scholarly journals Numerical model of spherical particle saltation in a channel with a transversely tilted rough bed

2009 ◽  
Vol 57 (3) ◽  
pp. 182-190 ◽  
Author(s):  
Nikolay Lukerchenko ◽  
Siarhei Piatsevich ◽  
Zdenek Chara ◽  
Pavel Vlasak
Keyword(s):  
Numerical Model ◽  
Spherical Particle ◽  
Particle Trajectory ◽  
Particle Diameter ◽  
Shear Velocity ◽  
Rough Bed ◽  
Angle Of Deviation ◽  
Bed Slope ◽  
Straight Lines ◽  
Particle Saltation

Numerical model of spherical particle saltation in a channel with a transversely tilted rough bedThis paper deals with the numerical simulation of spherical particle saltation in a channel with a rough transversely tilted bed. The numerical model presented is based on the 3D model of spherical particle saltation developed by the authors, which takes into account the translational and rotational particle motion. The stochastic method and the concept of a contact zone were used for the calculation of a particle trajectory and its dependence on the bed lateral slope, particle diameter, and shear velocity. The effect of the bed lateral slope results in a deviation of the particle trajectory from the downstream direction. Some examples of the calculation are presented. The trajectories of the saltating particles starting their movements from one point were calculated and it was shown that they are of random character and together create a bundle or fascicle of trajectories. It was found that the centrelines of the bundles can be approximated by the straight lines for low and moderate values of the bed transverse slope, i.e. slopes less than 20°. The angle of deviation of the centreline from the downstream direction increases when the bed lateral slope and/or the particle diameters increase. However, with increasing shear velocity, the deviation angle decreases. Due to the lateral bed slope the particles are sorted according to their size, and the criteria for sorting particles were defined. An example of the particle sorting was calculated and the separable and non-separable regions were determined.

scholarly journals 3D Numerical Model of the Spherical Particle Saltation in a Channel with a Rough Fixed Bed

2009 ◽  
Vol 57 (2) ◽  
Author(s):  
Nikolay Lukerchenko ◽  
Siarhei Piatsevich ◽  
Zdenek Chara ◽  
Pavel Vlasak ◽  
Zdeněk Chára ◽  
...  
Keyword(s):  
Numerical Model ◽  
Spherical Particle ◽  
Fixed Bed ◽  
3D Numerical Model ◽  
Particle Saltation

scholarly journals Field test of a new snow-particle counter (SPC) system

1993 ◽  
Vol 18 ◽  
pp. 149-154 ◽  
Author(s):  
Takeshi Sato ◽  
Tadashi Kimura ◽  
Taminoe Ishimaru ◽  
Toshisuke Maruyama
Keyword(s):  
Wind Speed ◽  
Mass Flux ◽  
Particle Trajectory ◽  
Particle Diameter ◽  
Blowing Snow ◽  
Fraunhofer Diffraction ◽  
Wind Speed Profile ◽  
Particle Counter ◽  
Sampling Volume ◽  
Snow Particle

The optical system of the snow-particle counter (SPC), which was developed by Schmidt in 1977, has been improved. A laser diode is used as a light source, achieving uniform sensitivity to a blowing snow particle regardless of the location of particle trajectory within a sampling volume. The light entering a slit, which may be affected by a blowing snow particle, is perfectly detected by use of a piano-cylindrical lens and a dual-type photodiode. A signal processor has been developed to get output voltage proportional to the mass flux of blowing snow.From the estimates based on blowing snow characteristics and wind speed profile, the new SPC system can accurately detect all the particles of effective sizes at least at a height above 0.1 m when the wind speed at a height of 1 m is less than 15 m s−1.Considering the Fraunhofer diffraction by both the wire and the particle, the relation between a particle diameter and sensor output of the new SPC system is derived from the calibration with spinning wires.Mass flux obtained with the new SPC system was found to be close to that with a snow trap. The system was operated continuously for at least nine days using two 35 A h lead batteries.

