Simulation Analysis Of Flow Field Research Articles

Simulation study on flow field regulation of flotation column with stirring device

ABSTRACT Flow field regulation plays an important role in the optimization of column flotation units with agitation function. This paper aims to discuss the regulating effect of baffle design on the flow field in stirred column flotation units by numerical simulation. A series of geometric models of changing baffle structure and layout were established, and detailed flow field simulation analysis was carried out by using COMSOL software. The results show that the internal flow field of the traditional standard cylindrical tank will cause the solid particles to adhere to the wall movement and the bubbles to the middle area, resulting in the uneven distribution of particles and bubbles, and the internal flow field is not conducive to the mineralization process and the stability of the foam layer. This limitation can be significantly improved by introducing baffles. The results show different baffle shapes and layouts are as follows: wide and narrow on top, narrow on the bottom and wide on top, and only arranged at the bottom of the column body, can increase the average turbulent kinetic energy in the collision zone by 22%, 46% and 43%, and the average turbulent dissipation rate by 18%, 43% and 36%, respectively, while maintaining the turbulence intensity in the transport zone. Among them, the baffle plate with wide top and narrow bottom has the best effect. Arranging baffles with a length shorter than 2/3 of the height of the cylinder at the upper part inside the cylinder can also enhance the turbulence intensity in the collision zone, but at the same time, it also increases the turbulence intensity in the transport zone. Moreover, as the length of the baffle decreases, the enhancement effect becomes stronger. Since this method significantly affects the transport zone, it is more suitable for columnar mixing devices. The study also reveals that by adjusting the proportion of wide and narrow baffles, the center of the turbulent region can be laterally shifted to the short baffles, and the flow field distribution can be adjusted. Meanwhile, with the increase in the number of long baffles, the intensity of the flow field in the device will gradually decrease. By moving the center of the turbulent region to the side inlet, the particle dispersion can be accelerated, but in general, the particles will accumulate toward the region with lower turbulence intensity. These findings have important guiding significance for the design and optimization of the flow field of the stirred column flotation unit, which is helpful in improving the agitation uniformity and flotation efficiency.

Study on Traction Characteristics of Point Contact State under Oil–Air Lubrication

Oil–air lubrication technology is commonly utilized in the lubrication design of traditional components to reduce friction between contact pairs. This study focuses on testing the point-contact friction pairs of two quantitative valves using a self-made oil–air lubrication traction force machine with a G95Cr18 disk and ball as the friction pairs. The test data are analyzed using a four-parameter exponential model. Additionally, a calculation model of the oil–air lubrication flow field is established, defining boundary conditions and conducting flow field simulation analysis. The results of the ball and disk test show that the traction coefficient increases with load and decreases with entrainment speed. Furthermore, when the air-speed is 12 m/s, the traction coefficient is lower for the oil supply of 6 mL/min than for the oil supply of 1.5 mL/min. According to CFD analysis, the volume fraction of the oil phase in the contact area increases with the increase of entrainment speed when the slip–roll ratio is 0.1. The theoretical values from the four-parameter exponential model align well with the experimental results, and the fitting accuracy is higher than 0.95.

Model establishment and flow field simulation analysis of high torque screw motor in ultra-deep well

Abstract To explore the distribution law of the flow field in the inner annular flow channel of the stator-rotor of the high-torque screw drill tool and determine the key performance parameters of the tool under different drilling fluid densities and flow rates, a physical model for fluid simulation was established with the 7/8 head screw motor as the research object to study the distribution law of the flow field and the output torque of the rotor at different flow rates and densities, and a comparative analysis was made with the actual test. The results show that the pressure of the internal flow channel is mainly concentrated at the entrance of the flow channel and the wall of the flow channel. The flow rate in the thick fluid domain is high, the flow rate in the thin fluid domain is low, and the flow rate in the thinnest area is about zero. The relationship between displacement pressure drop and output torque presents a positive correlation. When displacement increases, the output torque of the screw increases, and the relationship between displacement and torque presents a linear increase. The torque and displacement of fluid simulation under ideal conditions are larger than the actual test parameters. In the actual test, the drilling fluid temperature and experimental equipment factors affect the performance of the screw motor. In the process of fluid simulation, the setting of boundary conditions should refer to the real situation as much as possible to improve the accuracy of simulation results. The difference between fluid simulation and actual test parameter values is small and the trend is the same, so fluid simulation can guide practical application and reduce cost to a certain extent.

