Groll, Rodion
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Groll, Rodion
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Groll, Rodion
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GND
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Item-typ:Veröffentlichung, picFoam: An OpenFOAM based electrostatic Particle-in-Cell solverpicFoam is a fully kinetic electrostatic Particle-in-Cell (PIC) solver, including Monte Carlo Collisions (MCC), for non-equilibrium plasma research in the open-source framework of OpenFOAM. The solver’s modular design, based on the same principles used in OpenFOAM, makes it highly flexible, by allowing the user to choose different methods at run time, and extendable, by building upon templated modular classes. The implementation of the PIC method employing the finite volume method, allows it to simulate on arbitrary geometries in one to three dimensions. OpenFOAM’s barycentric particle tracking is used effectively to perform charge and field weighting from the Lagrangian particle based description to the Eulerian field description and backwards without computational expensive particle searching algorithm. picFoam also includes open and general circuit boundary models for the description of real plasma devices.Wissenschaftlicher ArtikelBand:26238 18 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Prediction of particle-laden pipe flows using deep neural network modelsAn accurate and fast prediction of particle-laden flow fields is of particular relevance for a wide variety of industrial applications. The motivation for this research is to evaluate the applicability of deep learning methods for providing statistical properties of the carrier and dispersed phases in a particle-laden vertical pipe flow. Deep neural network (DNN) models are trained for different dependent variables using 756 high-fidelity datasets acquired from point-particle large-eddy simulations for different values of Stokes number, St, bulk particle volume fraction, , and wall roughness, , for the range , and . The considered parameter space corresponds to the inertia-dominated regime and covers a large extent of the typical conditions in powder-based laser metal deposition. We find that the DNN models capture the nonlinear dynamics of the system and recreate the statistical properties of the particle-laden pipe flow. However, DNN predictions of the particle statistics are of higher accuracy compared to the fluid statistics, which is attributed to the highly non-monotonic dependence of the fluid statistics on the control parameters. Owing to significantly decreased time-to-solution, the trained DNN models are promising as surrogate models to expedite model development and design process of various industrial applications.Wissenschaftlicher ArtikelBand:35Heft:833 28 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Computational modeling of a ventilation concept for a lunar habitat laboratoryHuman spaceflight demands systems like habitats that provide a livable environment for humans on long duration missions on other planets. This challenge includes the layout of several life support subsystems according to comfort criteria, including air management and the ventilation of supply air. A main goal of the ventilation system is to ensure a comfortable room climate with fresh air while being able to remove waste heat of other habitat systems. In this project we propose a ventilation distribution for a habitat laboratory using the design of MaMBA (Moon and Mars Base Analog) as an example geometry. We evaluate its performance with different exhaust configurations and boundary conditions via numerical simulations with OpenFOAM 6s’ buoyantBoussinesqPimpleFoam solver. Comfort criteria are set according to literature values to ensure a good mixing of the supply and ambient air with a low probability of uncomfortable drafts. First results showed that a cooling system with only one cooling loop, the room ventilation, does not provide an acceptable solution. Therefore a secondary cooling loop, rack ventilation, is proposed. It absorbs the heat of the electrical devices like the scientific instruments, inside the racks, and releases heated air at the rack's bottom in the direction of the room exhaust vents. The combination of two cooling loops can fulfill most of the comfort criteria and should therefore be integrated in the design of the habitat's ventilation system.Wissenschaftlicher ArtikelBand:9Heft:247 21 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Correction of second-order slip condition for higher Knudsen numbers by approximation of free-molecular diffusionThe computational predictions of channel and pipe flows with classical models and no-slip condition at the wall reach excellent results for lower Knudsen numbers (Kn) only. Linear slip models reach a very good approximation of measurement results over the region of 10−3 < Kn < 10−1. The numerical results of higher-order slip models match experimental data up to Kn ≈ 1. The present work derives an analytical model for the transition from the slip regime to the free-molecular flows by the superposition of diffuse molecular boundary reflection and the molecular diffusion inside the bulk flow. The methodology of the present publication models the mass flow resulting from the molecular diffusion for the approximation of the mass flow in microchannels and micropipes for the regime of molecular mass flows (1 < Kn < 100) in an excellent way. The present model shows good agreement with the former models, measurement data, and direct simulation Monte Carlo results for the complete region from the transitional regime up to free-molecular flow (10−2 < Kn < 102).Wissenschaftlicher ArtikelBand:32Heft:919 15