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1	Experimental and computational study of the behaviour of free-cells in discharging silos Mack, Stuart Anderson January 2011 (has links) This study aims to deduce an appropriate shape and density for an electronic free-cell that could be placed into a silo so that position and other desired physical parameters could be recorded. To determine how density and shape affects the trajectory and displacement of free cells, the trajectory and displacement of cylindrical, cuboid and triangular prism free-cells of equivalent volume was investigated in a discharging quasi 3D silo slice. The free-cells were placed at twelve different starting positions spread evenly over one half of the 3D slice. Tests were conducted using a monosized batch of spherical particles with a diameter of approximately 5 mm. Tests were also conducted in a binary mixture consisting of particles of different sizes (5 mm/4 mm) and the same density (1.28 g/cm3) and a binary mixture consisting of particles of different size (6 mm/5 mm) and different densities (1.16 g/cm3/1.28 g/cm3).The rotation of the free cells was also briefly discussed.Computer simulations were conducted using the Discrete Element Method (DEM). The simulation employed the spring-slider-dashpot contact model to represent the normal and tangential force components and the modified Euler integration scheme was applied to calculate the particle velocities and positions at each time step. One trial of each of the metal and plastic, cylindrical, cuboid and triangular prism free cells was compared with the average of three experimental trials. The trajectory and displacement of a representative particle positioned at the same starting position as the free cell was also obtained from DEM simulation and compared with the path and displacement of each of the free cells to determine which free cell followed the particle most closely and hence to determine a suitable free cell that would move with the rest of the grains. Spherical particles are idealised particles. Therefore tests were also conducted with a small number of polyhedral particles, to deduce their flow rate and the critical orifice width at which blockages were likely to form. Simulations were also conducted to test the feasibility of the DEM in modelling the behaviour of these polyhedral particles.Results indicate that for a free cell to move along the same trajectory and have the same displacement and velocity as an equivalent particle in the batch it should have a similar density to the majority of the other particles. A cylindrical free cell of similar density to the particles was found to follow the path of the representative particle more closely than the cuboid or triangular prism. Polyhedral particles were found to have a greater flow rate than spherical particles of equivalent volume. 621.31
2	The effect of tracers' physical properties on retention time measurements inside the conditioner of a pellet mill Salim, Esam A. January 1900 (has links) Master of Science / Department of Grain Science and Industry / Keith C. Behnke / The effect of tracer particle size on the accuracy of measuring retention time inside the conditioner of a pellet mill was studied. Three experiments were conducted using tracers with different particle sizes. The control retention time was calculated using the hold-up capacity method, while retention times for treatments were calculated using the pulse-input method. In addition to the previously prepared tracers, crystalline salt and powder color dye were used as tracers in this study to represent small particle tracers. In experiment one, large, medium, and small tracers were used. The treatment with large particle size was closer to the control with differences around 1.5%. Conversely, using the tracer with small particle size resulted in larger differences, approximately 18%. Two tracers were used in experiment two, resulted in 33% difference between treatment and control using a small particle size tracer, and a 10% difference using a tracer with similar particle size to the main materials. A tracer similar in particle size to the materials flowing inside the conditioner was used in the third experiment in addition to the salt and dye. Statistical analyses for this experiment indicated that particle size affects the accuracy of retention time measurements. There was a significant difference (P<0.05) in the comparison between salt and red color dye in treatment two, while there was no significant difference (P>0.05) between them in treatment one (same particle size). Moreover, in another comparison of the differences between treatments and their related controls, there was significant difference (P<0.05). However, the P-value for the red dye comparison (0.0126) was higher than that of salt (0.0026), which adds density as another influential factor that affects retention time measurement. Retention Time Pellet Mill Tracer Particle Size Tracer Physical Properties Conditioner Particle Size Agriculture, General (0473)
3	The significance of coherent flow structures for the turbulent mixing in wall-bounded flows / Die Bedeutung kohärenter Strukturen für die turbulente Vermischung in Wandgrenzschichten Kähler, Christian Joachim 01 July 2004 (has links) No description available. Mathematics and Computer Science Turbulenz Grenzschicht kohärente Struktur Korrelation Vermischung Turbulenzstatistik Turbulenzmodell Particle Image Velocimetry PIV Stereo PIV Mehrebenen PIV Tracer Partikel Seeding 530 Physik Turbulence boundary layer coherent structure correlation mixing turbulence statistics turbulence model Particle Image Velocimetry PIV Stereo PIV Multiplane PIV Multiplane Stereo PIV Dual plane PIV Tracer particle Seeding 30.20 33.05 33.14 33.18 33.38 50.21 50.33 RF RP

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