Fluent Model Research Articles

Enhancement of heat transfer utilizing small height twisted tape flat plate solar heat collector: A numerical study

The flat plate solar heat collector captures solar thermal energy for agricultural drying, heating houses and businesses, cooling food, and producing steam. Adding twisted tape inserts to the absorbent surface of a flat plate solar heat collector increases its efficiency. This article describes the absorber plate of twisted tape inserts and discusses the thermal and hydraulic performance achieved by varying the twist pitch and twist height. Computational fluid dynamics is performed for Reynolds numbers ranging from 5000 to 17000, relative twist height (TH/Dh) of 0.011-0.044, relative twisted tape inserts pitch (PTT/TH) of 49.95-73.2 and relative twist pitch (TP/TH) of 8-15. Heat transmission and friction factors owing to twisted tape inserts have been analyzed in depth using computational fluid dynamics, with analysis performed using the k-epsilon model in commercial ANSYS Fluent 19.2 software. A maximum thermal-hydraulic performance value of 2.41 is observed for the many twisted tape parameters, with, TH/Dh of 0.022, PTT/TH of 64.60, and TP/TH of 12.

Electron Target Cooling Analyses of the KIPT ADS Using MCNP and Ansys Fluent

This study presents multiphysics analyses of the electron target cooling system of the accelerator-driven system (ADS) of the Kharkiv Institute of Physics and Technology (KIPT) using MCNP and Fluent computer programs. MCNP has been used to transport electrons, gammas, and neutrons, and to calculate the energy deposition in the target materials. The MCNP mesh-tally data have been imported into Fluent by a C subroutine that has been compiled and linked to Fluent as a user-defined function. The KIPT ADS is located in Ukraine and was in operation until February 2022. The Fluent model is based on the computer-aided design files from the manufacturing process of the target assembly. The Fluent results for the reference case match very well the literature results obtained by STAR-CCM+ during the design phase. Other cases that differ from the reference one have been analyzed; in these cases, it is assumed a malfunction of the electron accelerator or of the water cooling system. The target cooling system operates normally for all the analyzed cases except when the inlet water mass flow rate is decreased. The transient analysis showed that the target cooling system can operate for 180 s with full power when the inlet water mass flow rate is decreased down by 75%.

Computational Analysis of Erosion Wear Rate by Multiphase Flow in Optimum Bend Ratio of Pipeline

Abstract: Pipe bends are an integral part of transportation system as they help by providing flexibility in the path. In this paper, flow of mono-dispersed particles with carrier flow is simulated using Computational Fluid Dynamics by implementing Eulerian two-phase model in FLUENT. This paper is a forward stepping stone as it depicts the effect of pipeline bend on flow characteristic such as erosion rate, concentration profile, wall shear stress, etc. after numerous researches on pressure drop and velocity profiles. In this paper, a two-phase fluid of silica sand, having mean diameter of 450 µm (density = 2650 kg/m3 ), and water are mixed at the ratio of 8.82% solid concentration by weight and flown through a pipeline with diameter 53.0 mm and the optimum pipe bend ratio of 5.60 for minimum pressure loss.

Study of Twisted Tape Inserts Segmental Application in Low-Concentrated Solar Parabolic Trough Collectors

This article presents the results of an analysis of heat enhancement intensification using twisted tapes in linear absorbers for low-concentration parabolic trough collectors, a technology frequently considered as a supplementary energy source for industrial heat production. This contribution proposes a segmented application of different twisted tapes to intensify heat absorption. A 33.7 mm tubular absorber placed in the collector focal point with an aperture of 1.8 m was selected. The temperature range of the heat transfer fluid was chosen at 60–250 °C. The impact of inserts with twisted ratios of 1, 2 and 4 on system operation was analysed using the Ansys Fluent and mathematical model. The models used were validated based on experimental results from a parabolic trough collector with solar simulator test bench. The results indicated that for the range of mass flow between 0.15–0.3 kg/s, the most optimal is applying twisted ratio 1, except for the highest-temperature section. In this section, it is more optimal to use an insert with a twisted ratio 2, due to the lower need for pumping and the higher efficiency increment. The long-term analysis for the case study plant indicated that the proposed approach increased power gain by 0.27%.

