Добірка наукової літератури з теми "Coolfluid 3 (open source CFD code)"

The paper discusses the significance of different types of skegs in a barge toward the pressure, fluid velocity and the ship’s total resistance. There are three kinds of skeg configurations: barge without skegs, skegs without deflection, and skegs with deflection. The barge was towed with forward speed were ranging across 3 knots – 9 knots. The simulations were conducted using an open-source RANS (Reynold Averaged Numerical Simulation) CFD code Open-FOAM. The simulations show that the skegs raise the barge’s resistance. The skegs with deflection have a bigger resistance amplification compared to skegs without deflection.

Abstract. Urban air quality issues are closely related to human health and economic development. In order to investigate street-scale flow and air quality, this study developed the atmospheric photolysis calculation framework (APFoam 1.0), an open-source computational fluid dynamics (CFD) code based on OpenFOAM, which can be used to examine microscale reactive pollutant formation and dispersion in an urban area. The chemistry module of APFoam has been modified by adding five new types of reactions, which can implement the atmospheric photochemical mechanism (full O3–NOx–volatile organic compound chemistry) coupled with a CFD model. Additionally, the model, including the photochemical mechanism (CS07A), air flow, and pollutant dispersion, has been validated and shows good agreement with SAPRC modeling and wind tunnel experimental data, indicating that APFoam has sufficient ability to study urban turbulence and pollutant dispersion characteristics. By applying APFoam, O3–NOx–volatile organic compound (VOC) formation processes and dispersion of the reactive pollutants were analyzed in an example of a typical street canyon (aspect ratio H/W=1). The comparison of chemistry mechanisms shows that O3 and NO2 are underestimated, while NO is overestimated if the VOC reactions are not considered in the simulation. Moreover, model sensitivity cases reveal that 82 %–98 % and 75 %–90 % of NO and NO2, respectively, are related to the local vehicle emissions, which is verified as the dominant contributor to local reactive pollutant concentration in contrast to background conditions. In addition, a large amount of NOx emissions, especially NO, is beneficial to the reduction of O3 concentrations since NO consumes O3. Background precursors (NOx/VOCs) from boundary conditions only contribute 2 %–16 % and 12 %–24 % of NO and NO2 concentrations and raise O3 concentrations by 5 %–9 %. Weaker ventilation conditions could lead to the accumulation of NOx and consequently a higher NOx concentration but lower O3 concentration due to the stronger NO titration effect, which would consume O3. Furthermore, in order to reduce the reactive pollutant concentrations under the odd–even license plate policy (reduce 50 % of the total vehicle emissions), vehicle VOC emissions should be reduced by at least another 30 % to effectively lower O3, NO, and NO2 concentrations at the same time. These results indicate that the examination of the precursors (NOx and VOCs) from both traffic emissions and background boundaries is the key point for understanding O3–NOx–VOCs chemistry mechanisms better in street canyons and providing effective guidelines for the control of local street air pollution.

