Esophageal transport is a physiological process that mechanically transports an ingested food bol... more Esophageal transport is a physiological process that mechanically transports an ingested food bolus from the pharynx to the stomach via the esophagus, a multilayered muscular tube. This process involves interactions between the bolus, the esophagus, and the neurally coordinated activation of the esophageal muscles. In this work, we use an immersed boundary (IB) approach to simulate peristaltic transport in the esophagus. The bolus is treated as a viscous fluid that is actively transported by the muscular esophagus, and the esophagus is modeled as an actively contracting, fiber-reinforced tube. Before considering the full model of the esophagus, however, we first consider a standard benchmark problem of flow past a cylinder. Next a simplified version of our model is verified by comparison to an analytic solution to the tube dilation problem. Finally, three different complex models of the multi-layered esophagus, which differ in their activation patterns and the layouts of the mucosal...
Abstract. In the paper a Direct Numerical Simulation (DNS) scheme, named Fluctuating Immersed MAT... more Abstract. In the paper a Direct Numerical Simulation (DNS) scheme, named Fluctuating Immersed MATerial (FIMAT) dynamics, for the Brownian motion of particles is presented. In this approach the thermal fluctuations are included in the fluid equations via random stress terms. ...
There are contradictory published data on the behavior of fluid slip at high shear rates. Using t... more There are contradictory published data on the behavior of fluid slip at high shear rates. Using three methodologies (molecular dynamics simulations, an analytical theory of slip, and a Navier-Stokes-based calculation) covering a range of fluids (bead-spring liquids, polymer solutions, and ideal gas flows) we show that as shear rate increases, the amount of slip, as measured by the slip length, asymptotes to a constant value. The results clarify the molecular mechanics of how slip occurs. Furthermore, they indicate that in this limit, molecular dynamics simulations must accurately account for heat transfer to the solid.
We present a computational algorithm for fully resolved numerical simulation (FRS) of rigid and d... more We present a computational algorithm for fully resolved numerical simulation (FRS) of rigid and deforming bodies moving in fluids. Given the deformation of the body in its own reference frame, the method solves for the swimming velocity of the body together with the surrounding flow field, and the hydrodynamic forces on the body. We provide the mathematical foundation of the
... A numerical method for fully resolved simulation (FRS) of rigid particleflow interactions in... more ... A numerical method for fully resolved simulation (FRS) of rigid particleflow interactions in complex flows. Sourabh V. Apte a , Corresponding Author Contact Information , E-mail The Corresponding Author , Mathieu Martin a and Neelesh A. Patankar b. ... Patankar et al. ...
Langmuir : the ACS journal of surfaces and colloids, Jan 2, 2009
An extreme water-repellent surface is designed and fabricated with a hierarchical integration of ... more An extreme water-repellent surface is designed and fabricated with a hierarchical integration of nano- and microscale textures. We combined the two readily accessible etching techniques, a standard deep silicon etching, and a gas phase isotropic etching (XeF2) for the uniform formation of double roughness on a silicon surface. The fabricated synthetic surface shows the hallmarks of the Lotus effect: durable super water repellency (contact angle>173 degrees) and the sole existence of the Cassie state even with a very large spacing between roughness structures (>1:7.5). We directly demonstrate the absence of the Wenzel's or wetted state through a series of experiments. When a water droplet is squeezed or dropped on the fabricated surface, the contact angle hardly changes and the released droplet instantly springs back without remaining wetted on the surface. We also show that a ball of water droplet keeps bouncing on the surface. Furthermore, the droplet shows very small co...
Computer Methods in Applied Mechanics and Engineering, 2005
In this paper we present a distributed lagrange multiplier (DLM) based Stokes flow algorithm for ... more In this paper we present a distributed lagrange multiplier (DLM) based Stokes flow algorithm for particulate flows. The entire fluidparticle domain is treated as a fluid. The fluid in the particle domain is ensured to move rigidly by adding a rigidity constraint. We modify the SIMPLER ...
