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A CFD analysis of the flow inside of the VMU MkII in micro-gravity conditions is presented. In the context of complementing the different calculations made by CSL professional using the ESATAN-TMS software, this thesis will contribute to support the existing data of the unit regarding the airflow and the components of the VMU.
After considering the characteristics and conditions of the flow inside this unit, the mathematical formulation of the problem is proposed. Then, the numerical implementation is presented and for this task, the finite volume method OpenFOAM software is used.
A CAD model of the VMU MkII is been loaded and re-built using the SALOME software. After the model is meshed using the snappyHexMesh OpenFOAM utility, a mesh convergence study has been performed defining the mesh where the final results will be obtained.
The results of the thesis display an impact of the bottom rails of the FPIU of 60% in the velocity field and a maximum discrepancy in velocity of 22:37% between the k-w and k-w SST turbulence models. On the other hand, it is observed that the mean temperatures of the components surpass the thermal requirements of the VCU by 4.2K for the VCU, by 53.38K for the CPU and by 97.95K for the SA50-120 modules. Also, the sensitivity analysis for the turbulent intensity at inlets shows that a 1% variation of the turbulent intensity at the inlets gives rise to an average variation of the velocity magnitude of 0.07%.
As a conclusion, it is important to underline that the inclusion of conduction in the
modeling and a different power distribution may be the reason why the mean temperatures
of the components are overestimated. Also, due to the lack of solid experimental
data it is not possible to confirm which turbulence model is more suitable for the case of
study. Finally, the small variations of the solution due to the sensitivity analysis may be
an indicator that the boundary condition for the turbulent kinetic energy at the inlets is
well posed.

heat transfer, turbulent flow, OpenFOAM, RANS --- Ingénierie, informatique & technologie > Ingénierie aérospatiale

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In predicting the resistance of ship hulls, experiments in towing tanks have been mostly performed before the extensive use of CFD applications. Time and cost turn out to be key factors in consideration along with the accuracy of results. High costs of experiments and limitations in testing several scenarios in towing tests led to an increased use of CFD codes for ship resistance and propulsion applications. Bureau Veritas (BV) Solutions has interests in developing in-house CFD codes in order to reduce license costs and to enable the engineers to contribute to the code development. One of these CFD tool is being jointly developed by Bureau Veritas (BV) and École Centrale de Nantes (ECN). It is based on OpenFOAM open-source libraries for obvious reasons of accessibility and cost. Its name is foamStar.
The work performed in this internship enabled to verify the robustness and sensitivity of foamStar in view of its industrial use on resistance cases. At first, multiple sensitivity studies both on numerical parameters and grid parameters were conducted. It showed the importance of good practices to optimise its use and highlighted some of the key setup options to be used. Moreover, some unstable cases/configurations were encountered showing the poor stability of foamStar, especially with regard to the mesh.
Then, the benchmark cases of KCS and DTMB 5415 hulls have been performed in calm water resistance computations. Good agreement was observed in resistance coefficients, free surface pattern and wave profiles between foamStar and experimental results. It can be said that foamStar can capture flow phenomena with the certain degree of accuracy. These results are encouraging and tend to validate the capability of the software for resistance predictions with a small tendency to over-estimate it.
For industrialisation purpose, the setup procedure to run foamStar calculations have also been automatized by modifying the BVS’s existing script. The workability and the reliability is well established by testing it on hull optimisation cases. In addition, the results obtained for this optimisation study showed that while over-estimating the resistance, foamStar results are in line with ISIS-CFD results with regard to relative comparison of the various hull forms tested. It is a positive outcome which tends to validate its use for such applications. However, it needs to be investigated further prior to any industrial use as one case is not enough for validation.

Hydrodynamics --- Ship Resistance --- foamStar --- OpenFOAM --- CFD Benckmark --- Hull Optimisation --- BVS --- ECN --- Ingénierie, informatique & technologie > Ingénierie mécanique

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The research in the field of Computational Fluid Dynamic in turbulent separated flows is a hot topic in the industrial and academic aerospace sector. Aeronautic industrial standards require each time better and more powerful CFD methods to inquire the behavior of turbulent flows as a consequence of their growing use in aeronautical design. They are extremely important in almost every engineering discipline, especially in those which are facing aerodynamic and structural design; as aerospace, vehicle or naval engineering.

