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Condensation occurs when the air temperature drops to its dew point, causing water vapors in the air to cool, lose kinetic energy, and transform into liquid droplets. This process is influenced by the relative humidity and temperature fluctuations, where lower temperatures reduce the air’s capacity to hold water vapor, resulting in the formation of liquid water droplets on cooler surfaces. The condensation process is fundamental to the operation of fog harvesting systems, where specialized meshes capture the transformed water droplets. However, the behavior of droplets attached to meshes under background airflow is not well understood. Consequently, controlling the motion and merging of these droplets with neighboring ones poses a significant challenge. In this study, for fog airflow, it is demonstrated that droplets on parallel meshes can aerodynamically interact with both downstream and upstream neighbors at different temperatures. These interactions lead to diverse behaviors, including alignment, coalescence, and repulsion. This study explores the key factors influencing the efficiency of material and design used for fog harvesting systems, and environmental conditions such as fog density and wind speed. The dynamical model includes the single-phase transport equation along with the $k-\mathrm{\Omega }$ SST (Shear Stress Transport (SST) k-omega) a subclass of RAS (Reynolds-Averaged Simulation) model. The computational analysis of fog harvesting mesh for water collection is performed in OpenFOAM (Open-source Field Operation And Manipulation). The Finite Volume Method (FVM) is employed for solution of the model to check the efficiency and effectiveness of fog harvesting computational designs. Using OpenFOAM, condensation, alignment and merging behaviors based on the interactions between wakes and droplets are visualized. The computational design enhances the surface area available for fog capture, thereby increasing the droplets collection efficiency and resulting in a higher yield of liquid water. The computational results obtained in this study can lead to more sustainable and efficient fog water collectors.

This paper aims to detect memory loss of the symmetry of blockades in ducts and how far the information on the asymmetry of the obstacles travels in the turbulent flow from computational simulations with OpenFOAM. From a practical point of view, it seeks alternatives to detect the formation of obstructions in pipelines. The numerical solutions of the Navier–Stokes equations were obtained through the solver PisoFOAM of the OpenFOAM library, using the large Eddy simulation (LES) for the turbulent model. Obstructions were placed near the duct inlet and, keeping the blockade ratio fixed, five combinations for the obstacles sizes were adopted. The results show that the information about the symmetry is preserved for a larger distance near the ducts wall than in mid-channel. For an inlet velocity of 5m/s near the walls the memory is kept up to distance 40 times the duct width, while in mid-channel this distance is reduced almost by half. The maximum distance in which the symmetry breaking memory is preserved shows sensitivity to Reynolds number variations in regions near the duct walls, while in the mid channel that variations do not cause relevant effects to the velocity distribution.

Slug flow is a two-phase fluid flow pattern, characterized by a series of liquid slugs dispersed by relatively large air bubbles. Air bubbles produced and trapped during the slug flow phenomenon conduct to interruption in flow which induces pressure and velocity fluctuations. These effects have destructive circumstances in conduits and conveyance structures. This paper deals with studying numerically two-phase flows using computational fluid dynamic (CFD) techniques performed in OpenFOAM (an open source software) by interFoam solver. Most of the previous concerning studies on slug flow were performed in micro-channels with small scales in which the expansion of the air bubbles was negligible. By contrast, we investigated the systems with large pressure drops which conduct to abrupt increases on the volume of air phase. The slug flow phenomenon could be created by introducing air and water with different velocities at inlet of a culvert with air to water velocity ratio varied from 1.1 to 34. First, this study focused on temporal and spatial variations of pressure and velocity along the culvert. After that, by dimensional analysis, the nondimensional parameters influencing the slug flow phenomenon are extracted and analyzed. Finally, different strategies for reducing the destructive effects of slug flow, including the shape and location of ribs, are evaluated and the best strategy is proposed.

