Three-dimensional Computational Fluid Dynamics Model Research Articles

Experimental and numerical study of the thermal response of a diesel fuel tank exposed to fire impingement

Fire exposure of diesel fuel tanks can lead to catastrophic accidents. In this study, a fire test was conducted with an 80 L cuboid fuel tank filled to 18% capacity with diesel. More importantly, an innovative three-dimensional computational fluid dynamics (CFD) model was developed aiming at predicting fuel tanks pressurization rate and temperature distributions in the inner fluid. The CFD model was verified using the experimental data and the result showed close agreement. Then, the attention was focused on the influence of different fire engulfment zones and filling levels on the thermal response of the diesel fuel tank. The results indicated that, when fire engulfed the bottom and sides of the diesel fuel tank, temperature stratification appeared in the vapor space and gradually diminished with increasing filling level; however, the liquid phase could be considered isothermal, which was dominated by the convection at the bottom. Additionally, the high filling level caused the pressurization of the fuel tank to slow down due to the absence of temperature stratification in the liquid phase. The combined experimental and numerical analysis can offer valuable guidance for improve the design of thermal protection systems and the fire risk management of fuel tank explosions.

Simulation of Sorption-Enhanced Steam Methane Reforming over Ni-Based Catalyst in a Pressurized Dual Fluidized Bed Reactor

Steam methane reforming is a major method of hydrogen production. However, this method usually suffers from low energy efficiency and high carbon-emission intensity. To solve this issue, a novel steam-methane-reforming process over a Ni-based catalyst in a pressurized dual fluidized bed reactor is proposed in this work. A three-dimensional computational fluid dynamics (CFD) model for the complex physicochemical process was built to study the reforming characteristics. The model was first validated against the reported data in terms of hydrodynamics and reaction kinetics. Next, the performance of the proposed methane-steam-reforming process was predicted. It was found that the methane-conversion ratio was close to 100%. The mole fraction of H2 in the dry-yield syngas reached 98.8%, the cold gas efficiency reached 98.5%, and the carbon-capture rate reached 96.4%. It is believed that the proposed method can be used for methane reforming with high efficiency and low carbon intensity.

Unsteady and three-dimensional computational fluid dynamics modelling of scroll expander for low-grade waste heat recovery transcritical carbon dioxide micro-scale power system

Recent developments in the field of renewable energy have led to a renewed interest in low-grade heat (< 500 K). The low-grade heat is widely wasted by the lack of efficient heat recovery technologies. It is also limited by the system size, which defines as the micro to small-scale (< 50 kW). Although ORC based unit has been implemented in this field, the CO2 based waste heat recovery units can be more capable in the size construction. The performance of the expander plays a vital role in the system’s efficiency. Thus, the current paper provides thermodynamic and CFD analysis of a scroll expander regarding a micro-scale T-CO2 recovery system (< 10 kW) with a 400 K low-grade heat source. In the current CFD model, all the fluid domains were constructed by structural mesh. It also successfully integrated with the thermodynamic table to simulate two-phase T-CO2. This model can be the first scroll expander model for T-CO2 power system and gap the bridge of utilising the scroll machinery in this field. The CFD methodology was successfully validated by the new-built testing platform and previous data. The energy performance of T-CO2 and ORC (R123) based scroll expanders are compared by isentropic and exergy efficiency. The results showed that isentropic and exergy efficiencies of T-CO2 were 7% and 14% higher than the R123. It also identified higher irreversibilities of T-CO2 by the exergy of the working fluids. The pressure and temperature distributions identified the over-expansion and reversed flow characteristics, and the pressure imbalance of the initial expansion chambers denoted the reversed flow.

