The behaviors of particle-wall collision for non-spherical particles: Modeling analysis

2020 ◽  
Vol 366 ◽  
pp. 137-143
Author(s):  
Jingyu Wang ◽  
Hairui Yang ◽  
Lele Feng ◽  
Man Zhang ◽  
Yuxin Wu ◽  
...  
2020 ◽  
Vol 363 ◽  
pp. 187-194 ◽  
Author(s):  
Jingyu Wang ◽  
Man Zhang ◽  
Lele Feng ◽  
Hairui Yang ◽  
Yuxin Wu ◽  
...  

Author(s):  
M. Sommerfeld

In wall-bounded gas-solid flows the wall collision process plays an important role and may be strongly affected by wall roughness and particle shape. The modelling of the particle-wall collision mostly relies on the assumption of spherical particles. To extend such models appropriately for non-spherical particles, two-dimensional kinetic simulations were performed for different particle shapes. This implies, that the particle translational and angular motion is calculated by considering the particle shape, however neglecting fluid dynamic effects. The change of the particle velocities during the impact and rebound process was calculated by solving the impulse equations together with Coulombs law of friction. The simulations were performed for a given initial particle velocity by varying impact angle and initial angular velocity. The results for 2000 particle wall collisions allowed us to derive the distribution functions of the impact parameters required to describe the wall collision process for non-spherical particles correctly. Moreover, other wall collision properties, such as rebound angle and velocity ratios could be determined. Finally also a comparison with measurements was possible.


Author(s):  
Brian Quintero Arboleda ◽  
Zeeshan Qadir ◽  
Martin Sommerfeld ◽  
Santiago Lain Beatove

The importance of numerical calculations (CFD) for supporting the optimization and lay-out of industrial processes involving multiphase flows is continuously increasing. Numerous processes in powder technology involve wall-bounded gas-solid flows where wall collisions essentially affect the process performance. In modelling the particle wall-collision process in the frame of numerical computations the general assumption is that the particles are spherical. However, in most practical situations one is dealing with irregular non-spherical particles or particles with a certain shape, such as granulates or fibers. In the case of non-spherical particle-wall collisions in confined flows, additional parameters such as roughness, particle shape and orientation play an important role and may strongly affect the transport behavior. The change of linear and angular velocity of the particle depends on these parameters, specifically the orientation and the radius of impact of the particles. In order to improve the non-spherical particle-wall understanding and modeling, in this work regular non-spherical particle-wall collisions in three dimensions are studied experimentally and computationally. For that purpose, cylindrical particles impacting a smooth wall at different angles are used. Single particle motion is tracked in space solving for both the translational and the rotational motion whereby the orientation of the non-spherical particle is obtained through the Euler angles and the Euler parameters. Once the particle touches the wall, the change of translational and angular velocity is determined by the non-spherical particle wall collision model. Experiments are made by shooting cylindrical non-spherical particles against a smooth plane wall at various impact angles and velocities. The collision event is recorded by two perpendicular arranged high-speed cameras. The experimental velocities obtained are used for validating the model.


Author(s):  
Daniel UGARTE

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.


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