On the definition of the shear velocity in rough bed open channel flows

2006 ◽  
Author(s):  
C Manes ◽  
D Pokrajac ◽  
I McEwan ◽  
J Finnigan ◽  
V Nikora
Keyword(s):  
Open Channel ◽  
Shear Velocity ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Rough Bed ◽  
Definition Of

scholarly journals Considerations over the floating speed of a particle in vacuum pneumatic conveying sytems in flour milling

2016 ◽  
Vol 20 (1) ◽  
pp. 65-76
Author(s):  
Tanase Tanase
Keyword(s):  
Spherical Particle ◽  
Particle Diameter ◽  
Pipe Diameter ◽  
Pneumatic Conveying ◽  
Specific Mass ◽  
Magnus Force ◽  
Spherical Form ◽  
Flour Milling ◽  
Mass Load ◽  
The Given

Abstract The present paper is a theoretical study aiming for to assess the influence of the different factors such as deviation from the spherical form of a particle, specific mass load of the pneumatic conveying pipe and the report between the particle diameter and the pipe diameter, over the floating speed of a particle. For a non-spherical particle, the Magnus force is affecting the floating speed of the given particle by increasing or decreasing it. The equation deducted within the present study, describes the movement of a particle or a fluid swirl under the resultant force with emphasis on the evaluation of the nature and magnitude of the Magnus force. The same Magnus Force explains the movement of the swirls in fluids, as for the wind swirls (hurricane) or water swirls. The next part of the study relate the report between the particle diameter and the pipe diameter as well as the specific loads of the pipe, to the same floating speed. A differentiation in denominating the floating speed is proposed as well as that for the non-spherical particle the floating speed should be a domain, rather than a single value.

Simulation of Angular Flow in a Shallow Basin Triggered by a Rotating Vertical Cylinder by SPH Method

2018 ◽  
Vol 881 ◽  
pp. 15-22
Author(s):  
Warniyati ◽  
Radianta Triatmadja ◽  
Nur Yuwono
Keyword(s):  
Numerical Model ◽  
Physical Model ◽  
Time Integration ◽  
Vertical Cylinder ◽  
Shear Velocity ◽  
Future Research ◽  
Sph Method ◽  
Virtual Particle ◽  
Real Particle ◽  
Particle Hydrodynamics

A simple numerical model has been generated for developing a code of Smoothed Particle Hydrodynamics (SPH) method. Those will be modified and used for future research. In this computational research domain is a square that consists of a real particle and virtual particle as the boundary treatment. In the initial condition, particle occupies a certain position. Circular flow has been generated by a rotating vertical cylinder to produce shear velocity to the real particle. The particles movement has been observed during time integration. A physical model has been constructed to compare the numerical model. The movement of real particles on the numerical model agrees with the movement of water particles on the physical model.

A Two-Dimensional Numerical Model for Shallow Water Flows over Variable Topographies

2014 ◽  
Vol 580-583 ◽  
pp. 1793-1798
Author(s):  
Biao Lv ◽  
Shao Xi Li
Keyword(s):  
Numerical Model ◽  
Shallow Water ◽  
Source Term ◽  
Unstructured Grids ◽  
Riemann Solver ◽  
Two Dimensional ◽  
Water Flows ◽  
Shallow Water Flows ◽  
Bed Slope ◽  
Good Agreement

Based on well-balanced Roe’s approximate Riemann solver, a numerical model is developed for the unsteady, two-dimensional, shallow water flow with variable topographies. In this model, an efficient methods are applied to treat the source terms and to satisfy the compatibility condition on unstructured grids. In the method, different components of the bed slope source term are considered separately and the compatible discretization of the components is presented. The newly developed model is verified against analytical solutions and measured date, with good agreement.

3D Numerical Simulation and PEPT Experimental Investigation of Pressurized Gas-Solid Fluidized Bed Hydrodynamic

2009 ◽  
Author(s):  
P. Fede ◽  
G. Moula ◽  
A. Ingram ◽  
T. Dumas ◽  
O. Simonin
Keyword(s):  
Numerical Model ◽  
Fluidized Bed ◽  
Particle Velocity ◽  
Particle Trajectory ◽  
Wall Region ◽  
3 Dimensional ◽  
The Core ◽  
Numerical Predictions ◽  
Model Predictions ◽  
Good Agreement

The present paper is dedicated to numerical and experimental study of the hydrodynamic of a non-reactive isothermal pressurized fluidized bed. Experimental data have been obtained using PEPT technique allowing to track a particle trajectory inside a dense fluidized bed. A specific post-processing approach has been developed to compute the Eulerian time-averaged particle velocity field. The comparison with 3-dimensional numerical model predictions shows a good agreement in the core of the fluidized bed. In contrast, in the near wall region the numerical model overestimate the downward particle velocity. The modification of particle phase wall boundary condition improves the numerical predictions.