Effect of structural parameters on diesel particulate filter trapping performance of heavy-duty diesel engines based on grey correlation analysis

Pressure drop and filtration efficiency are important indicators of capture performance of diesel particulate filter (DPF). In this paper, the DPF three-dimensional computational fluid dynamics (CFD) model developed by the three-dimensional software AVL Fire is used to investigate the influence of key structural factors on the capture performance. The results show that the pressure drop in DPF can be reduced by properly increasing the filter diameter, filter length, CPSI or reducing the wall thickness. Increasing the filter diameter, filter length and wall thickness or reducing CPSI in an appropriate range is conducive to improving the DPF filtration efficiency. In addition, based on the results of grey correlation analysis (GRA), the wall thickness, as the most significant structural factor, should be given priority in the design of DPF. This work has important reference value for optimizing DPF capture performance and extending its working time.

Influence of Operating and Electrochemical Parameters on PEMFC Performance: A Simulation Study

Proton exchange membrane fuel cell, or polymer electrolyte fuel cell, (PEMFC) has received a significant amount of attention for green energy applications due to its low carbon emission and less other toxic pollution capacity. Herein, we develop a three-dimensional (3D) computational fluid dynamic model. The values of temperature, pressure, relative humidity, exchange coefficient, reference current density (RCD), and porosity values of the gas diffusion layer (GDL) were taken from the published literature. The results demonstrate that the performance of the cell is improved by modifying temperature and operating pressure. Current density is shown to degrade with the rising temperature as explored in this study. The findings show that at 353 K, the current density decreases by 28% compared to that at 323 K. In contrast, studies have shown that totally humidified gas passing through the gas channel results in a 10% higher current density yield, and that an evaluation of a 19% higher RCD value results in a similar current density yield.

Simulation and experimental investigation of centrifugal-cast functionally graded aluminum-B4C composite

ABSTRACT The present work investigates the flow behavior simulation and experimental validation for Al 6061-10 wt% B4C functionally graded aluminium matrix composite (FGAMC) by varying rotational speeds in a horizontal centrifugal casting (HCC) mold. A three-dimensional computational fluid dynamics model considering particle transportation and solidification based on the multiphase volume of fluid was analyzed using Ansys Fluent software. Simulated Particle gradient formation was validated against experimental data of solidified Al/B4C FGAMC. Simulation and experimental results showed 6.06% and 8.11% thinner outer region for mold speed from 1200 to 1400 rpm respectively. On the contrary, a 27% and 37% broadened thickness was observed at the inner zone for the same. The simulation and experimentation are in good agreement, and results show the formation of B4C particles gradient from outer to inner zone of FGAMCs. In addition, the effect of centrifugal speed on solidification rate and particle distribution has been explored.

Thermal performance of a hybrid thermal management system based on the half helical coil coupled with air jet cooling for cylindrical Lithium-ion battery

The Battery Thermal Management System (BTMS) is crucial for the efficient and safe operation of Lithium-ion batteries (LIBs). It is challenging for liquid cooling to apply to areas of battery modules with complex surface forms, such as the positive and negative cell terminals, cell holders, etc. Herein, the thermal management scheme integrated with the half helical coil and air jet impingement is proposed for cylindrical LIBs. Heat is transferred from the LIBs' sides by helical flow and dissipated from the LIBs' ends by air jet impingement. The three-dimensional computational fluid dynamics model of battery modules with cell holders is developed. The thermal performance of the LIBs at various BTMS strategies, the number of turns of the helical coil, airflow inlet velocity, inlet temperature, and contact resistance are investigated. When the impinging air jets are arranged on both ends of the cylindrical form, the maximum values of temperature difference (ΔT) of the LIBs fall from 5.7°C to 4.0°C compared with that of liquid-based BTMS. The arrangement of the half helical duct divided into two separate sections reduces the coolant flow path length, which decreases the maximum temperature (Tmax) and ΔT to 28.9°C and 3.6°C. The proposed BTMS exhibits an enhanced heat dissipation performance and provides a design guideline for developing the hybrid BTMS.

CFD-based pesticide selection for a nozzle used in a six-rotor UAV in hover mode for tea spraying.

