The present work attempts to provide, for the first time to the best of the authors’ knowledge, a comprehensive comparison study about the parallel performance of different Computational Fluid Dynamics (CFD) codes which utilize the overset method to account for the relative motion in the computational domain which is required by the store separation simulations. Two commercial codes (Ansys Fluent and Simcenter STAR-CCM) and two open-source implementations were compared using a generic test case from the open literature utilizing the same mesh, the same hardware, and as much as possible, the same settings. The first open-source implementation was taken from a previous work of the first author, and the second implementation is presented in this work. The scalability and efficiency for the four codes were evaluated up to 2,048 processor cores. The results show that, the open-source implementations performance is satisfactory and even outperform the commercial codes (specially the second implementation) for the tested case.

Computational fluid dynamics (CFD) modelling of liquid embolic agents (Onyx) used in brain arteriovenous malformation (AVM) treatment to predict the distal penetration behavior.

Experimental dataset on wave–structure interaction in a sloshing tank with a flexible floating body

ABSTRACT An experimental and numerical study has investigated the heat transfer (HT) and friction characteristics of a solar air heater (SAH) duct roughened using a rectangular S‐shaped artificial roughness arrangement (inline and staggered). The thermal performance of SAH is studied with design variables such as the length of the relative roughness ( d/H = 1.33), the height of the relative roughness ( e/H = 0.271), and the distance between S ( b / H = 0.667) remaining constant as the Reynolds number ( Re ) ranges from 3000 to 10,000 and the angle of attack 60°. Relative roughness of pitch range p/H (1.667, 3.33, 5, and 6.667) for inline with relative roughness of length ( l/H ) (0.8335, 1.666, 2.5, and 3.335) for staggered. A three‐dimensional computational fluid dynamics (CFD) simulation is carried out using the CFD code, ANSYS Fluent, and the renormalization group k – ε turbulence model for solving turbulence terms in governing equations. It has been found that HT enhancement can be achieved by using an artificial roughness staggered arrangement at l/H = 0.8335 and e/D = 0.271 with an angle of attack ( α ) of 60°. Also offers the best thermal performance factor for the investigated range of 3.12.

One of the most inexhaustible forms of energy is the ocean wave. The conversion of this energy into a useful form of electrical energy is possible by a device of oscillating water column (OWC). This work aims to numerically analyse the effect of the triangular lip wall of the OWC wave energy converter on the hydrodynamic efficiency at different wave steepness conditions (Hi/λ), orifice ratios (ε), and relative openings (σ). This analysis uses commercial computational fluid dynamics (CFD) code ANSYS FLUENT software in a 3D numerical wave tank. The governing equations are discretized using FVM formulation, and the k-ε turbulence model is used. The inlet velocity method is used to generate the waves. The model was validated and verified with the experimental model published by Çelik and Altunkaynak (2019) and implemented for further improvement. The hydrodynamic efficiency (Eff) of the new model increases with relative openings increases and also increases with the decreases in wave steepness. This study shows an optimum efficiency of 76.30% at ε4 = 1.03%, σ =75%, and Hi/λ = 0.02. The information obtained from this numerical investigation of a new model is a highly relevant source, and it provides foresight in the design of the OWC wave energy converter.

ABSTRACT The current study focuses on tackling efficiency issues in photovoltaic (PV) systems caused by increased PV working temperature, leading to reduced electrical efficiency. To do so, a numerical investigation is conducted using a commercial computational fluid dynamics (CFD) code. The proposed solution involves cooling the PV system from the bottom of the photovoltaic thermal (PVT) system. Two distinct cooling methods are explored: air cooling at normal flow and water cooling with a specific mass flow rate (ṁw = 0.002 kg/s). The cooling effectiveness is systematically studied by varying the gap width between the cooling system and the PV, ranging from 1 to 10 cm. The overarching goal is to determine the optimal gap width that enhances both the electrical and thermal efficiencies of the PVT module under a radiation range of 300–1,000 W/m2. Notably, under 1,000 W/m2, the thermal efficiency is significantly improved with a 4 cm water gap width, reaching 50.02%, compared to 19.01% for a 5 cm air gap. The findings indicate that a 4 cm gap provides advantages in maintaining optimal electrical efficiency in the PVT system, particularly when water is utilized as the cooling medium, whereas a 5 cm gap is optimum for air cooling.