Suite à une requête de la Défense belge dans le cadre des applications CBRN (chimique, biologique, radiologique et nucléaire), l’objectif initial du travail était de simuler un cas CBRN réaliste a l’air libre (dispersion de particules après une explosion dans une ville), en appliquant la stabilisation Streamline-Upwind Petrov-Galerkin (SUPG) sur une méthode d’éléments finis (FEM), incluant une deuxième phase (particules). Pour cette simulation, les développements se font dans le code Coolfuid 3, un langage spécifique au domaine (DSL) écrit en C++. Cependant, les applications à l’air libre nécessitent de décrire correctement la couche limite atmosphérique (ABL). Cela n’a jamais été fait en utilisant des éléments finis stabilisés. Par conséquent, le défi de ce travail est de répondre à la question simple : Comment modéliser une ABL en s’appuyant sur la méthode de stabilisation SUPG. Afin de réduire le nombre d’éléments nécessaires pour une simulation résolvant toutes les échelles de turbulences jusqu’aux parois, l’ABL a été implémentée avec un modèle de paroi, puis vérifiée en 2D, tandis que quelques corrections (la résolution du maillage, la stabilité du profil de vitesse) ont également pu être menées. Néanmoins, l’implémentation 3D a révélé certaines oscillations parasites, laissant supposer à une origine numérique. Bien que la SUPG produise de la dissipation, cette dernière ne semble pas suffisante pour un écoulement à nombre de Reynolds aussi élevé. Par conséquent, pour ajouter de la dissipation, deux directions ont été suivies : Premièrement, une implémentation de l’évolution de la SUPG, la Méthode Variationnelle MultiScale (VMS), a été initiée. Cette dernière fournit un cadre combiné à la fois pour la stabilisation et la modélisation de la turbulence. Deuxièmement, deux formulations LES, connues pour leur comportement dissipatif, ont également été intégrées. Après avoir réduit les oscillations parasites, le profil de vitesse a été analysé. Finalement, pour permettre la comparaison avec un résultat DNS disponible, le nombre de Reynolds visqueux du domaine ABL a été réduit. Favorablement, et ceci également pour deux autres conditions, l’implémentation du modèle ABL a fourni des résultats se rapprochant le plus de la courbe DNS. En conclusion, nous avons déterminé deux méthodologies (LES et SUPG / VMS) qui ont le potentiel d’approcher l’écoulement ABL. La FEM stabilisée utilisant la SUPG a révélé qu’elle n’est actuellement pas encore suffisante pour éviter les oscillations parasites dans le cas d’un écoulement ABL. En revanche, la LES a fourni des résultats encourageants, ce qui prouve qu’un certain type de modèle de turbulence est indispensable. Cela souligne l’intérêt pour la méthode VMS, bien que celle-ci reste difficile à implémenter<br>In the context of a Chemical, Biological, Radiological, and Nuclear (CBRN) application for the Belgian Defense, the original objective of the work was to simulate a realistic open-air CBRN case (e.g. dispersion after an explosion of particles in a city), by applying the Streamline-Upwind Petrov-Galerkin (SUPG) stabilization on a nite element method (FEM), together with a second phase (i.e. particles). This would be done through the code Cool uid 3, a Domain Speci c Language (DSL) written in C++.However, open-air applications requires to describe the atmospheric bound-ary layer (ABL) correctly. This has never been done using stabilized FEM. Consequently, the challenge of this work is to answer the simple question: How to model an ABL taking advantage of the SUPG stabilization method.To reduce the number of elements produced by a wall-resolved simulation, the ABL was implemented with a wall model and veri ed in 2D, while a few corrections (e.g. grid scalability, stable velocity pro le) could also be adressed.However, the 3D implementation revealed spurious oscillations, suggesting a numerical origin. Although SUPG does provide dissipation, it seemed not su cient enough for such a high Reynolds ow. Consequently, two directions were followed to add numerical dissipation: Firstly, the implementation of an extended version of the SUPG, the Variational MultiScale method (VMS), was initiated. The latter provides a combined framework for stabilization and turbulence modeling. Secondly, two LES formulations, known for their dissipative behavior, were integrated.Having solved the spurious oscillations, the velocity pro le was analyzed. Eventually, the viscous Reynolds number for the ABL domain was reduced to enable the comparison with an available DNS result. Fortunately, rela-tive to the standard no-slip wall condition and to the friction velocity condi-tion, the wall model implementation provided the best result, although not matching.In conclusion, we ascertained two methodologies (LES and SUPG / VMS) that have the potential to approach the ABL ow. The stabilized FEM using SUPG revealed that it is currently not su cient to avoid spurious oscillations in the case of an ABL ow. In contrast, LES provided encouraging results for reduced Reynolds number, supporting that some kind of turbulence model is indispensable. This emphasizes that the implementation of VMS should be promising, although challenging

The Wells turbine is a self-rectifying device that employs a symmetrical blade profile, and is often used in conjunction with an oscillating water column to extract energy from ocean waves. The effects of solidity, angle of attack, blade shape and many other parameters have been widely studied both numerically and experimentally. To date, several 3-D numerical simulations have been performed using commercial software, mostly with steady flow conditions and employing various two-equation turbulence models. In this paper, the open source code Open-FOAM is used to numerically study the performance characteristics of a Wells turbine using a two-equation turbulence model, namely the Menter SST model, in conjunction with a transient fluid solver.