A key challenge for unmanned aerial vehicle (UAV) spraying sometimes used in tea plantations is the downwash flow structure there stronger than in crops. In addition, the UAV spray is affected by the relationship between the nozzle design and the pesticide. However, there is little current research on this aspect. As a preliminary step this study focuses on the most appropriate pesticide for a designated nozzle in a six-rotor UAV according to the nozzle-pesticide relationship using a three-dimensional computational fluid dynamics model. This model considers the downwash flow structure effect and nozzle spray performance in hover. Nozzle FVP110-02, widely used in six-rotor UAVs, is used as a representative nozzle and bifenthrin and tea saponin water, commonly used in tea plantations, are used as the pesticides. The downwash flow structure of the six-rotor UAV in hover was conveniently controlled by the flight height and rotational speed, thereby causing the turbulence to be more stable. For nozzle FVP110-02, bifenthrin was more appropriate than tea saponin water at the same concentration, whilst bifenthrin and tea saponin water at a concentration of 1:1000 showed the best performance under identical working conditions. The numerical model developed here was shown to be effective for investigating the relationship between nozzle and pesticide. Our findings will help to not only improve UAV spraying for tea cultivation but also provide guidelines for pesticide selection in crops. Further work will address the comparison of the rigorous qualification of the numerical simulations with the measurements by the field test. © 2023 Society of Chemical Industry.

Reduced modeling of liquid desiccant falling film absorbers

Liquid desiccant falling film absorbers are an energy-efficient solution for humidity control and dehumidification in buildings and cold stores. This work presents a reduced one-dimensional physics-based modeling approach for this technology and compares it to a high-fidelity three-dimensional computational fluid dynamics (CFD) model. Both models capture the complex heat and mass transfer mechanisms of vertical falling films on two opposing walls and a horizontal crossflow of air. Additionally, both models were verified against experimental data from previous work, and the results showed good agreement within the uncertainties of the measurement equipment. A parameter variation study was also performed, comparing the results of both models under conditions relevant to cold store applications. The reduced model was found to be over 400 times faster than the high-fidelity model, while still achieving an average difference of less than ±0.14K, ±1.3%, and ±3.9% for the calculated air outlet temperature, absorbed water vapor mass flow rate, and air-side pressure drop, respectively. The reduced model is suitable for optimization studies and easy to implement in system simulations, making it a valuable tool for the design and optimization of liquid desiccant systems.

Thermal improvement of heat exchanger with involve of swirl flow device utilizing nanomaterial

The main objective of this article is to increase the flow mixing within a tube; in this regard, the helical tape with external inserts was developed and studied. CuO based nanofluids was used as a working fluid, and a novel testing fluid model was based on the previous empirical formulation by a three-dimensional (3D) computational fluid dynamic model established for velocity, temperature profiles, exergy, and irreversibility for Reynolds number 5000 and 20,000. The impact of external inserts and Reynolds number were discussed on Nu, f, temperature, and Sgen. The insertion of external inserts increases the Nu and f. When Re increases from 5000 to 20000, Nu increments about 204.21% without external inserts in the twisted tape. For the twisted tapes with external inserts, Nu increases about 202.87%. With external inserts, the entropy generation is reduced to 45% at Re = 5000 and 7% when Re is increased from 5000 to 20,000. An increment in Nusselt number and frictional entropy generation and a reduction in friction factor and thermal irreversibility are observed with an increase in Reynolds number. Consequently, it can be determined that employing nanofluids and twisted tapes in heat exchanger decreases exergy losses and enhance heat transfer performance due to a decrement in thickness of thermal boundary layer.

