Fluid Simulation Software Research Articles

Novel Design and Computational Fluid Dynamic Analysis of a Foldable Hybrid Aerial Underwater Vehicle

Hybrid Aerial Underwater Vehicles (HAUVs), capable of operating effectively in both aerial and underwater environments, offer promising solutions for a wide range of applications. This paper presents the design and development of a novel foldable wing HAUV, detailing the overall structural framework and key design considerations. We employed fluid simulation software to perform comprehensive hydrodynamic and aerodynamic analyses, simulating the vehicle’s behavior during aerial flight, underwater navigation, water entry and exit, and surface gliding. The motion characteristics under different speed and angle conditions were analyzed. Additionally, a physical prototype was constructed, and experimental tests were conducted to evaluate its performance in both aerial and underwater environments. The experimental results confirmed the vehicle’s ability to seamlessly transition between air and water, demonstrating its viability for dual-environment operations.

Analysis of hydrofoil tip leakage vortex dynamic characteristics

The clearance exists inevitably between the turbine guide vanes and the fixed wall, and the resulting tip leakage vortex leads to the increase of hydraulic loss. Based on the fluid simulation software ANSYS CFX, the hydrofoil was numerically simulated under different flow velocity conditions. The trajectory and energy dissipation of the tip leakage vortex are discussed. The results show that the jet entrainment with the main flow to form the tip leakage vortex, which is mainly divided into main leakage vortex and separation vortex. The flow evolution of tip leakage vortex can be divided into three stages. The evolution of tip leakage vortex can be divided into three stages: independent development of main leakage vortex and separation vortex, fusion stage, and dissipation of main leakage vortex. The strongest turbulent kinetic energy dissipation occurs in the clearance, which confirms that the clearance causes non-negligible energy dissipation for hydraulic machinery. The results provide guidance for tip leakage vortex control of hydraulic hydrofoil.

Advancing particle forces and motion dynamics in centrifugal concentrator based on flow field simulation

ABSTRACT The forces and motion state of particles within the fluid domain of the Knelson concentrator have long been a focal point for researchers. Presently, Stokes’ flow laws are commonly employed as the basis for theoretical calculations. However, this approach somewhat deviates from reality due to challenges in determining the Reynolds number of particles in the centrifugal force field during practical work. Additionally, the relationship between the Reynolds number and the drag coefficient remains undetermined in certain ranges. This study presents a high predictive relationship curve, obtained using fitting software, to supplement and rectify the limitations in the existing relationship. Leveraging fluid simulation software, this research determines the Reynolds number of particles of different sizes and densities within the fluid, offering a methodological reference for similar flow field problems. A new drag coefficient function is proposed and validated for the Reynolds number range of 1 to 20, addressing a gap in existing theoretical models. The simulation results indicate that under the suitable separation conditions of −0.074 + 0.02 mm particles, the concentrate particles overcome the flushing effect of the reverse washing water and move in the opposite direction to the fluid. This advancement not only improves the theoretical framework but also offers significant academic and practical value by enhancing the efficiency of particle separation in the Knelson concentrator.

Online Flow Measurement of Liquid Metal Solutions Based on Impact Force Sequences: Modeling Analysis, Simulation, and Validation of Experimental Results.

Aiming at the existing high-temperature liquid metal flow online accurate measurement by the metal melt characteristics, installation space, and high-temperature environment adaptability limitations, this paper innovatively puts forward a soft measurement method based on the impact force generated in the fluid flow process as an observational variable series. Fluid mechanics theory and simulation software are used to analyze and verify the feasibility of the impact force as an observable variable to measure the flow rate, followed by the construction of the CNN-LSTM-CNN-Double (CLCD) flow measurement model of impact force and flow rate based on the parameters of the learning rate and the number of training times, and finally the construction of a test platform for the flow measurement, and the validity of the method is verified through actual operation.