Impacts of different characteristics of marine biofouling on ship resistance

Ship resistance research on marine biofouling is an old but hot topic which invokes plenty of studies recently. Previous studies on the surface roughness of ship hulls mainly focus on the height of micro-organisms or macro-organisms adhered to ship hulls without considering other components which may indeed play an important role in generating additional resistance. Many authors attempt to use a single parameter, for example, height of the biofoulers, to describe the hull roughness. Our research indicate that any single factor affecting ship hull roughness can not completely reflect the compositions of ship resistance. Here we propose a novel numerical model which enables more precise estimates of the contribution of each single component involving in the marine biofouling.The standard k−ε model of FLUENT is modified by considering the possible rotating, jetting, surging and swirling of fluid flowing over ship hulls due to characteristics of the marine biofoulers. Simulated results using the modified model at various speeds are compared with that using the original model, and an improvement of ship resistance is evident, quantitatively consistent with measured, indicating that the modified model behaves in a reasonable manner in simulating the relationship between ship resistance and ship surface roughness.The marine biofoulers affect ship resistance primarily by increasing the tangential surface shear stresses. Simulated results demonstrate that additional resistance caused by height, shape, hardness and density of the biofoulers accounts for up to ∼80% of total resistance in the heavy fouling condition (taking vessel “YOURIXX” as an example), implying an economic demand for good hull performance.

Self-cleaning performance of three bottom drain modes in circular culture tank: Experimental and numerical study

This work investigated the self-cleaning performance of three drain modes in circular bottom drain water tanks with tangential inlet. Removal experiments in center, eccentric and center-eccentric combined (dual) drain modes were carried out in a miniature tank with a diameter of 0.44 m and a depth of 0.215 m for a hydraulic retention time of 30 min using two artificial bio-wastes mimicking fish fecal and uneaten feed matters. The experiments were simulated by using the Eulerian model of FLUENT. The correlations between the numerical solutions and the experimental data confirm the adequate reproduction of the bio-waste removal behavior. It was confirmed that the self-cleaning performance of the center drain is four times greater than that of the eccentric drain under the same water supply condition. Since the water drainage speeds of the dual-drain were less than those of the other two drains under the same water supply condition, the order of precedence for self-cleaning performance was the center drain, dual-drain, and eccentric drain. According to numerical experiments in the full-size tank with a diameter of 9.15 m and a depth of 1.83 m for hydraulic retention times of 30 and 55 min, the above order was kept constant, but the self-cleaning performance of the center drain was reduced by 1.04 times of that in the eccentric drain. The numerical experiments of all possible dual, triple and quadruple bottom drain modes in the full-size tank with one center drain and three eccentric drains showed that an increase of the eccentric drains causes a decrease of the drainage speed and thus does not lead to a noticeable improvement in self-cleaning performance. Numerical experiments in a medium-size tank showed that the above order was also kept constant. The reason why the self-cleaning performance of the center-eccentric combined drain is lower than that of the center drain is that its reduced drainage speed does not have kinetic energy enough to push the bio-wastes up to the height of the outlet. The center drain has the best self-cleaning performance in the circular tanks with tangential inlet and if the drainage speed is not sufficiently increased, the multiple drain system might have negative effect on self-cleaning performance.

