Velocity Distribution Of Flow Field Research Articles

Physics Constrained High-Precision Data-Driven Modeling for Multi-Path Ultrasonic Flow Meter in Natural Gas Measurement.

Ultrasonic flow meters are crucial measuring instruments in natural gas transportation pipeline scenarios. The collected flow velocity data, along with the operational conditions data, are vital for the analysis of the metering performance of ultrasonic flow meters and analysis of the flow process. In practical applications, high requirements are placed on the modeling accuracy of ultrasonic flow meters. In response, this paper proposes an ultrasonic flow meter modeling method based on a combination of data learning and industrial physics knowledge. This paper builds ultrasonic flow meter flow velocity prediction models under different working conditions, combining pipeline flow field velocity distribution knowledge for data preprocessing and loss function design. By making full use of the characteristics of the physics and data learning, the prediction results are close to the real acoustic path flow velocity distribution; thus, the model has high accuracy and interpretability. Experiments are conducted to prove that the prediction error of the proposed method can be controlled within 1%, which can meet the needs of ultrasonic flow meter modeling and subsequent performance analysis in actual production.

Influence of aerodynamic pressure on dust removal by supersonic siphon atomization

At present, there are many problems in coal mine operation, such as formation of large amounts of dust, complex dust migration behavior, severe respiratory harm, poor on-site performance of spray dust removal technology under windy conditions, and low collection efficiency of respirable dust. To solve the above problems, the finite element method of computational fluid dynamics (CFD) was used. The Spalart-Allmaras turbulence model of COMSOL software and the tracking module for atomized particles broken by droplets were used. They were combined with the Fraunhofer diffraction principle to study the distributions of the velocity of the airflow field, droplet size, droplet velocity and wind resistance for a supersonic water siphonic atomization device. The influence of the above factors on dust removal at different aerodynamic pressures was studied experimentally. The relationships between spray characteristics, flow field velocity distribution, dust removal effect and spray characteristics were revealed. The research showed that with increasing pressure, the supersonic component accounted for an increased proportion of the flow field inside the nozzle, average velocity of the flow field increased, atomization efficiency increased, droplet particle size decreased, and droplet velocity increased. The particle size of the droplets first increased, then decreased and then increased with increasing spraying distance. Additionally, the range of high-speed fine droplet size fog increased with increasing pressure. At the same transverse wind speed, with increasing pressure, the deflection point of the fog field moved backward, and the wind resistance of the spray was enhanced. With the increase in aerodynamic pressure, the dust isolation and negative pressure effect of spray and the dust collection efficiency increased, and there was an optimal value for dust removal in a limited space. The reason was that when the pressure increased to a certain extent, the air flow reversed in the coil at the bottom of the limited space, which blew the dust that was not aggregated at the bottom away from the area where dust was falling. Thus, the dust was entrained in fog droplets but could not be removed from the air flow. The dust dispersion in the air flow after purification differed greatly at different pressures because the removal efficiency of dust in the 2.5–10 μm particle size range was mainly affected by the pressure. In a field study of a fully mechanized mining face, the fog curtain formed by the device covered the whole section under the condition of airflow disturbance with large transverse velocity, and the comprehensive respirable dust removal efficiency of the working area reached 92.3%. Thus, this method showed good wind resistance and dust removal performance. The study of this technology can provide a clean working environment and theoretical guidance for the safe production of coal in the future, especially for fully mechanized mining faces.

Hemodynamic investigation of a novel rotary displacement blood pump for extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) is a life support system used in the treatment of severe respiratory and circulatory failure. High shear stress caused by the high rotational speed of centrifugal blood pumps can cause hemolysis and platelet activation, which are among the major factors leading to the complications of the ECMO system. In this study, a novel blood pump named rotary displacement blood pump (RDBP), which can considerably reduce rotational speed and shear stress while ensuring the normal pressure flow relationship, was proposed. We employed computational fluid dynamics (CFD) analysis to investigate the performance of RDBP under adult ECMO support operating conditions (5 L/min with 350 mmHg). The efficiency and H-Q curves of the RDBP were calculated to evaluate its hydraulic performance, and pressure, flow patterns, and shear stress distribution were analyzed to estimate the hemodynamic characteristics in the pump. In addition, the modified index of hemolysis (MIH) was calculated for the RDBP based on a Eulerian approach. The hydraulic efficiency of the RDBP was 47.28%. The velocity distribution of flow field in the pump was relatively uniform. Most of the liquid (more than 75%) in the pump was exposed to low scale shear stress (<1 Pa), which was close to normal physiological conditions. The gap area was the main distribution location of high scale shear stress. The high wall shear stress (>9 Pa) volume fraction of the RDBP was small and located in the boundary areas between the rotor's edge and the housing. The MIH value of the RDBP was 9.87 ± 0.93 (mean ± SD). The RDBP can achieve better hydraulic efficiency and hemodynamic performance at lower rotational speed. The design of this novel pump is expected to provide a new direction for developing a blood pump for ECMO.

