approche, il est possible d'étudier dans un cadre linéaire le couplage entre les déformations d'une bulle et les effets hydrodynamiques. En appliquant ce formalisme, on peut dans un premier temps calculer l'écoulement de base autour de la bulle et sa géométrie d'équilibre, et dans un second temps développer une approche de stabilité globale prédisant les seuils d'instabilité et les propriétés des modes d'oscillation. Afin de développer cette méthode, des résultats sur les oscillations linéaires de bulles et de gouttes dans un fluide au repos et sans influence de la gravité sont tout d'abord présentés et comparés à des résultats théoriques existants. Puis, le principe du formalisme eulérien-lagrangien est illustré en prenant pour problème modèle l'équation de la chaleur formulée sur un domaine arbitrairement déformé. Ce principe est ensuite appliqué aux équations de Navier-Stokes, aboutissant à une version linéarisée autour d'un domaine de référence incluant de manière complète les couplages entre déformations de la géométrie et perturbations de l'écoulement. On met en oeuvre sur le système obtenu une méthode itérative de Newton donnant accès à l'état de base, c'est-à-dire à l'écoulement stationnaire autour de la bulle et à sa forme d'équilibre. Ce même système permet par la suite d'effectuer une analyse de stabilité globale de l'écoulement autour d'une bulle qui se déforme. L'algorithme développé est d'abord appliqué au cas d'une bulle piégée dans un écoulement d'étirement, permettant de décrire des formes d'équilibre dans des régimes stables et instables. Le cas de la bulle en ascension dans un fluide pur est ensuite abordé. Une étude paramétrique est conduite, couvrant une vaste gamme de liquides allant de l'eau pure à des huiles de silicone très visqueuses. Les états de base calculés par la méthode de Newton ainsi que les seuils d'instabilité des sillages sont en bon accord avec les résultats expérimentaux. Dans les cas des liquides très peu visqueux, notre approche décrit de manière plus précise les effets visqueux dans les couches limites et donne des résultats plus satisfaisants que les approches numériques existantes. Elle confirme par ailleurs que la déformation de la bulle joue un rôle mineur dans ces gammes de paramètres. Pour les liquides plus visqueux en revanche, on observe un couplage plus fort entre déformation et sillage. / This works deals with the coupling between time-dependent deformation, wake dynamics and path characteristics of a gas bubble in different configurations. An Eulerian-Lagrangian formalism is sought to formulate this problem in a moving domain having a small deformation compared to the reference configuration. This approach allows us to study the linear coupling between bubble deformations and hydrodynamic effects. This formalism makes it possible to first compute the base flow around a bubble and the corresponding steady shape, then to develop a global stability approach aimed at predicting the threshold of path instability and the properties of bubble oscillation modes. To develop this method, we first compute the linear oscillations of bubbles and drops in a quiescent fluid without gravity and compare them to existing theory. Then, the premise of the Eulerian-Lagrangian formalism is illustrated using a model equation, namely the heat equation written in an arbitrarily deformed domain. The same formalism is applied to the NavierStokes equations, yielding a linearized version of these equations in the neighbourhood of a reference domain, including the two-way coupling between shape deformations and perturbations of the base flow. With this system of equations at hand, we implement a Newton method that provides the steady state, i.e. the base flow around the bubble and its geometry. The same system allows us to carry out a global stability analysis of the flow past a deformable bubble. We first consider the situation where the bubble is trapped in a straining flow, for which we compute stable and unstable equilibrium shapes. We finally tackle the case of a buoyancy-driven bubble rising in a pure liquid. A parametric study is carried out over a wide range of liquids, from pure water to high-viscosity silicon oils. Steady states computed with the Newton method and instability thresholds are found to be in good agreement with experimental observations. For low-viscosity fluids, our approach captures the viscous effects that take place in the boundary layer better than existing computational approaches, yielding predictions for the onset of path instability in better agreemnt with observations. Furthermore, it confirms that time-dependent bubble deformations play a minor part for such liquids. In contrast, a stronger coupling between shape and path instabilities is observed in high-viscosity fluids