DBN-GABP model for estimation of aircraft wake vortex parameters using Lidar data

Aircraft wake turbulence is an inherent outcome of aircraft flight, presenting a substantial challenge to air traffic control, aviation safety and operational efficiency. Building upon data obtained from coherent Doppler Lidar detection, and combining Dynamic Bayesian Networks(DBN) with Genetic Algorithm-optimized Backpropagation Neural Networks(GA-BPNN), this paper proposes a model for the inversion of wake vortex parameters. During the wake vortex flow field simulation analysis, the wind and turbulent environment were initially superimposed onto the simulated wake velocity field. Subsequently, Lidar-detected echoes of the velocity field are simulated to obtain a data set similar to the actual situation for model training. In the case study validation, real measured data underwent preprocessing and were then input into the established model. This allowed us to construct the wake vortex characteristic parameter inversion model. The final results demonstrated that our model achieved parameter inversion with only minor errors. In a practical example, our model in this paper significantly reduced the mean square error of the inverted velocity field when compared to the traditional algorithm. This study holds significant promise for real-time monitoring of wake vortices at airports, and is proved a crucial step in developing wake vortex interval standards.

Simulation analysis of flow field and vortex-induced vibration characteristics of submarine cable under single/parallel-laying mode

Due to the long-term erosion of current, the submarine cable buried on the seabed surface easily causes fatigue damage to the lead sheath, which gradually progresses with time. In this paper, a two-dimensional spring-damping vortex vibration model is established considering the effect of transverse flow and in-line flow. The vortex-induced vibration response of suspended submarine cables under the influence of different parameters is simulated by using the slice method based on nested grids. The simulation model is used to simulate the flow field characteristics and vortex-induced vibration response of submarine cables under single laying and parallel laying conditions. The fluid-solid coupling mechanism between fluid and structure and the interaction law of parallel laying submarine cables are analyzed. Our study overcame the difficulty in testing the vortex-induced vibration of submarine cables and provided a viable method and empirical support for investigating the vortex-induced vibration properties of submarine cables and fatigue analysis.

Propeller flow field simulation analysis and structure optimization of multi-rotor UAV

Propeller lift characteristics are the most important parameter affecting the performance of multi-rotor UAVs. In this paper, the propellers of three airfoils, RAF 6, CLARK Y, and E214, are modeled in three dimensions. The flow field simulation analysis of the three models is carried out using FLUENT. After the simulation, it is found that the lift of CLARK Y is about 1100 N, which is the best effect, but there are problems, such as excess lift. Therefore, the wing shape of CLARK Y is optimized, and the lift force is about 700 N after optimization, which can meet the practical application requirements. It can provide some reference to the practical engineering application of UAVs.

Flow Field Simulation Analysis of Medium-Pressure Cyclone

Based on computational fluid dynamics (CFD) method, FLUENT software was used to analyze the flow field of the three-phase cyclone separator at medium pressure. Through the numerical simulation of the de-sanding efficiency of the cyclone, the flow field characteristics and separation efficiency of the cyclone were studied under this working condition, which provided a reference for the analysis of the cyclone under this working condition.

Sowing Machine for Scallop Seedling in Bottom-culture

The scallop is among the most important shellfish resource and is a proven candidate for aquaculture in many countries. In China, the scallop is generally bottom culture and artificial seeding. Artificial seeding on scallops is a difficult process with low production efficiency, high labor intensity, excessive cost low profit, and high rate of mortality and damage. In this paper, a sowing machine is developed for the bottom-sowing culture of the scallop. It consists of a transmission module, sows slide module, and buoyancy module. The structure and working mechanism of this machine are presented and analyzed in detail. The tests of experiments were conducted as well with the development machine. Through the simulation analysis of flow field of bottom-sown machine. The results show that the vortex area below the platform makes the scallop seedlings seedlings spread more evenly. In addition, the boat-shaped fairing at the head of the platform effectively reduces the water flow rate inside the platform, allowing the scallop seedlings to successfully leave the platform through the grille at the bottom of the platform after sowing. The control group efficiency is 26.67%; however, the optimized group efficiency average value is 57.97%. The cost of bottom sowing 1t scallop seedling was reduced from 1260 RMB to 124.4 RMB. It is proven that the design of the machine is feasible.

