Transient Computational Fluid Dynamics Research Articles

Performance Evaluation of a Tidal Current Turbine with Bidirectional Symmetrical Foils

As one might expect, tidal currents in terms of ebb and flood tides are approximately bidirectional. A Horizontal Axial Tidal Turbine (HATT) with unidirectional foils has to be able to face the current directions in order to maximize current energy harvesting. There are two regular solutions to keep a HATT always facing the direction of the flow, which are transferred from wind turbine applications. One is to yaw the turbine around the supporting structure with a yaw mechanism. The other is to reverse the blade pitch angle through 180° with a pitch-adjusting mechanism. The above solutions are not cost-effective in marine applications due to the harsh marine environment and high cost of installation and maintenance. In order to avoid the above disadvantages, a turbine with bidirectional foils is presented in this paper. A bare turbine with bidirectional foils is characterized in that it has nearly the same energy conversion capability in both tidal current directions without using the yaw or pitch mechanism. Considering the working conditions of the bidirectional turbine in which the turbine is installed on a mono-pile, the effect of the mono-pile on the turbine’s performance is evaluated in this paper, especially when the turbine is downstream of the mono-pile. The paper was focused on the evaluation of the hydrodynamic performance of the bidirectional turbine. The hydrodynamic performance of the bare bidirectional turbine without any supporting structure was evaluated based on a steady-state computational fluid dynamics (CFD) model and model tests. Performance comparison has been made between the turbine with bidirectional foils and the turbine with NACA foils. The effect of the mono-pile on the performance of the bidirectional turbine was studied by using the steady-state and the transient CFD model. The steady-state CFD model was used to evaluate the effect of the mono-pile clearance, which is the distance between the mono-pile and the turbine on the performance of the turbine. The transient CFD model was used to determine the time-dependent characteristics of the turbine, such as time-dependent power and drag coefficients. The results show that the bare bidirectional turbine has nearly the same energy conversion capability in both tidal current directions. The performance of the bidirectional turbine is inferior to the turbine with NACA foils. At the designed tip speed ratio, the power coefficient of the turbine with NACA foils is 0.4498, which increases by 1.6% compared to the 0.4338 of the bidirectional turbine. The turbine’s performance decreases due to the introduction of the mono-pile, and the closer the turbine is to the mono-pile, the greater effect on the turbine’s performance the mono-pile has. At the designed clearance of 1.5 DS, the presence of a mono-pile decreases the peak Cp value by 1.82% and 3.17% to a value of 0.4156 and 0.4004 for the turbine located in the mono-pile upstream and downstream, respectively. The mono-pile can result in the fluctuation of the turbine’s performance. This fluctuation will detrimentally harm the life of the turbine as it will lead to increased wear and fatigue issues.

Analysis of Oil-Injected Twin-Screw Compressor with Multiphase Flow Models

Growing demands for energy are motivating researchers to conduct in-depth analysis of positive displacement machines such as oil-injected screw compressors which are frequently used in industrial applications like refrigeration, oil and gas and air compression. The performance of these machines is strongly dependent on the oil injection. Optimisation of oil has a great energy saving potential by both increasing efficiency and reducing other impacts on the environment. Therefore, a three-dimensional, transient computational fluid dynamics study of oil injection in a twin-screw compressor is conducted in this research. This study explores pseudo single-fluid multiphase (SFM) models of VOF (Volume of Fluid) and a mixture for their capability to predict the performance of the oil-injected twin screw compressor and compare this with the experimental values. SCORGTM (Screw Compressor Rotor Grid Generator) is used to generate numerical grids for unstructured solver Fluent with the special interface developed to facilitate user defined nodal displacement (UDND). The performance predictions with both VOF and mixture models provide accurate values for power consumption and flow rates with low deviation between computational fluid dynamics (CFD) and the experiment at 6000 RPM and 7.0 bar discharge pressure. In addition, the study reflects on differences in predicting oil distribution with VOF, mixture and Eulerian-Eulerian two-fluid models. Overall, this study provides an insight into multiphase flow-modelling techniques available for oil-injected twin-screw compressors comprehensively accounting for the details of oil distribution in the compression chamber and integral compressor performance.