Slug flow is a flow pattern which occurs in conveyance systems containing a two phase-fluid flow. Large air bubbles entrapped along these systems interrupt the flow and conduct to undesirable pressures and their fluctuations. Most of the previous concerning studies on slug flow phenomenon were performed in micro-channels with small scales in which the expansion of the air bubbles was negligible. In contrast, we investigated the systems with large pressure drops which conduct to abrupt increases on the volume of air phase. In this research, the verification tests applying CFD techniques were performed in OpenFOAM software by interFoam solver. The performance of morning glory spillways is investigated under steady states. While during the occurrence of flood, by increasing the depth over the spillway crest, the discharge is augmented which conducts to entrap the air pockets with pressure and velocity fluctuations. These fluctuations influence on the life of structures and their performances. This study aimed on unsteady flow in a glory morning spillway and its consequences and proposing the measures for reducing the destructive effects of slug flow. The pressure and velocity fluctuation were considered as the indices for the performance of a hydraulic structure. Spatial and temporal variations of pressure and velocity along the spillway are evaluated. Also, the influences of spillway geometry on slug flow and the measures to attenuate its destructive effects are analyzed. The results showed that the better performances of morning glory spillway are coincided by the diameter of tunnel superior than the height of water above the crest.

This work aims to numerically simulate the dynamics of a channel flow with an obstruction since the moment we inject a fluid with an homogeneous velocity profile. The simulations uses the open source tools of the OpenFOAM platform, the pisoFoam and the LES turbulence model, describing in detail the velocity profiles of laminar and turbulent flows. We also perform a boundary layer mapping in the presence of an obstacle. We used three different domains to follow the evolution of the velocity profile while the fluid progresses downstream and passes the obstruction. The results reproduce the well-known results of laminar flow in a channel, as well as the average velocity profile in the turbulent regime and the occurrence of attachments by the obstruction. These preliminary results are used to validate the solvers and the mesh used. Next, an analysis of the velocity profile dynamics resulted in determining an exponential decay of the root mean square deviations of the homogeneous to the parabolic, and to the turbulent regime in the channel.

The impetus of this study is to provide an in-depth insight into the unsteady hydrodynamic characteristics of the cavitating flow, effects of the wavy leading edge (WLE) on the noise suppression mechanism due to a cavity cloud formation, which contains condensation, detachment, collapse, spanwise flow, streamwise velocity fluctuation, and shedding phenomenon. NACA 63₄-021 hydrofoil was considered with WLE having a wavelength of 25% and an amplitude of 5% of the mean chord length and was compared to a straight-leading-edge (SLE) hydrofoil at cavitation numbers of $\sigma =0.8$ and a chord-based Reynolds number of $7.2\times 10^5$. Counter-rotation vortices were produced between the peaks of the WLE hydrofoil by destroying the horseshoe vortex and delaying the tail vortex, changing the frequency. Here, the hydrodynamic forces have also been discussed in addition to the noise. The results showed that the leading-edge vortex formation and flow separation dynamics fundamentally differed between the SLE and the WLE hydrofoil. The main difference between the WLE and SLE hydrofoil turbulent flow is the formation of counter-rotating streamwise vortices pairs. We solved the cavitating flow using the large eddy simulation (LES) approach, as well as the Kunz mass transfer model, which is performed under the framework of the OpenFOAM package.

This study implements a new solver (reactiveInterFoam) to simulate the component mass transfer alongside deformable gas–liquid interfaces. Mass transfer from the rising bubble in a quiescent Newtonian fluid is simulated. An effect of bubble hydrodynamics on the simultaneous diffusion reaction and selectivity of the cyclohexane oxidation process is investigated on a two-dimensional axisymmetric domain. The color function volume of fluid (CF-VoF) technique is applied to capture the deformable interface, and the continuous species transfer method is used to monitor the gas–liquid mass transfer behavior. Several simulations have been conducted to validate the model reliability to forecast component mass transfer from the bubble to the liquid phase, bubble shape, and flow field. Simulation findings approved that the rate of mass transfer is a function of boundary’s concentration, layer thickness, and bubble surface area. Furthermore, the selectivity increases by decreasing bubble diameter in both spherical and ellipsoidal regimes. The small bubbles with a lower Reynolds number have higher average selectivity. Comparing the simulated bubble shape and the grace chart indicates that the suggested numerical method can perfectly predict bubble regimes. The absolute average relative deviation (AARD%) of 14.59% has been observed between the terminal velocities predicted by the numerical simulation and six experimental measurements.

