DEM simulation of percolating particles in binary mixtures

openThe aim of the thesis is to study the phenomenon of discharging of binary mixtures of granular material in order to better understand the percolation mechanism, which consists of the relative movement of small particles moving through the void space between the larger ones. The studied system consists of a silo which is filled with the binary mixture and subsequently discharged in funnel flow. The investigation was conducted using the LIGGGHTS simulator through which it was possible to represent the filling and discharging behavior of the granular material mixtures using DEM approach. In the first part of the thesis, the percolation phenomenon and the DEM approach are presented; then, will be described the parametric analysis conducted to find the parameters to introduce in DEM simulations. Finally, several simulations were conducted using binary mixtures with different diameter ratios and different compositions. The data obtained from the simulations were processed and compared with the experimental data in order to validate the results achieved.The aim of the thesis is to study the phenomenon of discharging of binary mixtures of granular material in order to better understand the percolation mechanism, which consists of the relative movement of small particles moving through the void space between the larger ones. The studied system consists of a silo which is filled with the binary mixture and subsequently discharged in funnel flow. The investigation was conducted using the LIGGGHTS simulator through which it was possible to represent the filling and discharging behavior of the granular material mixtures using DEM approach. In the first part of the thesis, the percolation phenomenon and the DEM approach are presented; then, will be described the parametric analysis conducted to find the parameters to introduce in DEM simulations. Finally, several simulations were conducted using binary mixtures with different diameter ratios and different compositions. The data obtained from the simulations were processed and compared with the experimental data in order to validate the results achieved

Alpha Cluster Structure in16O

The main purpose of the present work is the investigation of the α-cluster phenomenon in 16 O. The 12 C( 6 Li,d) 16 O reaction was measured at a bombarding energy of 25.5 MeV employing the Sao Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion detection technique. Resonant states around 4α threshold were measured and an energy resolution of 15 keV allows to define states previously unresolved. The angular distributions of the absolute cross sections were determined in a range of 4-40 degree in the center of mass system. The upper limit for the resonance widths was obtained, indicating that the α cluster structure information in this region should be revised

Hydraulic Characterization of Green Roof Substrates by Evaporation Experiments

Green roofs can be a valid solution for stormwater management in urban environments. The objective of this study was to develop a laboratory procedure for the hydraulic characterization of artificial substrates, used in the realization of green roofs, based on transient evaporation and steady-state unit hydraulic gradient (UHG) experiments. The retention, θ(h), and hydraulic conductivity, K(h), curves of two commercial substrates Terra Mediterranea® (TMT) and AgriTERRAM® (ATV) and a specifically developed substrate made by mixing peat, compost and sandy loam soil (MIX) were investigated. The unimodal van Genuchten–Mualem (VGM) hydraulic functions obtained by the direct evaporation method with different choices of the fitting parameters were compared with UHG measurements of K(h) conducted close to saturation. A numerical inversion of the transient evaporation experiments performed by Hydrus-1D software was also conducted, assuming that the hydraulic properties could be expressed either by unimodal or bimodal VGM models. The results indicated that an appropriate a priori choice of the residual water content parameter improved the estimation of the water retention curve. Moreover, the water retention data estimated from the direct evaporation method were not statistically different from those obtained with the inverse Hydrus-1D. The unsaturated hydraulic conductivity estimations obtained by the direct and inverse methods were highly correlated and the use of the bimodal VGM model improved the estimation of K(h) in the wet range. The numerical inversion of laboratory evaporation data with the hydraulic characteristics expressed by the bimodal VGM model proved to be a reliable and effective procedure for hydraulic characterization of artificial substrates, thus improving the reliability of simulated water fluxes in green roofs

Alpha Cluster Structure in 16

The main purpose of the present work is the investigation of the α-cluster phenomenon in 16O. The 12C(6Li,d)16O reaction was measured at a bombarding energy of 25.5 MeV employing the São Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion detection technique. Resonant states around 4α threshold were measured and an energy resolution of 15 keV allows to define states previously unresolved. The angular distributions of the absolute cross sections were determined in a range of 4-40 degree in the center of mass system. The upper limit for the resonance widths was obtained, indicating that the a cluster structure information in this region should be revised