Modified Design of Savonius Wind Turbine Blade for Performance Improvement

In the context of worldwide energetic transition, wind energy shows up as one of the most prominent renewable energy to provide an alternative for the conventional energy source. Therefore, new technologies of a wind turbine are developed, horizontal axis wind turbines have been extensively investigated and evolved. However, the development of vertical axis wind turbines is still an open and area of research, The main objective is to develop a more efficient type of wind turbines able to operate at low wind speeds to take hold maximum wind potential, The Savonius rotor goes with such conditions, however, it faces critical drawbacks, in particular, the low performance in comparison with horizontal axis wind turbines, as well, the blade in return of savonius wind turbine generates a negative torque leading to a decrement of turbine performance. The present work aims to investigate a modified model of the conventional Savonius rotors with a focus on improving the coefficient of power, transient computational fluid dynamics (CFD) simulations are carried out in an effort to perform a validation of numerical results according to experimental data, also to conduct a comparative analysis of both savonius models.

Hemodynamic effects of myocardial bridging in patients with hypertrophic cardiomyopathy.

Myocardial bridging (MB) is linked to angina and myocardial ischemia and may lead to sudden cardiac death in patients with hypertrophic cardiomyopathy (HCM). However, it remains unclear how MB affect the coronary blood flow in HCM patients. The aim of this study was to assess the effects of MB on coronary hemodynamics in HCM patients. Fifteen patients with MB (7 HCM and 8 non-HCM controls) in their left anterior descending (LAD) coronary artery were chosen. Transient computational fluid dynamics (CFD) simulations were conducted in anatomically realistic models of diseased (with MB) and virtually healthy (without MB) LAD from these patients, reconstructed from biplane angiograms. Our CFD simulation results demonstrated that dynamic compression of MB led to diastolic flow disturbances and could significantly reduce the coronary flow in HCM patients as compared with non-HCM group (P < 0.01). The pressure drop coefficient was remarkably higher (P < 0.05) in HCM patients. The flow rate change is strongly correlated with both upstream Reynolds number and MB compression ratio, while the MB length has less impact on coronary flow. The hemodynamic results and clinical outcomes revealed that HCM patients with an MB compression ratio higher than 65% required a surgical intervention. In conclusion, the transient MB compression can significantly alter the diastolic flow pattern and wall shear stress distribution in HCM patients. HCM patients with severe MB may need a surgical intervention.NEW & NOTEWORTHY In this study, the hemodynamic significance of myocardial bridging (MB) in patients with hypertrophic cardiomyopathy (HCM) was investigated to provide valuable information for surgical decision-making. Our results illustrated that the transient MB compression led to complex flow patterns, which can significantly alter the diastolic flow and wall shear stress distribution. The hemodynamic results and clinical outcomes demonstrated that patients with HCM and an MB compression ratio higher than 65% required a surgical intervention.

Numerical study on the effect of blade surface deterioration by erosion on the performance of a large wind turbine

As the demand for the development of onshore wind farms in areas with low wind speeds and large offshore wind farms increases, the size of the wind turbine and its rotor has also increased rapidly. An increase in the rotor diameter implies an increase in the relative wind velocity (with respect to each cross section in the radial direction of the blade) near the tip region of the blade. This in return accelerates the surface damage caused by the erosion of the leading edge, thereby increasing the frequency of maintenance and lowering competitiveness in the cost of energy. In this study, computational fluid dynamics (CFD) analysis was performed to analyze the correlation between the leading-edge erosion damage and output performance of the blade. CFD simulations were performed using a tip airfoil (NACA 64_618) and a full-scale wind turbine (NREL 5 MW) based on the state of erosion of discarded blades considering approximately 12 years of maintenance-free operation. The irregular erosion at the airfoil leading edge results in premature stall phenomena and reduces the aerodynamic efficiency. Thus, the accurate analysis of the flow separation point and flow change is necessary. Therefore, three-dimensional transient CFD analysis was performed to consider the complex flow generated on the blade surface. The erosion at the leading edge reduced the airfoil lift by up to 23% and drag by 100%, reducing the aerodynamic efficiency, which in effect reduced annual energy production by up to 4%.

