Permeability and the structure of porosity in particulate materials

Permeability is an important property that arises in many fields of study. The ability to predict the permeability for a particular material is necessary as it affects the design of many materials handling and storage solutions. There are an abundance of equations that predict permeability for specific applications, but the underlying theory for these equations remains constant. Key factors affecting permeability that appear in many equations are the pore space, individual pore size, and pore connectivity. Many existing equations seek to quantify these factors in some form, with void ratio, particle diameter and tortuosity the most commonly used. Each of these factors is investigated throughout this thesis to further investigate their influence on permeability. These factors are investigated with specific reference to two equations; the Ergun equation and the Kozeny-Carman equation, and with specific reference to two types of materials; spherical particle mixtures and fibrous particle mixtures. Numerical simulation methods are used to build assemblies of spherical and fibrous particles. The assemblies of particles are used to extract fundamental information regarding the pore size and connectivity. The average size of the individual voids can be found as well as the average length the flowing fluid takes through the voids of the material. The use of the simulated assemblies to find material properties such as these allows for new insight into the structure of these types of packed beds. This new insight allows for an improvement in the way permeability is characterised for the materials studied in this thesis.