Numerical Simulation Analysis of Flow Field on Repetitive Pellet Injector with Single-Screw Extruder in CFETR

Pellet injection (PI) is the preferred fueling method in the future fusion reactor. It is particularly important to study the flow field characteristics of the frozen fuel extrusion process for the future steady operation of the pellet injector. In order to study the influence of groove depth on extrusion flux and conveying capacity, the flow field characteristics of a repetitive pellet injector with a single-screw extruder in the China Fusion Engineering Test Reactor (CFETR) was numerically simulated with POLYFLOW software. Thus, information about pressure field, viscous heating, and velocity field distribution was obtained. The results indicate that to a certain extent, increasing the groove depth (while maintaining the gaps between the screw and extrusion cylinder) is beneficial for the conveying capacity and pressure building capacity. The results of the numerical simulations show that at a screw speed of 120 rpm, screw outer diameter of 20 mm, screw length of 230 mm, screw groove depth of 6 mm, and screw prism gap of 0.3 mm, solid hydrogen can be stably extruded, and the velocity of the extruded ice at the nozzle is 0.15 m/s, which meets the design requirement of the CFETR PI system. These results also provide good references for structure design and performance optimization of the CFETR pellet injector.

Design and Test of the Structure of Extractor Negative Pressure Zone of Sugarcane Chopper Harvester

Given the problems of the high trash content and loss rate for mechanized sugarcane harvesting, taking the HN4GDL-194 sugarcane chopper harvester extractor developed by South China Agricultural University as the research object, three types of extractor negative pressure structures were designed and internal flow field simulation analysis was conducted. Simulation results showed that the aerodynamic performance of the flow field in the negative pressure area of the extractor negative pressure structure two is the best and the wind velocity and negative pressure are the largest. The measurement results of wind velocity, wind pressure, and flow showed that the changing trend in the actual value of wind velocity and wind pressure is basically consistent with the simulation value. The relative error between the actual flow of the air outlet and the simulation value is less than 10% under different speeds, indicating that the simulation has high accuracy. Field tests of the original extractor and the optimal extractor were conducted. The test results for the trash content showed that when the feeding rate was 1.5 kg/s, there was no significant difference in the trash content between the optimal extractor and the original extractor under various fan speeds. When the feeding rate increased to 7.5 kg/s and the fan speed was low (950 r/min) and medium (1100 r/min), the trash content of the optimal extractor was significantly lower than that of the original extractor, decreasing 2.5% and 1.63%, respectively. The loss rate test results showed that when the fan speed is low and high (1250 r/min), there is no significant difference between the loss rate of the optimal extractor and the original extractor. When the fan speed was 1100 r/min and the feeding rate was 1.5, 4.5, and 7.5 kg/s, compared with the original extractor, the loss rate of the optimal extractor decreased by 0.53%, 0.21%, and 0.19%, respectively.

Piezo-enhanced photocatalytic performance of ZnO nanorod array for pollutants degradation in dynamic water: Insight into the effect of velocity and inner flow field

The piezoelectric effect, which can promote photocatalytic degradation of pollutants, has attracted great attention. However, the effect of hydrodynamic factors on the performance is still unclear in the water-driven piezo-enhanced photocatalytic process. Herein, ZnO nanorod array on porous substrate was employed to study the effect of hydrodynamic factors on piezo-assisted photocatalysis. Flow field simulation analysis based on computational fluid dynamics (CFD) indicates that velocity notably affects the piezo-photocatalytic process. Meanwhile, the porous structure of substrate promotes the formation of micro-turbulence, which also significantly improve the piezopotential of ZnO and further enhance the catalytic performance. Density functional theory (DFT) calculations further reveal the vulnerable sites attacked by reactive species, thereby proposing the possible degradation pathway of pollutant. This study illustrates the important role of hydrodynamic factors in piezo-photocatalytic process and provides a feasible way for in-situ purification of pollutants in urban sewerage and drainage.

Optimization of the Structural Parameters of a Plastic Centrifugal Pump

The structural design parameters of a plastic centrifugal pump were calculated and modeled, and flow field simulation analysis of the model was performed using CFD, in the framework of an orthogonal design method (or experiment). The inlet mounting angle β1, outlet mounting angle β2, wrap angle ϕ, and impeller inlet diameter D1 of the pump impeller were the four factors assumed for the application of the orthogonal experiment, using the efficiency and Net Positive Suction Head (NPSH) as evaluation indices. Moreover, taking the maximum efficiency and minimum NPSH of the plastic centrifugal pump as the evaluation factors, the parameters of the pump impeller were re-optimized through the Taguchi algorithm (leading to the following optimal combination: inlet diameter 35 mm, inlet angle 26°, outlet angle 27°, and wrap angle 110°). The minimum NPSH and the maximum efficiency have been found to be 0.957% and 61.5%, respectively.