CFD-based Estimation of Friction Factor in Rough Pipes with Herschel-Bulkley Fluids

The appropriate estimation of frictional losses in a pipeline system is essential. So far, little attention has been paid to determining the friction factors with non-Newtonian fluids, especially in rough pipes. This study aims at calculating the friction factor using validated three-dimensional Computational Fluid Dynamics models in Ansys CFX. Steady-state computations are performed with three different incompressible Herschel-Bulkley fluids in rough pipes with relative roughness of the inner pipe surface ε = 0.0005 – 0.01. A power-law type bath gel as a test fluid is used for experiments to validate our numerical model. The numerical results are compared with the measured values and also with numerous existing friction factor estimation models with the help of generalization of the Reynolds number in the relevant engineering range of Regen = 100 – 40,000. This paper shows that the existing approximations can not accurately describe the friction factor with pseudoplastic fluids in rough pipes. On the contrary, in the case of Bingham plastic fluid, a new, explicit calculation relation is found in a unified form accepted by the literature.

Thermal Analysis of Water-Cooling Permanent Magnet Synchronous Machine for Port Traction Electric Vehicle

To further increase the torque/power density of a permanent magnet synchronous machine (PMSM) employed for a port traction electric vehicle, improving the thermal dissipation capacity of the cooling system used in the PMSM has become more and more important. This paper focuses on the thermal analysis of a water-cooling 200 kW PMSM for a port traction electric vehicle. First, the size parameters of the machine and the thermal property parameters of the materials used for each component are given. Based on the heat transfer theory, a fast evaluation method for a transient temperature rise in the water-cooling machine under multiple operating conditions is proposed. A lumped parameter thermal network (LPTN) model is established, and the temperature distributions of the machine at different operating conditions are analyzed. Second, under the same conditions, based on computational fluid dynamics (CFD), a three-dimensional (3D) CFD model is constructed. The influence of different cooling structures on temperature distribution is studied. The validity of the proposed fast evaluation method for a transient temperature rise in water-cooling machines under multiple operating conditions is verified. Finally, the results of the CFD and LPTN calculation are verified by experiments; the maximum temperature deviation of the rated speed/rated power operating condition is 8.5%. This paper provides a reference for the design and analysis of port traction electric vehicle machines.

Effects of Entrance Shape and Blast Pocket on Internal Overpressure Mitigation for Protective Tunnels Exposed to External Detonation on the Ground

This study presents a numerical analysis to reduce the overpressure inside protective tunnels for external detonations. A three-dimensional computational fluid dynamics model of a tunnel subjected to detonation for a hemispherical charge with a charge weight of 555 kg and a standoff distance of 7.6 m was established, based on a mesh sensitivity study to obtain an optimal element size, stability analysis of overpressure, and validation study to evaluate the accuracy of the numerical results based on Unified Facilities Criteria (UFC) 3-340-02. A parametric analysis was performed using the validated numerical model to investigate the effects of the entrance shape and blast pockets on the reduction in the maximum overpressure. The maximum overpressures were effectively reduced as the slope angle of the tunnel entrance decreased and the length of the blast pocket divided by the tunnel width decreased. An optimized shape of the tunnel was proposed based on the numerical results, where the peak overpressures were reduced by a maximum of 64.5%. This study aims to protect facilities, personnel, and equipment and further reduce construction costs by lowering the overpressure rating of blast valves in protective tunnels.

Numerical Simulation and Experiment of Dust Suppression Device of Peanut Whole-Feed Combine Using Computational Fluid Dynamics

Peanut whole-feed combines discharge a large amount of dust while harvesting, causing serious air pollution and detrimental environmental change. To reduce the dust emission from peanut whole-feed combines, a cyclone separation dust suppression device for peanut whole-feed combines was proposed in this study. A three-dimensional computational fluid dynamics (CFD) model coupled with dust particles and dust emission airflow was established to simulate the effect of a dust suppression device on capturing dust particles. Then, the effectiveness of the dust suppression device was verified by a dust suppression test system on a peanut whole-feed combine. The results show that when the inlet wind velocity of the dust suppression device increased from 15 m/s to 25 m/s, the separation efficiency of the measured value fluctuated between 90.79% and 96.07%, while the simulated value fluctuated between 95.18% and 96.59%. Moreover, the particle size of the discharged dust particles was significantly reduced under the action of the dust suppression device. The discharged dust particle size constant of the measured value was 8.6 μm, while the simulated value was 5.1 μm. The study methods and results can provide a reference for the dust suppression optimization of peanut whole-feed combines and similar agricultural machines.

