Amit Kunte | IIT Madras (original) (raw)
Papers by Amit Kunte
We investigate the mixing characteristics of dry granular material while draining down a silo wit... more We investigate the mixing characteristics of dry granular material while draining down a silo with multiple exit orifices. The mixing in the silo, which otherwise consists of noninteracting stagnant and flow regions, is observed to improve significantly when the flow through specific orifices is stopped intermittently. This momentary stoppage of flow through the orifice is either controlled manually or is chosen by the system itself when the orifice width is small enough to cause spontaneous jamming and unjamming. We observe that the overall mixing behavior shows a systematic dependence on the frequency of closing and opening of specific orifices. In particular, the silo configuration employing random jamming and unjamming of any of the orifices shows early evidence of chaotic mixing. When operated in a multipass mode, the system exhibits a practical and efficient way of mixing particles.
We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered... more We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered significantly by having more than one exit orifice. For the hoppers with small orifice widths, inter-mittent flow through one orifice enables the resumption of flow through the adjacent jammed orifice, thus displaying a sequence of jamming and unjamming events. Using discrete element simulations, we show that the total amount of granular material (i.e. avalanche size) emanating from all the orifices combined can be enhanced by about an order of magnitude difference by simply adjusting the inter-orifice distance. The unjamming is driven primarily by fluctuations alone when the inter-orifice distance is large, but when the orifices are brought close enough, the fluctuations along with the mean flow cause the flow unjamming.
Chemical Engineering Science
Enhanced Mixing of particulate matter in multi orifice silos Silos and hoppers have a ubiquitous ... more Enhanced Mixing of particulate matter in multi orifice silos Silos and hoppers have a ubiquitous existence in several industries which handle material in a powdered form. In some instances silos/hoppers act as a feeder to a particular process while in some other instances silos are used for processing material (e.g. nuclear pebble bed reactors). One of the key factors which affects the efficient design of a silo is the flow pattern and mixing of the material which drains down the silo and exits from the orifice. Typically, a silo (flat bottomed) or a hopper (conical bottomed) consists of a single orifice/exit either located centrally or at the periphery, which is wide enough to prevent jamming of the flowing particles. Such systems have been widely studied using experiments and numerical simulations to understand the flow and mixing behaviour of the particles. In this work we provide newer insights about particle dynamics occurring in a flat bottomed silo having more than one orific...
Physical Review E, 2014
We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered... more We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered significantly by having more than one exit orifice. For the hoppers with small orifice widths, intermittent flow through one orifice enables the resumption of flow through the adjacent jammed orifice, thus displaying a sequence of jamming and unjamming events. Using discrete element simulations, we show that the total amount of granular material (i.e. avalanche size) emanating from all the orifices combined can be enhanced by about an order of magnitude difference by simply adjusting the inter-orifice distance. The unjamming is driven primarily by fluctuations alone when the interorifice distance is large, but when the orifices are brought close enough, the fluctuations along with the mean flow cause the flow unjamming.
Physical Review E
We investigate the mixing characteristics of dry granular material while draining down a silo wit... more We investigate the mixing characteristics of dry granular material while draining down a silo with multiple exit orifices. The mixing in the silo, which otherwise consists of noninteracting stagnant and flow regions, is observed to improve significantly when the flow through specific orifices is stopped intermittently. This momentary stoppage of flow through the orifice is either controlled manually or is chosen by the system itself when the orifice width is small enough to cause spontaneous jamming and unjamming. We observe that the overall mixing behavior shows a systematic dependence on the frequency of closing and opening of specific orifices. In particular, the silo configuration employing random jamming and unjamming of any of the orifices shows early evidence of chaotic mixing. When operated in a multipass mode, the system exhibits a practical and efficient way of mixing particles.
A two-dimensional elliptic computational fluid dynamics model of a microburner is solved to study... more A two-dimensional elliptic computational fluid dynamics model of a microburner is solved to study the effects of microburner wall conductivity, external heat losses, burner dimensions, and operating conditions on combustion characteristics and the steady-state, self-sustained flame stability of propane/air mixtures. Large gradients are observed, despite the small scales of the microburners. It is found that the wall thermal conductivity is vital in determining the flame stability of the system, as the walls are responsible for the majority of the upstream heat transfer as well as the external heat losses. Furthermore, there exists a range of flow velocities that allow stabilized combustion in microburners. It is found that the microburner dimensions strongly affect thermal stability. Engineering maps denoting flame stability are constructed and design recommendations are made. Finally, comparisons with methane/air systems are made.
