Simulation Of Three-dimensional Flow Field Research Articles

Three-dimensional numerical study on reducing hypersonic blunt body drag and aeroheating with spike-aerodisk-bleed air channel

Shock drag and aeroheating are major problems faced by hypersonic vehicles. This study proposes a novel three-dimensional model combining spike-aerodisk with a bleed air channel featuring multiple lateral nozzles for drag and aeroheating reduction. The high-temperature and high-pressure air at the stagnation point of the aerodisk is introduced into the channel and ejected laterally through multiple nozzles to modify the flow field structure and reduce drag and aeroheating. In contrast to previous research employing a two-dimensional axisymmetric assumption, our innovation considers the structure of the exit nozzles and the spacing between nozzles. Due to multiple lateral nozzles, the connection thickness between nozzles can lead to asymmetric flow phenomena. Three-dimensional flow field simulation has been employed with the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the shear stress transport (SST) k-ω turbulence model. The effects of the convergence half-angle of the channel inlet, the divergent angle of the nozzle, and the nozzle position on modifying the characteristics of the flow field are studied. Increasing the convergence half-angle of the channel inlet can further push away the reattachment shock, but when it exceeds 60°, the drag reduction performance degrades. Reducing the divergent angle of the nozzle and increasing the number of nozzles can reduce the drag coefficient and the peak value of the Stanton number. However, when the divergent angle is reduced to 10°, the performance of reducing drag and aeroheating is weakened. In the range of research parameters, when the convergence half-angle is 60°, the divergent angle is 15°, and the nozzles are located in the middle of the spike, compared with the plain spike-aerodisk model, the drag coefficient and peak Stanton number of the combined model are further reduced by 17.8 % and 34.8 %, respectively. Our findings confirm that a multi-nozzle can effectively reduce drag and aeroheating while the channel structure is viable in practice.

Numerical Simulation of Three-Dimensional Flow Field of a Gas Centrifuge with a Curved Scoop

Numerical Simulation of Three-Dimensional Flow Field of a Gas Centrifuge with a Curved Scoop

Internal Flow Field Analysis of Twin-Screw Compressor Based on Three-Dimensional Numerical Simulation

Twin-screw compressor is a kind of rotary positive displacement pump with excellent performance. Due to its advantages of reliable operation, high efficiency, low noise and multiphase mixed transportation, it has been widely used in the fields of energy power, biomedicine, refrigeration and air conditioning, petrochemical industry, industrial construction and other rudder fields. In recent decades, although the study of screw compressor is more in-depth, but the three-dimensional flow field simulation design of twin screw compressor still needs breakthrough. In this paper, 3d flow characteristics of twin screw compressor are studied based on CFD numerical simulation. In this paper, CFD software is used for numerical simulation of twin screw compressor, and the distribution of pressure cloud, temperature cloud and velocity cloud of internal flow field is obtained.

Fluid-structure coupling analysis of inlet ball valve on pumped-storage power station under extreme conditions

While pumped storage power stations (PSPSs) provide clean energy, they are also facing many problems of safe operation. Inlet ball valves bear the brunt of the impact and disturbance from upstream pressure pipeline under extreme conditions on PSPSs. Artificially change the wicket gate and ball valve closing laws can improve the extremums of key indicators. However, the internal flow field in ball valves is complex, and the internal flow field interacts with the external structure. The performance impact studied only by the indicators of the ball valve inlet and outlet is far from enough. In this study, three-dimensional flow field simulation of an inlet ball valve on PSPS was carried out, and the Realizable k-ε turbulence model was selected to simulate the pressure and velocity changes of the flow field inside the ball valve under load rejection conditions. Based on the theory of fluid-structure coupling and CFX dynamic grid, the response characteristics of the ball valve mechanical structure after being subjected to transient flow field were studied, the distribution of related performance parameters of the structure was obtained, and the mechanism that causes stress, strain and total deformation was analyzed. This study found that the ball valve structure is significantly affected by the three-dimensional transient flow of water under extreme conditions of load rejection. The safety of the ball valve can be enhanced by setting expansion joints and strengthening the base.

INVESTIGATION OF DEBRIS PARTICLES DISTRIBUTION IN ELECTRICAL DISCHARGE MACHINING OF MICRO-HOLES ARRAY

Micro-holes array and micro-electrodes array are widely used in biomedical industry, aerospace industry and micro-electromechanical systems. The machining of micro-holes array is a difficult problem for traditional machining technology. Currently electrical discharge machining technology (EDM) is an alternative machining technology for the fabricating of micro-holes array in high strength and hardness of metal material because of it is free from mechanical force. However, distribution and concentration of debris particles in the discharge gap easily leads to the intensive distribution of discharge positions, which significantly influences machining performance of EDM of micro-holes array. In this study, a three-dimensional flow field simulation model of ultrasonic assisted EDM of micro-holes array is proposed by FLUENT software. The effect of ultrasonic vibration and the depth-to-diameter ratio on debris particles distribution in ultrasonic assisted EDM of micro-holes array will be investigated by numerical simulation. It is shown that reducing the depth-diameter ratio and increasing the ultrasonic amplitude and frequency are beneficial to enhance the exhaustion of debris particles out of the discharge gap and decrease the concentration of debris particles in the discharge gap. In addition, machining experiments are carried out.