Aerostatic and aerodynamic stability of a suspension bridge during early erection stages

During the early erection stages of suspension bridges, the flow field around the girder with a short length exhibits three-dimensional characteristics that affect the wind-resistant performance of bridges. To accurately extract the aerodynamic coefficients and flutter derivatives of a box girder during the early erection stages, three-dimensional computational fluid dynamics (CFD) models that balance accuracy and efficiency were established. Different angles of attack of the approaching flow were considered and the flow-field characteristics were discussed. With non-uniform wind loads distributed along the bridge axis, the aerostatic and aerodynamic stability of the bridge was investigated. The results show that the aerostatic and self-excited forces acting on the outer segments are different from those acting on the inner segments. The aerodynamic stability of the bridge is worse during the early erection stages. The end effect of the girder on the flow field is beneficial for the aerodynamic stability. Meanwhile, the structural aerostatic response has significant effects on the aerodynamic stability, which is also related to the angle of attack of approaching flow. Improvements in the aerodynamic stability can be achieved by adding counterweights inside the box girder.

Deep learning-based hemodynamic prediction of carotid artery stenosis before and after surgical treatments.

Hemodynamic prediction of carotid artery stenosis (CAS) is of great clinical significance in the diagnosis, prevention, and treatment prognosis of ischemic strokes. While computational fluid dynamics (CFD) is recognized as a useful tool, it shows a crucial issue that the high computational costs are usually required for real-time simulations of complex blood flows. Given the powerful feature-extraction capabilities, the deep learning (DL) methodology has a high potential to implement the mapping of anatomic geometries and CFD-driven flow fields, which enables accomplishing fast and accurate hemodynamic prediction for clinical applications. Based on a brain/neck CT angiography database of 280 subjects, image based three-dimensional CFD models of CAS were constructed through blood vessel extraction, computational domain meshing and setting of the pulsatile flow boundary conditions; a series of CFD simulations were undertaken. A DL strategy was proposed and accomplished in terms of point cloud datasets and a DL network with dual sampling-analysis channels. This enables multimode mapping to construct the image-based geometries of CAS while predicting CFD-based hemodynamics based on training and testing datasets. The CFD simulation was validated with the mass flow rates at two outlets reasonably agreed with the published results. Comprehensive analysis and error evaluation revealed that the DL strategy enables uncovering the association between transient blood flow characteristics and artery cavity geometric information before and after surgical treatments of CAS. Compared with other methods, our DL-based model trained with more clinical data can reduce the computational cost by 7,200 times, while still demonstrating good accuracy (error<12.5%) and flow visualization in predicting the two hemodynamic parameters. In addition, the DL-based predictions were in good agreement with CFD simulations in terms of mean velocity in the stenotic region for both the preoperative and postoperative datasets. This study points to the capability and significance of the DL-based fast and accurate hemodynamic prediction of preoperative and postoperative CAS. For accomplishing real-time monitoring of surgical treatments, further improvements in the prediction accuracy and flexibility may be conducted by utilizing larger datasets with specific real surgical events such as stent intervention, adopting personalized boundary conditions, and optimizing the DL network.

