A homogenised model for flow, transport and sorption in a heterogeneous porous medium

A major challenge in flow through porous media is to better understand the link between microstructure and macroscale flow and transport. For idealised microstructures, the mathematical framework of homogenisation theory can be used for this purpose. Here, we consider a two-dimensional microstructure comprising an array of obstacles of smooth but arbitrary shape, the size and spacing of which can vary along the length of the porous medium. We use homogenisation via the method of multiple scales to systematically upscale a novel problem involving cells of varying area to obtain effective continuum equations for macroscale flow and transport. The equations are characterised by the local porosity, a local anisotropic flow permeability, an effective local anisotropic solute diffusivity and an effective local adsorption rate. These macroscale properties depend non-trivially on the two degrees of microstructural geometric freedom in our problem: obstacle size and obstacle spacing. We exploit this dependence to construct and compare scenarios where the same porosity profile results from different combinations of obstacle size and spacing. We focus on a simple example geometry comprising circular obstacles on a rectangular lattice, for which we numerically determine the macroscale permeability and effective diffusivity. We investigate scenarios where the porosity is spatially uniform but the permeability and diffusivity are not. Our results may be useful in the design of filters or for studying the impact of deformation on transport in soft porous media.

Fluctuations of anisotropic flow from the finite number of rescatterings in a two-dimensional massless transport model

We investigate the fluctuations of anisotropic transverse flow due to the finite number of scatterings in a two-dimensional system of massless particles. Using a set of initial geometries from a Monte Carlo Glauber model, we study how flow coefficients fluctuate about their mean value at the corresponding eccentricity, for several values of the scattering cross section. We also show how the distributions of the second and third event planes of anisotropic flow about the corresponding participant plane in the initial geometry evolve as a function of the mean number of scatterings in the system.

Anisotropic Flow Measurements of Identified Hadrons with MPD Detector at NICA

The primary scientific mission of the Multi-Purpose Detector (MPD) at the accelerator Nuclotron-based Ion Collider facility (NICA) (Dubna) is to investigate the properties of strongly interacting matter at high net-baryon densities. The goal of this work is to study the performance of the MPD detector for directed and elliptic flow measurements of identified hadrons by using the realistic Monte Carlo simulations of heavy-ion collisions at energies sNN = 4.5 − 11 GeV.

Study of Quinoline Insoluble (QI) Removal for Needle Coke-Grade Coal Tar Pitch by Extraction with Fractionalized Aliphatic Solvents and Coke Formation Thereof

Various fractionalized solvents with different paraffinicities were adopted to maximize the efficiency of the quinoline insoluble (QI) extraction process for coal tar pitch. In addition, highly pressurized conditions combined with raised temperature (4 bar at 300 °C) were used to accelerate the reaction kinetics of the extraction process. The QI content of purified coal tar pitch was analyzed to be 0.1% at a process yield of up to 72% as a solvent with a K-factor of 10 and above was used. Purified coal tar pitch was then processed to form anisotropic coke using a lab-scale tube bombe reactor. The texture observed under a polarized light microscope showed an anisotropic flow domain, a unique morphological feature of needle coke. The additives and reaction conditions used in this study for QI extraction for coal tar pitch were found to be effective and feasible as preliminary processing in needle coke production.