This paper presents the development of a multiphysics coupled framework of Monte Carlo neutronics iMC and OpenFOAM Computational Fluid Dynamics codes for molten salt reactor (MSR) analysis. The overall coupling scheme is handled, including the framework structure and iteration scheme. Also, related techniques to enhance the accuracy and efficiency of the coupling are introduced, such as delayed neutron precursor tracking. The framework is applied to a simple molten salt reactor model and achieves a converged solution. In addition, sensitivity studies on the neutronics mesh are performed. The research demonstrates the capability of the iMC-OpenFOAM coupled framework to achieve a converged solution and provides significant insights into the analysis of the MSRs.

The modeling of atmospheric pollutant dispersion in complex environments, particularly around buildings in urban areas, presents a significant challenge for environmental studies and air quality. This study aims to advance the development and application of Eulerian models for pollutant dispersion, utilizing Code_Saturne, a computational fluid dynamics (CFD) code. The approach is based on modeling the Reynolds-averaged Navier-Stokes (RANS) equations, incorporating closure via the simple gradient diffusion hypothesis (SGDH) to simulate the pollutant dispersion in airflow disturbed by a building, under uniform wind conditions and homogeneous turbulence. A comparative analysis of different building heights is conducted to assess their impact on flow structures and pollutant concentration distribution. The results underscore the considerable influence of urban obstacles on dispersion, leading to the formation of accumulation and recirculation zones that significantly modify pollutant distribution patterns. The proposed methodology validates the effectiveness of RANS-SGDH Eulerian modeling for studying atmospheric dispersion in urban areas, offering valuable insights for urban planning and air pollution management. Future work will focus on applying this approach to a real-world case in a Moroccan urban environment, further enhancing its relevance for practical environmental studies.

<div>The objective of the current study is to systematically evaluate the battery thermal runaway heat release rate through chemical kinetics and then study its effect on battery module and pack level. For this purpose, a chemistry solver has been developed, capable of simultaneously solving the thermal runaway kinetics in multiple battery cells with the cell-specific chemistry model and battery active material compositions. This developed solid body chemistry (SBC) solver assumes a homogeneous system in the specified geometrical selection. A 3D representation can be achieved by setting up multiple solver selections in one solid domain (battery cell) as the SBC solver is capable of handling multiple selections, chemistry models, and battery active material compositions. Further, the SBC solver is fully integrated in a commercial three-dimensional computational fluid dynamics (3D-CFD) code. Thus, enabling to simulate the real-life thermal runaway applications covering the battery module and battery pack including relevant physicochemical processes involved. In addition to the direct solution of the chemical kinetics, an alternative approach is proposed for pack-level thermal runaway simulations where kinetically extracted heat release rate is used. As demonstrated in the results and discussion, the SBC solver is able to accurately reproduce the initiation and propagation of thermal runaway on a cell level and provides significant insights when coupled with a 3D-CFD solver on a module- and pack-level simulations and thus understanding the real-life hazard scenarios in the battery safety management.</div>

In this work, we conducted a numerical study of cavitating nanofluid flow through a Venturi. The objective is to investigate the influence of nanoparticles in the base fluid on the cavitation phenomenon. The computational fluid dynamics code (CFD) was selected with a cavitation model. The mixture model for multiphase flow and the k-ω SST turbulence model were adopted. Three fluids were chosen: water, Cu/water and TiO2/water with different volume franctions of nanoparticle (0%, 10% 20%, 30%) . The simulation was conducted with inlet and outlet pressures set at 700 kPa and atmosphere pressure respectively. The numerical results are compared with the previous experimental and numerical data for flow without nanoparticle. The obtained results found that, the presence of the nanoparticles in the base fluid lead to a slight increase in the static pressure, the position of pressure recovery a significant decrease in fluid velocity and an increase in the vapor fraction formation in the flow. Also, the increase of the nanoparticle volume fractions φ results a decrease in the pressure recovery position, fluid velocity and an increase in the vapor fraction formation. Therefore, the presence of nanoparticles in the base fluid promotes the phenomenon of cavitation.