We investigate the mixing characteristics of dry granular material while draining down a silo wit... more We investigate the mixing characteristics of dry granular material while draining down a silo with multiple exit orifices. The mixing in the silo, which otherwise consists of noninteracting stagnant and flow regions, is observed to improve significantly when the flow through specific orifices is stopped intermittently. This momentary stoppage of flow through the orifice is either controlled manually or is chosen by the system itself when the orifice width is small enough to cause spontaneous jamming and unjamming. We observe that the overall mixing behavior shows a systematic dependence on the frequency of closing and opening of specific orifices. In particular, the silo configuration employing random jamming and unjamming of any of the orifices shows early evidence of chaotic mixing. When operated in a multipass mode, the system exhibits a practical and efficient way of mixing particles.
We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered... more We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered significantly by having more than one exit orifice. For the hoppers with small orifice widths, inter-mittent flow through one orifice enables the resumption of flow through the adjacent jammed orifice, thus displaying a sequence of jamming and unjamming events. Using discrete element simulations, we show that the total amount of granular material (i.e. avalanche size) emanating from all the orifices combined can be enhanced by about an order of magnitude difference by simply adjusting the inter-orifice distance. The unjamming is driven primarily by fluctuations alone when the inter-orifice distance is large, but when the orifices are brought close enough, the fluctuations along with the mean flow cause the flow unjamming.
Chemical Engineering Science
Enhanced Mixing of particulate matter in multi orifice silos Silos and hoppers have a ubiquitous ... more Enhanced Mixing of particulate matter in multi orifice silos Silos and hoppers have a ubiquitous existence in several industries which handle material in a powdered form. In some instances silos/hoppers act as a feeder to a particular process while in some other instances silos are used for processing material (e.g. nuclear pebble bed reactors). One of the key factors which affects the efficient design of a silo is the flow pattern and mixing of the material which drains down the silo and exits from the orifice. Typically, a silo (flat bottomed) or a hopper (conical bottomed) consists of a single orifice/exit either located centrally or at the periphery, which is wide enough to prevent jamming of the flowing particles. Such systems have been widely studied using experiments and numerical simulations to understand the flow and mixing behaviour of the particles. In this work we provide newer insights about particle dynamics occurring in a flat bottomed silo having more than one orific...
Physical Review E, 2014
We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered... more We show that the flow of granular material inside a 2-dimensional flat bottomed hopper is altered significantly by having more than one exit orifice. For the hoppers with small orifice widths, intermittent flow through one orifice enables the resumption of flow through the adjacent jammed orifice, thus displaying a sequence of jamming and unjamming events. Using discrete element simulations, we show that the total amount of granular material (i.e. avalanche size) emanating from all the orifices combined can be enhanced by about an order of magnitude difference by simply adjusting the inter-orifice distance. The unjamming is driven primarily by fluctuations alone when the interorifice distance is large, but when the orifices are brought close enough, the fluctuations along with the mean flow cause the flow unjamming.
Physical Review E
We investigate the mixing characteristics of dry granular material while draining down a silo wit... more We investigate the mixing characteristics of dry granular material while draining down a silo with multiple exit orifices. The mixing in the silo, which otherwise consists of noninteracting stagnant and flow regions, is observed to improve significantly when the flow through specific orifices is stopped intermittently. This momentary stoppage of flow through the orifice is either controlled manually or is chosen by the system itself when the orifice width is small enough to cause spontaneous jamming and unjamming. We observe that the overall mixing behavior shows a systematic dependence on the frequency of closing and opening of specific orifices. In particular, the silo configuration employing random jamming and unjamming of any of the orifices shows early evidence of chaotic mixing. When operated in a multipass mode, the system exhibits a practical and efficient way of mixing particles.
A two-dimensional elliptic computational fluid dynamics model of a microburner is solved to study... more A two-dimensional elliptic computational fluid dynamics model of a microburner is solved to study the effects of microburner wall conductivity, external heat losses, burner dimensions, and operating conditions on combustion characteristics and the steady-state, self-sustained flame stability of propane/air mixtures. Large gradients are observed, despite the small scales of the microburners. It is found that the wall thermal conductivity is vital in determining the flame stability of the system, as the walls are responsible for the majority of the upstream heat transfer as well as the external heat losses. Furthermore, there exists a range of flow velocities that allow stabilized combustion in microburners. It is found that the microburner dimensions strongly affect thermal stability. Engineering maps denoting flame stability are constructed and design recommendations are made. Finally, comparisons with methane/air systems are made.