Numerical Simulation and Analysis of a Vertical Centrifuge

In order to solve the separation efficiency problem of the vertical centrifuge. First, understand the working principle and dynamic theory of the centrifuge, preliminarily design the technical parameters from the experience and experimental data of the prototype, solid works model, specify the overall structure scheme, and complete the virtual assembly. Secondly, the work performance is verified. The production capacity is calculated with power to meet the design requirements. Then, to verify the design strength and deformation meet the design requirements. Then, the finite element numerical analysis of the internal flow field. The FLUENT software is used to analyze the internal flow field velocity distribution and the turbulent kinetic energy of the centrifuge. Finally, a solid phase distribution rule analysis was performed to investigate the effect of particle diameter size on the separation performance at a suitable particle volume fraction.

Investigation of distribution uniformity of distributor for biogas slurry application based on CFD analysis

A horizontal distributor for biogas slurry application was proposed to explore the distribution performance through CFD analysis and verified by field test. The rheological properties of biogas slurry were analyzed at first, and key parameters were obtained for the next simulation. The effects of distribution modes, inlet direction, and outlets number on the velocity distribution of flow field and mass flow rate of the horizonal distributor were investigated by CFD simulations. Results of rheological properties indicated that biogas slurry was a non-Newtonian fluid and exhibited shear-thinning behavior. It can be well described by power-law model. The simulation results showed that the geometry of rotor, especially the block numbers was the main factor that determining the fluid movement and trajectory of distribution and output. The mode rotor 1 with two blocks reached the lowest variable coefficient of mass flow rate (4.49%), indicating a higher degree of uniformity. The upward inlet direction would obtain less dead zone, and the distributor with an even outlets number would possess more uniform distribution and less dead zone. The field test of the distributor with rotor 1, upward inlet direction, and 24 outlets has been carried on to verify the simulation results, the variable coefficient of mass flow was 13.06%, which was slightly higher than the simulation (9.23%), but it still within the range of requirement (<15%). The proposed model and the findings of this work are of guiding significance for the study of the utilization technology and equipment of liquid biogas residue. Keywords: distributor, biogas slurry, distribution uniformity, rheological properties, CFD DOI: 10.25165/j.ijabe.20231601.7460 Citation: Fu J J, Chen Y S, Xu B X, Ma B, Wang P J, W A B, et al. Investigation of distribution uniformity of distributor for biogas slurry application based on CFD analysis. Int J Agric & Biol Eng, 2023; 16(1): 45–52.

A particle image velocimetry investigation of the flow field close to a heave plate for models of different scales

Semi-submersible floating wind turbines are generally equipped with heave plates to introduce additional hydrodynamic damping and decrease the platform’s natural frequency. Scale effects are one of the most critical problems concerning the accuracy of model-scale experiments on these damping-augmenting devices. The current research aimed to assess the impact of the scale factor on the flow physics of oscillating circular solid plates. Forced oscillation flow visualisation model-scale experiments were performed on three geometrically similar one-leg columns of a semi-submersible platform equipped with a circular solid flat heave plate. The forced oscillation tests were performed in the range of extreme and operational Keulegan–Carpenter numbers (KCs) for two different frequencies of the heave plate’s oscillatory motion. A submersible two-dimensional (2D) three-component (3C) Stereoscopic Particle Image Velocimetry (Stereo-PIV) system was employed to measure the flow field velocity distribution. The Stereo-PIV images were obtained at four positions in the oscillation cycle. The investigation focused on detecting scale effects on the velocity and vorticity for the three models of different scales. Similarities in centre positions, shape, and contours between the three models were visualised for the measured velocity field. The computed vorticity field also revealed similarities in centre positions, shape, and contours among the three different scales. Following up on previous works focusing on the hydrodynamic forces on oscillating circular solid plates, the outcomes of this paper also confirm that, for the considered case study, the correct choice of the motion amplitude (KC) impacts the flow physics of the model tests more than the scale factor.