Abstract Liquid hydrogen storage stands out among various storage and transportation methods for its high efficiency. However, accidental leaks of liquid hydrogen pose safety hazards due to the formation of hydrogen clouds. Therefore, a research project developed a three-dimensional numerical model using the open-source computational fluid dynamics (CFD) code OpenFOAM. The accuracy of the numerical simulations was validated by comparing the results with experiments conducted by NASA. An innovative approach called the “air wall” has been proposed as an enhanced safety measure alternative to traditional fencing systems. The air wall consists of a series of upward air outlets designed to intercept the lateral diffusion of low-temperature, high-density hydrogen. The air wall alters the trajectory of hydrogen, increasing convection and diffusion rates and effectively reducing the hazardous range of hydrogen dispersion. The protective efficacy of the air wall was verified through numerical simulations. The geometric model was based on modifications to fencing designs from NASA experiments. Comparative analysis between the traditional cofferdam and the innovative air wall revealed significant differences in hydrogen dispersion trajectories. The research findings demonstrate that the air wall provides a safer option for mitigating the consequences of liquid hydrogen leaks.

Error mechanisms intrinsic to legacy computational fluid dynamics (CFD) effectively compromise physics of fluids fidelity prediction of current CFD codes. Rigorously derived cubically nonlinear calculus alterations to Navier–Stokes (NS) partial differential equation (PDE) systems annihilate these legacy CFD error mechanisms, 1) spatial discretization-induced algebraic instability, 2) space-time discretization-generated phase aliasing, 3) artificial/numerical stabilization schemes, 4) discrete algebra theorization, 5) absence of local/global error estimates and error quantification, 6) physics-based Reynolds stress tensor modeling, 7) incompressible mass conservation, pressure, multiply connected domains, 8) iterative linear algebra admitted convergence stall. Weak formulation continuous Galerkin finite element (FE) algorithms for compressible and incompressible NS and the time-averaged/space-filtering altered PDE systems quantitatively validate these rigorous theoretical alteration leading to, 1) fourth order accuracy in physical space, wavenumber space and time on any mesh, 2) derivation of local/global error estimates and asymptotic convergence rates for FE p = 1,2,3 trial space basis implementations in NS PDE intrinsic norms, 3) analytically closed space-filtered NS PDE prediction of laminar profile velocity incipient transition, separation, turbulent profile reattachment then relaminarization, and finally, 4) matrix differential calculus identification of weak form nonlinear contributions to the quadratic convergent Newton iteration algorithm Jacobian.

To investigate the means for improving molten salt heat transfer components, helically rifled tubes, a passive heat transfer enhancement, are investigated in this study. The investigation focused on predictions of thermal performance relevant to molten salts used in fission, fusion, and concentrated solar power plants. Currently, there are limited systematic studies for helical rifling heat transfer enhancements as opposed to corrugated, internal finned, or repeating ribbed tubes. For this study, the computational fluid dynamics (CFD) code Nek5000/NekRS was used to simulate different convective flow regimes for different molten salts (i.e. fluorides, chlorides, and nitrate salts). The outcomes from the CFD investigations involved both frictional pressure drop (friction factor) and heat transfer coefficient (Nusselt number) predictions for a range of turbulent Reynolds numbers and Prandtl numbers spanning from unity “1” to 25. The friction factor results were observed to have increased by a percent difference of 35% to 48% compared to plain tube data. This is consistent with boiler tube results from groups such as Lam et al. and Pan et al. The CFD predictions resulted in the Nusselt number (heat transfer) increasing substantially with increasing Prandtl numbers for helically rifled tubes. It was also found that that the Nusselt number was observed to have minimal increases for all Reynolds numbers at Prandtl numbers close to unity. Using the predicted thermal performance information (friction factor and Nusselt number), the thermal performance factor of the helically rifled tubing was calculated as compared to plain tubes. It was found that the thermal performance factor was higher for Prandtl numbers larger than unity. However, it was determined that the thermal performance decreased for all Reynolds numbers when fluids with Prandtl numbers at or below unity were analyzed. Overall, this study presents a useful starting point for future investigations of helically rifled tubing in molten salt applications.