Analysis of Senegal Type Vertical Axis Wind Turbines Arrangement in Wind Farm

Background: In a wind farm, the wind speed of the downstream wind turbine will be lower than the wind speed of the upstream wind turbine due to the influence of the wake. Therefore, the wake of wind turbines is one of the uncertain factors predicting the annual power generation of the wind farms. The study on the wake can effectively improve the efficiency of power generation. The arrangement of vertical axis wind turbines in wind farms is rarely studied. Therefore, it is important to study the vertical layout of wind turbines under the influence of wakes to obtain the best layout and unit spacing. Objective: The objective of this study is to obtain the optimal layout and unit distance of wind turbines in Senegal wind farms by studying the arrangement of Senegal vertical axis wind turbines in wind farms. Methods: Based on the ANSYS CFX flow field calculation module, the fluid dynamics model of the Senegal fan was established and the flow field simulation analysis was carried out. Based on the Jensen wake model and its improved model, three layout methods for the wind farm wind turbines were proposed: two units were arranged in series, two units were arranged in parallel, and three units were staggered. Through the simulation model, the wind energy utilization coefficient and wind speed of the wind turbine in the wind farm were obtained. Results: The optimal separation distance between the units was analyzed from four different angles: wind energy utilization coefficient, torque analysis, downstream tail flow and wind speed cloud contour. Finally, based on the optimal arrangement and unit distance, a triangular staggered wind farm composed of 10 units was established, and the integrated flow field characteristics of the whole wind farm were simulated and analyzed. The integrated flow field wake characteristics of the wind farm were obtained. Conclusion: In all the three arrangements, the optimum distance between the units must be three times the diameter of the wind turbine. This arrangement ensures that most of the units are unaffected by the wake, the area affected by the low-velocity wake of the wind farm is small, and the area affected by the high-speed wake is large.

Flow Field Simulation Analysis of Train Siphon Toilet with Variable Pipe Diameter Based on the Investigation of Siphon Performance

The performance of siphon toilets in trains with varied pipe profiles were investigated. The profiles of the siphon pipe are varied based on the diameter of the pipe along the pipe length. The flushing process was simulated by using CFD method. The starting time, the duration, the siphon mass flow rate, the negative pressure in the siphon pipe were recorded and selected as siphon performance indexes. The results showed that for the same type of siphon pipe, the siphon performance becomes worse with the increase of the maximum pipe diameter as the minimum pipe diameter is 45mm. The simulation confirms that the performance of the siphon toilet with the pipe diameter varying from large to small then to large is the best; the performance of the siphon with a pipe diameter varying from small to large then to small is the worst. The qualitative results may provide some suggestions for relevant industrial designs.

Analysis and Research on the Working Parameters of Colloidal Spraying for the Thermal Insulation Layer of Rocket Tank

In this paper, the working parameters of DW-1 type colloid spray coating for rocket tank insulation are analysed and studied, and the optimal working parameters are determined. Firstly, a flow field simulation analysis model of thermal insulation layer DW-1 colloid spray is established, the spray flow field simulation of different spraying working parameters is performed. Then the relationship between the flow field characteristics such as spray speed and atomization uniformity and the spraying working parameters are initially determined. After that, an analytical model of droplet impact is established to study the influence of spraying speed on the impact dynamics and spreading quality of the droplet, and the optimal working parameters of colloidal spraying are determined.

Simulation Analysis of Flow Field in Engine Compartment of a Rear-Mounted Exhaust

The numerical simulation of the flow field in the engine compartment of a car is the basis for the evaluation and research of the air flow characteristics in the engine compartment. In this paper, the computational fluid simulation software STAR-CCM+ was applied to simplify the vehicle model of a rear-mounted exhaust. The surface wrapper and surface remesher were used to obtain the whole vehicle surface mesh. Combining with the vehicle wind tunnel model was generated the volume mesh based on Trim mesh sub-regional method. Then, the finite element model of the car engine compartment was established. Three-dimensional flow field in engine compartment was analyzed under reasonable boundary conditions, and found the reflow at climbing is more apparent as compared with that at high constant speed. Then the flow rate experiment of the whole vehicle was obtained wind speed value of the windward surface of the radiator. The error between the simulated value and the experimental value is within 10%, indicating that the simulation model established in this paper is reliable and possesses high simulating accuracy.