Study on Optimization of Nozzle Angle for Oxygen-Rich Side-Blown Lead Melting Furnace

Taking an oxygen-rich side-blown lead melting furnace made by a company as the research object, the three-dimensional design software Solidworks was used to construct a model at an equal scale, and established a physical model which is in line with the actual system. Based on the determination of the physical properties of the slag phase and metal phase in the furnace, the VOF multiphase flow model and standard turbulence model in FLUENT were used to simulate the gas–liquid multiphase flow. By adjusting the different inclination angles of the spray gun, we analyzed the distribution changes of key indicators, such as the flow field, average turbulent kinetic energy and gas content in the furnace. At the same time, it was found that the turbulent kinetic energy in the middle of the furnace was large, which could strengthen the winding effect of the material and the best arrangement. The gas content of the upper part of the oxygen gun was high, and the gas content in the middle of the furnace was higher than that in the wall area on both sides and showed a gradual downward trend. If the inclination angle of the spray gun is too small, the agitation of the lower melting area is not strong enough, On the contrary, if the inclination angle is too large, the local flow rate of the sedimentation area increases and the gas content is low. The optimal tilt angle of the spray gun is between 10° and 15°.

Development of a Three-Dimensional CFD Model and OpenCV Code by Comparing with Experimental Data for Spillway Model Studies

This article presents a three-dimensional CFD model and OpenCV code by comparing the flow over the spillway with the experimental data for use in spillway studies. A 1/200-scale experimental model of a real dam spillway was created according to Froude similarity. In the experimental studies, velocity and water depth were measured in four different sections determined in the spillway model. A three-dimensional ANSYS Fluent model of the spillway was created and the simulations of the flows occurring during the flood were obtained. In the numerical model, the two-phase VOF model and k-epsilon turbulence model are used. As a result of the numerical analysis, velocity, depth, pressure, and cavitation index values were examined. The velocity and depth values obtained with models were compared and a good agreement was found between the results. In addition, in this study, a different technique based on image processing is developed to calculate water velocity and depth. A floating object was placed in the spillway channel during the experiment and the movement of the object on the water was recorded with cameras placed at different angles. By using the object tracking method, which is an image processing technique, the position of the floating object was determined in each video frame in the video recordings. Based on this position, the velocity of the floating object and its perpendicular distance to the bottom of the channel was determined. Thus, an OpenCV-Python code has been developed that determines the velocity and water depth of the floating object depending on its position. The floating object velocity values obtained by the algorithm were compared with the velocity values measured during the experimental model, and new velocity correction coefficients were obtained for the chute spillways.

An open source framework for advanced Multi-physics and multiscale modelling of solid oxide fuel cells

Solid oxide fuel cells are high-efficiency renewable energy devices and considered one of the most promising net-zero carbon energy technologies. Numerical modelling is a powerful tool for the virtual design and optimisation of the next-generation solid oxide fuel cells but needs to tackle issues for incorporating the multi-scale character of the cell and further improving the accuracy and computational efficiency. While most of solid oxide fuel cell models were developed based on closed source platforms which limit the freedom of customisation in numerical discretization schemes and community participation. Here, an open source multi-physics and multiscale platform for advanced SOFC simulations consisting of both cell- and pore-scale performance models was developed using OpenFOAM. The modelling aspects are elucidated in detail, involving the coupling of various physical equations and the implementation of the pore-scale electrode in the performance model. The entire platform was carefully validated against experimental data and the other numerical models which were implemented in commercial software ANSYS Fluent and based on the lattice Boltzmann method. The cell-scale model is subsequently employed to study the effects of different fuels, i.e., pure hydrogen and different ratios of pre-reformed methane gas under various operating temperatures. It is found that the cell-scale model reasonably predicts the effects of these parameters on the cell performance, aligning well with the Fluent model. This study further identified the size of representative element volume with respect to the current density for the anode via the pore-scale model where the realistic microstructures reconstructed by a Xe plasma focused ion beam–scanning electron microscopy are employed as computational domains. It is found that a volume element size of 1243 voxels is sufficient to yield the representative current density of the whole. All these numerical investigations show that OpenFOAM is a potential multi-physics and multi-scale computational platform that is capable of accurately predicting both cell-scale and pore-scale performance and spatial information of solid oxide fuel cells. The developed models are also made public in GitHub to inspire community to further develop around it.

