Sediment transport and bed evolution in a 180∘ curved channel with lateral intake: Numerical simulations using Eulerian and Discrete Phase models

2020 ◽  
Vol 31 (08) ◽  
pp. 2050113
Author(s):  
H. Montaseri ◽  
K. Tavakoli ◽  
S. Evangelista ◽  
P. Omidvar
Keyword(s):  
Sediment Transport ◽  
Numerical Simulations ◽  
Numerical Models ◽  
Three Dimensional ◽  
Secondary Flows ◽  
The Other ◽  
Discrete Phase Model ◽  
Two Phase ◽  
Bed Topography ◽  
Discrete Phase

Lateral intakes are hydraulic structures used for domestic, agricultural and industrial water conveyance, characterized by a very complex three-dimensional morphodynamic behavior: since streamlines near the lateral intake are deflected, some vortices form, pressure gradient, shear and centrifugal forces at the intake generate flow separation and a secondary movement, responsible for local scour and sediment deposition. On the other side, the modeling of flows, besides the sediment transport, in curved channels implies some more complications in comparison with straight channels. In this research, this complex process has been investigated experimentally and numerically, with the mechanism of sediment transport, bed topography evolution, flow pattern and their interactions. Experiments were performed in the Laboratory of Tarbiat Modares University, Iran, where a U-shaped channel with a lateral intake was installed and dry sediment was injected at constant rate into a steady flow. Due to the spiral flow, the bed topography changes significantly and the bed forms in turn affect the sediment entering the intake. Different from the previous works on this topic which were mainly based on laboratory experiments, here, Computational Fluid Dynamics (CFD) numerical simulations with FLUENT software were also performed, specifically with the two-phase Eulerian Model (EM) and Discrete Phase Model (DPM), at the aim of evaluating their performance in reproducing the observed physical processes. This software is used for a large variety of CFD problems, but not much for simulating sediment transport phenomena and bed topography evolution. The comparison of the results obtained through the two models against the laboratory experimental data proved a good performance of both the models in reproducing the main features of the flow, for example, the longitudinal and vertical streamlines and the mechanism of particles movement. However, the EM reveals a better performance than DPM in the prediction of the secondary flows and, consequently, of the bed topography evolution, whereas the DPM well depicts the particles pattern, predicts the location of trapped particles and determines the percentage of sediment entering the intake. The numerical models so calibrated and validated were applied to other cases with different positions of the intake in the bend. The results show that mechanism of sediment entrance into the intake varies in different position. If the intake is installed in the second half of the bend, the sediment accumulates along the inner bank of the bend and enters the intake from downstream edge of intake; on the other side, if it is placed in the first half of the bend, the sediment accumulates along both the inner and the outer bends and, therefore, more sediment enters the intake. Also the results of the simulations performed with the DPM model for different positions of the lateral intake show that for all discharge ratios, the position of 120∘ is the one which guarantees the minimum ratio of sediment diverted to the intake (Gr).

Droplet Formation in a Microchannel T-Junction With Different Step Structure Position

2020 ◽  
Vol 143 (7) ◽  
Author(s):  
Mohammad Yaghoub Abdollahzadeh Jamalabadi ◽  
Rasoul Kazemi ◽  
Mohammad Ghalandari
Keyword(s):  
Nusselt Number ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Droplet Formation ◽  
Continuous Phase ◽  
Flow Path ◽  
The Other ◽  
Two Phase ◽  
Fluid Behavior ◽  
Discrete Phase

Abstract In this study, numerical simulation of formation of droplet within T-shaped microchannel is investigated. Three-dimensional, transient and two-phase numerical solution for four different microchannels with different stepping positions in the flow path was performed. Various parameters such as volume fraction, Nusselt number, pressure, Reynolds number, and temperature are discussed. The results show that the location of stepped barriers in the flow path affects the process of droplet formation, its number and size in the microchannel and should be considered as an important factor in determining the fluid behavior in the microchannel. It was observed that by placing half of the step at the entrance and the other half after the entrance, the continuous phase (S3 mode) was formed in 37.5 s compared to the other modes. The droplets were also smaller in size and more in numbers. It was also observed that the maximum value for the Nusselt number was obtained for the S2 mode where the step was located just above the discrete-phase entrance. In addition, the pressure at the inlet was higher and the flow velocity increased after the step and its pressure decreased, and continued to decrease due to frictional path.