Numerical study of desalination by vacuum membrane distillation – Transient three-dimensional analysis

The performance of vacuum membrane distillation (VMD) modules can be optimized through careful selection of design parameters. The present study examines how the addition of cylindrical filaments in the feed channel increases momentum mixing and the overall performance of VMD modules under different operating inlet conditions. Three-dimensional transient Computational Fluid Dynamics (CFD) simulations are conducted using Wall-Adapting Local Eddy-Viscosity (WALE) subgrid-scale Large Eddy Simulation (LES) turbulence model. Local concentration, temperature, and flux are coupled at the membrane surface to predict the rate of water vapor diffused through the membrane by Knudsen and viscous diffusion mechanisms. The predicted and measured vapor flux agrees reasonably well; validating the employed model. The small-scale eddies induced by the presence of spacer filaments promote mixing in the module, thus the temperature and concentration polarization is alleviated and the water vapor flux is immensely improved. The insertions of filaments in the feed channel increase the water permeate rate by more than 50% at higher feed flow rates and inlet temperatures. The pressure drop by the spacer reduces the allowable module length by one order of magnitude, but the module length increases two folds at feed temperature 80°C. Even though the power consumption of the module containing the filaments is increased, the addition of filaments is strongly recommended since the required power for the process could be supplied from readily available low-grade heat source.

Thermal management of edge-cooled 1 kW portable proton exchange membrane fuel cell stack

Comprehensive numerical analyses are conducted to study the influence of thermal management on performance of 1 kW edge-cooled proton exchange membrane fuel cell stack without external humidification. The experimental stack and numerical three-dimensional computational fluid dynamics model are characterized by several novelty aspects. Two numerical approaches are considered and compared for a prescribed load profile: (i) lumped model and novel (ii) real-time transient computational fluid dynamics model incorporating realistic modeling of forced air convection on the edge-cooling of the stack. The novelty of the developed computational fluid dynamics model is the capability to give insight in the transient results in only a fraction of time vs. experimental testing (40 min vs. 4 h) and other computational fluid dynamics models of fuel cells which are only capable of steady-state analysis. The developed computational fluid dynamics model is used to study the influence of (i) bipolar plate materials (ii) operating delta pressure along the flow field and (iii) different cooling fin configurations on the water and heat balance inside the stack. The results indicate that (i) maximal and average temperatures of the stack are almost linearly correlated to the thermal conductivity of bipolar plate materials and maximal temperatures can be significantly higher (ii) the operating delta pressure can be manipulated to increase the performance of the stack and (iii) the cooling fin redesign has major influence on the overall temperature uniformity across the stack. Additionally, the heat transfer between the stack and metal hydride tank is studied.

Numerical Investigation of Liquid Water Transport Dynamics in Novel Hybrid Sinusoidal Flow Channel Designs for PEMFC

This study numerically investigates liquid water dynamics in a novel hybrid sinusoidal flow channel of a proton exchange membrane fuel cell (PEMFC). The two-phase flow is examined using a three-dimensional, transient computational fluid dynamics (CFD) simulation employing the coupled level set and volume of fluid (VOF) method. Simulations for hybrid and non-hybrid sinusoidal flow channels, including a straight flow channel, are compared based on their water exhaust capacities and pressure drops. Additionally, the effects of inlet gas velocity, wall wettability, and droplet interaction in the flow channel on the dynamic behaviour of liquid water are investigated. Results reveal that the novel hybrid sinusoidal channel designs are consistent in terms of quicker water removal under varying hydrophilic wall conditions. Also, it is found that the liquid surface coverage, detachment, and removal rate depends on droplet proximity to the walls, inlet gas velocity, and wall contact angle. Also, the time a droplet makes contact with the side walls affect the discharge time. Additionally, there is an improvement in the gas velocity magnitude and vertical component velocity across the hybrid sinusoidal channel designs. Therefore, the unique geometric configuration of the proposed hybrid design makes it a viable substitute for water management in PEMFC applications.