Three-dimensional flow field simulation of steady flow in the serrated diffusers and nozzles of valveless micro-pumps

This paper presents a three-dimensional flow field simulation of the steady flows through diffusers and nozzles with straight or serrated-sided walls to analyze the effect of the channel structure on the flow characteristics. The pressure and velocity profiles in the diffusers and the nozzles as well as the net volumetric flow rate are determined. Our simulation demonstrates that the pressure and velocity profiles in the serrated diffuser/nozzles are more complicated than those with the straight-sided wall, while the net steady flow rate with the straight-sided wall increases monotonically with the increase of the pressure difference, the steady flow rate with serrated sided walls increases gradually to reach a maximum and then decreases with the increase of the pressure difference. The results suggest that the number of the sawteeth plays a significant role in optimizing the design of serrated diffusers and nozzles for improving the transport efficiency of valveless micro-pumps.

Numerical simulation of flow field in the pneumatic compact spinning systems using Finite Element Method

PurposePneumatic compact spinning is the most widely used compact spinning method at present, in which the negative pressure airflow is used to condense the fiber in order to decrease the spinning triangle and improve the yarn qualities. Therefore, the research on flow field in the condensing zone is always the emphasis for pneumatic compact spinning. The paper aims to discuss these issues.Design/methodology/approachBy using finite element method (FEM), the flow field in two kinds of pneumatic compact spinning was studied. Taking three kinds of cotton yarns as examples, with the help of high-speed camera system OLYMPUS i-SPEED3, the motion trajectory of fiber strand in the condensing zone was obtained. Three-dimensional physical models of the condensing zone of the two compact spinning systems were obtained according to the measured parameters of practical spinning systems.FindingsIt is shown that on the both left edge of B1 line and right edge of B2 line, the airflow inflows to the center line of suction slot, and the condensed effects are produced, correspondingly. In the condensing zone, there are three condensing processes acting on the fiber strand, including the rapid condensing effects in the front condensing zone, the adequately condensing effects in the middle condensing zone, and stable output effects in the back condensing zone.Originality/valueBy using FEM, numerical simulations of three-dimensional flow field in condensing zone for two kinds of pneumatic compact spinning with lattice apron were presented, and corresponding spun yarn qualities were analyzed.

Simulation of Three-Dimensional Flow Field around Unconventional Bridge Piers

Simulation of Three-Dimensional Flow Field around Unconventional Bridge Piers

Research on pneumatic compact spun yarn quality

Compact spinning is one of the most important improvements of traditional ring spinning, which is implemented by adding a fiber condensing device to condense the fiber bundle and decrease the spinning triangle. Pneumatic compact spinning is the most widely used compact spinning method at present. Compact spinning with perforated drum and compact spinning with lattice apron are the two main kinds of pneumatic compact spinning. Therefore, in this paper, comparison analysis of yarn quality between compact spinning with perforated drum and compact spinning with lattice apron is presented. First, 9.7 tex cotton-combed yarn is spun in three different kinds of pneumatic compact spinning systems, including two kinds of compact spinning with perforated drum: Rieter’s COM4 and complete condensing spinning system (CCSS), and one lattice apron compact spinning system: Toyota’s four-line compact spinning. The test results of yarn qualities show that comparing with other two kinds of compact spinning systems, the yarn spun in CCSS has the best evenness, least long hairiness, and slightly lower strength. Then, the properties of spun yarns are analyzed using two methods. First, using Fluent Software, numerical simulations of three-dimensional flow field in condensing zone of three kinds of compact spinning system are presented, respectively. Second, the fiber movements in condensing zones are captured using high speed camera system OLYMPUS i-speed3.