Full-scale computational fluid dynamics study on wind condition of the long-span Queensferry Crossing Bridge

To date, the majority of numerical modelling [computational fluid dynamics (CFD)] studies on long-span bridges have been carried out on scaled physical models, and without field-data for validation. For the first time, a full-scale bridge aerodynamic CFD study was conducted in this paper. A full-scale three-dimensional CFD model of the middle span and central tower of the Queensferry Crossing, United Kingdom, was created. The aim of this work was accurately simulating the wind field around the bridge. The CFD simulations were developed in OpenFOAM with the k − ω SST turbulence model. Atmospheric boundary layer inflows were configured based on wind profiles provided by a full-scale Weather Research and Forecasting (WRF) model. CFD predictions were validated with field data which were collected from an on-site Structural Health Monitoring System. The simulated fluctuating wind field closely satisfied the characteristic of field data and demonstrated that the modelling approach had good potential to be used in practical bridge aerodynamic studies. Meanwhile, comparisons and sensitivity analyses on mesh density provided a reference modelling approach for any future works on full-scale bridge aerodynamic models. Additionally, a cylindrical-like domain was applied in bridge aerodynamics for the first time and verified as being a convenient and reliable way to be used in bridge studies that involve changes in yaw angle.

Modeling-Based Design of the Control Pattern for Uniform Macrostep Morphology in Solution Growth of SiC

In the solution growth of the SiC crystal, macrosteps with sufficient height on an off-axis substrate are required to reduce defects and achieve a high-quality grown layer. However, over-developed macrosteps can induce new defects and adversely affect the crystal quality. To better understand and control the behavior of macrosteps corresponding to the control parameters of the growth system, a simulation method that consists of a global two-dimensional computational fluid dynamic (CFD) model, a local three-dimensional CFD model near the growth front, and a kinetics model that describes the movement of macrosteps on the crystal surface is proposed. The simulation method is first applied to investigate the effect of the crystal rotation speed on macrostep morphology. Although the results indicate that a higher crystal rotation speed results in less step bunching, constantly rotating the crystal in one direction is demonstrated to be incapable of yielding a uniform macrostep distribution on the whole surface. Accordingly, a sophisticated control pattern is designed by periodically switching the flow direction underneath the crystal surface, where the proposed simulation method is critical to determine detailed control-parameter values. When the control pattern suggested by the simulation is used, a grown crystal with a uniform macrostep morphology and ideal step height on the whole surface is obtained in the practical experiment.

Investigation of airflow through porous zones: Integrating computational fluid dynamics modeling into mine ventilation network simulation

ABSTRACT Using mine ventilation network (MVN) software to model airflow through porous zones in underground mining operations is arduous due to its complex and dynamic nature. However, accurately measuring airflow is essential to control underground mine air quantity and quality. This study integrated the computationally expensive conjugate porous media model into versatile MVN software to efficiently analyze airflow through the porous zone. In MVN software, a novel friction factor coefficient was compiled into the broken rock-filled drawpoint model, which was later verified against the three-dimensional (3D) computational fluid dynamics model. Several simulations were conducted to ensure model reliability by varying the porosity and broken rock diameter of the porous zone. Results demonstrate that the novel friction factor coefficient can accurately predict airflow through porous media using MVN software and reduce computation time by > 99% compared to the 3D solver. In addition, sensitivity analyses were conducted to assess the effects of various factors on the system. This method enables mine ventilation engineers to effectively plan the rapidly changing underground MVN.

Computational Fluid Dynamics-based Simulation and Design of a Horizontal Tidal Turbine System

Tidal phenomena, the rhythmic rise and fall of sea waters due to gravitational forces among celestial bodies like the Sun, Earth, and moon, offer a dependable source of renewable energy. Tidal energy, with its predictability and high energy density, is an attractive sustainable option. Tapping into this energy requires a specialized device, the tidal turbine, where the rotor plays a vital role. The rotor converts the kinetic energy of incoming tides into useful mechanical energy, evaluated through thrust, torque, and power efficiency. This study focuses on designing a horizontal tidal turbine using a three-dimensional Computational Fluid Dynamics (CFD) model with ANSYS Fluent software. Input parameters are based on real-world measurements of the average current velocity of 1 m/s obtained using Acoustic Doppler Current Profiler (ADCP). The paper serves two purposes: validating the applied design approach and analysing crucial design factors. By confirming design compatibility and assessing factor properties, the research contributes to optimizing tidal turbine efficiency and its feasibility as a sustainable energy source.