Design and optimization of dry powder jet cleaning nozzles for airport navigation lights

The research of this work is based on the nozzle design and optimization of dry powder (NaHCO3) jet cleaning system for airport navigation aid lamps. In this cleaning system, compressed air drives dry powder (NaHCO3) abrasive, and a gas-solid mixed high-speed jet is sprayed onto the surface of the luminaire through the nozzle to scour and clean the dirt attached to the surface of the luminaire. Based on the computational fluid dynamics and flow field theory, three types of nozzle structures, namely tapered nozzle, Laval nozzle, and flat nozzle, were studied; the DPM (Deformable part model) model in Fluent was used to analyze the internal and external flow fields of the nozzle mixed with the gas-solid two-phase flow to obtain the velocity field, pressure field and nozzle wear rate of the mixed gas, and the flat nozzle was selected and the nozzle parameters were optimized. The optimized level combination of flat type nozzle structure is obtained with a flat width of 4mm, flat height of 24.5mm, and flat length of 55mm.

Numerical and Experimental Investigation of Aerodynamic Noise Generated by Subsonic Axial Fan Using Hybrid Approach

This research work reports the study and investigation of aerodynamically generated noise characteristics of the fan using a hybrid numerical approach. Numerical results are compared with the experimental results. The experiment is conducted to determine the sound power radiated by the fan. This experiment is carried out in the reverberant and anechoic chambers as a test environment. The axial subsonic fan is considered for the study. Detailed experimental work is reported in the first section, and in the second section, numerical simulation results are reported. Flow analysis is carried out using unsteady Navier Stokes based equations with a Large Eddy Simulation scale resolving turbulence model in the commercial solver Ansys Fluent. Fluctuating components of velocity and density are computed for further calculation of acoustics. The flow results from the simulation are compared with the flow results obtained in the experiment. As the aerodynamic performance of the fan is validated and shows good agreement with experiment, it is followed by an aeroacoustics analysis performed in the MSC Actran Acoustics solver. The Lighthills analogy is used to compute the flow noise generation and propagation terms. Sound power characteristics are studied with the help of one third octave band and narrow band analysis. Overall sound power is computed in MSC Actran and is compared with the experiment. Also, the sound power computed in Ansys Fluent is compared with an experiment and shows good agreement This work also reports the detailed computational methodology for fan noise prediction for any type of fan application

Comparative Analysis of Numerical Methods Regarding the Backflow Investigation in Tunnels of Zentrum am Berg

The efficiency of tunnel ventilation systems is commonly evaluated through numerical modelling. In this survey, two CFD models were developed by means of Fire Dynamic Simulator and Ansys Fluent software. The simulation results were used to assess the model performance in studying the backflow distribution in a real tunnel. A full-scale experiment to evaluate the ventilation conditions in the western railway tunnel was carried out in Zentrum am Berg. The velocity values were obtained for 90 examined points located at 10 cross-sections along a 100-meter tunnel part. The results showed good agreement in velocity variation trends from field measurements and those predicted by numerical models. At cross-sections more distant from the fan outlets, the FDS and Fluent models overestimated the flow velocities to a different extent. The simulated backflow development corresponds well to the observed three specified regions (initial, transitional, and developed) with distinctive flow structures. The FDS calculations confirmed the registered spontaneous changes in flow direction at points with a prevailed flow direction in the vicinity of the jet fans. Despite some discrepancies in results, the comparative analysis of two numerical models showed their applicability in the backflow investigation.

CFD Simulation of Heat Transfer Characteristics in a Rectangular Duct with Trapezoidal Turbulence Promoters

The heat transfer rate from the hot surface to the coolant flow increases by placing the ribs on the surface of the coolant flow passage. The effect of turbulence promoters with different angle of attack and with a fixed tapered angle on the heat transfer characteristics in a rectangular stationary duct is considered for this study. Here turbulence promoters increase the heat transfer in the duct. The examination has been conducted on the rectangular smooth duct and rectangular duct with inverted V-shaped ribs of a different angle of attack. The rib angle attack of 45º, 60º, 90º and tapered angle 20º (fixed) on the top surface of the rib are considered. The rib blockage ratio and pitch ratio are 0.0553 and 10 respectively. The heat transfer characteristics are compared with Reynolds number of 6000. The heat transfer and computational flow analysis are conducted by k-epsilon turbulence model in ANSYS FLUENT. The tapered angled cross-sectional inverted V-shaped ribs of 60º shown high average heat transfer coefficients among the 45º, 60º and 90º smooth duct.