Finite element(FE) method has been used to model cutting process since 1970s. However, it requires special techniques to cope with the difficulties in simulating extremely large strain when compare to static or small deformation problems. With the advancement of FE techniques, researchers can now have a deeper insight of the mechanism of material flow and chip formation of metal cutting process. Even the stagnation effect of the workpiece material in front of the cutting edge radius can be captured by using FE techniques such as Remeshing and Arbitrary Lagrangian Eulerian(ALE) formulation. However most of this models are limited to plane strain assumption which means they are 2-dimensional. Although 3D models are existing in the literatures, most of them employ Remeshing technique which is very computationally intensive and has many critics regarding its accuracy due to its frequent remeshing and mapping process. The rest of the 3D models employ Lagrangian formulation. The 3D models by Lagrangian formulation have the same limitations and drawbacks as in 2D models, as it requires failure criteria and in most of the cases predefined partition surfaces are also required. ALE technique on the other hand resolves all the drawbacks of the other formulations, it not only inherits the advantages of the other techniques but also has its own unique advantages such as it can simulate a longer time span up to couple seconds more economically by fixing the number of elements used. Although it's commonly accepted that ALE formulation is superior to other formulations of techniques in modeling metal cutting process, its usage is only limited to 2D models. Limited 3D ALE metal cutting models is available in the literature. Thus the main objective of this research is to explore the possibility of building a 3D metal cutting model with ALE formulation. The reliability and limitations will also be studied. Furthermore, Couple Eulerian-Lagrangian(CEL) formulation is a recent developed formulation that has a lot of potential in modeling metal cutting process in 3D. It will be compared with ALE models to study its potential and limitations in modeling metal cutting process. A new frictional model will also be proposed, which suggests that the frictional phenomenon in metal cutting is a consolidated effect of both friction between material interface and shear yield of the workpiece material. This idea provide a brand new perspective of viewing the friction phenomenon of metal cutting compared to those existed models. / Thesis / Master of Science (MSc)

Fuel sprays play a major role in order to achieve the required combustion characteristics and pollutant emissions reduction on internal combustion engines, and thus, an accurate prediction of its behavior is required to perform reliable engine combustion and pollutant simulations. A great effort both on experimental and theoretical studies of spray atomization and dispersion has been performed in the latest years. As a result, Computational Fluid Dynamics (CFD) calculations have become a standard tool not only for spray physics understanding but also for design and optimization of engine spray systems. However, spray modeling in its different uses in the Internal Combustion Engine (ICE) context is still nowadays a challenging task due to the complex interrelated phenomena taking place, some of them still not fully understood. Primary atomization and secondary breakup, droplet collision, coalescence and vaporization, turbulent interactions between phases have to be solved under high Reynolds (so they are turbulent) and Weber numbers conditions due to the high speed (~500 m/s) and small nozzle diameter (~100 µm) imposed by current engine injection systems technologies. Moreover, Taylor numbers cover a wide range, according to the composition of the injected liquid. Those conditions make experimental observations quite challenging and probably insufficient, especially in the very near nozzle region, where primary atomization takes place. Most of the CFD spray models are currently based on the Discrete Droplet Method. The continuous liquid jet is discretized into 'blobs' or 'parcels', which consists in a number of droplets with the same characteristics. A Lagrangian method is applied to track the liquid phase parcels, which are subject to breakup according to atomization models mainly based on the linear instability theory proposed by Reitz and later extended by Huh and Gosman for liquid turbulence effects to be considered. This approach has been successfully applied b / Khuong ., AD. (2012). The Eulerian-Lagrangian Spray Atomization (ELSA) Model of the Jet Atomization in CFD Simulations: Evaluation and Validation [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17237