Falling water film modeling is crucial for the thermal hydraulic analysis of passive containment cooling system in advanced light water reactors. A dynamic liquid film model has been developed in the 3-D parallel CFD code GASFLOW-MPI to track the water film transport over the external surface of the steel containment. The gas phase, both inside and outside of the containment, the steel containment and the falling water film are coupled with each other through the essential source terms of inter-phase transport. The model has been verified by the Nusselt solution. Since very few useful experimental data can be found in the open literature, we compared the numerical results of GASFLOW-MPI and COMMIX code which is considered to be reliable because the code has been validated by the experimental data of the Westinghouse small/large scale integral test facilities. A passive containment cooling system has been simulated using the dynamic film model in GASFLOW-MPI. Good agreement was obtained when compared to the COMMIX results, regarding the water film thickness, velocity and temperature. The effect of mesh sensitivity on the heat and mass transfer needs further study. Further work is required concerning the heat transfer, evaporation and boiling at the interface of water film and gas mixtures in the annular space. Local film dry-out model will be implemented in the GASFLOW-MPI. In general, the calculation results using the dynamic film model positively demonstrated the capability of CFD code GASFLOW-MPI in simulation of passive containment cooling system.

Using the computational fluid domain for propagation of ocean waves have become an important tool for the calculation of highly nonlinear wave loading on offshore structures such as run-up, wave slamming and non-linear breaking wave kinematics. At present, there are many computational fluid dynamics (CFD) codes available which can be employed to calculate water wave propagation and wave induced loading on structures. For practical reasons, however, the use of these codes is often limited to the propagation of regular uni-directional waves initiated very close to the structure, or to investigating the properties and loading due to measured waves by fitting a numerical wave to a measured wave profile. The present paper focuses on the propagation of steep irregular and short crested wave groups up to the point of breaking. Indeed, this is challenging because of the highly nonlinear behavior of irregular wave groups as steepness increases and they approach the point of breaking. The complexity further increases with the introduction of short-crestedness requiring computation in a large 3-dimentional domain. Two CFD codes are used in this comparison study which are believed to be well conditioned for wave propagation, the commercial code ComFLOW (available through the ComFLOW JIP project) and the open-source code BASILISK. The primary objective of this paper to show the two CFD codes capability of recreating measured irregular wave groups, using the known linear wave components from the model test as input to fluid domain. Wave elevation is measured at several locations in the close vicinity of the focus point. The comparison is carried out for a selection of events with variation in steepness, wave spreading and wave spectrum.

Multi-physics coupling analysis is one of the most important fields among the analysis of nuclear power plant. The basis of multi-physics coupling is the coupling between neutronics and thermal-hydraulic because it plays a decisive role in the computation of reactor power, outlet temperature of the reactor core and pressure of vessel, which determines the economy and security of the nuclear power plant. This paper develops a coupling method which uses OPENFOAM and the REMARK code. OPENFOAM is a 3-dimension CFD open-source code for thermal-hydraulic, and the REMARK code (produced by GSE Systems) is a real-time simulation multi-group core model for neutronics while it solves diffusion equations. Additionally, a coupled computation using these two codes is new and has not been done. The method is tested and verified using data of the QINSHAN Phase II typical nuclear reactor which will have 16 × 121 elements. The coupled code has been modified to adapt unlimited CPUs after parallelization. With the further development and additional testing, this coupling method has the potential to extend to a more large-scale and accurate computation.