THERMODYNAMIC CONSIDERATIONS FOR THE APPLICATION OF LIQUEFIED NATURAL GAS AS TRANSPORTATION FUEL

This study aims to analyze the thermodynamic considerations for the application of liquefied natural gas (LNG) as a transportation fuel. It is designed to solve transport fuel problems and tackle public health issues associated with vehicular engine emission, and vehicle fuel shortages. It considers the economic and technical viability of applying low-temperature fluid as fuel in an LNG-fuel Spark Ignition Engine through computer simulation. Process design configuration was achieved using the User Define Function (UDF) in fluid simulation software (ANSYS Fluent), Finite Element Analysis and Aspen Hysys. 12 kg capacity volume cryogenic tank design was done through Autodesk inventor with an initial temperature of -162 0C and pressure of 1 bar and ambient temperature application ranges of 20 0C to 40 0C. The ANSYS simulation result showed a thermodynamic effect of heat and mass transfer rate range of 1.6% to 7% W/m 2k concerning the time taken by the tank to absorb heat through temperature ranges of -155 0C to 250 0C. Also, 0.04kg/s was the total volume of boil-off gas (BOG) produced, while the maximum exhaust gas emissions recorded was 0.254kg/s. The advantage of this technology was the minimal volume of greenhouse gases released during combustion relative to gasoline and diesel, signifying less pollution, and buttressing the applicability and adoption of LNG-Fuel as a transport fuel.

The Influence of Insertion Depth of Inorganic Materials on Solidification Microstructure and Segregation of 2.5-ton 42CrMo Ingot

In this work, a novel internal heat absorption technology using inorganic material rods is employed during the solidification process of steel ingots, aiming to control their solidification and improve the quality of the final product. The study investigates the effect of the insertion depth of inorganic materials on the solidification microstructure and macrosegregation of 2.5-ton 42CrMo ingots. The mechanical properties of samples from the product are also tested. A numerical simulation model for casting 2.5-ton ingots is established and implemented in Ansys Fluent fluid simulation software, with inorganic material rods set at different preset depths. The simulation explores the physical processes of the melting and floating of inorganic materials in molten steel, as well as their effects on the temperature and flow fields of the material. The results show that deeper insertion of inorganic materials (200 mm from the hot top) reduces the tendency for macrosegregation compared to that at the insertion depth of 100 mm. Specifically, the positive segregation area decreases by 10.35%, while the negative segregation area decreases by 15.32%. Moreover, deeper insertion results in a significant refinement of the solidification microstructure, ultimately enhancing the mechanical properties of the products machined from the ingots (i.e., the yield strength increased by 4.7%). The numerical simulation results indicate that as the placement depth of inorganic materials in the ingot mold increases, the cooling effect becomes more significant, the flow area of molten steel initiated by the inorganic materials expands, and the linear velocity of the double-circle flow increases. This further explains why the solidification quality of the ingots improves with the increasing placement depth of inorganic materials.

Terahertz wave propagation characteristics in SMM-based three-dimensional plasma fluid

During the return to the atmosphere of a hypersonic vehicle in adjacent space, a plasma sheath forms on the surface of the vehicle, which blocks normal electromagnetic communications. The ‘blackout’ phenomenon caused by plasma sheaths has received much attention. This paper focuses on the American RAM-C vehicle as the research object, and utilizes the fluid simulation software USim to numerically simulate the pressure, temperature, and electron density under different flight conditions, and based on the simulation results, selects the appropriate electron density and plasma collision frequency, introduces the terahertz (THz) wave, and adopts the scattering matrix method (SMM) to study the propagation characteristics of the vertically incident non-uniform magnetized plasma with the terahertz wave. Among other things, the transmission characteristics of terahertz waves in the plasma are affected by the flight altitude and flight angle of attack of the vehicle. The conclusions indicate that the transmissivity of terahertz wave transmission in plasma increases, and the reflectivity and absorptance decrease with increasing flight altitude and flight angle of attack. Under the condition of controlling other flight parameters unchanged, the plasma frequency and collision frequency decrease with the increase of flight altitude. The larger the flight angle of attack is, the larger the plasma frequency and collision frequency are. The electron density on the wall surface of the vehicle was also tested, and it was found that the lowest electron density was found at the tail end of the leeward surface. This study can provide some theoretical references for mitigating the ‘blackout’ phenomenon of re-entry vehicles.