Esophageal transport is a physiological process that mechanically transports an ingested food bol... more Esophageal transport is a physiological process that mechanically transports an ingested food bolus from the pharynx to the stomach via the esophagus, a multilayered muscular tube. This process involves interactions between the bolus, the esophagus, and the neurally coordinated activation of the esophageal muscles. In this work, we use an immersed boundary (IB) approach to simulate peristaltic transport in the esophagus. The bolus is treated as a viscous fluid that is actively transported by the muscular esophagus, and the esophagus is modeled as an actively contracting, fiber-reinforced tube. Before considering the full model of the esophagus, however, we first consider a standard benchmark problem of flow past a cylinder. Next a simplified version of our model is verified by comparison to an analytic solution to the tube dilation problem. Finally, three different complex models of the multi-layered esophagus, which differ in their activation patterns and the layouts of the mucosal...
Abstract. In the paper a Direct Numerical Simulation (DNS) scheme, named Fluctuating Immersed MAT... more Abstract. In the paper a Direct Numerical Simulation (DNS) scheme, named Fluctuating Immersed MATerial (FIMAT) dynamics, for the Brownian motion of particles is presented. In this approach the thermal fluctuations are included in the fluid equations via random stress terms. ...
There are contradictory published data on the behavior of fluid slip at high shear rates. Using t... more There are contradictory published data on the behavior of fluid slip at high shear rates. Using three methodologies (molecular dynamics simulations, an analytical theory of slip, and a Navier-Stokes-based calculation) covering a range of fluids (bead-spring liquids, polymer solutions, and ideal gas flows) we show that as shear rate increases, the amount of slip, as measured by the slip length, asymptotes to a constant value. The results clarify the molecular mechanics of how slip occurs. Furthermore, they indicate that in this limit, molecular dynamics simulations must accurately account for heat transfer to the solid.
We present a computational algorithm for fully resolved numerical simulation (FRS) of rigid and d... more We present a computational algorithm for fully resolved numerical simulation (FRS) of rigid and deforming bodies moving in fluids. Given the deformation of the body in its own reference frame, the method solves for the swimming velocity of the body together with the surrounding flow field, and the hydrodynamic forces on the body. We provide the mathematical foundation of the
... A numerical method for fully resolved simulation (FRS) of rigid particleflow interactions in... more ... A numerical method for fully resolved simulation (FRS) of rigid particleflow interactions in complex flows. Sourabh V. Apte a , Corresponding Author Contact Information , E-mail The Corresponding Author , Mathieu Martin a and Neelesh A. Patankar b. ... Patankar et al. ...
Langmuir : the ACS journal of surfaces and colloids, Jan 2, 2009
An extreme water-repellent surface is designed and fabricated with a hierarchical integration of ... more An extreme water-repellent surface is designed and fabricated with a hierarchical integration of nano- and microscale textures. We combined the two readily accessible etching techniques, a standard deep silicon etching, and a gas phase isotropic etching (XeF2) for the uniform formation of double roughness on a silicon surface. The fabricated synthetic surface shows the hallmarks of the Lotus effect: durable super water repellency (contact angle>173 degrees) and the sole existence of the Cassie state even with a very large spacing between roughness structures (>1:7.5). We directly demonstrate the absence of the Wenzel's or wetted state through a series of experiments. When a water droplet is squeezed or dropped on the fabricated surface, the contact angle hardly changes and the released droplet instantly springs back without remaining wetted on the surface. We also show that a ball of water droplet keeps bouncing on the surface. Furthermore, the droplet shows very small co...
Computer Methods in Applied Mechanics and Engineering, 2005
In this paper we present a distributed lagrange multiplier (DLM) based Stokes flow algorithm for ... more In this paper we present a distributed lagrange multiplier (DLM) based Stokes flow algorithm for particulate flows. The entire fluidparticle domain is treated as a fluid. The fluid in the particle domain is ensured to move rigidly by adding a rigidity constraint. We modify the SIMPLER ...
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Papers by Neelesh Patankar