Within the current combustor design process, the combustor performance and sizing is mainly estimated using Prelim Design Tools, which are based on empirical correlations. In order to investigate these preliminary designs in more detail, the application of CFD within the preliminary combustor design process has steadily increased. However, the generation of CFD solutions is a time consuming process, since it requires adapted CAD models and the generation of meshes before the actual CFD computations can be performed. Moreover, it has to be assured that the meshes are suitable for the computational code, which may require several iterations within the grid generation process. Next the manual setting of the boundary conditions for CFD is also prone to errors and the post-processing of the CFD results is generally time consuming. Therefore, an advanced approach of an automated preliminary combustor design process has been developed within the 7th framework of the European research project IMPACT-AE, based on the knowledge obtained in the 6th framework of the European research project INTELLECT D.M. The processes developed are based on improved and robust knowledge-based-engineering tools for modern low NOx combustor geometries. The advanced approach comprises a KBE preliminary design tool with improved Rolls-Royce in-house design rules for modern low NOx high efficiency combustors. It is based on fully featured 3-D parametric combustor models, including the pre-diffuser, the injector, the flame tube and the casing parts. An unstructured automatable meshing-tool CFS BOXERMesh is used to generate high quality meshes. Subsequent CFD analyses are performed using an unstructured Rolls-Royce in-house combustion CFD code PRECISE-UNS and the post-processing is performed using the open source tool ParaView. The choice of these tools is based on their ability to be fully automated using appropriate scripts and information. To create a strong linkage between these tools a KBE interface-tool and a database were implemented. These tools manage the individual processes fully automatically, including e.g. the transfer of geometry parameters to the CAD models; the gathering of the combustion chamber dependent boundary conditions and numerical parameters for the CFD analysis; or the generation of tool-internal automation scripts, using interface-tool input and database information. Several grid refinement studies were performed to define an automated mesh refinement strategy, using scaled cell sizes for each combustor feature. Furthermore, a mixing port diameter scaling and a detailed post-processing procedure are described.

Here the premixed Conditional Moment Closure (CMC) method is used to model the recent PIV and Raman turbulent, enclosed reacting methane jet data from DLR Stuttgart [1]. The experimental data has a rectangular test section at atmospheric pressure and temperature with a single inlet jet. A jet velocity of 90 m/s is used with an adiabatic flame temperature of 2,064 K. Contours of major species, temperature and velocities along with velocity rms values are provided. The conditional moment closure model has been shown to provide the capability to model turbulent, premixed methane flames with detailed chemistry and reasonable runtimes [2]. The simplified CMC model used here falls into the class of table lookup turbulent combustion models where the chemical kinetics are solved offline over a range of conditions and stored in a table that is accessed by the CFD code. Most table lookup models are based on the laminar 1-D flamelet equations, which assume the small scale turbulence does not affect the reaction rates, only the large scale turbulence has an effect on the reaction rates. The CMC model is derived from first principles to account for the effects of small scale turbulence on the reaction rates, as well as the effects of the large scale mixing, making it more versatile than other models. This is accomplished by conditioning the scalars with the reaction progress variable. By conditioning the scalars and accounting for the small scale mixing, the effects of turbulent fluctuations of the temperature on the reaction rates are more accurately modeled. The scalar dissipation is used to account for the effects of the small scale mixing on the reaction rates. The original premixed CMC model used a constant value of scalar dissipation, here the scalar dissipation is conditioned by the reaction progress variable. The steady RANS 3-D version of the open source CFD code OpenFOAM is used. Velocity, temperature and species are compared to the experimental data. Once validated, this CFD turbulent combustion model will have great utility for designing lean premixed gas turbine combustors.

This paper details the design, validation and verification of two implicit modelling techniques used to model an Air-Cooled Condenser (ACC) in the computational fluid dynamics (CFD) code environment of OpenFOAM (Open Source Field And Manipulation). The actuator disk model was chosen as the axial flow fan model and the heat exchanger model was implemented as an A-frame, or Delta frame, heat exchanger commonly found on power stations. Both models were validated and verified. A 30 fan ACC was verified against previous literature. The results for all validation and verification procedures showed good agreement with respective data. Three different fan configurations in an ACC were compared at different wind speeds namely the A-fan, B2a-fan and a Combined ACC. The study showed small differences between ACCs with regard to fan and thermal performance. However, the B2a-fan ACC consumed 20% less power than the A-fan ACC and 3–10% less power than the Combined ACC. This performance increase was most prominently show-cased by the increased heat-to-power ratio with the B2a-fan exhibiting heat-to-power ratios of 110 W/W compared to 96 W/W for the A-fan.

