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Rohit Maitri

Bio: Rohit Maitri is an academic researcher from Eindhoven University of Technology. The author has contributed to research in topics: Heat transfer & Supercritical fluid. The author has an hindex of 4, co-authored 15 publications receiving 71 citations. Previous affiliations of Rohit Maitri include Indian Institutes of Technology & University of Western Ontario.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a simple one-dimensional numerical thermal-hydraulic model based on a finite-difference scheme has been developed to predict steady and unsteady thermal hydraulic behavior of supercritical water flow at various operating conditions.

26 citations

Journal ArticleDOI
TL;DR: In this article, the authors compare the flow behavior of viscoelastic surfactant (VES) solutions and Newtonian fluids through two different model porous media having similar permeability: (a) a 3D random packed bed and (b) a microchannel with periodically spaced pillars.
Abstract: We compare the flow behavior of viscoelastic surfactant (VES) solutions and Newtonian fluids through two different model porous media having similar permeability: (a) a 3D random packed bed and (b) a microchannel with a periodically spaced pillars. The former provides much larger flow resistance at the same apparent shear rate compared to the latter. The flow profile in the 3D packed bed cannot be observed since it is a closed system. However, visualization of the flow profile in the microchannel shows strong spatial and temporal flow instabilities in VES fluids appear above a critical shear rate. The onset of such elastic instabilities correlates to the flow rate where increased flow resistance is observed. The elastic instabilities are attributed to the formation of transient shear induced structures. The experiments provide a detailed insight into the complex interplay between the pore scale geometry and rheology of VES in the creeping flow regime.

23 citations

Journal ArticleDOI
TL;DR: In this paper, an accurate and stable sharp interface immersed boundary method (IBM) is presented for the direct numerical simulation of particle laden flows, which is based on the direct-forcing method by incorporating the ghost-cell approach implicitly.

11 citations

Journal ArticleDOI
TL;DR: In this paper, a control system design method for the Canadian supercritical water cooled reactor (SCWR), known as CANDU SCWR, is developed in which the main dynamic of this reactor can be represented as a multiple input and multiple output (MIMO) system governed by highly non-linear partial differential equations.

10 citations

Journal ArticleDOI
TL;DR: The effects of elasticity and shear thinning are isolated by comparing a Newtonian fluid, a purely elastic (Boger) fluid, and a shear-thinning elastic fluid to investigate the influence of channel structure and fluid rheology on non-inertial migration of non-Brownian polystyrene beads.
Abstract: In this work, we investigate the influence of channel structure and fluid rheology on non-inertial migration of non-Brownian polystyrene beads. Particle migration in this regime can be found in biomedical, chemical, environmental and geological applications. However, the effect of fluid rheology on particle migration in porous media remains to be clearly understood. Here, we isolate the effects of elasticity and shear thinning by comparing a Newtonian fluid, a purely elastic (Boger) fluid, and a shear-thinning elastic fluid. To mimic the complexity of geometries in real-world application, a random porous structure is created through a disordered arrangement of cylindrical pillars in the microchannel. Experiments are repeated in an empty channel and in channels with an ordered arrangement of pillars, and the similarities and differences in the observed particle focusing are analyzed. It is found that elasticity drives the particles away from the channel walls in an empty microchannel. Notably, particle focusing is unaffected by curved streamlines in an ordered porous microchannel and particles stay away from pillars in elastic fluids. Shear-thinning is found to reduce the effect of focusing and a broader region of particle concentration is observed. It is also noteworthy that the rheological characteristics of the fluid are not important for the particle distribution in a randomly arranged pillared microchannel and particles have a uniform distribution for all suspending fluids. Moreover, discussion on the current discrepancy in the literature about the equilibrium positions of the particles in a channel is extended by analyzing the results obtained in the current experiments.

