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Ahmed Mohamed Ali Ashour

Basic information

Name : Ahmed Mohamed Ali Ashour
Title: Lecturer
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Personal Info: Ph.D. in Physics Otto von Guericke University, Magdeburg Germany. M.Sc. in Physics, Faculty of Science, Ain Shams University. B.Sc. in Physics, Faculty of Science, Ain Shams University. View More...


Certificate Major University Year
PhD Philosophy in Science (Experimental Physics) Magdebuarg University - Germany 2018
Masters Science - Physics Ain shams University - Faculty Of Science 2011
Bachelor Science - Physics Ain shams - Egypt 2006

Teaching Experience

Name of Organization Position From Date To Date
المعهد التكنولوجى العالى العاشر من رمضان المعهد التكنولوجى العالى العاشر من رمضان 01/01/2006 01/01/2008

Researches /Publications

Flow of anisometric particles in a quasi-two-dimensional hopper - 01/0

Ahmed Mohamed Ali Ashour

Balázs Szabó, Zsolt Kovács, Sandra Wegner, David Fischer, Ralf Stannarius, and Tamás Börzsönyi


The stationary flow field in a quasi-two-dimensional hopper is investigated experimentally. The behavior of materials consisting of beads and elongated particles with different aspect ratio is compared.We show, that while the vertical velocity in the flowing region can be fitted with a Gaussian function for beads, in the case of elongated grains the flowing channel is narrower and is bordered with sharper velocity gradient. For this case, we quantify deviations from the Gaussian velocity profile. Relative velocity fluctuations are considerably larger and slower for elongated grains.

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Silo outflow of soft frictionless spheres - 01/1

Ahmed Mohamed Ali Ashour

Torsten Trittel, Tamás Börzsönyi, and Ralf Stannarius


Outflow of granular materials from silos is a remarkably complex physical phenomenon that has been extensively studied with simple objects like monodisperse hard disks in two dimensions (2D) and hard spheres in 2D and 3D. For those materials, empirical equations were found that describe the discharge characteristics. Softness adds qualitatively new features to the dynamics and to the character of the flow.We report a study of the outflow of soft, practically frictionless hydrogel spheres from a quasi-2D bin. Prominent features are intermittent clogs, peculiar flow fields in the container, and a pronounced dependence of the flow rate and clogging statistics on the container fill height. The latter is a consequence of the ineffectiveness of Janssen’s law: the pressure at the bottom of a bin containing hydrogel spheres grows linearly with the fill height.

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Elongated grains in a hopper - 01/0

Ahmed Mohamed Ali Ashour

Tamás Börzsönyi, Ellák Somfai, Balázs Szabó1, Sandra Wegner, and Ralf Stannarius


Flow and clogging of granular materials in a 3-dimensional hopper is investigated experimentally. We use X-ray tomography and optical methods to study this phenomenon for spherical and elongated particles. The X-ray tomograms provide information on the bulk of the hopper filling, and allow to determine the particle positions and orientations inside the silo, as well as spatial variations of the local packing density. We find that particles show a preferred orientation and thereby an enhanced order in the flowing zone of the silo. Similarly to simple shear flows, the average orientation of the particles is not parallel to the streamlines but encloses a certain angle with them. The clogged state is characterized by a dome, i. e. the geometry of the layer of grains blocking the outflow. The number of grains forming this blocking layer is larger for elongated grains compared to the case of spheres of the same volume.

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Linking bottleneck clogging with flow kinematics in granular materials: The role of silo width - 01/0

Ahmed Mohamed Ali Ashour

D. Gella, D. Maza, I. Zuriguel, R. Arévalo and R. Stannarius


We demonstrate experimentally that clogging in a silo correlates with some features of the particle velocities in the outlet proximities. This finding, that links the formation of clogs with a kinematic property of the system, is obtained by looking at the effect that the position of the lateral walls of the silo has on the flow and clogging behavior. Surprisingly, the avalanche size depends nonmonotonically on the distance of the outlet from the lateral walls. Apart from evidencing the relevance of a parameter that has been traditionally overlooked in bottleneck flow, this nonmonotonicity supposes a benchmark with which to explore the correlation of clogging probability with different variables within the system. Among these, we find that the velocity of the particles above the outlet and their fluctuations seem to be behind the nonmonotonicity in the avalanche size versus wall distance curve.

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Outflow and clogging of shape-anisotropic grains in hoppers with small apertures - 01/0

Ahmed Mohamed Ali Ashour

S. Wegner, T. Trittel, T. Börzsönyi and R. Stannarius


Outflow of granular material through a small orifice is a fundamental process in many industrial fields, for example in silo discharge, and in everyday’s life. Most experimental studies of the dynamics have been performed so far with monodisperse disks in two-dimensional (2D) hoppers or spherical grains in 3D. We investigate this process for shape-anisotropic grains in 3D hoppers and discuss the role of size and shape parameters on avalanche statistics, clogging states, and mean flow velocities. It is shown that an increasing aspect ratio of the grains leads to lower flow rates and higher clogging probabilities compared to spherical grains. On the other hand, the number of grains forming the clog is larger for elongated grains of comparable volumes, and the long axis of these blocking grains is preferentially aligned towards the center of the orifice. We find a qualitative transition in the hopper discharge behavior for aspect ratios larger than E6. At still higher aspect ratios 48–12, the outflowing material leaves long vertical holes in the hopper that penetrate the complete granular bed. This changes the discharge characteristics qualitatively.

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