A one-way coupled numerical magnetic field and CFD simulation of viscoplastic compressible fluids in MR dampers

Recent developments in employment of magnetorheological (MR) fluids in different applications heighten the need for better understanding of their non-linear flow characteristics. In this paper, the modelling of the dynamic hysteretic behaviour of a twin-tube MR damper via a novel one-way coupled numerical approach is presented. The approach couples the Finite Element Analysis (FEA) of the MR damper magnetic circuit with the Computational Fluid Dynamics (CFD) analysis of the fluid flow field. A User-Defined Function (UDF) predefines the fluid shear-rate-dependent apparent viscosity into the CFD solver according to the magnetic field density attained from the FE solver. Two transient CFD cases are presented, one of them studies the flow in the damper as an incompressible single-phase flow, while the other accounts for the effect of fluid compressibility in the liquid-gas domain as a two-phase flow. The validation of the proposed numerical approaches is achieved via the direct comparison with the published experimental measurements for the same MR damper. It has been found that the fluid compressibility affects the hysteretic behaviour of MR dampers greatly. Moreover, the flow field shows the distributions of pressure, velocity and viscosity contours. In particular, the results show higher non-Newtonian viscosity in the throttling area and lower Newtonian viscosity elsewhere. Furthermore, it is shown that the variation of some design parameters of the damper, such as the width of magnetic poles, input current and frequency of the piston motion, has significant effects on the damper behaviour.

Impacts of Internal Carotid Artery Revascularization on Flow in Anterior Communicating Artery Aneurysm: A Preliminary Multiscale Numerical Investigation

The optimal management strategy of patients with concomitant anterior communicating artery aneurysm (ACoAA) and internal carotid artery (ICA) stenosis is unclear. This study aims to evaluate the impacts of unilateral ICA revascularization on hemodynamics factors associated with rupture in an ACoAA. In the present study, a multiscale computational model of ACoAA was developed by coupling zero-dimensional (0D) models of the cerebral vascular system with a three-dimensional (3D) patient-specific ACoAA model. Distributions of flow patterns, wall shear stress (WSS), relative residence time (RRT) and oscillating shear index (OSI) in the ACoAA under left ICA revascularization procedure were quantitatively assessed by using transient computational fluid dynamics (CFD) simulations. Our results showed that the revascularization procedures significantly changed the hemodynamic environments in the ACoAA. The flow disturbance in the ACoAA was enhanced by the resumed flow from the affected side. In addition, higher OSI (0.057 vs. 0.02), prolonged RRT (1.14 vs. 0.39) and larger low WSS area (66 vs. 50 mm2) in ACoAA were found in the non-stenotic case. These acute changes in hemodynamics after revascularization may elevate the rupture risk of ACoAA. The preliminary results validated the feasibility of predicting aneurismal hemodynamics characteristics in revascularization procedures by using multiscale CFD simulations, which would benefit the management of this group of patients.