Simulation of an Aero-Engine Bearing Compartment Using Two-Way Transition Between Lagrangian Droplets and a Three-Dimensional Eulerian Liquid Film

2019 ◽  
Author(s):  
Jean-Sebastien Dick ◽  
Vivek Kumar ◽  
Pravin Nakod ◽  
Federico Montanari
Keyword(s):  
Liquid Film ◽  
Fluid Model ◽  
Three Dimensional ◽  
Mesh Size ◽  
Liquid Structure ◽  
Discrete Phase Model ◽  
Two Phase ◽  
Aero Engine ◽  
Discrete Phase ◽  
Modeling Strategy

Abstract This paper presents a new hybrid two-phase flow numerical model. It uses the Discrete Phase Model (DPM) and the Volume of Fluid model (VoF) to study the interaction between air, oil droplets and films in a bearing compartment. It allows transition from a trackable Lagrangian particle, such as a droplet, into a continuous liquid structure in a Eulerian frame of reference. The transition can also be performed in the opposite direction, where a continuous liquid structure can be converted back into a trackable particle if specific requirements are met. The method is designated as DPM-VoF-DPM throughout this paper. Test cases capturing the impingement of a droplet in a liquid film are performed to assess its effectiveness. The simulation of a simplified bearing compartment is compared with measurements and results obtained using a standard VoF modeling approach. Mechanisms which are usually modeled such as droplet splashing, film separation, and droplet stripping, can now be physically captured with reduced computing resources by allowing transition from continuous liquid structures to discrete parcels. The employed modeling strategy allows for high resolution of the oil film at the walls and tracking of the droplets while minimizing mesh size and computing needs. Current results suggest that the proposed DPM-VoF-DPM method can be an efficient and accurate tool for locating air and oil in aero-engine transmission systems.

Numerical simulation of sediment transport in a U-shaped channel with lateral intake: Effects of intake position and diversion angle

2019 ◽  
Vol 30 (09) ◽  
pp. 1950071 ◽  
Author(s):  
Keivan Tavakoli ◽  
Hossien Montaseri ◽  
Pourya Omidvar ◽  
Stefania Evangelista
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Transport Mechanism ◽  
Discrete Phase Model ◽  
Reference Time ◽  
Bed Topography ◽  
Discharge Ratio ◽  
Discrete Phase ◽  
Sediment Particles ◽  
Good Agreement

In this work, the mechanism of sediment transport in a U-shaped channel with a lateral intake is investigated experimentally and numerically, together with the processes of sediment entry into the intake itself and formation of bed topography. Dry sediment is injected into a steady flow in a rigid channel with a bend and sediment particles are traced in time. In order to validate the numerical model, the three components of the flow velocity, as well as the sediment path in time and the diverted sediment ratios, are measured experimentally. A numerical Discrete Phase Model (DPM) is then applied to study the effect of the intake position and diversion angle on the sediment transport mechanism in the bend. The DPM has, in fact, the capability of specifying for each particle its position relative to a reference time and space and, thereby, it is used in this study to analyze the phenomenon evolution and determine the sediment particles diverted into the intake. The comparison between the experimental data and the DPM numerical results shows a good agreement. In order to investigate the mechanism of sediment transport and to evaluate the percentage of the diverted sediments, a parametric study is then conducted through the numerical model, with different positions of the outer bend of the channel, diversion angles of the lateral intake and diversion discharge ratios. The results show that the mechanism of sediment entry into the lateral intake is affected by the diversion discharge ratio. For low discharge ratios, the mechanism of sediment entry to the lateral intake only consists of continuous entrance from the upstream edge of the intake. With the increase of the discharge ratio, it consists of a continuous entrance from the downstream edge and a periodic entrance from the upstream edge of the intake. The DPM results show that, for all diversion discharge ratios, the minimum percentage of sediment entered into the lateral intake corresponds to the position of 120∘ and diversion angle equal to 50∘.