Abstract This study numerically investigates the impact of local topographic relief on the three‐dimensional near‐surface wind field over actual hilly terrain. The numerical simulations are performed with a computational fluid dynamics (CFD) code using the Reynolds‐averaged Navier–Stokes equations over a hilly island off the southeast coast of China. A novel evaluation method which selects ERA‐5 reanalysis data as the background wind field to match the CFD inlet is proposed to validate the performance of the simulated wind field. The assessment results show that the simulated CFD wind field exhibited satisfactory performance, as indicated by the small values of the root‐mean‐squared errors of the wind speed (0.40 m·s−1) and wind direction (16.31°). Variations in wind speed ratios (S) with different slope angles and horizontal slope lengths are examined and compared with current building load codes. It is found that the wind speed acceleration (S > 0) and deceleration (S < 0) are more pronounced near the surface than at upper levels, and the vertical range of the simulated wind field influenced by the actual hilly terrain far exceeds that considered in all load codes. At a given horizontal slope length, the horizontal wind speed ratio first increases and then decreases after reaching a critical slope angle in both uphill and downhill conditions. The current load codes are suggested to be optimized for areas with steep slopes and gentle downhill slopes.

The objective of this study was to investigate which of the two most common sluice passage types (i.e. culvert- and venturi-type passages) for a tidal power plant has a better discharge capacity. The discharge capacity of sluice passages was estimated using computational fluid dynamics (CFD) code Flow-3D. The total flow rate through sluice passages (and resultant power output) was further investigated and compared using 0-D modelling in a case study of the Taedong barrage, the DPR Korea. The results of CFD and 0-D modelling indicated that a culvert-type passage showed superior discharge capacity and resultant power output over a venturi-type passage in the case that the outlet area of the two passages was the same. In this case, therefore, the number of venturi-type passages required for the target power generation will be significantly increased, which will result in an increase in the complexity and cost of the construction and operation for the tidal power plant. In summary, it can be concluded that the results obtained in this study will help researchers to choose carefully sluice passage types to improve the discharge capacity and the resultant power output for tidal range power plants.

Our work involves a numerical simulation of a turbulent flow that crosses a turbine blade for different orientation angles using a computational fluid dynamics (CFD) code. The turbine's performance mainly depends on the characteristics and efficiency of the blades for optimal orientation angle position. The numerical simulation is based on the finite volume method for the differential equations discretization; different schemes have been used to solve these equations such as first upwind, second upwind, and power law. The turbulence model used in this study is the standard k-epsilon model. The equations governing the flow are solved by the Semi-Implicit Method for Pressure-linked Equations SIMPLE algorithm. The results obtained allow for identifying and characterizing the flow around the blade by plotting the dynamic field, the pressure coefficient, and the Mach number.

Due to the advanced capabilities of modern computational fluid dynamics (CFD) codes and developed models and algorithms, numerical simulation has become an efficient tool for studying two-phase flows, analyzing the entire totality of the processes occurring in them, and obtaining the data on flow local characteristics, which are difficult to measure directly. Active efforts taken for incorporating new models into various CFD codes should be accompanied by their cross-verification, the results of which can serve as a basis for selecting the most accurate, efficient, and universal models and algorithms. In this article, the results obtained from the solution of the problem about the condensation of R-142b refrigerant saturated vapor in a horizontal tube in the wall conjugate statement using two CFD codes, ANES and ANSYS Fluent, are analyzed. The copper tube’s inner diameter is 28 mm, its length is 2.75 m, wall thickness is 2 mm, and the total mass flux is 47 kg/(m2 s). The studies are of relevance for heat recovery installations based on the organic Rankine cycle. The calculations were carried out using the modified Lee model that we suggested previously, and which has been implemented in the ANES CFD code developed at the Department of Engineering Thermophysics, NRU MPEI. The cross verification of the VOF algorithms implemented in the ANES and ANSYS Fluent codes has shown that the results of modeling the saturated vapor condensation in a horizontal tube obtained using the above-mentioned codes are in good agreement with each other and are close to the empirical dependences recommended in the literature sources (M. Shah) for calculating the condensation in a horizontal channel. Data on the distribution of local heat-transfer characteristics over the tube’s inner wall are presented, which demonstrate that the heat-transfer coefficient features an essential nonuniformity over both the tube length and perimeter.