Numerical Modelling of the Influence of Argon Flow Rate and Slag Layer Height on Open-Eye Formation in a 150 Ton Steelmaking Ladle

A transient computational fluid dynamics (CFD) modelling approach was used to study the complex multi-phase flow in an argon-stirred industrial scale ladle with a nominal capacity of 150 tons. During the stirring process, when gas was injected through the porous plug from the bottom into the steel bath, it breaks up into bubbles and infringes the slag layer creating an open-eye. The volume of fluid model was used to investigate the open-eye formation process in the simulations. In the numerical simulations, the open-eye area changed from 0.7 to 2.24 m2 with the increment of argon flow rate from 200 to 500 NL/min for slag layer thickness of 40 cm. Furthermore, the influence of slag layer height on the open-eye area was investigated. An argon flow rate of 200 NL/min was able to break the slag layer for slag layer height of 40 cm, and the open-eye formation was not possible for the same flow rate when the slag layer height was elevated from 40 to 55 cm. The numerical simulation results were validated against industrial measurements carried out at Outokumpu Stainless located in Tornio, Finland. The numerical simulation results of dynamics and time-averages of the slag area showed a good agreement when compared to the industrial measurements. To conclude, it is necessary to define gas flow rate based on the slag layer height to have an open-eye suitable for alloying.

Comparative inhalation exposure/toxicology analysis of e-cigarette vapors with different puffing behaviors using PBPK-CSP-CFD approach

The overarching purpose of this study is to develop a numerical prediction method for assessment of human health risks caused from the inhalation exposure of various contaminants generated by electronic cigarettes (e-cigarettes). In this study, the inhalation exposure to contaminants, generated from e-cigarette smoking under two types of puffing behaviours was quantitatively estimated adapting a coupled physiologically based pharmacokinetic (PBPK)–computational fluid dynamics (CFD) model to a numerical respiratory tract model. Heterogeneous contaminants concentration distributions inside the respiratory tract were predicted through transient CFD simulations. For evaluating adsorption flux onto respiratory tissue surface, tissue surface contaminants concentrations of respiratory tract were calculated by using two concepts: partition coefficient between air-phase and tissue-phase and analogy of flux conservation. Contaminants concentration distributions inside the tissue were analyzed by using PBPK model. Through the coupled PBPK-CFD analyses, we indicated total fractions of contaminants inhaled from e-cigarette: (i) adsorbed onto tissue surface of respiratory tract, (ii) transported to deeper bronchial regions, and (iii) released into the indoor environment by exhalation. Basically, we indicated total respiratory uptake as a health risk factor of e-cigarette user and total amount of chemicals released into the indoor environment by exhalation as data which enable us to analyze second-hand and third-hand effects against non-user and indoor air quality.

One-way fluid-structure interaction of a medium-sized heliostat using scale-resolving CFD simulation

Vortex shedding and the resultant transient loadings on a medium-sized heliostat are investigated in this paper. Reynolds-Averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) of a simplified version of an operational heliostat, the LH-2, is used as a validation case for mean loads and to define the orientations used for fluid-structure interaction (FSI): maximum drag in the upright position, and maximum torque-tube moment at an elevation of 60° relative to the vertical. Optimized Atmospheric Boundary Layer profiles for mean flow and turbulence intensity were implemented as the inlet flow boundary condition for both the RANS and Stress-Blended Eddy Simulation (SBES) simulations, with the latter using the synthetic turbulence technique, the Vortex Method, at the inlet. The SBES results show a strong likeness to the experimental results of Peterka et al. (1986) with a comparable mean and peak loading distribution. The transient SBES CFD pressure was implemented in a one-way FSI simulation to obtain the structural response of the heliostat to the transient wind loading. The results show that the response of the heliostat conformed to and depended on the mode shapes and frequencies of the heliostat structure more so than the vortex shedding frequencies. For the upright case, the Strouhal number obtained was within 8% of that obtained from an experimental study in literature, with the main vortex-shedding frequency shown to be 0.5 Hz. When excited with this wind, the structure responded with the third modal frequency of 2.7 Hz. The 60° elevation case also responded mainly with the third mode of 2.6 Hz being excited, but the response was significantly influenced by a combination of higher modes located around 6 Hz. The results from the transient structural analysis using the temporal SBES heliostat surface pressure fields as input indicate that the method holds promise in predicting the transient response of heliostats. Importantly it can be concluded that due to the difference in frequencies between the vortex shedding and modal frequencies, the structure is safe from self-excitation.