Numerical investigation of sequential water entry for two projectiles at varied entry angles

In this paper, the effect of the water entry angle on the sequential water entry process of two projectiles was investigated numerically. A numerical method is established based on the STAR-CCM+ fluid simulation software, which employs the finite volume method, the volume of fluid multiphase flow model, and overlapping grid technology. The validity of the numerical method was confirmed by comparing the simulation results with experimental data. The sequential water entry processes are simulated at angles of 90°, 75°, 60°, 45°, and 30°, respectively. The flow field characteristics, motion stability, and drag reduction of both projectiles are analyzed. The results show that projectile 1 generates a series of air bubbles shedding from its cavity's tail, which distorts projectile 2's cavity. This air bubble reduces the wet area at projectile 2's head, enhancing its drag reduction capability. Projectile 1's motion remains unaffected by projectile 2 under varying water entry angles, while distinct motion characteristics are observed in projectile 2 due to significant interference from projectile 1. These results provide valuable theoretical insights for further research on sequentially launched trans-media weapons.

Numerical Simulation Analysis of Hydrogen Leakage and Diffusion in Tunnel

In order to study the actual situation of accidental hydrogen leakage of fuel cell buses in tunnels, and to provide certain safety countermeasures when hydrogen leakage occurs in tunnels, a tunnel in Nanjing was taken as the research object by using the fluid simulation software Fluent, and the influence of external factors on hydrogen leakage and diffusion was explored from the angle of leakage rate. The simulation results show that after hydrogen leaks for a period of time, the distribution of hydrogen concentration will form an obvious layered structure with the increase of time. The higher the leakage rate, the higher the rate of hydrogen concentration rise in space, and the smaller the leakage rate, the smaller the area of explosion danger in space.

An intelligent continuous bladder irrigation monitoring and control system: Development and preliminary assessment

Abstract Objectives: To design an intelligent continuous bladder irrigation monitoring and control system and preliminarily assess its sensitivity of the early warning of flushing anomalies. Methods: According to the principle of bladder irrigation, an intelligent continuous bladder irrigation monitoring and control system was designed. The Amesim fluid simulation software was used to establish a parameterized simulation model for the bladder perfusion process and simulate the dynamic changes of bladder pressure and volume under different perfusion speeds to assess the sensitivity of the early warning of flushing anomalies. Results: The intelligent system consisted of 3 parts: the monitoring part (a flushing fluid inlet flow monitoring device, a flushing fluid outlet flow monitoring device, and a flushing fluid outlet color recognition sensor), the transition part (a control motherboard), and the regulation part (an alarm device, an electric control device for flushing fluid input speed, and a squeezing device for flushing waste fluid line). The data of the parameterized simulation model for the bladder perfusion process suggested that the sensitivity of the system was acceptable. Conclusion: The intelligent bladder irrigation system can automatically detect, report, and resolve signal abnormalities, thereby achieving the closed-loop management of bladder irrigation. The intelligent system might be used in clinical settings to reduce the burdens of nurses and promote patients’ recovery.

Surgical procedure of intratympanic injection and inner ear pharmacokinetics simulation in domestic pigs.