<div>Aluminum 6061 is extensively used in industry and welding and additive manufacturing (AM) of Al6061 offer flexibility in manufacturing. Solid-state welding and AM processes can overcome the shortcomings of fusion-based processes, such as porosity and hot cracking. In this thesis, friction stir welding and friction stir additive manufacturing, which are both based on the concepts of friction stir processing (solid-state), were studied. The welding parameters for a sound weld during friction stir welding of Al6061-T6 alloy were determined based on the experimental and numerical analysis. Formation of tunnel defects and cavity defects was also studied. A Coupled Eulerian-Lagrangian (CEL) finite element model was established to analyze the process, where the workpiece was modeled as an Eulerian body, and the tool as Lagrangian. The model was validated by conducting experiments and correlating the force measured by a three-axis dynamometer. The experimentally validated simulation model was used to find an optimum parameter set for the sound weld case.</div><div>To demonstrate the friction stir additive manufacturing process, a 40 mm × 8 mm × 8 mm (L×B×H) material was fabricated by adding five 1.6 mm thick plates. A similar coupled Eulerian-Lagrangian based finite element model was used to predict the effects of sound process parameters, such as the tool’s rotational speed and the translational speed. The temperature predicted by the model was used to predict the microhardness distribution in the sample and to further elucidate the hardness change in the weld zone, which showed a good agreement with the experimental results. The microstructure of the samples was analyzed, and the mechanical properties of the additive manufactured samples were characterized and compared with those of other AM techniques via tensile tests and tensile shear tests.</div>

Dans l’industrie pharmaceutique, la granulation sèche par compactage à rouleaux est un procédé d’agglomération de poudres en granulés pour améliorer les propriétés d’écoulement nécessaire pour le procédé de compression en matrice. Comprendre le procédé de compactage à rouleaux et optimiser l’efficacité de production est limitée par l’utilisation de l’approche expérimentale à cause du coût élevé des poudres, le temps des essais et la complexité du procédé. Dans ce travail, une méthode d’éléments finis en 3D, est développée dans le but d’identifier les paramètres critiques du matériau et du procédé pour le contrôle de la qualité de la production. Le modèle de comportement de Drucker-Prager Cap est utilisé pour décrire le comportement en compression de poudres et sa calibration est déterminée à partir des essais standard. Pour surmonter la complexité liée à l’existence de deux mécanismes différents, l’alimentation en poudre par une vis sans fin et le compactage entre les rouleaux, une nouvelle méthode d’interfaçage entre la méthode des éléments discrets (DEM) employée pour décrire l’écoulement dans l’alimentation et la méthode des éléments finis (FEM) utilisée pour le compactage entre les rouleaux est développée. Enfin, pour une modélisation de compactage de rouleaux plus réaliste, prenant en compte la variation de l’entrefer entre les rouleaux, une nouvelle approche de couplage Euler-Lagrange est proposée. Les résultats de simulations par éléments finis montrent clairement l’effet des différents paramètres du procédé sur les distributions de pression et de densité dans la zone de compactage. En outre, les résultats montrent que l'utilisation de plaques de confinement de la poudre entre les rouleaux, développe une distribution de pression et de densité non homogène dans le compact, avec une densité plus élevée au centre et plus faible aux bords. D'autre part, l’utilisation de rouleaux dont l’un est surmonté d’une jante de confinement, a montré une distribution de propriétés globalement plus uniforme sur la largeur du compact avec des valeurs légèrement plus élevées aux bords qu’au centre. La méthodologie combinant les méthodes DEM & FEM montre clairement une corrélation directe entre la vitesse des particules entraînées par la vis dans la zone d’alimentation et la pression du rouleau. Tous les deux oscillent avec la même période. Cela se traduit par un compact anisotrope avec un profile de densité variant de manière sinusoïdale le long de sa largeur. Afin d'étudier la capacité du modèle à prédire les propriétés des compacts produits par compactage à rouleaux, les prédictions par simulations numériques sont comparées aux données de la littérature et validées par des mesures spécifiques. / In the pharmaceutical industry, dry granulation by roll compaction is a process of size enlargement of powder into granules with good flowability for subsequent die compaction process. Understanding the roll compaction process and optimizing manufacturing efficiency is limited using the