Transient 3D CFD Simulation of a Stationary Vane, Oil Free, Rotary Compressor

The evaluation of a newly designed oil-free rotary compressor is presented based on transient 3D Computational Fluid Dynamics (CFD) simulations. The simulations are performed at low compression ratios and low pressure ratios and low rotational speeds. To place the results into context, the data presented in related literature was processed and summarized. The methods related to the CFD model of the newly designed compressor were developed, summarized and evaluated. The accessed CFD data are in good agreement with the results of the former rolling piston compressor related investigations. The oil free operation prevents the contamination of the working fluid from lubricant. Since the compressor is planned to work in open cycle within the sensitive environment of thermal heat sources contamination free operation has to be accomplished. However, oil-free operation also results in significantly lower performance based on the modelling results.

Aerodynamic interference of yachts sailing upwind on opposite tacks

When two sailing yachts pass each other on opposite tacks, the downwind (or leeward) yacht passes through the wake of its upwind (or windward) counterpart. To date there has been no study that has quantified the changes in drive force, apparent wind, or distance sailed to windward associated with these manoeuvres, although it is of interest to the development of racing yacht tactics.In this study a transient computational fluid dynamics model of yachts passing each other on opposite tacks is developed. Data is presented for a range of separation distances. For close crossing distances the drive force on the windward yacht may be reduced during the encounter, while the leeward yacht experiences a net increase in drive force. The change in drive force is primarily due to the change in the apparent wind angle induced by the other yacht. A leeward yacht changing its course to take advantage of this shift in the apparent wind can achieve a gain of 14 of a boat-length in the distance travelled to windward.

CFD Analysis of flow around fish

The study of fish like bodies in the liquid is a challenging research area in the fields of bio-locomotion and biomimetics. The power and maneuvering of swimming fish will help a lot in the field of underwater vehicles. Mainly the effect of tail oscillation and abdomen oscillation on fluid flow around such a body is highly unsteady, generating vortices and requiring detailed analysis of fluid-structure interactions. In the present context, a computational fluid dynamic (CFD) simulation of a tilapia fish has been developed to study about the fluid flows around this body when moving in water using the k-epsilon turbulence model. A parametric analysis of the variables that affect the flow surrounding the body is presented, along with flow visualizations. In the present study, a detailed unsteady and transient CFD analysis of the effect of tail and abdomen oscillation on the fluid flow around the fish has been studied. The simulation produces a motion of the tail and abdomen in the (x, y) plane, with both the tail and abdomen oscillating in the form of a sinusoidal wave. Detailed CFD analysis is done and results in terms of the aerodynamic force coefficients namely the lift and drag coefficients, pressure contour and velocity contour have been presented and discussed for the linear motion of fish along z-axis along with periodic oscillations of tail and abdomen in the (x,y) plane. It was observed that both the aerodynamic coefficients and forces came out to be very less which paves way for the motion of the fish with high efficiency. The analysis provided by the simulations has allowed the flow surrounding the tilapia fish undergoing periodic oscillations along with a linear motion to be studied in detail.

Influence of tool thread pitch on material flow and thermal process in friction stir welding

A three-dimensional transient computational fluid dynamics model is developed to analyze the influence of tool thread pitch on the material flow and thermal process in friction stir welding (FSW) of aluminum alloy plates. Four tool designs with different thread pitch are considered, the information of material flow velocity in the shear layer is extracted by analyzing the distribution of the tracking particles which are released at the starting points of streamlines, and the effect of thread pitch on material flow velocity is examined. Pin thread can effectively prevent the speed sudden change at advancing side, which is easy to occur with unthreaded pin. The total heat generation decreases with increase in thread pitch, which results in the decrease in peak temperature in FSW process. The calculated and measured thermal cycles and thermo-mechanically affected zone boundary match with each other.