Introduction: One major obstacle in validating drugs for the treatment or prevention of hearing loss is the limited data available on the distribution and concentration of drugs in the human inner ear. Although small animal models offer some insights into inner ear pharmacokinetics, their smaller organ size and different barrier (round window membrane) permeabilities compared to humans can complicate study interpretation. Therefore, developing a reliable large animal model for inner ear drug delivery is crucial. The inner and middle ear anatomy of domestic pigs closely resembles that of humans, making them promising candidates for studying inner ear pharmacokinetics. However, unlike humans, the anatomical orientation and tortuosity of the porcine external ear canal frustrates local drug delivery to the inner ear. Methods: In this study, we developed a surgical technique to access the tympanic membrane of pigs. To assess hearing pre- and post-surgery, auditory brainstem responses to click and pure tones were measured. Additionally, we performed 3D segmentation of the porcine inner ear images and used this data to simulate the diffusion of dexamethasone within the inner ear through fluid simulation software (FluidSim). Results: We have successfully delivered dexamethasone and dexamethasone sodium phosphate to the porcine inner ear via the intratympanic injection. The recorded auditory brainstem measurements revealed no adverse effects on hearing thresholds attributable to the surgery. We have also simulated the diffusion rates for dexamethasone and dexamethasone sodium phosphate into the porcine inner ear and confirmed the accuracy of the simulations using in-vivo data. Discussion: We have developed and characterized a method for conducting pharmacokinetic studies of the inner ear using pigs. This animal model closely mirrors the size of the human cochlea and the thickness of its barriers. The diffusion time and drug concentrations we reported align closely with the limited data available from human studies. Therefore, we have demonstrated the potential of using pigs as a large animal model for studying inner ear pharmacokinetics.

Direct numerical simulation of laminar, transitional and turbulent radially inward flow between closely spaced corotating disks

This study describes direct numerical simulation (DNS) of radially inward spiralling corotating disk flow with a narrow disk spacing, using the open source solver Nek5000 and the supercomputer SuperMUC-NG at Leibniz Supercomputing Centre. Knowledge about laminar and turbulent regime boundaries in this flow scenario is important for modelling and performance prediction of friction turbines. Simulations are performed in differently sized sections of the flat annulus that is formed by two opposing corotating disk surfaces. Three sets of operating conditions are covered, from the laminar, transitional and turbulent region of a previously determined stability chart respectively. Directly downstream of the inlet boundary, the flow is artificially perturbed with a random body force acting normal to the disk surfaces. Fourier analysis of the DNS flow field reveals that the artificial perturbation is dampened across all wavenumbers for the laminar conditions, while at the transitional conditions a small range of modes is weakly amplified towards the outlet. The identified unstable modes were previously correctly predicted by linear stability analysis. Comparison to experimental velocity profile measurements from a previous study at the same transitional operating conditions suggests strongly perturbed flow during the experiment. For inflow conditions leading to turbulent flow, average velocity profiles from DNS coincide with those from experiment and from commercial fluid simulation software with turbulence modelling (ANSYS CFX). Close to the walls, turbulent dissipation and turbulent kinetic energy distributions do not agree with the ANSYS CFX results. Friction Reynolds number settles at about 118 after turbulent flow has developed from the initial perturbation. Two point correlations and corresponding energy spectra are presented.

Numerical simulation of basic oxygen furnace rotating tapping

The rotation speed of the basic oxygen furnace (BOF) and the shape of the tapping hole have an important influence on the amount of slag carryover during the tapping process. The CFD fluid simulation software Fluent is used to analyze the flow field of the 210 t BOF rotation tapping process. The results revealed that the amount of slag carryover in the early stage is the largest when the tapping hole inclination angle is 0° and the rotation speed is 1.0 r/min. The flow field analysis shows that this is caused by the fluctuation of molten steel and slag, which makes the slag flow into the tapping hole again. The case of a rotation speed of 1.2 r/min shows the least amount of slag carryover. By comparing the three kinds of tapping holes, it can be known that a reduction in the tapping hole diameter brought a decrease in yield loss and a decrease in amount of slag carryover. As the height of molten steel decreases, the shear stress on the tapping hole decreases. The increase in the diameter of the tapping hole increases the shear stress, which in turn increases the wear of the refractory material.