Numerical Simulation of Kelvin–Helmholtz Instability and Boundary Layer Stripping for an Interpretation of Melt Jet Breakup Mechanisms

The present study is aimed at investigating the ability of a CFD modeling of liquid–liquid jet breakup to resolve the principal mechanisms relevant to jet breakup as well as submillimeter-scale drop size. It is generally known that jet leading edge breaks up by boundary layer stripping (BLS), and jet lateral surface breaks up by Kelvin–Helmholtz instability (KHI). The jet breakup rate as well as the resulting particle size are important parameters that would largely govern the intensity of a steam explosion in severe reactor accidents. First, a two-dimensional simulation of KHI along the melt-liquid coolant interface was performed using the VOF model in ANSYS Fluent with fine meshes as small as 0.02 mm. The dominant wavelength obtained by FFT analysis of calculated melt volume fractions showed that the fastest growing wavelength from the linear analysis of KHI is seen only at the very early development of the instability, and it increases gradually. Second, a three-dimensional simulation of BLS was performed, and the shapes and sizes of the melt particles were obtained. The particle size distributions from KHI and BLS simulations were compared with COLDJET experimental data of Woods metal and water, and it showed that the finer drops of one millimeter or smaller are produced by Kelvin–Helmholtz instability, and the drops of a few millimeters in diameter are mainly produced by boundary layer stripping.

Numerical Calculation and Analysis of Water Dump Distribution Out of the Belly Tanks of Firefighting Helicopters

Helicopters are more and more widely used for water dumping in fire extinguishing operations nowadays. Increasing attention is being paid to improving helicopter firefighting efficiency. Water distribution onto the ground from the helicopter tank is a key reference target to evaluate firefighting efficiency. Numerical simulations and calculations were carried out concerning water dumping out of the belly tank of a helicopter using the VOF (Volume of Fluent Model) model and mesh adaptation in ANSYS Fluent, and the effects of two parameters, the height of the tank above the ground and the wind speed, on the wake flow and water distribution were discussed. The results showed that for forward flight, the higher the forward flight speed, the less the average water depth on the ground. Similar results were obtained for flight height. The average water depth was one order of magnitude less than in the cases of the corresponding hovering helicopter for a given wind speed. As for hovering flight, the higher the wind speed, the less the average water depth on the ground. The simulation results were basically consistent with the conclusions of water dump tests of fire-fighting equipment carried by helicopters. For example, when the helicopter flew at a forward flight speed of 15 m/s and the tank bottom was 30 m above the ground, the area covered by the dumped water would be 337.5 m2, and the average water depth accumulated per square meter would be 0.3 cm. This result was close to the 0.34 cm obtained under Hayden Biggs’s test condition with a forward flight speed of 70 km/h and a height above the ground of 24 m.

Pragmatic development in deaf and hard of hearing children: A review

ABSTRACT Despite the advances in technology and sign language awareness, many Deaf and Hard of Hearing (DHH) children have language delays as a consequence of difficulty accessing a language model. These delays are often particularly pronounced in the domain of pragmatics, where the language user takes into account the people they are communicating with and their shared access to current context. This review considers the effect childhood deafness can have on pragmatic development, reviewing studies of the pre-linguistic stage, early linguistic communication and more advanced pragmatics as measured both by general pragmatic checklists and more specific assessments of information structure and inference, deception and non-literal language (including sarcasm), and conversation. Where present, delays are consistently explained by the cumulative effects of access to a fluent natural language model, which affects both the acquisition of linguistic forms and the social and cognitive skills needed to use them in interaction. Implications for educators are briefly considered.