Gravity currents modify their flow characteristics in the presence of an obstacle. Also, the flow path to the dam reservoirs is not always direct. Since no studies have addressed the feedback between the hydrodynamics of a gravity current in a curved channel and the location effects of the obstacle, in this research, a Lock-exchange density current flows in a 120${}^{\circ }$ bending channel. The numerical simulation has been performed using OpenFOAM software. The models include no-obstacle curved channel and a curved channel with an obstacle in different positions concerning the increased radius of the curved channel. Results indicated that the obstacle directed the concentration towards the banks, with its maximum value tending from the outer to the inner bank, especially in the tail. The tail longitudinal velocity maximized near the channel bed in areas far from the obstacle, and in the outer bank in areas near it. The secondary flow reduces its lowest and most different pattern observed around the obstacle. In displacing the latter, if the front has at a certain distance, the secondary flow does not change much, but if it has at the channel end, the post-obstacle secondary flow would increase as the obstacle neared the Lock.

Partial differential equations may explain anything from planetary movement to tectonic plate, yet it is notoriously difficult to resolve them. Turbulence is present in nearly all fluid flows, and pure laminar flow is extremely unusual in practice. The Large Eddy Simulation (LES) computational model is employed for the simulation of turbulence flow on a spillway having four inlets with a single outlet. Such flows are observed at hydroelectric power dams all over the world. The fluctuated flows produced a large amount of energy in terms of electricity that costs a very low amount compared to the energy obtained in tidal power sectors. In the production of hydropower energy, the flow simulation is of great interest. This paper focuses on the study of turbulence kinetic energy with the help of a LES model. The spillway considered in this paper contains four inlets and a single outlet. The four inlets will allow more flow which will insert more pressure nearer the outlet. The kinetic energy is computed at the inlets and outlet in the turbulent flow. The fluctuated velocity along with the mean velocity at the inlets and outlet is also computed along with the pressure. The C++-based programming is made, which is simulated in Open-source Field Operation and Manipulation (OpenFOAM). The graphs are presented for a better understanding of readers.

In this study, the center of a concave surface was analytically studied using the volume of fluid approach to simulate hollow and dense droplets on a variety of solid obstacles. OpenFoam software was used to carry out the numerical simulations. The hollow droplet’s fluid phase, Glycerine, has an outer diameter of 5.25 mm and its gas phase, air, has a diameter of 4 mm. We looked at the laminar flow of an incompressible Newtonian fluid phase. Jet characteristics and droplet collision hydrodynamic behavior were investigated. Due to the interaction between droplets and shells on the obstacle’s surface and the concave surface, which causes a pressure difference and improves fluid movement, the largest jet size is consequently produced in rectangular obstacles. The sharp obstacle, on the other hand, molds the jet’s shortest length and height.

The random structure model of porous media is constructed by the gravity packed method, which can give a random packed structure that is similar to the actual packed bed structure by simulating the free fall, collision and stacking process of pellets via the OpenFOAM. Different from the existing ordered structure model of porous media, the structure model adopted in this paper has strong randomness since it simulates the actual generation process of the porous media material. Meanwhile, the following batch modeling instructions are completed with the MATLAB, which can ensure that the random structure model of porous media has the advantages of high similarity with the actual porous structure and rapid modeling.

A liquid jet injector is a biomedical device intended for drug delivery. Medication is delivered through a fluid stream that penetrates the skin. This small diameter liquid stream is created by a piston forcing a fluid column through a nozzle. These devices can be powered by springs or compressed gas. In this study, a CFD simulation is carried out to investigate the fluid mechanics and performance of needle free injectors powered specifically by compressed air. The motion of the internal mechanisms of the injector which propels a liquid jet through an orifice is simulated by the moving boundary method and the fluid dynamics is modeled using LES/VOF techniques. In this paper, numerical results are discussed by comparing the fluid stagnation pressures of the liquid jet with previously published experimental measurements obtained using a custom-built prototype of the air-powered needle free liquid injector. Performance plots as a function of various injector parameters are presented and explained.