experimental approach due to the high cost of powder, time-consuming and the complexity of the process. In this work, a 3D Finite Element Method (FEM) model was developed to identify the critical material properties, roll press designs and process parameters controlling the quality of the product. The Drucker-Prager Cap (DPC) model was used to describe the powder compaction behavior and was determined based on standard calibration method. To overcome the complexity involving two different mechanisms of powder feeding by the screw and powder compaction between rolls, a novel combined approach of Discrete Element Method (DEM), used to predict the granular material flow in the feed zone and the Finite Elements Method (FEM) employed for roll compaction, was developed. Lastly, for a more realistic roll compaction modelling, allowing the fluctuation of the gap between rolls, a Coupled-Eulerian Lagrangian (CEL) approach was developed. FEM simulation results clearly show the effect of different process parameters on roll pressure and density distribution in the compaction zone of powder between the rolls. Moreover, results show that using a cheek-plates sealing system causes a nonuniform roll pressure and density distribution with the highest values in the middle and the lowest at the edges. On the other hand, the resultant pressure and density distributions with the rimmed-roll obtained higher values in the edges than in the middle and overall a more uniform distribution. The combined DEM-FEM methodology clearly shows a direct correlation between the particle velocity driven by the screw conveyor to the feed zone and the roll pressure, both oscillating in the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its length. To validate the results, the simulations are compared with literature and experimentally measured values in order to assess the ability of the model to predict the properties of the produced ribbons.

ABSTRACT In the first part of this study, a determinist mathematical approach is used to describe any kind of pollutant migration in groundwater. This theoretical background is focused on the miscible displacement and the particularities of the multiporous media are discussed. Subsequently, an objective numerical tool is developed to solve the convection-dispersion equations including immobile water effect, degradation, and adsoption. Among all the available techniques, two finite element methods in fixed meshing grids have been programmed: -the F.U.P.G. method (Full Upwind Petrov Galerkin), using a space-time upwinded weighting function with optimized coefficients, -the H.E.L.M. method (Hybrid Eulerian Lagrangian Method), using the eulerian lagrangian approach with reverse node tracking. Those two schemes are tested on a large number of reference problems. The model have been applied to study the behaviour of solutes (nitrates mainly) in the cretaceous chalk of the Hesbaye area (Belgium). Experimentations have been performed on domains of increasing size (laboratory tests, in situ tracer tests). For each interpretation, the particularities of the context have been taken into account, and miscible transport coefficients have been objectively determined. Hence, the medium is well characterized and the scale effect is quantified. This leads to previsional applications. RESUME Ce travail débute par le développement dun formalisme mathématique déterministe pour décrire, en toute généralité, la propagation de polluants dans les eaux souterraines. Cette étude théorique permet de situer le problème posé (pollution miscible diluée) dans un cadre plus large, et de souligner les particularités dun milieu à porosité multiple. Dans un second temps, un outil numérique objectif est mis au point pour résoudre les équations de convection-dispersion avec effet deau immobile, dégradation, et adsorption. Parmi le grand nombre des procédés existants, deux méthodes par éléments finis en maillage fixe ont été programmées : -la méthode F.U.P.G. (Full Upwind Petrov Galerkin) basée sur un décentrage des fonctions de pondération, optimum dans le temps et lespace, -la méthode H.E.L.M. (Hybrid Eulerian Lagrangian Method) utilisant un processus eulerien lagrangian avec traçage inverse des positions nodales. Les deux schémas sont testés sur de nombreux problèmes de référence. Ensuite, ce modèle est appliqué à des situations pratiques pour étudier le comportement de solutés (nitrates notamment) dans laquifère crayeux du Crétacé de Hesbaye (Belgique). Des domaines de taille croissante sont étudiés (essais de laboratoire, traçage in situ). A chaque étape, les coefficients de transport miscible sont déterminés de façon objective, en tenant compte de la spécificité des tests. Ainsi, leffet déchelle peut être quantifié et il est possible denvisager des scénarios prévisionnels.

