Three-dimensional Computational Fluid Dynamics Research Articles

Numerical simulation of binary component separation with perforated-on sheets of the structured packing

In this research work, we proposed a modern structured packing (SP) with perforated sheets with a specific surface area of 860[Formula: see text][Formula: see text]/[Formula: see text], which was determined using numerical techniques. This work aims to evaluate the major characteristics of PACK-860 for instance, height equivalent to a theoretical plate (HETP), dry pressure drop (DPD) and wet pressure drop (WPD). Additionally, the flow construction was defined for specific packing via computational simulation. To evaluate the value of HETP, DPD and WPD, the three-dimensional (3D) computational fluid dynamics (CFD) simulation with the Eulerian–Eulerian (EE) multi-phase method applied in this paper. According to the findings of this research, the performance of the mass transfer (MT), WPD and DPD was enhanced with the perforated-on sheets of packing. Based on the observation, numerical results are consistent well with the theoretical data which reveals the consistency of CFD tools for modeling methods to separation applications.

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.

Computational Fluid Dynamics Study of Particle Deposition on Human Lung Dynamic: A Comparison Between the Healthy and Fibrotic Lung

AbstractThe lung is the human organ mainly affected by the severe coronavirus disease (COVID-19) caused by the novel coronavirus SARS-CoV-2. In this pathology, the dynamic lung function and the respiratory mechanics are compromised, leading to the development of the ARDS (acute respiratory distress syndrome). The resulting damage is the progressive reduction of gas exchange and death in the most critical patients. For these reasons, it is important to study and analyze how this virus adversely affects lung dynamics. The main objective of the present paper proposes a modeling method of SARS-CoV-2 virus particles spread in the 23rd generation of lung tree and the mechanical estimation of how a severe stage of COVID-19 characterized by pulmonary fibrosis affects the alveolar sac expansion and hence the breathing capability of the sick person. In this context, the dynamic analysis of the influence of SARS-CoV-2 spread on human lung under real conditions has been shown by means of a numerical approach. Therefore, a multiphase three-dimensional computational fluid dynamics (CFD) study is performed to estimate the COVID-19 virus particles dispersion throughout a simplified model of the 23rd generation of the bronchial tree, at the alveolar region. Then, a fully coupled fluid-structure interaction (FSI) with the mesh morphing technique and solid displacement characteristics are used to obtain and evaluate a realistic wall displacement during the expansion of the alveolar sac. A comparison is made between a healthy and a diseased lung. These phases are studied under cyclic steady-state conditions The novelties of this analysis are: first, the innovative CFD method proposed in order to model the particles spread inside the alveolar region, and second the evaluation of how the presence of Sars-Cov-2 can affect the mechanical properties of the alveolar sac and damage the lung function of a sick person at an advanced stage of infection, such as a person affected by pulmonary fibrosis.

High-Dimensional Multiobjective Optimization of an Aeroengine Combustor Based on Cubic Polynomial

This paper innovatively designs a surrogate model for the performance of aeroengine high-temperature rising combustor based on cubic polynomials. According to the comparison of the one-dimensional calculation method, the three-dimensional computational fluid dynamics (CFD) numerical simulation, and the experiment, the feasibility of the one-dimensional (1D) calculation method and the reliability of the sample data calculated by this method are proved. The predictions of the metamodel were compared with those calculated by using the 1D program, and the root-mean square errors of the two target parameters were 0.000077% and 0.001725%. Based on this, sets of test data were used to verify the accuracy of using the surrogate model. The test results were compared with those of an artificial neural network (ANN) model and the 1D program. The root-mean square error (RMSE) of the cubic polynomial model and the ANN model in terms of combustion efficiency and total pressure loss were 0.0150% and 0.0107%, and 0.1628% and 0.3032%, respectively. A global sensitivity analysis identified the oil-to-gas ratio and the total inlet pressure as the most important factors affecting the combustion efficiency and total pressure loss. Particle swarm optimization (PSO) was used to obtain the optimal nondominant Pareto solution set. It provides physical insights for the optimization design of aeroengine combustor.

