The simulation of heat pipe microreactors is an active area of research. In this paper, a thermal analysis of a heat pipe microreactor motivated by the eVinci™ design is performed. Thorough ...discussion on the modeling of heat pipes without a dedicated heat pipe modeling code, such as Sockeye, is also provided. The performance of two heat pipe modeling techniques is compared, one a more accurate approach which explicitly tracks heat pipe temperatures, and the other an approximation which simplifies the thermal hydraulic model development. One-way coupling is used where the Serpent neutronics code is used to generate a power distribution which is applied in an OpenFOAM model to calculate a temperature distribution. After a detailed convergence analysis, the core temperature distribution resulting from a core with control drums facing outward, or fully withdrawn, is compared with one having the control drums facing inward, or fully inserted. Finally, a parametric analysis was performed where the thermal resistances associated with the heat pipe model were varied and core temperatures were tracked. It was observed that the relationship between average and maximum core temperatures had a highly linear relationship to the thermal resistances used in the heat pipe model.
•OpenFOAM performs thermal simulations on an eVinci-like microreactor.•Serpent code generates power distribution; OpenFOAM calculates temperature.•A simplified heat pipe model based on a thermal resistance network is used.•Different iterative procedures for solving temperatures are explored.
This study addresses the computational challenges in fluid flow simulations arising from demanding computational grids, required to capture the temporal and length scales involved. Our approach ...focuses on the pressure solver, as this is a resource-intensive component in Computational Fluid Dynamics (CFD) solvers. We achieve this by integrating a Machine Learning (ML) surrogate model with an incompressible fluid flow solver. We created two variants of an ML-enhanced CFD solver which were able to reduce the number of iterations required by the CFD pressure solver during unsteady flow simulations. Consequently, the simulations yielded comparable drag coefficients and Strouhal numbers, accompanied by an eightfold decrease in execution time. The performance enhancements are attributed to reduced computational effort per temporal iteration and early-stage forcing on the simulation dynamical behavior when using the ML-based surrogate models. This research introduces an approach to enhance the computational efficiency of fluid flow analyses by incorporating surrogate models to aid the pressure solver in CFD simulations. We propose a Hybrid CFD solver, ie. a physics-informed solver enhanced with data-driven surrogate models.
The objective of the present work is to investigate wave run-up around a monopile subjected to regular waves inside a numerical wave flume using the Computational Fluid Dynamics (CFD) toolbox ...OpenFOAM®. Reynolds-Averaged Navier-Stokes (RANS) turbulence modelling is performed by applying the k-ω SST model. Boundary conditions for wave generation and absorption are adopted from the IHFOAM toolbox. Simulations of propagating water waves show sometimes excessive wave damping (i.e. a significant decrease in wave height over the length of the numerical wave flume) based on RANS turbulence modelling. This anomaly is prevented by implementing a buoyancy term in the turbulent kinetic energy equation. The additional term suppresses the turbulence level at the interface between water and air. The proposed buoyancy-modified k-ω SST turbulence model results in an overall stable wave propagation model without significant wave damping over the length of the flume. Firstly, the necessity of a buoyancy-modified k-ω SST turbulence model is demonstrated for the case of propagating water waves in an empty wave flume. Secondly, numerical results of wave run-up around a monopile under regular waves using the buoyancy-modified k-ω SST turbulence model are validated by using experimental data measured in a wave flume by De Vos et al. (2007). Furthermore, time-dependent high spatial resolutions of the numerically obtained wave run-up around the monopile are presented. These results are in line with the experimental data and available analytical formulations.
•Simulations of wave run-up around a monopile in a wave flume using OpenFOAM®.•RANS turbulence modelling causes wave damping over the length of the flume.•A buoyancy-modified k-ω SST turbulence model is proposed to avoid wave damping.•The buoyancy-modified turbulence model is validated with experimental results.
dsmcFoam+ is a direct simulation Monte Carlo (DSMC) solver for rarefied gas dynamics, implemented within the OpenFOAM software framework, and parallelised with MPI. It is open-source and released ...under the GNU General Public License in a publicly available software repository that includes detailed documentation and tutorial DSMC gas flow cases. This release of the code includes many features not found in standard dsmcFoam, such as molecular vibrational and electronic energy modes, chemical reactions, and subsonic pressure boundary conditions. Since dsmcFoam+ is designed entirely within OpenFOAM’s C++ object-oriented framework, it benefits from a number of key features: the code emphasises extensibility and flexibility so it is aimed first and foremost as a research tool for DSMC, allowing new models and test cases to be developed and tested rapidly. All DSMC cases are as straightforward as setting up any standard OpenFOAM case, as dsmcFoam+ relies upon the standard OpenFOAM dictionary based directory structure. This ensures that useful pre- and post-processing capabilities provided by OpenFOAM remain available even though the fully Lagrangian nature of a DSMC simulation is not typical of most OpenFOAM applications. We show that dsmcFoam+ compares well to other well-known DSMC codes and to analytical solutions in terms of benchmark results.