Numerical and Experimental Investigation on the Feasibility of Horizontal Drilling With a New Type of Jet Mill Bit

Recently, a new type of jet mill bit (JMB) has been introduced to improve the cutting transport efficiency in horizontal drilling by comminuting cuttings into dust-like particles immediately after the cuttings are generated. To promote the application of JMBs in the field, in this work, JMBs were further improved by including junk slots (JS) all around to allow cuttings to flow through the annulus and thereby prevent sticking from occurring while tripping out. Moreover, numerical and experimental investigations on the feasibility of horizontal drilling with the new type of JMB were carried out. The finite element method was used to analyze the strength of the new type of JMB, and flow field simulation analysis was also performed for JMBs with different sizes of JS. The simulation results indicated that the weakest point of the JMB was located at the bit connection instead of the bit frame, and it was demonstrated that the structural strength of the JMB met the requirements of actual working conditions. The JMB JS had a negative effect on promoting the upward return of cuttings from the bottom of the hole, and the larger the slot sizes were, the more negative the effects. Through a trip-out experiment with the new type of JMB, this paper studied the influence of the slot size on the trip-out process safety. The experimental results indicated that the minimum safe slot width was 60 mm. Finally, in a synthesis of the simulation and experimental results, the reasonable range of slot width was determined to be 60–70 mm; the aforementioned range was the most suitable for the bit based on safety and efficiency considerations. This paper provides guidance for the improvement and application of JMBs.

Study on the key structure parameters of a gravity settling chamber based on a flow field simulation

A gravity settling chamber plays an important role in improving the effect of the dust removal when it is selected as a dust collector in a pneumatic cleaning system for cleaning a subway tunnel. The settling rate and the indexes evaluating the secondary blowing are studied to assess the effect of the dust removal in this paper. Regarding the length of the settling chamber, the height of the inlet duct, and the diameter and height of the outlet duct as the variables of the key structures, a flow field simulation analysis of the gravity settling chamber with different heights of the dust accumulation is carried out, then the key structure parameters are optimized by means of the experimental method of uniform design. Finally, the settling chamber with an excellent dust removal effect is obtained. Major conclusions can be drawn as follows. (1) The maximum velocity and the mean velocity ratio of the airflow near a dust accumulation surface are important evaluation indexes for judging the secondary blowing. (2) The maximum velocity near a dust accumulation surface usually doesn’t appear on the vertical plane through the axis of the inlet duct or the outlet duct. (3) An excellent settling effect can be ensured during the whole cleaning process only when the maximum design height of the dust-accumulation surface is considered as a key working condition. (4) An excellent settling effect can be realized if the settling chamber without any filtering device and affiliated baffle structure are long enough. (5) The secondary blowing can be avoided if the inlet and outlet of the setting chamber are far away from the dust-accumulation surface. This study has a good guiding significance for the design of gravity settling chamber.

Study on Breakage Cause of Copper Pipe

Copper pipe was widely used in the pipeline of seawater system. Comprehensive characteristics of pipe were analysed. Pressure and velocity were selected as representations of primary static and dynamic characteristics of the pipeline; the breakage reason of water supply pipe was studied through flow field simulation analysis and pipeline metallographic analysis. There was a phenomenon of excessive flow velocity and obvious erosion corrosion in bending pipe; the result showed that erosion corrosion is the direct cause of pipeline breakage. By improving the copper pipe manufacturing press, increasing the pipeline size and bending radius can effectively prevent pipeline damage.

Experimental research on process stability in pulsed electrochemical machining of deep narrow grooves with high length-width ratio

With respect to deep narrow groove structures with high length-width ratio and high depth-width ratio (particularly when the ratio is greater than 10), the cathode rigidity and flow-field stability deteriorate during the electrochemical machining (ECM) process. To improve the machining efficiency and process stability of deep narrow grooves with high length-width ratio, a hollow slice cathode with stiffeners was designed and optimized to meet the rigid requirements using the method of one-way fluid-solid coupling finite element analysis. Additionally, the effects of cathode stiffener size, stiffener distribution, and cathode vibrating feed mode on the flow field in the machining gap were investigated using the flow-field simulation analysis method. The simulation results indicate that cavitation and electrolyte starvation in the machining gap are avoided with a reasonable stiffener design, and the renewal of electrolyte in the machining gap is improved with a reasonable vibration motion. Contrast experiments were performed based on the simulation results. The experimental results verified that the optimal design of stiffeners and the reasonable cathode vibration improve the stability of the flow field. Moreover, process stability and machining efficiency of ECM of deep narrow grooves with high length-width ratio improve with the adoption of the optimal vibrating feed parameters.