The Remotely Operated Vehicle, so called “ROV” which has crawler based moving system is considered as one of the appropriate underwater vehicles for seafloor exploration or seabed resources development [1][2][3][4][5][6][7]. The advantages of crawler driven ROV are to be able to stay on a fixed sea bottom location and to be capable to do heavy works such as digging the seafloor. However, the ROV moving on the sea bottom with crawler based driving system easily turn over due to the buoyancy and hydrodynamic forces [8][9][10][11][12]. Therefore, it is important to know the moving capability of the ROV on the sea bottom for the design point of view. The authors have shown the condition for the normal running of the ROV which moves on horizontal and inclined flat sea bottom by means of a simple dynamic model [11]. Normal running means that the ROV runs without bow-up or stern-up situations and the crawlers touch the ground normally. The normal running condition of ROV indicates the constrained condition of the relation between gravity and buoyancy center locations for any given design parameters such as geometry, weight, displacement and running speed of the ROV. Though this method estimates the ROVs’ moving capability with acceptable accuracy, the hydrodynamic forces on the ROV and its application point are required for accurate estimation. In the previous research, those quantities are roughly estimated from the past experimental investigations. The present study investigated the flow around the crawler driven ROV which runs on seafloor with CFD (Computational Fluid Dynamics) analysis to evaluate the characteristics of hydrodynamic forces acting on the ROV. The open source CFD code, OpenFOAM [13] was applied for flow calculation and the results were validated with model experiments. By using the calculated hydrodynamic forces on ROV, the moving capability of ROV was evaluated with a method the authors had shown. The estimates of the running capability of the ROV by using the CFD calculations are quite different from past estimations in some running conditions.

Current understanding of blast induced traumatic brain injury (TBI) mechanisms is incomplete and limits the development of protective and therapeutic measures. Animal testing has been used as a surrogate for human testing. The correlation of animals to human responses is not well understood with a limited set of experimental data, because of ethical concerns and cost of live animal tests. The validated computational animal models can be used to supplement and improve the granularity of available data at a significantly reduced cost. A whole-body porcine high-fidelity computational model was developed based on the image data. The hyper-viscoelastic model was used for soft tissues to capture the rate dependence and large strain nonlinearity of the material. The shock wave interaction with a porcine subject in a shock tube was simulated using computational fluid dynamics (CFD) models, via a combination of 1-D, 2-D and 3-D numerical techniques. The shock wave loads were applied to the exterior of the porcine finite element (FE) model to simulate the pressure wave transmission through the body and capture its biomechanical response. The CFD and FE problems are solved using the explicit Eulerian and Lagrangian solvers, respectively, in the DoD Open Source code CoBi. The computational models were validated by comparing the simulation results with experimental data at specific instrumented locations. The predicted brain tissue stress-strain fields were used to determine the areas susceptible to blast induced TBI by using published mechanical injury thresholds. The validated porcine model can be used to better understand TBI and how injury in animals corresponds to injury in humans. The coupled Eurlerian and Lagrangian approaches developed in this paper can be extended to other simulations to improve the solution accuracy.

In consideration of the extremely rapid progress in turbomachinery technology after the WWII, when the first gas engine was run, modern turbomachinery could be considered a young subject. Developments in computational power and numerical techniques since the 1940s, totally changed designer’s perspectives, giving them the possibilities to increase power and sophistication of design tools consolidated by years of laboratory and field tests from the 1940’s and 1950’s. A huge database from which, we believe, “there is still so much to be learned” (Cumpsty, 1986) [1]. On the other hand turbomachinery performance correlations, or even design procedures, have tended to be developed in individualistic ways. A reason for this has been the use of different approaches within engineering companies and the development of customized design tools and correlation of previous experience or performance optimization. These circumstances reflected in an extraordinary knowledge, hided by confidentiality and intellectual property issues. In this respect, proprietary design techniques acts as a barrier to the dissemination of concepts at the early stages such as the university. This paper illustrates the design process of an industrial fan as taught at Sapienza, University of Rome, during lectures of Turbomachinery Design. Objective of the class was to help students learn to develop their own design tools from the available suggested literature Horlock (1958, 1962, 1966) [2] [3] [4], Dixon (1975) [5], Lakshminarayana (1995) [6], Cumpsty (1989) [1] and Lewis (1996) [8]. Moreover, the activities were oriented to the use of open source software, specifically Scilab, used to code preliminary design and optimization routines as well as OpenFoam for the CFD verification step.