Computational fluid dynamics investigation of particle intake for nasal breathing by a moving body

Particle intake by human breathing is important for developing relevant estimates of exposure in the indoor environments; however, relatively few studies are devoted to the influence from human activities. This study evaluates the nasal inhalability of micron particles for a manikin in motion by transient computational fluid dynamics (CFD) simulations. The model was built using a full-scale manikin with key facial features at the nose and mouth. The manikin was moving at a speed of 0.8 m/s through stagnant air in an indoor environment achieved by dynamic mesh. Three nasal inhalation rates of 15, 27, and 40 LPM (litres per minute) and four particle sizes (7, 22, 52, and 82 μm) were considered. The particle intake fraction was calculated to quantify the nasal inhalability of particles over different conditions. Fluid flow field of the motion-induced wake flow and particle trajectories were visualized to reveal the principles of the particle inhalability for a body in motion. This study quantifying the particle intake for a moving manikin will help to characterize a more holistic scenario for respiration modellings and developing estimates of exposure affected by human activities.

Evolution of all-glass nearly Zero Energy Buildings with respect to the local climate and free-cooling techniques

This paper presents research on the nearly Zero Energy Buildings (nZEB) metrics of an all-glass office building with advanced multi-layer six-pane glass and building integrated photovoltaic (BIPV) façade structures in different climate conditions. The study was carried out in the following steps: i) development of a time series model of dynamic thermal response of multi-layer six-pane glass and BIPV façade structures on the basis of transient computational fluid dynamics simulations, ii) integration of the façade structure dynamic model into the building dynamic model by adapting TRNSYS software code, iii) determination of the final energy balance including heating, cooling, ventilation, lighting, and on-site electricity production, iv) nZEB metrics evaluation considering night-time cooling by ventilation, evaporation cooling and hybrid ventilation of case study office buildings. It is shown that energy need for the cooling of the studied office building is dominant in all considered climate conditions, although it can be decreased up to 23% in most favourable considered climate conditions by implementing free cooling techniques. The case study buildings with BIPV structures on their east and west façades meet more stringed nZEB criteria; in addition, final energy demand decreases by 17–37% in comparison to the reference all-glass building. In the case of all-BIPV buildings, the final energy demand is decreased by 36–48%. Such buildings can significantly contribute to the mitigation of global climate change, as BIPV electricity production exceeds the building's energy demand.

Physical and CFD Modeling of the Effect of Top Layer Properties on the Formation of Open‐Eye in Gas‐Stirred Ladles With Single and Dual‐Plugs

In secondary steelmaking, the optimal size and position of open‐eye is important for effective alloying practice. In the current work, the effect of the top layer thickness and density on the formation of open‐eye in a gas stirred ladle was investigated. A one‐fifth scale water model of 150‐ton ladle was established with single and dual plug configurations for the physical modeling measurements. Air, water and three different oils were used to simulate the argon, liquid steel and slag in the water model, respectively. A transient Computational Fluid Dynamics (CFD) model based on Eulerian Volume of Fluid (VOF) approach was developed for numerical modeling of the fluid flow behavior. The physical modeling results show that the relative open‐eye area decreases from 46.7 to 5.6% when top layer thickness was increased from 0.75 to 7.5 cm using a gas flow rate of 7.5 NL min−1. The effect of the number of plugs on the open‐eye area for the same range of top layer thickness mentioned above was also studied. The relative open‐eye area generated due to the gas injection through the dual plugs decreased from 49.9 to 5.8%. To study the effect of top layer properties, rapeseed oil, castor oil and paraffin oil were employed for studying the effect of density and dynamic viscosity on the open‐eye formation. The results revealed that a larger open‐eye is formed when the density is increased. Furthermore, it was found out that the density of the upper phase dominates the open‐eye formation while dynamic viscosity has only minor effect. The results obtained from numerical simulations and physical modeling were found to be in good agreement.