A Comparative Study of the Buoyancy-Opposed Wall Jet using Different Turbulent Models

A comparative study of the buoyancy-opposed wall jet has been carried out using RANS methods (including RNG model, Realizable k-ε model, and two low Reynolds number k-ε models) and LES methods (including the subgrid scale model developed by Smagorinsky et al.(1963), Germano et al. (1991) and Kim et al. (1997)). The capability of each turbulence model to predict the flow field and temperature field in mixing stage was investigated. The results show that the k-ε series model can accurately predict the velocity distribution of flow field under isothermal case. However, in the case of buoyancy, due to the assumption of turbulent normal stress isotropy, the trend of temperature change in the mixing region and transition position existed an obvious deviation with experimental data. The LES methods, solved directly the large scale vortices, take into account the influence of turbulence stress anisotropy in the mixing region on the temperature change and capture the temperature change trend over the whole domain accurately. Due to the application of the subgrid kinetic energy transport equation, KET model has certain advantages in numerical simulation of similar engineering flow phenomenon.

A Study of Drag Reduction on Cylinders with Different V-Groove Depths on the Surface

In this study, the drag reduction effect is studied for a cylinder with different V-groove depths on its surface using a k-ω/SST (Shear Stress Transport) turbulence model of computational fluid dynamics (CFD), while a particle image velocimetry (PIV) system is employed to analyze the wake characteristics for a smooth cylinder and a cylinder with different V-groove depths on its surface at different Reynolds numbers. The study focuses on the characteristics of the different V-groove depths on lift coefficient, drag coefficient, the velocity distribution of flow field, pressure coefficient, vortex shedding, and vortex structure. In comparison with a smooth cylinder, the lift coefficient and drag coefficient can be reduced for a cylinder with different V-groove depths on its surface, and the maximum reduction rates of lift coefficient and drag coefficient are about 34.4% and 16%, respectively. Otherwise, the vortex structure presents a complete symmetry for the smooth cylinder, however, the symmetry of the vortex structure becomes insignificant for the V-shaped groove structure with different depths. This is also an important reason for the drag reduction effect of a cylinder with a V-groove surface.

Aeroacoustics-driven jet-stream wind energy harvester induced by jet-edge-resonator

Wind energy harvesting has attracted attention for the past few decades as a potential solution to supply sustainable power for wireless sensors network (WSN). In this paper, we reported an aeroacoustics-driven piezoelectric energy generator (APEG) without moving parts to scavenge wind energy. Aeroacoustics principle, a complex Multiphysics process including the coupling among physics fields of fluid, solid, acoustics and electricity, was used for converting wind energy to mechanical energy applied on the APEG. At 79.6 m/s jet velocity, the APEG delivers high closed-circuit current (4.7 mA) at 1.5 kΩ, open-circuit voltage (12.9 V), and large average output power (15.5 mW). This result was further validated by powering up different commercial electronic devices. Moreover, the complex aeroacoustics principle was studied both experimentally and theoretically. The velocity distribution of flow field and stress distribution of piezoelectric unit were simulated and analyzed. The proposed APEG with simple structure, small volume and high performance is promising for supplying sustainable power for WSN at harsh environment such as high-speed aircrafts.

Numerical Study on the Effect of Three Novel Strengthening Components on Water Evaporation in 3D Spouted Beds

The hydrodynamics of the gas–solid two-phase flow and vaporization of the water phase in an integral multijet spout-fluidized bed (IMJSFB) and spouted beds with spherical longitudinal vortex generators (LVGs) and an integral swirling blade nozzle (ISBN) was numerically simulated. These three novel strengthening components are adopted for the strengthening of the radial mixing of particles, promoting the uniformity of the flow field velocity distribution, and increasing the water vaporization rate. The simulation results show that the three novel strengthening components can promote the uniformity of fluid flow velocity distribution in beds, and the promotion effect is arranged in descending order as follows: LVGs > swirling blades > multijet. In the case of water vaporization, the LVGs, swirling blade, and multijet mainly promote the vaporization of water near the generators, in the spout zone, and the zone near the side nozzles, respectively. Among them, the swirling blade contributes the most to water vaporization, followed by the multijet and then LVGs. In addition, when the gas inlet velocity and temperature are 11.2 m/s and 520 K, respectively, water vaporization is most obviously boosted.