This present master thesis centers its work exploring the turbulent separated flow physics and vortex detachment in a simple flat plate geometry. In the first place, the flat plate profile was considered static at an angle of attack of 30 degrees and 4e4 Re. In the second case, the flat plate was moved with a large oscillation angle of attack at a determined frequency of rotation in pitching motion. The simulation results were compared with experiments, trying to reproduce the reality of the flow behavior and detecting possible discrepancies.

For every case, a mesh refinement study was performed, reducing the numerical error to stabilize the solution. The aerodynamic coefficients, shedding frequency and vortex detachment results were presented for unsteady RANS and DDES approaches with two solvers: OpenFOAM and SU2, both open-source software. Moreover, a certain sensitivity analysis was accomplished to discern how the span-length or the pivot point parameter might affect the results. The analysis was completed shifting the turbulence modeling; Spalart-Allmaras and k-omega SST model of Menter were both verified.

The results in the static plate show a better approach with DDES method than with RANS, finding those pretty acceptable for both solvers. The high angle induces separation, increasing the relative error in the aerodynamic coefficients. The DDES case was able to predict the reality with an error around 8%. The shedding frequency was exactly the same that the one detected in the experiment, both in 3D URANS and DDES. On the other hand, the performances with OpenFOAM for the pitching plate have distortions when the plate is moved in rigid motion, although in SU2 those results were quite accurate, with errors bellow 5%. The k-omega SST model has positive consequences in the static plate, reducing the relative errors for both codes. However, in the pitching mode, the S-A model presents a better approach for both solvers, even if the outcomes in OF are quite poor.
Finally, and with the aim of further understanding the physics of the phenomena, the data resulting from the DDES cases were decomposed by using a Dynamic Mode Decomposition algorithm to extract the mode shapes.

CFD --- Unsteady RANS --- Detached-Eddy Simulations --- Turbulent separated flows --- OpenFOAM --- SU2 --- DMD --- Ingénierie, informatique & technologie > Ingénierie aérospatiale

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"The book provides a resource for understanding the effluent discharge mechanisms and approaches for modeling them. It bridges the gap between the fundamentals of jets and numerical techniques in hydraulic engineering by integrating the numerical modeling techniques in effluent discharge modeling. The book will benefit both academics and professional engineers working in the area of environmental fluid mechanics and using effluent discharge modeling. With a detailed discussion on performing numerical modeling of effluent discharges in various ambient waters, with different discharge configurations, the book covers the application of OpenFOAM in predictive and regulatory simulations"--

Sewerage. --- Égouts. --- Sewage disposal. --- Eaux usées --- Viscosity. --- Viscosité. --- Programming languages (Electronic computers) --- Langages de programmation. --- Évacuation. --- OpenFOAM (Computer program) --- Égouts. --- Eaux usées --- Viscosité. --- Évacuation.

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With current infrastructure, meeting the ever-growing demand for electrical energy across the globe is becoming increasingly difficult. The widespread adoption of both commercial and residential non-dispatchable renewable energy facilities, such as solar and wind, further taxes the stability of the electrical grid, often causing traditional fossil fuel power plants to operate at lower efficiency, and with increased carbon emissions. Hydropower, as a proven renewable energy technology, has a significant part to play in the future global electrical power market, especially as increasing demand for electric vehicles will further amplify the need for dispatchable energy sources during peak charging times. Even with more than a century of proven experience, significant opportunities still exist to expand the worldwide hydropower resources and more efficiently utilize existing hydropower installations. Given this context, this Special Issue of Energies intended to present recent developments and advancements in hydropower design and operation. This Special Issue includes five articles, authored by international research teams from Japan, Pakistan, Sweden, Norway, the United States, and China. The authors bring the collective expertise of government research laboratories, university professors, industry research engineers, computer scientists, and economists. The articles explore advancements in hydroturbine and pump-turbine design, power plant operation, auxiliary equipment design to mitigate environmental damage, and an exploration of community-owned small hydropower facilities.

community development --- community ownership --- small hydropower --- SHP --- renewable energy --- crowdfunding --- FIT --- community-based business --- agricultural cooperative --- hydropower --- pumped hydro storage --- low-head --- counter-rotating --- pump-turbine --- transient sequences --- shutdown --- startup --- OpenFOAM --- CFD --- sand trap --- sediment transport --- particle --- multiphase --- hybrid power --- neural networks --- pumped-storage hydro --- solar --- photovoltaic --- pump turbine --- pump mode --- slight opening --- flow deflection --- dynamic meshing technique --- n/a