Influence of Inlet Vane and Wrap Angles on Cavitation Behavior of a Centrifugal Pump

This comprehensive study focuses on the relationship between the inlet vane and wrap angles of a centrifugal pump impeller and its cavitation behavior. The objective is to propose a new design for cavitation performance enhancement of the pump by reducing the required net positive suction head (NPSHR). To render a detailed study, the variations of the mentioned angles were examined both at hub and shroud. A three-dimensional two-phase parametric computational fluid dynamics (CFD) study was conducted and variations of inlet blade and wrap angles at hub and shroud were investigated separately. After validating the experimental results with the pump model, the pump parameterization process was carried out, and pump geometry was re-defined with its geometrical properties. The characteristic curves of the parameterized pump and pump model were in agreement with each other. Numerical cavitation tests were performed and the NPSHR values of each design were calculated for four different operating conditions. Results showed that cavitation performance increase was achieved with angle variations at the best efficiency point (BEP) but, this situation led the pump to operate exposed to cavitation at high flows (HF) for some designs. Therefore, the design with the best cavitation performance increased at BEP and HF was proposed as a new design. During numerical simulations, shear stress transport (SST) turbulence model and Rayleigh–Plesset equation were used.

A Cartesian grid-based two-dimensional plus time method for simulating ship bow waves

Numerical modeling of ship bow waves is still hard work, partly due to their multiscale features. Direct three-dimensional (3D) computational fluid dynamics simulation could be an appropriate choice to investigate the problem. However, limited by computational resources, small scale phenomena such as spraying and wave breaking that could be observed during the ship wave generation process are usually simplified or not fully distinguished in a 3D simulation. In order to accurately capture the small scales flow field information with the available computational resource, a new Cartesian grid-based two-dimensional plus time (2D+t) method is developed in this paper, which is suitable for 3D slender ships. With this method, a 3D steady ship wave-making problem is transformed into a 2D unsteady wave-making problem of a deformable body. The boundary velocity of the deformable body is obtained with a novel interpolation algorithm, which is then enforced on the background Cartesian grid by a newly proposed immersed boundary method. The pressure boundary condition on the surface of the deformable body is explicitly considered in the solution of the pressure Poisson equation. Moreover, an extra open boundary condition is applied to the upper boundary of the computational domain to achieve a better conservation. The proposed model is validated with selected cases, showing that the model is capable of simulating both non-wave-breaking and wave-breaking problems.

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.

Computational modelling and simulation of Trombe walls as a passive ventilation system under an oceanic climate

As buildings' energy consumption has become of outstanding importance, much more attention is being paid to passive solar design strategies such as Trombe walls (TWs) in view of their implementation. Nowadays, such a device is considered a promising alternative to ensure a transition to renewable energies. Thereby, a three-dimensional Computational Fluid Dynamics (3D CFD) numerical transient analysis of a passive Trombe wall integrated in a test room has been implemented to investigate dynamic and thermal fields prevailing there. Two configurations have been considered herein. The first configuration includes an uninsulated TW. In the second configuration, we propose an insulated TW. From the simulation results, the proposed idea would offer improved thermal performance where the conductive and convective flows are more pronounced and the temperature can be maintained within 16–21°C. Likewise, the outside temperature of the insulated TW can reach around 25°C.

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.

Artificial neural network-based streamline tracing strategy applied to hypersonic waverider design

Streamline tracing in hypersonic flows is essential for designing a high-performance waverider and intake. Conventionally, the streamline equations are solved after obtaining the velocity field over a basic flow field from simplified flow differential equations or three-dimensional computational fluid dynamics. The hypersonic waverider shape is generated by repeatedly applying the streamline tracing approach along several planes. This approach is computationally expensive for iterative waverider optimization. We provide a novel strategy where an Artificial Neural Network (ANN) is trained to directly predict the streamlines without solving the differential equations. We consider the standard simple cone-derived waverider using Taylor–Maccoll equations for the conical flow field as a template for the study. First, the streamlines from the shock are solved for a wide range of cone angle and Mach number conditions resulting in an extensive database. The streamlines are parameterized by a third-order polynomial, and an ANN is trained to predict the coefficients of the polynomial for arbitrary inputs of Mach number, cone angle, and streamline originating locations. We apply this strategy to design a cone-derived waverider and compare the geometry obtained with the standard conical waverider design method and the simplified waverider design method. The ANN technique is highly accurate, with a difference of 0.68% from the standard method in the coordinates of the waverider. The performance of the three waveriders is compared using Reynolds averaged Navier–Stokes simulations. The ANN-derived waverider does not indicate severe flow spillage at the leading edge. The new ANN-based approach is 20 times faster than the standard method.

