Abstract: Powders and grains are the second most widely used materials in industries after simple fluids. These materials show both solid-like and fluid-like behavior. Unlike simple fluids, their rheology is not well understood due to a lack of a suitable constitutive law. Since decades, researchers have attempted to develop theories for granular flows based on soil plasticity theory, kinetic theory, non-equilibrium statistical mechanics and non-local approaches. Till now, many theories are developed based on simplified assumptions, but these assumptions have not been rigorously tested. Choosing a suitable flow configuration, which can provide a benchmark for testing the strengths and shortcomings of the existing theories, is also challenging. In this talk, the gravity flow through a vertical channel will be discussed, which is found to be more appropriate among other simple flow configurations to test different theories. This type of flow occurs in many industry settings, like flow through storage silos and bins, and in transportation via pipes. The predictions of some recently developed theories (compressible \mu(I) class of models, non-local models, and kinetic theory-based models) are compared with the data obtained from flow experiments and discrete element-based computer simulations. A detailed analysis of the flow shows that there are different shear zones, each with distinct dynamical properties. None of the theories capture these different shear zones, and have the ability to predict all flow features well. Our work highlights the need for more work to develop a suitable model which can predict the features of these different shear zones well. A preliminary attempt is made to propose such a model.
Bio:
Bhanjan Debnath is a Chemical Engineer. He has held visiting positions at University of California-San Diego and San Diego State University after receiving his Masters and PhD from IISc Bengaluru. He was a Dharam Hinduja scholar from 2009-2015. Recently, he was awarded Prof. NR Kuloor Memorial Institute medal for best PhD thesis in Chemical Engineering by Engineering Sciences division of IISc. His research concerns the flow of granular materials, biophysics of extracellular matrix tissue and self-assembly of proteins forming biomolecular condensates. Apart from research and academics, he likes to Meditate, play Tabla, Chess, sketching, and cooking. He belongs to a Bengali family from Agartala, Tripura nestled in the mountains and greenery in the North-East part of India.