Program title: dsmcFoam+
Program Files doi:http://dx.doi.org/10.17632/7b4xkpx43b.1
Licensing provisions: GNU General Public License 3 (GPL)
Programming language: C++
Nature of problem: dsmcFoam+ has been developed to help investigate rarefied gas flow problems using the direct simulation Monte Carlo (DSMC) method. It provides an easily extended, parallelised, DSMC environment.
Solution method: dsmcFoam+ implements an explicit time-stepping solver with stochastic molecular collisions appropriate for studying rarefied gas flow problems.
References: All appropriate methodological references are contained in the section entitled References.
The exploration of multifunctional systems to harvest wave energy has become increasingly prominent in recent research. This paper presents a comprehensive investigation into the effectiveness of ...utilizing a wave energy converter (WEC) not only for energy generation but also as a coastal protection measure. Among the various types of WECs, the Oscillating Water Column (OWC) stands out as particularly promising due to its inherent advantages and notable efficiency. The versatility of the OWC allows for standalone installation or integration into hybrid systems, such as combining it with breakwaters. While numerous studies have examined the integration of OWCs with Caisson-type breakwaters, research on their integration with Semi-circular breakwaters (SCBW) is scarce. This study fills this gap by utilizing the open-source computational fluid dynamics (CFD) tool, OpenFOAM, to analyze the hydrodynamic performance of an OWC embedded within an SCBW. The numerical findings are validated against existing experimental data, enabling a thorough comparative analysis between the performance of an isolated OWC and a hybrid OWC integrated with SCBW. The investigation delves into various parameters, including wave amplification factor, chamber air and water pressure, external water pressure, energy transfer efficiency from chamber water to air, and wave run-up over the SCBW face. The results conclusively demonstrate that an OWC integrated with SCBW exhibits superior hydrodynamic performance compared to standalone configurations.
•Comparison of hydrodynamic performance of an isolated and hybrid OWC is investigated.•The effect of wavelength and wave steepness on the hydrodynamic performances of both OWC systems are reported.•Sloshing phenomena inside the OWC chamber are discussed.•Energy loss from chamber water to the air chamber has been investigated.•Effect of runup over the face of SCBW and the effects of the harbour wall on the efficiency of the OWC are also studied.
This paper presents a new methodology allowing the discretisation of phase specific transport equations within the Volume-of-Fluid interface capturing method framework. The method uses a sharp ...interface algorithm to compute the transport of species concentration. The interface reconstruction and advection is provided by the geometric advection scheme isoAdvector1 implemented in the OpenFOAM® library. When discretising the transport equation for species, lack of consistency with the free surface advection scheme can lead to numerical errors, causing conservation or boundedness issues. This work addresses the issue of consistency in convective transport of species and is divided in two parts. First, a new interpolation procedure is used to compute face values from cell-centered values. Then, the diffusive operator of the transport equation is corrected. Finally, a set of test cases are presented to validate the transport equation's consistency with the free surface advection. Species transport across the interface is not part of the scope of this article, however, this methodology can further be used to study mass transfer at the gas-liquid interface using additional mass source terms that are not discussed here.
•A new methodology to discretize a transport equation for species concentration has been described.•This methodology is consistent with the geometric Volume-of-Fluid method isoAdvector which is available in OpenFOAM.•The developments made in this work avoid artificial mass transfer between the phases.•Diffusive fluxes were also corrected to avoid non-physical fluxes using the species concentration inside the phase.
Coral reefs consist of various alive elements with specific biological functions. Tubular sponges, as the main coral reefs' constituents, have a marvelous mechanism. They receive nutrients by ...suctioning from the perforated body (Ostia) and pumping the un-digested materials through the water column from the top mouth (Osculum). This mechanism can be an inspiration for making a device to control or improve sediment/pollutant transport. In the current study, an attempt has been made to evaluate an inspired concept's effects on flow hydrodynamics. In this regard, OpenFOAM® V. 1812 (interFOAM solver) and image processing technique were deployed. The perforated finite-height cylinders (height to diameter ratio of 2.5) with various suction/pump discharges (i.e., J = 150, 300, 350, 400, 450, and 600 lit/h) were considered. The results indicated that increasing the outflow discharge (J ≥ 600 lit/h) could widen the wake by flapping the shear layer. In the vertical plane, the results showed that dipole vortices turned into quadrupole vortex. On the free surface, tip-vortices and counter-rotating vortex pairs (CRVP) generated saw-toothed vortices on two sides of the cylinder. Generating these unique vortices is proof of enhancing the momentum exchange through the water column.