Numerical Simulation for Two-Phase Flow Field of FGD Scrubber in Ship

2013 ◽  
Vol 739 ◽  
pp. 450-453
Author(s):  
Yong Zheng Gu ◽  
Zhi Feng Dong ◽  
Quan Jin Kuang ◽  
Jie Liu ◽  
Yu Zhao Zhang
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Optimization Design ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Phase Flow ◽  
Discrete Phase Model ◽  
Two Phase ◽  
Discrete Phase

Discrete phase model was used for three-dimensional numerical simulation of two-phase flow in the ship FGD scrubber. The κ-ε model and SIMPLE algorithm were adopted in the calculation. The results showed that adding porous baffles improved the distribution of flow field in the scrubber. The gas velocity in the scrubber became uniformity and the flue gas resistance decreased when the sprays worked. Under the action of the spray, the differential pressure of spray area changed greatly. The simulation plays a certain role in guiding the structural optimization design of scrubber.

Effect of position of the fiber transport channel on fiber motion in the high-speed rotor

2021 ◽  
pp. 004051752110018
Author(s):  
Rui Hua Yang ◽  
Chuang He ◽  
Bo Pan ◽  
Hongxiu Zhong ◽  
Cundong Xu
Keyword(s):  
High Speed ◽  
Channel Model ◽  
Three Dimensional ◽  
Discrete Phase Model ◽  
Transport Channel ◽  
Rotor Spinning ◽  
Fiber Motion ◽  
Discrete Phase ◽  
Airflow Field ◽  
Fiber Transport

The task of the fiber transport channel (FTC) is to transport the fibers from the carding roller to the rotor. Its geometric position in the spinning machine has a strong influence on the characteristics of the airflow field and the trajectory of the fiber motion in both the rotor and the FTC. In this paper, a three-dimensional pumping rotor spinning channel model was established using ANSYS-ICEM-CFD software with three different positions of the FTC (positions a–c). Further, the simulations of air distribution were performed using Fluent software. In addition, the discrete phase model was used to fit the fiber motion trajectory in the rotor. The simulation results showed that among the three types of FTC, position b is the optimal condition. The gradients of airflow velocity in the channel at position b were greater than those of the other two positions, which is conducive to straightening of the fiber.

Numerical Simulation of Two-Phase Flow inside and outside a Swirl Nozzle for Dispersing Superfine Powder

2012 ◽  
Vol 505 ◽  
pp. 170-174
Author(s):  
Wei Dong Shi ◽  
Liang Zhang ◽  
Hai Yan He ◽  
Jiang Hai Liu ◽  
Liang Chen
Keyword(s):  
Total Pressure ◽  
Concentration Distribution ◽  
Gas Flow ◽  
Reynolds Stress Model ◽  
Phase Flow ◽  
Discrete Phase Model ◽  
Two Phase ◽  
Discrete Phase ◽  
Particle Group ◽  
Nozzle Structure

In this paper, a swirl nozzle is established to disperse superfine powder aerodynamically. And Reynolds stress model (RSM) is adopted to simulate the strongly swirling, compressible and transonic gas flow in the nozzle and its rear. Combined with discrete phase model (DPM), the concentration distribution of particle group in size of 2.5μm is studied. The simulated results show that, the distribution of swirl strength is determined basically by the nozzle structure, while the total pressure has little effect on it; compared with an irrotational nozzle, the swirl nozzle could achieve a better dispersing effect for superfine powder.

scholarly journals Prediction of Horizontal Pneumatic Conveying of Large Coal Particles Using Discrete Phase Model

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Daolong Yang ◽  
Ge Li ◽  
Yanxiang Wang ◽  
Qingkai Wang ◽  
Jianping Li ◽  
...  
Keyword(s):  
Simulation Method ◽  
Phase Model ◽  
Pneumatic Conveying ◽  
Discrete Phase Model ◽  
Two Phase ◽  
Coal Particles ◽  
Large Particles ◽  
Discrete Phase ◽  
Field Velocity ◽  
Conveying System