In power plants using large utility coal-fired boilers for generation of electricity the coal is pulverised in coal mills and then it has to be pneumatically transported and distributed to a larger number of burners (e.g. 30-40) circumferentially arranged in several rows around the burning chamber of the boiler. Besides the large pipework flow splitting devices are necessary for distribution of an equal amount of pulverised fuel (PF) to each of the burners. So called trifurcators (without inner fittings or guiding vanes) and ''riffle'' type bifurcators are commonly used to split the gas-coal particle flow into two or three pipes/channels with an equal amount of PF mass flow rate in each outflow cross section of the flow splitting device. These PF flow splitting devices are subject of a number of problems. First of all an uneven distribution of PF over the burners of a large utility boiler leads to operational and maintenance problems, increased level of unburned carbon and higher rates of NOX emissions. Maldistribution of fuel between burners caused by non uniform concentration of the PF (particle roping) in pipe and channel bends prior to flow splitting devices leads to uncontrolled differences in the fuel to air ratio between burners. This results in localised regions in the furnace which are fuel rich, where insufficient air causes incomplete combustion of the fuel. Other regions in the furnace become fuel lean, forming high local concentrations of NOX due to the high local concentrations of O2. Otherwise PF maldistribution can impact on power plant maintenance in terms of uneven wear on PF pipework, flow splitters as well as the effects on boiler panels (PF deposition, corrosion, slagging). In order to address these problems in establishing uniform PF distribution over the outlet cross sections of flow splitting devices in the pipework of coal-fired power plants the present paper deals with numerical prediction and analysis of the complex gas and coal particle (PF) flow through trifurcators and ''riffle'' type bifurcators. The numerical investigation is based on a 3-dimensional Eulerian- Lagrangian approach (MISTRAL/PartFlow-3D) developed by Frank et al. The numerical method is capable to predict isothermal, incompressible, steady gas- particle flows in 3-dimensional, geometrically complex flow geometries using boundary fitted, block-structured, numerical grids. Due to the very high numerical effort of the investigated gas-particle flows the numerical approach has been developed with special emphasis on efficient parallel computing on clusters of workstations or other high performance computing architectures. Besides the aerodynamically interaction between the carrier fluid phase and the PF particles the gas-particle flow is mainly influenced by particle-wall interactions with the outer wall boundaries and the inner fittings and guiding vanes of the investigated flow splitting devices. In order to allow accurate quantitative prediction of the motion of the disperse phase the numerical model requires detailed information about the particle-wall collision process. In commonly used physical models of the particle-wall interaction this is the knowledge or experimental prediction of the restitution coefficients (dynamic friction coefficient, coefficient of restitution) for the used combination of particle and wall material, e.g. PF particles on steel. In the present investigation these parameters of the particle-wall interaction model have been obtained from special experiments in two test facilities. Basic experiments to clarify the details of the particle-wall interaction process were made in a test facility with a spherical disk accelerator. This test facility furthermore provides the opportunity to investigate the bouncing process under normal pressure as well as under vacuum conditions, thus excluding aerodynamically influences on the motion of small particles in the near vicinity of solid wall surfaces (especially under small angles of attack). In this experiments spherical glass beads were used as particle material. In a second test facility we have investigated the real impact of non-spherical pulverised fuel particles on a steel/ceramic target. In this experiments PF particles were accelerated by an injector using inert gas like e.g. CO2 or N2 as the carrier phase in order to avoid dust explosion hazards. The obtained data for the particle-wall collision models were compared to those obtained for glass spheres, where bouncing models are proofed to be valid. Furthermore the second test facility was used to obtain particle erosion rates for PF particles on steel targets as a function of impact angles and velocities. The results of experimental investigations has been incorporated into the numerical model. Hereafter the numerical approach MISTRAL/PartFlow-3D has been applied to the PF flow through a ''riffle'' type bifurcator. Using ICEM/CFD-Hexa as grid generator a numerical mesh with approximately 4 million grid cells has been designed for approximation of the complex geometry of the flow splitting device with all its interior fittings and guiding vanes. Based on a predicted gas flow field a large number of PF particles are tracked throughout the flow geometry of the flow-splitter. Besides mean quantities of the particle flow field like e.g. local particle concentrations, mean particle velocities, distribution of mean particle diameter, etc. it is now possible to obtain information about particle erosion on riffle plates and guiding vanes of the flow splitting device. Furthermore the influence of different roping patterns in front of the flow splitter on the uniformness of PF mass flow rate splitting after the bifurcator has been investigated numerically. Results show the efficient operation of the investigated bifurcator in absence of particle roping, this means under conditions of an uniform PF particle concentration distribution in the inflow cross section of the bifurcator. If particle roping occurs and particle concentration differs over the pipe cross section in front of the bifurcator the equal PF particle mass flow rate splitting can be strongly deteriorated in dependence on the location and intensity of the particle rope or particle concentration irregularities. The presented results show the importance of further development of efficient rope splitting devices for applications in coal-fired power plants. Numerical analysis can be used as an efficient tool for their investigation and further optimisation under various operating and flow conditions.