Numerical simulation of three-dimensional flow field in compact spinning with Hollow Roller

Purpose – Condensing roller is the most key parts of compact spinning system. Hollow Roller is one of the most important kinds of condensing roller, the surface structure of which influences the flow field in condensing zone directly and affects the qualities of spun yarn. The purpose of this paper is to study the effect of Hollow Roller surface structure on flow field in condensing zone is investigated by using Fluent Software. Design/methodology/approach – In this paper, the effect of Hollow Roller surface structure on flow field in condensing zone is investigated by using Fluent Software. The numerical simulations of the three-dimensional flow field in Hollow Roller compact spinning with two different kinds of roller surface structure, round hole structure and strip groove structure, are given according to the three-dimensional physical model of condensing zone. The flow velocity and static pressure distributions in condensing zone are given. Findings – It is shown that the flow velocity streamline distribution is denser with strip groove structure than that of round hole structure, especially on the center line of strand, and flow velocity value is also larger in both Y-Z and X-Y cross-sections, and in X-Z cross-section shows the embracing inlet airflow, which is benefit for fiber condensing directly and improving negative pressure use efficiency. Furthermore, the simulations with three strip groove widths 0.4, 0.8 and 1.2 mm are given. The theatrical results obtained are illustrated by experiments. Originality/value – In this paper, the effect of Hollow Roller surface structure on flow field in condensing zone is investigated by using Fluent Software in detail. A more accurate three-dimensional physical model of condensing zone is given. A new kind of strip groove structure of Hollow Roller is proposed. The theatrical results obtained are illustrated by experiments, and lay a foundation for practical Hollow Roller design.

The Effect of Non-Return Nalve on Micro Injection Molding Machine

The micro injection molding machine (MIMM) is used to produce precision plastic products. The non-return valve (NRV) on the screw head of injection machine plays the role of preventing the melt back discharge during injection process. The sensitivity of non-return valves opening and closing affects the quality of the product. In this paper, numerical simulation of three-dimensional flow field is generalized by the Newtonian isothermal fluid method. Then, five kinds of different structural parameters of NRV are designed, and the pressure field, the pressure difference is simulated by the Polyflow software. At last, the pressure field, and the pressure difference on both side of NRV are analyzed and compared. The best structure parameter of NRV is decided. The simulation results are useful for the NRV design.

Numerical simulation of three-dimensional flow field of a paddle-spiral ribbon impeller

Impeller is the core component of stirrer, which is widely applied in many industrial fields, therefore more and more endeavor is made to design and optimize its structure, in order to improve the efficiency and reliability of stirrer. In this paper, a paddle-spiral ribbon impeller is introduced. 3-D numerical simulation is carried out to study the mixing performances of four different combined forms of this kind of impeller. In the numerical studies, unstructured grid and multi-reference frame (MRF) are used; standard k-ε turbulent model and mixture model are adopted to simulate the mixing process of solid-liquid two-phase flow. From the non-steady state simulations, velocity field, mixing time and power consumption are obtained. The results indicate that this kind of impeller is effective for stirring serious fluid. The fist combination form of paddle-spiral ribbon impeller has the best stirring performance.

Numerical Simulation and Impeller Optimization of a Centrifugal Pump

The three-dimensional flow field simulation of a centrifugal pump was presented by using commercial CFD code. In order to study the most suitable turbulence model, the three known turbulence models of Standard k-ε, RNG k-ε, Realizable k-ε were applied to simulate the flow field of the MJ125-100 centrifugal pump and predict the performance of the pump. The simulation results of head and efficiency were compared with available experimental data, and the comparison showed that the result of the numerical simulation by RNG k-ε model had the best agreement. Additionally, the effect of number of blades on the efficiency of pump was studied. The number of blades was changed from 4 to 7. The results showed that the impeller with 7 blades had the highest efficiency.

Analysis of Flow Field for Stirring Tank with Complicated Cavities Based on FLUENT

The internal structure of blender truck’s stirring tank is complicated, and accurate analysis of its flow field is important for design and manufacture. This paper carries out numerical simulation of three-dimensional flow field in mixing process by the compute fluid dynamics (CFD) software FLUENT, uses the multi-reference frame and standard k-ε turbulence model to simulate the density in three different conditions. The research result indicates that RNG k-ε turbulence model can simulate the internal flow field in the stirring tank. The tank has a series of advantages, such as large displacement, few left sand, low consumed power and short mixing time, and it has good promotional value.

Transient, Three-Dimensional Flow Field Simulation through a Mechanical, Trileaflet Heart Valve Prosthesis

Thromboembolic complications are one of the major challenges faced by designers and researchers in development of artificial organs with blood-contacting devices such as heart valve prostheses, especially mechanical valves. Besides increasing the thrombogenic potential, these valves change the hydrodynamic performance of the heart. In this study, the flow through a trileaflet, mechanical heart valve prosthesis was modeled with transient computational fluid dynamics to analyze flow patterns causing thrombus formations on valves. The valve was simulated under conditions of a test rig (THIA II), which was specially designed to analyze different valves with respect to thrombosis. The main goal of this study was to mimic the exact conditions of the test rig to be able to compare numerical and experimental results. The boundary conditions were obtained from experimental data as leaflet kinematics and pressure profiles. One complete cycle of the valve was simulated. Numerical flow and pressure results were analyzed and compared with experimental results. Shear stress and shear rates were determined with respect to thrombogenic potential, especially in the pivot regions, which seem to be the main influence for activation and deposition of thrombocytes. Approximately 0.7% of the blood volume moving through the fluid domain of the valve was exposed to shear rates high enough to cause platelet activation. However, shear rates of up to 20,000 s⁻¹ occurred in pivot regions. The pressure differences between the simulation and experimental data were approximately 2.5% during systole and increased up to 25% during diastole. The presented method, however, can be used to gain more information about the flow through different heart valve prostheses and, thus, improve the development process.