The numerical simulations of the flow in nasal airways were performed for two different clinical cases. The results comprised the distributions of scalars at five different sections and included contours of pressure, velocity magnitude, turbulent kinetic energy and vorticity magnitude. Simulations showed the air branching occurring at the inferior meatus is unaffected by the variations in the volumetric flow rate or the changes in the flow regime through the olfactory cleft. However, the contractions and the following rapid change in the cross-section of the nasopharynx preclude the upward penetration of the vacuum field set by the lungs during the inhalation process. As a result, considerably low velocities and significant cross-sectional nonuniformities are observed, which lead to the appearances of the secondary flow structures and strong unsteadiness. Increased interactions between the airflow and the walls of the nasal cavity resulted in an increase in the vorticity on the right middle meatus and upper inferior meatus. The vorticity was also very high in the nostrils, where the flow was not fully developed.

Under water cavitation occurs when the liquid changes the phase into its vapor due to the local pressure is lower than the water saturation pressure. If a body is moving very fast under water, the local pressure around it at a certain flow regime will be lower than the water saturation pressure. The cavitation around the body will occur. Following the increase of the intensity of the cavitation, a cloud cavitation will occur. Under the cloud cavitation occurrence, the cavitation is unsteady and periodic, which involves formation, detachment and collapse of sheet cavities. In this paper, large Eddy simulation (LES) is employed together with a mixture assumption and a finite rate mass transfer modeling into OpenFOAM to study the cavitation phenomena. The validation comparisons of numerical simulations with experiments of a sphere under water are performed. After the validation, a full submarine model with sail and appendages under water is studied. The submarine is under water around 450 m deep with a moving speed at 60 m/s. It is found that the cavitation changes under the different cavitation numbers (from 1.0 to 0.1). Small cavitation numbers induce a large area cavitation, whereas large ones reduce this phenomenon. A supercavitation, which can be described as a large bubble, is found around the high speed submarine at cavitation number equals to 0.1.

Risk management of loss of containment at facilities processing or storing liquid flammable fluids is crucial in order to ensure safe operations. To control the risk, an extensive set of safety functions are in general implemented in design, for example systems that minimize the occurrence for initiating events (e.g., spontaneous leak of flammable material due to fatigue) and measures that reduce explosion loads arising in case of delayed ignition of the dispersed fluid mixed with air. Effective ventilation of the released fluid that potentially generates an explosive atmosphere (gas and/or droplets generated from the liquid phase) is one of the crucial barrier elements to mitigate the explosion hazard. Hence, the gas explosion hazard in enclosed modules with poor ventilation is of particular concern as a flammable mixture may accumulate even for small release rates. This may result in both high likelihood of ignition and considerable explosion loads in case of ignition due to the big amount of chemical energy taking part in the combustion process relative to the size of the enclosure. Computational fluid dynamics (CFD) methods are increasingly being used to characterize the consequences of leaks of flammable fluid in complex geometries, both modeling of the initial gas dispersion process and the resulting explosion and fire loads following from the combustion process in case of ignition. This paper presents an advanced methodology based on the CFD tool OpenFOAM for detailed assessment of the transient gas dispersion process and the associated likelihood of ignition for leaks of flammable fluid inside enclosures. The objective is to understand how to optimize the design of safety functions that affect the fire and explosion risk picture. This custom made tool, denoted cloudIgnitionFoam, accounts for the transient gas leak behavior based on real-time gas detection, subsequent initiation of emergency shutdown (ESD) and blow down systems and computes ignition probability based on the transient history of the dispersed gas cloud. The consistent methodology based on the CFD technology available in OpenFOAM and its ability to present the results in detail leverages the risk-based decision process. Measures that can be assessed quantitatively includes number and types of gas detectors and their optimal positioning, ignition source isolation, gas detection system voting philosophy, capacity of depressurization system and structural integrity of explosion barriers.

For existing offshore fixed platforms it is often the case that the air gap between the deck and the sea surface is not adequate and the extreme waves will encroach on the deck resulting in large wave-in-deck loads. Factors that result in inadequate air gap are seabed subsidence, sea-level increasing due to climate change and more onerous predictions of extreme crest heights.