CHF enhancement for a finned surface in flow boiling with explanations based on vapor observations

In this study, effects of a finned structure on downward-facing flow boiling were investigated. Compared to a bare surface, a heated surface with a finned structure has a higher CHF and heat transfer coefficient. Two high-speed cameras were utilized to observe boiling behaviors from the downward view and side view. Under low heat flux conditions, there existed a front zone and wake zone due to the existence of the extended heating surface, which was confirmed by a numerical simulation. The bubbles tended to escape from two sides of the extended surface. Under high heat flux conditions, two vapor films formed due to the existence of the finned structure, allowing more water to be supplied to the surface. Meanwhile, the existence of the fin enhanced the turbulence and made the flow field velocity distribution non-uniform, thus enhancing heat transfer and CHF. The maximum vapor film thickness of finned surface was larger than that of the bare surface. A larger maximum volume of vapor generating on the surface suggested a larger amount of latent heat consumption and thus, leading to a bigger CHF. These results demonstrated the potential of CHF enhancement using the finned structure design.

CFD Numerical Modelling of Spontaneous Combustion of Loose Coal in High Caved Area of Underground Roadway

Coal fires are serious health and safety hazards throughout the world. In underground, coal spontaneous combustion process often starts with the inside of coal, which makes it difficult to determine the ignition point. For example, the coal fire happened in high caved area of roadway is often hard to be noticed. Once the smoke appears, it has already been late to take control measures. In this paper, Simulation analysis of microcirculation flow field velocity distribution, temperature distribution and the possible distribution of the coal spontaneous combustion zone are preformed which could provide a good scientific and reasonable understanding of the fire risk due to microcirculation in loose coal in underground roadway.

Effect of barbed tubular electrode corona discharge EHD flow on submicron particle collection in a wide-type ESP

In an electrostatic precipitator (ESP), the electrohydrodynamic (EHD) flow induced by the corona discharge is formed from the coupling of ionic wind and primary flow. This kind of non-laminar flow has a notable impact on submicron particle collection. The barbed tubular electrode is commonly used in industrial dust removal due to its high corona discharge intensity and fine particle collection efficiency, as well as its low inception voltage. However, the specific EHD flow functionary mechanism induced by the ESP's corona discharge for the purpose of submicron particle movement and collection has yet to be evaluated. In this work, a Particle Image Velocimetry (PIV) system was used to investigate EHD flow characteristics under this type of corona discharge. The experimental variables included barb tip orientation (in observation planes), primary flow velocity, and applied voltage. Based on the submicron particles' force and the entire flow field's velocity distribution within the ESP, we proposed two mechanisms for this type of corona discharge—“vacuum vortex obstruction” and “high-speed flow driven deposition,” and determined that submicron particle re-entrainment is closely related to both phenomenon.

Finite element analysis of nozzle selection based on high pressure water jet technology

High-pressure water jet technology is an emerging type of welding joint strengthening process in recent years, which has unique advantages such as non-polluting, high efficiency, and can strengthen some complicated welds that in dead end position such as fillet welds. However, there is no supporting water jet strengthening nozzle domestically, so this paper uses the computational fluid dynamics method to simulate the internal and external flow fields of the nozzle, which is the most commonly used four conical convergence nozzles with different structure of the current water jet technology, making the flow field velocity distribution of the four nozzles and the impact pressure on the target surface compared and analysed. The results show that the impact pressure and axial speed of the conical short-line nozzle are slightly smaller than that of the conical (13°) nozzle, but conical short-line nozzle’s jet collection property and stability are superior to the other types of nozzles. Therefore, the conical short-line nozzle should be selected when the high-pressure water jet technology is utilized for welding joint reinforcement.

Study on key parameters of a new abrasive flow machining (AFM) process for surface finishing

The conventional abrasive flow machining (AFM) and its derivatives (i.e., magneto, electro-chemical, and ultrasonic-aided AFMs) demand special machining devices, which limits the application and dissemination of AFM. A new AFM is developed in this study, which demands no extra special devices except for a tool bar made with cemented carbide. The effect of dynamic viscosity of abrasive medium, standoff distance, and tool bar rotating speed on pressure and velocity distributions of flow field is investigated using a numerical model. Moreover, experiments are conducted to explore the influence of abrasive-laden medium and process key parameters on this new AFM finishing effect. The results indicate that the pressure and velocity of flow field reach their maximum at the middle of the minimum standoff distance between tool bar and workpiece. The optimum abrasive grain size utilized in this AFM is found to be related to the minimum standoff distance between tool bar and workpiece during finishing process. The obtained optimum tool bar rotating speed, traverse speed, and number of processing cycles are 19,200 r/min, 500 mm/min, and 500 cycles, respectively. This new AFM is anticipated to become an efficient and economic tool for surface finishing.