Numerical Model on Hydrodynamic Impact from HZM Bridge

2014 ◽  
Vol 580-583 ◽  
pp. 2146-2149
Author(s):  
Jie He ◽  
Ying Jun Sun ◽  
Xin Sheng Zhao
Keyword(s):  
Numerical Model ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Hydrodynamic Impact ◽  
Variable Bottom ◽  
Triangular Cell ◽  
Bed Slope ◽  
The Pearl River ◽  
Volume Method

In this paper, a 2D model for the simulation of shallow water flow by convection and diffusion over variable bottom is presented, which is based on the FVM (finite volume method) over triangular unstructured grids. The format of Reo’s approximate Riemann is adopted to solve the flux terms. And the bed slope source term is treated by split in the form of the flux eigenvector. For the diffusion terms, the divergence theorem is employed to obtain the derivatives of a scalar variable on each triangular cell. The numerical model is adopted to simulate the hydrodynamic impact from HZM (Hongkong-Zhuhai-Macao) bridge on Pearl River estuary. The simulated results show that the HZM bridge has little influence on the distribution of hydrodynamic environment in the Pearl River estuary.

Sampling, testing and modeling particle size distribution in urban catch basins

2014 ◽  
Vol 70 (11) ◽  
pp. 1873-1879 ◽  
Author(s):  
G. Garofalo ◽  
M. Carbone ◽  
P. Piro
Keyword(s):  
Particle Size ◽  
Numerical Model ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Diameter ◽  
Experimental Treatment ◽  
Catch Basin ◽  
Traffic Intersection ◽  
Parking Lot ◽  
Catch Basins

The study analyzed the particle size distribution of particulate matter (PM) retained in two catch basins located, respectively, near a parking lot and a traffic intersection with common high levels of traffic activity. Also, the treatment performance of a filter medium was evaluated by laboratory testing. The experimental treatment results and the field data were then used as inputs to a numerical model which described on a qualitative basis the hydrological response of the two catchments draining into each catch basin, respectively, and the quality of treatment provided by the filter during the measured rainfall. The results show that PM concentrations were on average around 300 mg/L (parking lot site) and 400 mg/L (road site) for the 10 rainfall-runoff events observed. PM with a particle diameter of <45 μm represented 40–50% of the total PM mass. The numerical model showed that a catch basin with a filter unit can remove 30 to 40% of the PM load depending on the storm characteristics.

Experimental Measurements of Forces on Loose Particle in Motion Over Rough Bed Under Waves Using Oblique Particle Image Velocimetry

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Sanjay N. Havaldar ◽  
Francis C. K. Ting
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Fluid Layer ◽  
Fluid Velocity ◽  
Particle Diameter ◽  
Single Layer ◽  
Wave Direction ◽  
Loose Sediment ◽  
Image Velocimetry ◽  
Rough Bed

Magnitude and phase of major forces that act on a loose non-cohesive particle (sediment) on single layer fixed rough bed (longitudinal slope 2%) were determined from experiments in a laboratory flume under waves. The loose particles were glass spheres of diameter 1.58 ± 0.1 mm and specific gravity 2.5. The range of wave-height-to-water-depth (H/h) ratio in the experiments was 0.366 < H/h < 0.521. The measurement plane was parallel to the bed and located at a height of ½ loose particle diameter (ds) above the rough bed. Grayscale morphological image processing methods were used to separate the fluid and loose sediment phases from the same oblique particle image velocimetry (OPIV) image based on their signature sizes. The OPIV calibration method is presented and validated with conventional particle image velocimetry (PIV) method. Loose particle velocity and accelerations along with the associated fluid velocity and fluid total accelerations in the wave direction were determined simultaneously by processing OPIV used to compute magnitude and phase of major forces that act on the loose sediment particle. It was observed that for same wave period (T), an increase in H/h ratio has a dominant effect on sediment displacements onshore. The phase along with magnitude of the major driving force (drag and fluid accelerations) plays an important role at initiation of loose sediment from its rest position. It is suspected that the loose particle overcomes a critical bed friction force with higher H/h ratio as magnitude of drag force is higher. The resultant force then displaces the sediment onshore which experiences sliding and or rolling motions very close to bed, in a thin fluid layer over maximum protrusion of bed sediments. At the instance, the gravitational force plus bed frictions overcomes the lift force the loose particle attains a new position onshore.

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