Mean and slowly varying wave loads on floating offshore wind turbines (FOWTs) need to be estimated accurately for the design of mooring systems. The low-frequency drift forces are underestimated by potential flow theory, especially in steep waves. Viscous forces on columns is an important contributor which could be included by adding the quadratic drag of Morison formulation to the potential flow solution. The drag coefficients in Morison equation can be determined based on an empirical formula, CFD study, or model testing. In the WINDMOOR project, a FOWT support structure, composed of three columns joined at the bottom by pontoons and at the top by deck beams, is studied using CFD. In order to extract the KC-dependent drag coefficients, a series of simulations for the fixed structure in regular waves is performed with the CFD code STAR-CCM+. In this study, the forces along each column of the FOWT are analyzed using the results of CFD as well as potential flow simulations. The hydrodynamic interactions between the columns are addressed. A methodology is proposed to process the CFD results of forces on the columns and extract the contribution of viscous effects. Limitations of the Morison drag model to represent extracted viscous forces in steep waves are investigated. The obtained drag coefficients are compared with the available data in the literature. It is shown that accounting for potential flow interactions and nonlinear flow kinematics could, to a large degree, explain the previously reported differences between drag coefficients for a column in waves. Moreover, it is shown that the proposed model can capture the contribution of viscous effects to mean drift forces for fixed columns in waves.

Flame impingement heat transfer is implemented in many industrial applications. The laminar premixed Bunsen flame, impinging on a flat cold surface, represents a basic model for the validation of computational fluid dynamics (CFD) codes, used for the simulation of industrial processes. Meanwhile, as the present paper demonstrates, some features of basic flame configurations are not well-reviewed. The present paper reports on the direct numerical simulation of the thermofluidic field in a laminar premixed impinging Bunsen flame in comparison with advanced optical measurements. The results reveal the phenomenon of the central recirculation zone formation between the tip of the Bunsen flame cone and the cold surface. Cooled combustion products concentrate inside this zone, resulting in reduced heat transfer near the flow axis. All three tested chemical kinetic mechanisms (GRI-Mech 3.0, SanDiego, RMech1) provide reasonable predictions of the observed phenomenon, which explain previous experimental observations on the reduced heat transfer at the central axis of impinging flames. Moreover, the most detailed mechanism, GRI-Mech 3.0, predicts an elevated concentration of NOX pollutants caused by the mentioned phenomenon.

ABSTRACTIn this work, we discuss recent experiences related to the development and enhancement of a hybrid stochastic computational fluid dynamics (CFD) solver, the C++ version of the Implicit/Explicit (IMEX) time‐advancement algorithm used in the one‐dimensional turbulence‐based (ODT) large eddy simulation (LES) model, abbreviated as ODTLES. After being ported from Fortran 90, the current capabilities of the C++ code are restricted to the reproducibility of turbulent channel flow simulations with respect to the former Fortran code version that was able to achieve reasonable agreement with available reference direct numerical simulation (DNS) for low to moderate Reynolds number turbulent channel flows. This is far from satisfactory so that current efforts are centered on improving the solver code structure through comprehensive refactoring, robust unit testing, and strict adherence to code style guides, following the principles of Clean Code. We focus the discussion on a methodology to balance unit, regression, and integration testing, here for the LES component of the code. The objective is to frame a starting point that is relevant also for other CFD codes, irrespective of whether they utilize conventional or novel discretization or flow modeling approaches.