Comparative Analysis of Dynamic Behavior of Liquid Droplet Impacting Flat and Circular Wires

The performance of droplets captured by the wire mesh demister in a seawater desalination system seriously affects the quality of water desalination. Therefore, it is of great significance to study the droplet impact in the wire mesh demister to improve the demister’s efficiency. In this paper, a two-dimensional model of the droplet impacting the wire is established. The processes of the droplet impacting a flat wire and a circular wire are simulated by using the VOF model in Fluent, and a comparative analysis is conducted. The results demonstrate that both wires experience spreading and splashing stages, but when the wire is circular, the length of the lifted lamella is longer, the peak force on the wall is larger, the splash’s start time is earlier, and the number of secondary droplets is greater; the variation rule of the force on the wall caused by the change of initial velocity is similar, and the increase in initial velocity will promote the occurrence of splash phenomenon, but the role of the initial velocity on the splash effect is more obvious for the circular wire; and when the droplet impacts the flat wire, the influence of incident angle on the critical splash velocity is non-monotonic, but the critical splash velocity increases with an increase in incident angle when the wire is circular.

Simulation study on flow behavior around a wall-mounted finite height square cylinder with corner chamfer

Current work aims to investigate the effect of applying corner chamfer on the wake of the square cylinder and understand the effect that various chamfer sizes have on the flow characteristics. The study also involves the understanding of the weakening of the wake, thus, possible improvement in structural integrity. The result of applying various corner chamfer on flow, mainly the plate cylinder juncture region, the tip region, and the wake region around the wall-mounted finite height square cylinder are investigated. The Aspect Ratio (AR) is kept at 4. The investigation employed the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model in Fluent. Flow characteristics for the square cylinder without chamfer were validated against wind tunnel experimental results at a Reynolds number of 12,000 involving a similar geometry. Three cylinders with increasing corner chamfer were studied, and their results, as well as a comparison with the simple square cylinder, are discussed in this paper. The results in the wake region for various vertical and horizontal planes of the bluff body were analyzed. By applying a corner chamfer, a decrease in the wake was observed. By increasing the chamfer, improvement in the flow was observed, i.e., a reduction in drag coefficient, a smaller horseshoe vortex zone, wake region behind the cylinder was reduced, Strouhal number increased, and vortex structure diminish quicker.

Numerical simulation of the impact and freezing stage of supercooled droplets on the ship superstructure surface in the Arctic route

Icing not only affects the stability and safety of Arctic navigation ships but also damages the facilities on board and endangers the safety of personnel. The icing result on the ship’s surface is closely related to the icing process of water droplets on the surface. In the icing process of supercooled water droplets colliding with the ship surface, the impact and icing are coupled with each other. This process is extremely sensitive. The final ice type and physical parameters will change due to the external disturbance. Therefore, in order to obtain accurate ship icing results, the micro impact icing process of water droplets on the surface needs to be considered. From the microscopic point of view, using the numerical simulation method of solidification/melting model in Fluent, this article analyzes the effects of undercooling, contact angle, and droplet impact on the microscopic solidification process of supercooled droplets, and the results show that 1) droplet impact affects the droplet volume; 2) as the impact velocity increases, the freezing time decreases; 3) in the case of the same impact velocity, the freezing time and cooling time vary very closely even if the degree of undercooling and contact angle are different.

Numerical Modelling of Discharging the Lithium-Sulphur Batteries in Ansys Fluent

Lithium-sulfur batteries appear to be an exciting technology for energy storage due to their many advantageous properties. Due to its low weight and high energy, this technology could be used in aviation, aerospace or in heavy electric vehicles or even for mobile applications. This article investigates possible approaches for modelling of lithium-sulfur batteries. A new method using Ansys Fluent add-on Multi-Scale Multi-Domain battery module, originally designed for lithium-ion batteries, is presented. Battery characteristics are described through an equivalent circuit model, which can capture its complex characteristics. The results suggest that the built-in Ansys Fluent model can be successfully extended for 3D modelling of lithium-sulfur batteries. The critical point of the simulation is the precise definition of equivalent circuit model parameters.