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•The suction/pumping causes vortex streets types I, II, and III to emerge.•Tip vortex and CRVP generate a saw-toothed vortex on the free surface.•The wake widening occurred for sponges with high outflow discharge.•Numerical experiments were performed by OpenFOAM software.•An image processing technique was deployed to capture the re-circulation zones.
When a heat pipe is used as a cooling system for road vehicles, it is subject to acceleration which can adversely affect its thermal performance. In this study, we investigate the possibility of ...applying heat pipes for the cooling of power modules subject to time-varying power dissipation and time-dependent acceleration vectors whose projection along the heat pipe axis is up to 3g. The problem is tackled by modelling the heat pipe through a lumped parameter thermal network (LPTN). A numerical algorithm is used to solve the equations of LPTN representing the heat pipe. The code is then coupled with a 3D CFD solver (OpenFOAM) to perform a 1D/3D co-simulation and test the applicability of heat pipes as the cooling system in high-performance cars.
•Lumped Parameters Thermal Network to simulate heat pipes under acceleration;•1D/3D co-simulation with OpenFOAM to study power module temperature distribution;•Investigation, through an application, of the effect of accelerations on the thermal performance of heat pipes.
Hydrogen is an ideal energy source and plays an important role in increasingly global energy issues and environmental problems. Liquid hydrogen (LH2) has many advantages over other storage methods, ...especially in terms of energy density. However, it may cause enormous harm once it leaks accidently. LH2 leakage is a complex multiphase process involving evaporation, condensation, transfer of mass and heat, and dispersion. In order to study LH2 transportation and storage systems safety, a research project has been carried out to develop a 3D numerical model using an open-source CFD code, OpenFoam, for investigating LH2 accidental release scenarios. Since the release of LH2 is a very complex process, our strategy is to study it step by step. Therefore, in this paper we present our research work at the first stage, a dispersion process of room-temperature gaseous hydrogen without multiphase flow. A small-scale hydrogen release conducted by Sandia National Laboratories is simulated. In this experiment, room-temperature gaseous hydrogen is injected upwards into the air from a small hole with a 1.91 mm diameter. The situations of Froude (Fr) number = 99, 152, and 268 are studied, respectively. The behavior of hydrogen at different Fr numbers is discussed. When high-speed hydrogen enters the air, the speed and concentration of hydrogen decrease rapidly. In addition, the greater the speed, the faster it decays. The result shows a close range of hydrogen reach. Details about the numerical model are introduced. The simulation results are used to verify the validity of the developing numerical model for dispersion and mixing of multi-species. The simulated concentrations and velocity distribution are analyzed and compared with experimental data. The simulation shows a good agreement with the data of Sandia National Laboratories. The agreement between experiments and simulations is measured using the Pearson correlation coefficient (>0.98), which indicates excellent consistency. In the next step, we will integrate the multiphase flow and phase change into the current model. The phase change of liquid hydrogen and air will be simulated to study the release of liquid hydrogen.
•Using the open-source CFD code OpenFOAM for simulation of hydrogen jet.•A good agreement between the simulations results and experimental data has been found in this paper.•When high-speed hydrogen is injected into the air, both velocity and concentration drop rapidly.•Final concentration is not sensitive to different injection velocity.
In this work a 1D finite volume based model using coupled meshes is introduced to capture potential and species distribution throughout the discharge process in a lithium–bismuth liquid metal battery ...while neglecting hydrodynamic effects, focusing on the electrochemical properties of the cell and the mass transport in electrolyte and cathode. Interface reactions in the electrical double layer are considered through the introduction of a discrete jump of the potential modelled as periodic boundary condition to resolve interfacial discontinuities in the cell potential. A balanced-force like approach is implemented to ensure consistent calculation at the interface level. It is found that mass transport and concentration gradients have a significant effect on the cell overpotentials and thus on cell performance and cell voltage. By quantifying overvoltages in the Li||Bi cell with a mixed cation electrolyte, it is possible to show that diffusion and migration current density could have counteractive effects on the cell voltage. Furthermore, the simulated limiting current density is observed to be much lower than experimentally measured, which can be attributed to convective effects in the electrolyte that need to be addressed in future simulations. The solver is based on the open source library OpenFOAM and thoroughly verified against the equivalent system COMSOL multiphysics and further validated with experimental results.
•A charge and species transport model for liquid metal batteries (LMBs) is developed.•The OpenFOAM model is capable to simulate the full battery and thoroughly verified.•Ohmic and concentration overpotentials in LMBs are investigated and quantified.•Determined cell currents indicate the presence of fluid flow in the electrolyte.
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