The transport or the separation of solid particles or droplets suspended in a fluid flow is a common task in mechanical and process engineering. To improve machinery and physical processes (e.g. for coal combustion, reduction of NO_x and soot) an optimization of complex phenomena by simulation applying the fundamental conservation equations is required. Fluid-particle flows are characterized by the ratio of density of the two phases gamma=rho_P/rho_F, by the Stokes number St=tau_P/tau_F and by the loading in terms of void and mass fraction. Those numbers (Stokes number, gamma) define the flow regime and which relevant forces are acting on the particle. Dependent on the geometrical configuration the particle-wall interaction might have a heavy impact on the mean flow structure. The occurrence of particle-particle collisions becomes also more and more important with the increase of the local void fraction of the particulate phase. With increase of the particle loading the interaction with the fluid phase can not been neglected and 2-way or even 4-way coupling between the continous and disperse phases has to be taken into account. For dilute to moderate dense particle flows the Euler-Lagrange method is capable to resolve the main flow mechanism. An accurate computation needs unfortunately a high number of numerical particles (1,...,10^7) to get the reliable statistics for the underlying modelling correlations. Due to the fact that a Lagrangian algorithm cannot be vectorized for complex meshes the only way to finish those simulations in a reasonable time is the parallization applying the message passing paradigma. Frank et al. describes the basic ideas for a parallel Eulererian-Lagrangian solver, which uses multigrid for acceleration of the flow equations. The performance figures are quite good, though only steady problems are tackled. The presented paper is aimed to the numerical prediction of time-dependend fluid-particle flows using the simultanous particle tracking approach based on the Eulerian-Lagrangian and the particle-source-in-cell (PSI-Cell) approach. It is shown in the paper that for the unsteady flow prediction efficiency and load balancing of the parallel numerical simulation is an even more pronounced problem in comparison with the steady flow calculations, because the time steps for the time integration along one particle trajectory are very small per one time step of fluid flow integration and so the floating point workload on a single processor node is usualy rather low. Much time is spent for communication and waiting time of the processors, because for cold flow particle convection not very extensive calculations are necessary. One remedy might be a highspeed switch like Myrinet or Dolphin PCI/SCI (500 MByte/s), which could balance the relative high floating point performance of INTEL PIII processors and the weak capacity of the Fast-Ethernet communication network (100 Mbit/s) of the Chemnitz Linux Cluster (CLIC) used for the presented calculations. Corresponding to the discussed examples calculation times and parallel performance will be presented. Another point is the communication of many small packages, which should be summed up to bigger messages, because each message requires a startup time independently of its size. Summarising the potential of such a parallel algorithm, it will be shown that a Beowulf-type cluster computer is a highly competitve alternative to the classical main frame computer for the investigated Eulerian-Lagrangian simultanous particle tracking approach.