6 citations


Cited by
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01 Jan 2007

1,932 citations

01 Nov 2002
TL;DR: An efficient ghost-cell immersed boundary method (GCIBM) for simulating turbulent flows in complex geometries is presented in this paper, where a boundary condition is enforced through a ghost cell method.
Abstract: An efficient ghost-cell immersed boundary method (GCIBM) for simulating turbulent flows in complex geometries is presented. A boundary condition is enforced through a ghost cell method. The reconstruction procedure allows systematic development of numerical schemes for treating the immersed boundary while preserving the overall second-order accuracy of the base solver. Both Dirichlet and Neumann boundary conditions can be treated. The current ghost cell treatment is both suitable for staggered and non-staggered Cartesian grids. The accuracy of the current method is validated using flow past a circular cylinder and large eddy simulation of turbulent flow over a wavy surface. Numerical results are compared with experimental data and boundary-fitted grid results. The method is further extended to an existing ocean model (MITGCM) to simulate geophysical flow over a three-dimensional bump. The method is easily implemented as evidenced by our use of several existing codes.

740 citations

Journal ArticleDOI
01 Mar 2020-Small
TL;DR: In this article, microfluidic tools can shed light on the physics underlying the flow of polymer solutions in porous media at high Wi and low Re, and they elucidate how steady and unsteady flow behavior depends on pore geometry and solution properties, and how polymerinduced effects impact nonaqueous fluid recovery.
Abstract: Polymer solutions are frequently used in enhanced oil recovery and groundwater remediation to improve the recovery of trapped nonaqueous fluids. However, applications are limited by an incomplete understanding of the flow in porous media. The tortuous pore structure imposes both shear and extension, which elongates polymers; moreover, the flow is often at large Weissenberg numbers, Wi, at which polymer elasticity in turn strongly alters the flow. This dynamic elongation can even produce flow instabilities with strong spatial and temporal fluctuations despite the low Reynolds number, Re. Unfortunately, macroscopic approaches are limited in their ability to characterize the pore-scale flow. Thus, understanding how polymer conformations, flow dynamics, and pore geometry together determine these nontrivial flow patterns and impact macroscopic transport remains an outstanding challenge. This review describes how microfluidic tools can shed light on the physics underlying the flow of polymer solutions in porous media at high Wi and low Re. Specifically, microfluidic studies elucidate how steady and unsteady flow behavior depends on pore geometry and solution properties, and how polymer-induced effects impact nonaqueous fluid recovery. This work thus provides new insights for polymer dynamics, non-Newtonian fluid mechanics, and applications such as enhanced oil recovery and groundwater remediation.

83 citations

Journal ArticleDOI
TL;DR: In this article, a large amount of experimental data were obtained from the experiments supplementing the extensive database previously compiled for fossil fuel-fired power plants, and prediction methods for heat-transfer coefficient were developed from various databases.

80 citations

Journal ArticleDOI
15 Jan 2018
TL;DR: It is found that viscoelastic polymers and surfactant solutions can displace more oil compared to Newtonian fluids and nearly inelastic shear thinning polymers at similar Ca numbers, suggesting a close link between enhancement of oil recovery and appearance of elastic instabilities.
Abstract: Hypothesis Multiphase flow through porous media is important in a number of industrial, natural and biological processes. One application is enhanced oil recovery (EOR), where a resident oil phase is displaced by a Newtonian or polymeric fluid. In EOR, the two-phase immiscible displacement through heterogonous porous media is usually governed by competing viscous and capillary forces, expressed through a Capillary number Ca, and viscosity ratio of the displacing and displaced fluid. However, when viscoelastic displacement fluids are used, elastic forces in the displacement fluid also become significant. It is hypothesized that elastic instabilities are responsible for enhanced oil recovery through an elastic microsweep mechanism. Experiments In this work, we use a simplified geometry in the form of a pillared microchannel. We analyze the trapped residual oil size distribution after displacement by a Newtonian fluid, a nearly inelastic shear thinning fluid, and viscoelastic polymers and surfactant solutions. Findings We find that viscoelastic polymers and surfactant solutions can displace more oil compared to Newtonian fluids and nearly inelastic shear thinning polymers at similar Ca numbers. Beyond a critical Ca number, the size of residual oil blobs decreases significantly for viscoelastic fluids. This critical Ca number directly corresponds to flow rates where elastic instabilities occur in single phase flow, suggesting a close link between enhancement of oil recovery and appearance of elastic instabilities.

53 citations