Effects of measuring positions on the measured aerodynamic performance of a centrifugal compressor

This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software. By arranging virtual probes at different positions in both inlet and outlet planes, the aerodynamic performance of the centrifugal compressor is measured and compared with each other. Then effects of measuring positions on measurement results are discussed. The results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point probe. The inlet total pressure data can be accurate when they are measured using a 3-point rake. The outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point rake. Increasing tangential measuring positions at the outlet is effective to improve the test accuracy. When the outlet total pressure and total temperature are respectively measured at 3 tangential positions, the data can be almost accurate.

Numerical Simulation of Three-Dimensional Cathode Flow Field of ECM for Inner-Wall Rectangle Weight-Reduction Blind Groove

In order to design the flow field of the NC-Electrochemical Machining (NC-ECM), a three-dimensional physical model of the flow passage is constructed based on the characteristic of the fluid flow, and three-dimensional flow field simulation is conducted with the applications of the Reynolds time-averaged Navier-Stokes equations and standard k- turbulence numerical model, velocity vectors on workpiece surface are calculated respectively based upon the three cathode outlet slots under the steady electrochemical machining condition. The present analysis show that electrolyte insufficiency appeared on workpiece surface for initial cathode flow field, and the experiment results verified the correctness of numerical simulation.

Experimental measurement and numerical simulation for flow field and film cooling effectiveness in film-cooled turbine

Numerical simulation of three-dimensional flow field and film cooling effectiveness in film-cooled turbine rotor and stationary turbine cascade were carried out by using the κ-ɛ turbulence model, and the predictions of the three-dimensional velocities were compared with the measured results by Laser-Doppler Velocimetry (LDV). Results reveal the secondary flow near the blade surface in the wake region behind the jet hole. Compared with the stationary cascade, there are the centrifugal force and Coriolis force existing in the flow field of the turbine rotor, and these forces make the three-dimensional flow field change in the turbine rotor, especially for the radial velocity. The effect of rotation on the flow field and the film cooling effectiveness on the pressure side is more apparent than that on the suction side as is shown in the computational and measured results, and the low film cooling effectiveness appears on the pressure surface of the turbine rotor blade compared with that of the stationary cascade.

Numerical simulation of three-dimensional flow field with strong swirl in vortex tube

In order to understand the flow behavior inside the tube distinctly, a three-dimensional physical model of vortex tube is constructed according to flow's movement characteristic and three-dimensional flow field with strong swirl inside the tube is simulated by the usage of practical "Realizable κ–e" turbulent numerical model. From the simulated velocity field, the distributions of tangential, axial and radial velocity as well as the recirculating flow patterns are investigated. In addition, the strategy of non-dimensional comparisons between numerical results and previous experimental data is applied to validate numerical data indirectly. Satisfactory agreements are observed between them. The numerical results show that flow motion inside the vortex tube presents extraordinary complicated behavior. The swirling flow inside the vortex tube consists of two regions with an outer region of quasi-free vortex flow sur-rounding an inner region of quasi-forced vortex flow. From view of the composition of axial and swirl motion, the flow inside the tube consists of periphery flow and inner flow. With radial and swirl motion considered, the helical flow exits inside the vortex tube. There is also a recirculating flow inside the tube when the composite motion of radial and axial movement are analyzed. The peripheral and inner flows exchange heat and mass through the enveloping surface of zero axial velocity in the form of recirculating flow because the enveloping surface of zero axial velocity is the interface between peripheral and inner flow.

Numerical Study of Nonreacting Gas Turbine Combustor Swirl Flow Using Reynolds Stress Model

This paper presents recent research on the use of a Reynolds stress turbulence model (RSTM) for three-dimensional flowfield simulation inside gas turbine combustors. It intends to show the motivations for using the RSTM in engine flow simulation, to present a further validation of the RSTM implementation in the KIVA code using the available experimental data, and to provide comparisons between RSTM and k-ε turbulence model results for chemically nonreacting swirling flows. The results show that, for high-degree swirl flow, the RSTM can provide predictions in favorable agreement with the experimental data, and that the RSTM predicts recirculations and high velocity gradients better than does the k-ε turbulence model. The results also indicate that the choice of swirler has a significant influence on the structure of the combustor flowfield.