The pneumatic conveying focusing on gas-solid two-phase flow plays an important role in a conveying system. Previous work has been conducted in the fields of small particles, where the size was less than 5 mm; however, there are few studies regarding large sizes (>5 mm). In order to predict the horizontal pneumatic conveying of large coal particles, the coupling methods based on the Euler–Lagrange approach and discrete phase model (DPM) have been used for the simulated research. Compared with the experimental results under the same working condition, the particle trajectory obtained by simulation is similar to the particle distribution at the same position in the experiment, and it turns out that the simulation method is feasible for the horizontal pneumatic conveying of large particles. Multifactor simulations are also carried out to analyse the effects of particle size, flow field velocity, solid-gas rate, and pipe diameter on the wall abrasion during horizontal pneumatic conveying, which provides simulation reference and design guide for pneumatic conveying of large particles.

THREE-DIMENSIONAL ASPECTS OF RE-ENTRY IN EXPERIMENTAL AND NUMERICAL MODELS OF VENTRICULAR FIBRILLATION

1999 ◽  
Vol 09 (04) ◽  
pp. 695-704 ◽  
Author(s):  
V. N. BIKTASHEV ◽  
A. V. HOLDEN ◽  
S. F. MIRONOV ◽  
A. M. PERTSOV ◽  
A. V. ZAITSEV
Keyword(s):  
Ventricular Fibrillation ◽  
Numerical Simulations ◽  
Numerical Models ◽  
Three Dimensional ◽  
Spiral Waves ◽  
Excitable Media ◽  
Ventricular Wall ◽  
Two Dimensional ◽  
Key Features ◽  
Scroll Waves

Ventricular fibrillation is believed to be produced by the breakdown of re-entrant propagation waves of excitation into multiple re-entrant sources. These re-entrant waves may be idealized as spiral waves in two-dimensional, and scroll waves in three-dimensional excitable media. Optically monitored, simultaneously recorded endocardial and epicardial patterns of activation on the ventricular wall do not always show spiral waves. We show that numerical simulations, even with a simple homogeneous excitable medium, can reproduce the key features of the simultaneous endo- and epicardial visualizations of propagating activity, and so these recordings may be interpreted in terms of scroll waves within the ventricular wall.

scholarly journals Numerical simulation of multiphase flow in ventilation mill and channel with louvers and centrifugal separator

2011 ◽  
Vol 15 (3) ◽  
pp. 677-689 ◽  
Author(s):  
Mirko Kozic ◽  
Slavica Ristic ◽  
Mirjana Puharic ◽  
Boris Katavic
Keyword(s):  
Multiphase Flow ◽  
Numerical Simulations ◽  
Volume Fraction ◽  
Complex Geometry ◽  
Mixture Distribution ◽  
Flow Simulation ◽  
Centrifugal Separator ◽  
Discrete Phase Model ◽  
Discrete Phase ◽  
Lagrange Approach

This paper presents the results of numerical flow simulation in ventilation mill of Kostolac B power plant, where louvers and centrifugal separator with adjustable blade angle are used. Numerical simulations of multiphase flow were performed using the Euler-Euler and Euler-Lagrange approach of ANSYS FLUENT software package. The results of numerical simulations are compared with measurements in the mill for both types of separators. Due to very complex geometry and large number of the grid cells, convergent solution with the Eulerian model could not be obtained. For this reason the mixture model was employed resulting in very good agreement with measurements, concerning the gas mixture distribution and velocity at the main and secondary burners. There was large difference between the numerical results and measurements for the pulverized coal distribution at the burners. Taking into consideration that we analyzed dilute mixture with very low volume fraction of the coal, the only choice was the Euler-Lagrange approach, i.e. discrete phase model limited to volume fraction of the discrete phase less than 10-12%. Obtained distributions of the coal at the burners agree well for both types of separators.

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