In this paper, a numerical approach based on NewWave theory [Tromans et al. (1991), Proc. 1st Int. Offshore and Polar Engineering Conf., Vol. 3, Edinburgh, UK, pp. 64–71] has been developed to represent the extreme wave conditions and implemented into the framework of an open source software, OpenFOAM, to predict the wave-in-deck loading. The results have been compared with published FLOW-3D simulations using Stoke’s 5th order wave theory for a simple box representing the Ekofisk platform deck in the Norwegian sector of the North Sea [Iwanowski et al. (2002), Proc. 21st Int. Conf. Offshore Mechanics and Artic Engineering, June 23–28, 2002, Oslo, Norway].

Among the many mature and commercial AM technologies, fused deposition modeling (FDM) is a popular technology commonly used for modeling, prototyping, and production applications. In this process, a filament thermoplastic material is fed into a liquefier chamber, melted to a liquid state, and deposited layer by layer through a nozzle to form the 3D part. As a result, part can be designed in a more freedom way, and fabricated quickly and rapidly to a desired shape. However, different combination of processing parameters may influence the final part quality greatly, which hinders wider application of this technique. In order to investigate the influence of processing parameters on the final part quality, a viscoelastic multi-phase solver is developed, with capability for dynamic meshing and based on OpenFOAM. The solver directly simulates the deposition process of FDM. By implementing this solver for different boundary conditions and geometry, we can evaluate the printed part quality for varied processing conditions. More importantly, the tool enables efficient optimization of the processing conditions for specified material parameters and desired print quality.

Pollutant control is one of the key concerns in the design of buildings, for the sake of occupational health, safety and environment sustainability. In particular, risk analyses related to emergency leakage of chemicals from storage tanks or chemical processes have aroused increasing attentions in recent days, as well as the effectiveness of mitigation measures in order to eliminate, reduce and control the risks. In this paper, a CFD methodology with nonreactive chemical gases treated as passive scalars has been developed to simulate the gas dispersion across urban environments, subject to atmospheric boundary layer wind conditions. Special treatments to maintain the consistency in atmospheric boundary layer flow profiles, turbulence modeling and boundary conditions have also been accounted for. The proposed CFD methodology for gas dispersion has been implemented in the open source CFD code — OpenFOAM. It has been validated by modeling the gas dispersions for two urban-related test cases: the CODASC street canyon test case measured in a laboratory wind tunnel and the Mock Urban Setting Test (MUST) field experiment conducted in the desert area of Utah State. Effects of turbulent Schmidt number (Sc_t have been primarily addressed in this study. Statistical analyses about the discrepancies between predicted and experimental data have been carried out and statistical performance measures are used to quantify the accuracy of the proposed methodology. Simulations results from passive scalar transport equation demonstrate good agreement with experimental data, though tracer gases heavier than the atmospheric air were used in both the measurements. Furthermore, sensitivity tests also indicate that the accuracy of the simulation results is sensitive to the value of turbulent Schmidt number.

The paper presents numerical study of flow induced noise sources in a horizontal Francis turbine. The spiral case, the runner and the draft tube are used as noise sources. The sound pressure, power spectrum density and sound pressure level caused by the various noise sources at the receiver are numerically simulated. Analysis was performed by OpenFOAM code. FW-H acoustic model is used to calculate the sound pressure signal at the receiver. The numerical simulation results show that the spiral case is the main noise source of the horizontal Francis turbine.

OpenFOAM is an object-oriented C++ library of classes and routines of use for writing CFD codes. It has a set of basic features similar to any commercial CFD solver, such as turbulence models and discretization schemes. The paper presents the numerical studies of sediment wear in a centrifugal pump impeller using OpenFOAM code, which is an Open Source CFD Package. The 3-D turbulent particulate-liquid two-phase flow equations are employed in this study. Hashish erosion model was implemented in this code. The sand volume fraction distribution, sand erosion rate distribution, wall shear strain rate distribution and wall stress distribution in the impeller were analyzed. Simulation results have shown that the main sediment wear of impeller is at the suction side of the inlet and the pressure side of the outlet.