Experimental detection of bubble-wall interactions in a vertical gas–liquid flow

Abstract Bubble motions and bubble-wall interactions in stagnant liquid were experimentally investigated by high-speed CCD and PIV technique with the main feature parameters such as Eotvos numbers Eo = 0.98–1.10, Morton number Mo = 3.21 × 10 − 9 and Reynolds numbers Re = 180 ~ 190. The effect of bubble injecting frequency and the distance S between the gas injection nozzle and the wall on the statistical trajectory of bubbles, average velocity distribution of flow field and Reynolds shear stress were studied in detail. It was shown that the combination of bubble injecting frequency and the distance S caused different bubble motion forms and hydrodynamic characteristics. When the normalized initial distance was very little, like S ⁎ ≈ 1.2 (here S ⁎ = 2 S / d e , and d e is the bubble equivalent diameter), bubbles ascended in a zigzag trajectory with alternant structure of high and low speed flow field around the bubbles, and the distribution of positive and negative Reynolds shear stress looked like a blob. With the increase of distance S ⁎ , bubbles' trajectory would tend to be smooth and straight from the zigzag curve. Meanwhile, with the increase of bubble injecting frequency, the camber of bubble trajectory at 20 y S ⁎ ≈ 3.6, the low-frequency bubbles gradually moved away from the vertical plane wall in a straight trajectory and the high-frequency bubbles gradually moved close to the vertical wall in a similar straight trajectory after an unstable camber motion. Under the circumstances, high-speed fluid was mainly distributed in the region between the wall and the bubbles, while the relative large Reynolds shear stress mainly existed in the region far away from the wall.

Numerical Investigation of the Flow Characteristics of Liquid Film in the Process of Falling Film Evaporation

In order to study the flow characteristics of fluid falling film evaporation in a vertical pipe and obtain the dynamic parameters of steam-water two-phase flow, a three dimensional numerical simulation on flow behavior of falling film evaporation was carried out to capture the free surface of falling liquid film with the volume of fluid (VOF) model. The steam-water two-phase flow dynamic characteristics including liquid film flow pattern, liquid film thickness, wall shear stress and velocity distribution of flow field were analyzed through changing feed flow velocities. The results show that under different inlet flow velocities, the average thickness of liquid film from simulation agrees with empirical value well. The film thickness decreases sharply in the entry section which is less than 100mm. The change of wall shear stress is similar to that of film thickness along flow direction, but the change of film thickness has hysteresis quality. Under the influence of gravity and wall shear stress, the accelerated motion and decelerated motion of liquid film alternate, and the flow velocity inside liquid film increases with the distance from liquid film to wall surface, and reaches the maximum at the steam-water interface.

Pressure drop and permeability of three-dimensional virtual fibrous medium

Pressure drop is one of the principal performances of the fibrous filtration medium. Traditional computational studies in this area are based on typical unrealistic two-dimensional geometries, with the fibre just placed in a lattice perpendicular to the flow. So in this paper, a three-dimensional virtual fibrous material was developed by means of visual basic application. In the virtual fibrous material, the fibres were arranged randomly by computer and the flow field of virtual fibrous material was calculated. The influence of constructive parameters on pressure drop and permeability was investigated. Simulation shows that flow field velocity distribution was not symmetric. Filtration velocity decreased when the air flew through the fibres, whereas the fluid velocity increased significantly when the distance between fibres was large. Obvious vortex formed in the fibre space areas. The pressure drop was tested experimentally, and the result was compared with that of theoretical and semi-empirical formula calculation. Experimental and simulation data were in agreement with Davies' empirical formula. The simulation result reveals that the pressure drop of fibrous medium increased linearly with the increase of filtration velocity. Moreover, pressure drop non-linearly increased with the increasing solid volume fraction. Simulation results of pressure drop were in good agreement with the predictions of Davies' empirical formula.

Dynamic Response Analysis of Submarine Pipeline under Action of Current

It’s important to study the vibration characteristic of submarine pipelines under current for reducing the harmful vibration. Research on fluid-structure interaction of submarine pipeline under current was presented. The pressure and velocity distribution of flow field around pipe with different velocity of flow were studied by ANSYS finite element software. The results show that the pipe is under the action of drag force along the direction of flow. The drag force increases with the flow velocity.

Analysis and Numerical Simulation of Flow Field in Centrifugal Pump

The inner flow field of centrifugal pump is complex and presents a characteristic of three-dimensional turbulence. Used Solidworks software to establish a three-dimensional model of the pump and impeller, completed the numerical simulation of centrifugal impeller flow field based on the turbulence model and Fluent software, obtained the static pressure and velocity distribution of flow field, provided basis for the design and optimization of the subsequent product.