Current Research:

1. Stress distribution in granular columns: Tall silos, storing granular materials, collapse every now and then, causing huge economic losses. H.A. Janssen reported the saturation of vertical normal stress with the depth of filling, which is known as the Janssen effect. How does particle shape, container shape affect this phenomenon? We find answers to these questions which might help design silos in a better way.

2. Avoiding hopper clogging in the presence of obstacles: Hoppers are used in industries to control granular material discharge. When the hopper outlet size becomes nearly comparable to the particle diameter, discharge flow becomes intermittent with the formation of clogs above the outlet. Placing a fixed obstacle closely above the outlet reduces the probability of clogging. We investigate the role of surface roughness of the obstacles on hopper clogging. How does the particle shape affect the clogging phase diagram? 

3. Slow flows of non-spherical granular materials: Flows of spherical grains have been well-investigated, and rheological constitutive equations have been developed. Recently, studies reported a significant influence of particle shape on the flows and the constitutive equations. We explore flows of non-spherical grains in the low shear rate limit where shear banding is likely to happen.  

Past Research:

1. Shear banding instability in cohesive granular media: This project investigated in detail the shear banding in cohesive granular media using numerical simulations and showed that all the crucial features of this phenomenon are similar to what is observed in other complex fluids. This work also presented a simple model to replicate all the findings in numerical simulations. 

2. Investigation of rheology of cohesive granular media: This project examined in detail the flows of cohesive granular media down an inclined plane, employing numerical simulations, and found an effective adhesion force which is a function of the inter-particle adhesion, stiffness, and inelasticity of the particles to control the flow. Based on this observation, this study also proposes new constitutive relations for flows of cohesive grains. 

3. Investigation of rheology of non-spherical granular media: This work was among the first set of studies taking the first step in investigating real-life non-spherical granular media. This study showed that the flows of dumbbell-shaped grains could be described using the existing visco-plastic rheological framework proposed for spherical grains, incorporating an extra parameter called the aspect ratio of the grains. 

4. Ordering transition in granular flows down an inclined channel: This project discovered a novel disordered-to-ordered flow transition in granular flows promoted by the frictional sidewalls of an inclined channel. The rheological curves for disordered flows for low particle-wall friction coefficients matched with those obtained from unbounded three-dimensional flows down an inclined plane. However, they deviated significantly from those obtained for ordered flows for high particle-wall friction coefficients. 

5. Kinematics of granular flows on a conical heap: This work experimentally studied the kinematics of a three-dimensional granular surface flow on a conical heap. This first part of the work examined the dynamics of the growth of a conical heap, and the second part measured the surface velocity and layer thickness profiles of the surface flow down the formed heap.