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.

Experimental Study of Effect of Injection Timing on Port Fuel Injection Gasoline, Port Fuel Injection Compressed Natural Gas, and Direct Injection Compressed Natural Gas Engine Performance, Combustion, and Emissions Characteristics

Abstract Compressed natural gas (CNG) has gained popularity due to its wide availability, higher efficiency, and lower emissions compared to gasoline. However, the lower flame speed characteristics of CNG with conventional port injection reduce the CNG engine volumetric efficiency and power output. CNG's lower gas jet momentum during a low load operation creates a non-uniform air-fuel mixture that affects ignition and combustion quality. Direct injection of CNG with optimum injection timing is expected to improve volumetric efficiency, ignition quality, and combustion process. In this study, a comparative study on the effect of end-of-injection (EOI) timing on volumetric efficiency, thermal efficiency, combustion duration, and emissions was carried out in a single-cylinder port fuel injection (PFI) spark-ignition engine using gasoline and CNG, and direct injection (DI) spark ignition engine using CNG. The experiments were performed at two-part load operations of 20% and 40% throttle at 900 and 1500 rpm. Experimental results indicate that the PFI CNG engine is more influential in EOI timing than gasoline engines. The performance of the PFI CNG engine is improved when the injection occurs during the intake valve open period compared to the closed valve period with higher thermal efficiency, volumetric efficiency, and indicated mean effective power (IMEP). A shorter flame development angle and combustion duration were observed when EOI timing was in the open intake valve condition. DI CNG improved volumetric efficiency at advanced EOI timing compared to the PFI CNG engine. However, the combustion process is critically dependent on injection timing and air-fuel mixing duration. A three-dimensional computational fluid dynamics simulation was conducted to evaluate the effect of advanced and retarded EOI timing on DI CNG engine's in-cylinder turbulent kinetic energy development and in-cylinder equivalence ratio near the ignition point. An excess advanced EOI timing resulted in stratified rich and retarded EOI timing results in loss of turbulence energy, leading to a slightly rich and lean mixture for advanced and retarded EOI timing, respectively. Hence, an optimum EOI timing provides a conducive environment to initiate the combustion and flame front propagation. Further, advanced EOI timing was required at higher throttle opening and engine speed. The emissions in DI CNG were also greatly affected by EOI timing.

Behavior of Premixed Sooting Flame in a High-Pressure Burner

The second-order factor effect of burner optical ports and edge inter-matrices (EIM) and the first-order factor of pressure on the soot formation process and behavior of premixed sooting flames in a high-pressure burner are numerically investigated here. Three-dimensional computational fluid dynamics (CFD) simulations of a premixed flame C2H4/air at p = 1.01 and 10 bar using a one-step chemistry approach are first performed to justify the satisfied predictability of the prospective axisymmetric two-dimensional (2D) and one-dimensional (1D) simulations. The justified 2D simulation approach shows the generation of an axial vorticity around the EIM and axial multi-vorticities due to the high expansion rate of burnt gases at the high pressure of 10 bar. This leads to the development of axial multi-sooting zones, which are manifested experimentally by visible luminous soot streaks, and to the boosting of soot formation conditions of a relatively low-temperature field, &lt;1800 K, and a high mixing rate of gases in combustion around and above the EIM location. Nevertheless, a tolerable effect on the centerline soot volume fraction (fV) profile, fV &lt; 3%, is manifested only at high heights above the burner of the atmospheric sooting flame C2H4/air ϕ = 2.1, and early at the high pressure of 10 bar of this flame, fV &lt; 10%. Enhancing the combustion process reactivity by decreasing the rich equivalence ratio of the fuel/air mixture and/or rising the pressure results in the prior formation of soot precursors, which shifts the sooting zone upstream.

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.

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.

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.