Simulation research of fire water cannon nozzle based on fluent

Fire water cannon is the main equipment in fire protection work, which is evolving towards large flow, long distance and high shooting. As an important core component of fire water monitor, the structural design of nozzle plays an important role in jet performance. The Fluent fluid simulation software was used to simulate the internal flow field of the fire nozzle model with different outlet diameters and convergence angles. The average jet velocity and turbulent kinetic energy under different parameters were compared to obtain the optimal size parameters of the fire nozzle. The results show that when the inlet diameter is 100 mm, the inlet pressure is 1.2 MPa, the length of the rectifier section is 95 mm, the outlet diameter is 50 mm, and the convergence angle is 11 °, the jet performance of the fire monitor nozzle is the best. The simulation results can provide reference for the structural design and practical application of fire water monitor nozzle.

CO Diffusion Study and Spatial and Temporal Variation Modeling during the Construction Period of the Plateau Railroad Tunnel.

In order to investigate the diffusion law of CO gas in the vicinity of the tunnel boring face of the plateau long tunnel, to improve the efficiency of tunnel smoke exhaust, and to derive the spatial-temporal variation model of CO concentration for predicting the concentration of CO at different times and in different cross sections under specific environments, a CO diffusion model of a tunnel in Yunnan was established by using Ansys Fluent Fluid Simulation Software, and the CO transport characteristics under different conditions were simulated by taking the ventilation time, wind speed, and location of the air ducts as the influencing factors. The results show that the wind flows from the mouth of the wind pipe after the wind speed decreases, the diffusion area increases and arrives at the face of the direction of the rebound in the jet stream of new wind, and the return wind under the joint action of the vortex produced obviously, to reach the wind pipe mouth after the tunnel wind flow field, basically tends to stabilize. When the wind pipe mouth was arranged in the arch waist, 20 m away from the boring face, the inlet wind speed was 9 m/s and the ventilation time was 30 min; the CO concentration in the tunnel was reduced to below the maximum allowable concentration value. Moreover, the concentration of CO in the tunnel at the moment of 15 min of ventilation has a nonlinear positive correlation with the change of distance L from the boring face, while at the cross section of the air outlet of the wind pipe L = 20 m, the ventilation time is from 1 to 30 min and the concentration of CO at the cross section has a nonlinear decreasing trend with the ventilation time, which can be deduced according to the different space-time change models.

Analysis of Flow-Induced Vibration Control in a Pontoon Carrier Based on a Pendulum-Tuned Mass Damper

The pendulum-tuned mass damper (PTMD) is a widely used vibration-damping device capable of transferring and dissipating structural vibration energy, resulting in reduced structural amplitude, and offering both structural and performance advantages. Given the susceptibility of the submerged expendable conductivity, temperature, and depth profiler (SSXCTD) buoyancy platform to flow-induced vibrations during the upwelling process, the PTMD effectively suppresses the main structure’s amplitude under flow field effects. To this end, we investigated the application and design of the PTMD in the SSXCTD buoyancy platform and analyzed its vibration reduction performance. Moreover, we conducted finite volume simulations of the structure using ANSYS FLUENT fluid simulation software, providing insights into its motion under flow field effects and validating the PTMD’s effectiveness in mitigating the buoyancy platform’s flow-induced vibrations. Our research results demonstrate that the PTMD effectively alleviates the impact of seawater flow on the buoyancy platform, leading to a significant improvement in its operational stability. The proposed research methodology and findings serve as valuable references for the design and optimization of other expendable marine detection equipment.

Research on Erosion Characteristics of the Sleeve-Type Blowdown Valve in the Shale Gas Gathering and Transportation Station

Summary In the shale gas separation and sewage system, the separator removes the sand and sewage in the produced gas and releases the sand-carrying sewage to the blowdown pipeline. As an important throttling component in this system, the sleeve-type blowdown valve is severely eroded during operation. To address the problem, this paper carries out numerical research on the erosion characteristics during the real opening and closing process of the sleeve-type blowdown valve based on the FLUENT fluid simulation software. The change of the erosion at different velocities, sand mass flow, sand size, and shape coefficient is analyzed, and the main factor affecting the erosion characteristics is evaluated. Based on the above research, a novel blowdown valve is proposed, and the erosion characteristics and flow performance before and after improvement are compared. The results show that when the velocity is 8 m/s, the maximum erosion rate after improvement is 4.79×10−5 kg/(m2·s). Compared with the maximum erosion rate before improvement of 1.22×10−2 kg/(m2·s), the erosion inhibition rate reaches 99.6%. Moreover, the pressure loss is obviously reduced after the improvement, and the flow capacity is enhanced. This provides useful guidance for the improvement of blowdown valves and ensures the safe operation of shale gas production.

Computational fluid dynamics modeling of a wafer etch temperature control system

Next-generation etching processes for semiconductor manufacturing exploit the potential of a variety of operating conditions, including cryogenic conditions at which high etch rates of silicon and very low etch rates of the photoresist are achieved. Thus, tight control of wafer temperature must be maintained. However, large and fast changes in the operating conditions make the wafer temperature control very challenging to be performed using typical etch cooling systems. The selection and evaluation of control tunings, material, and operating costs must be considered for next-generation etching processes under different operating strategies. These evaluations can be performed using digital twin environments (which we define in this paper to be a model that captures the major characteristics expected of a typical industrial process). Motivated by this, this project discusses the development of a computational fluid dynamics (CFD) model of a wafer temperature control (WTC) system that we will refer to as a “digital twin” due to its ability to capture major characteristics of typical wafer temperature control processes. The steps to develop the digital twin using the fluid simulation software ANSYS Fluent are described. Mesh and time independence tests are performed with a subsequent benchmark of the proposed ANSYS model with etch cooling system responses that meet expectations of a typical industrial cooling system. In addition, to quickly test different operating strategies, we propose a reduced-order model in Python based on ANSYS simulation data that is much faster to simulate than the ANSYS model itself. The reduced-order model captures the major features of the WTC system demonstrated in the CFD simulation results. Once the operating strategy is selected, this could be implemented in the digital twin using ANSYS to view flow and temperature profiles in depth.

Magnetic circuit design of MR controller for improving the performance of the suspension

Magnetorheological (MR) damper is widely used in civil engineering, heavy-duty vehicles to speed up safely, and so on. In this paper, an MR controller for adjusting the stiffness and damping of a semi-active air suspension is designed to improve the vibration resistance of the Electric Multiple Units suspension system. The 3D magnetic field simulations of the MR controller are carried out. The influences of factors such as shaft material, damping channel width, cylinder wall thickness on the magnetic induction intensity at the damping channel are studied. An orthogonal experiment is carried out and the optimal combination of the structural parameters is determined. Then, the four working conditions of the MR controller are simulated and analyzed, respectively, and its structure is improved to ensure its stability. Finally, using fluid simulation software analysis, it can be seen that due to the fluidity of magnetorheological fluids (MRFs), the heat generated by the coil has little effect on MRFs.

Numerical Simulation of Slag Entrainment by Vortex Flux during Tapping at Converter.

In order to improve the yield of steel produced in the converter and the quality of the molten steel, and to understand the distribution of the flow field in the converter and ladle during the steelmaking process, the CFD fluid simulation software Fluent 2020 R2 was used to analyze the flow field of the converter static steelmaking process. The aperture of the steel outlet and the timing of the vortex formation under different angles were studied, as well as the disturbance level of the injection flow in the ladle molten pool. The study revealed that in the steelmaking process, the emergence of tangential vectors caused the entrainment of slag by the vortex, whereas in the later stages of steelmaking, the turbulent flow of slag disrupted the vortex, resulting in its dissipation. When the converter angle increases to 90°, 95°, 100°, and 105°, the eddy current occurrence time is 43.55 s, 66.44 s, 68.80 s, and 72.30 s, and the eddy current stabilization time is 54.10 s, 70.36 s, 70.95 s, and 74.26 s, respectively. When the converter angle is 100-105°, it is suitable to add alloy particles into the ladle molten pool. When the tapping port diameter is 220 mm, the eddy current inside the converter changes and the mass flow rate of the tapping port is "oscillating". When the aperture of the steel outlet was 210 mm, the steelmaking time could be shortened by about 6 s without affecting the internal flow field structure of the converter.