Other affiliations: National University of Singapore, Massachusetts Institute of Technology, General Electric
Bio: Srikanth Vedantam is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Grain boundary & Dissipative particle dynamics. The author has an hindex of 19, co-authored 62 publication(s) receiving 1220 citation(s). Previous affiliations of Srikanth Vedantam include National University of Singapore & Massachusetts Institute of Technology.
28 Dec 2001-
Abstract: In a gas turbine having a chordal hinge seal between an inner rail of each nozzle segment and an annular axially facing sealing surface of a nozzle support ring, a supplemental seal is disposed between the support ring and inner bands of the nozzle segments on a lower pressure side of the chordal hinge seals. To minimize or prevent leakage flow across the chordal hinge seals, a generally U-shaped supplemental seal having reversely folded U-shaped marginal portions is received in a cavity formed in the axially extending sealing surface of the inner rail of the nozzle segment. At operating conditions, the marginal portions seal against the base of the cavity and the annular sealing surface of the nozzle support ring to prevent leakage flow past the chordal hinge seal from entering the hot gas path. To install the supplemental seal, the seal is first compressed and maintained in a compressed state by applying one or more wraps about the supplemental seal or an epoxy to secure the seal when compressed in the cavity. At operating temperatures, the retention means releases the seal to engage marginal portions against opposite sealing surfaces of the nozzle segment and support ring.
19 Jan 2006-Physical Review E
TL;DR: This work presents an approach by which the time and memory requirements are drastically reduced relative to standard algorithms and allows the use of an unlimited number of phase-field variables to perform simulations without the associated burden on computational time or memory.
Abstract: Phase-field models have emerged as a successful class of models in a wide variety of applications in computational materials science. Multiphase field theories, as a subclass of phase-field theories, have been especially useful for studying nucleation and growth in polycrystalline materials. In theory, an infinite number of phase-field variables are required to represent grain orientations in a rotationally invariant free energy. However, limitations on available computational time and memory have restricted the number of phase-field variables used in the simulations. We present an approach by which the time and memory requirements are drastically reduced relative to standard algorithms. The proposed algorithm allows us the use of an unlimited number of phase-field variables to perform simulations without the associated burden on computational time or memory. We present the algorithm in the context of coalescence free grain growth.
15 Nov 2007-Langmuir
13 Oct 2007-Langmuir
TL;DR: It is reported that the contact angle is independent of area void fraction for surfaces with microcavities, which correspond to situations when the advancing contact line is continuous, in contrast with Cassie-Baxter theory, which uses areavoid fraction as the determining parameter, regardless of the type of roughness.
Abstract: Cassie-Baxter theory has traditionally been used to study liquid drops in contact with microstructured surfaces. The Cassie-Baxter theory arises from a minimization of the global Gibbs free energy of the system but does not account for the topology of the three-phase contact line. We experimentally compare two situations differing only in the microstructure of the roughness, which causes differences in contact line topology. We report that the contact angle is independent of area void fraction for surfaces with microcavities, which correspond to situations when the advancing contact line is continuous. This result is in contrast with Cassie-Baxter theory, which uses area void fraction as the determining parameter, regardless of the type of roughness.
15 Sep 2014-Wear
Abstract: In this paper, we study the wear resistance of multi-layered composites of Cu/SiC + Gr hybrid composites prepared by layer compaction and pressure sintering. The tribological behavior and wear resistance of the composites were evaluated at a range of sliding speeds (5, 10, 30 and 35 m/s) in a laboratory scale inertia brake dynamometer for brake friction material applications. The wear surface morphology and mechanisms were studied using scanning electron microscopy (SEM), XRD, and stereoscopy. The microstructure of the composites was also characterized using SEM and optical microscopy and the mechanical response in compression and flexure was evaluated. The results of these tests indicate that the density, wear resistance, braking behavior and mechanical response can be significantly improved by the presence of a layer of copper away from the sliding surface. The presence of the layer also improved friction and wear resistance significantly. The formation of mechanically mixed tribolayer and oxides (Fe 3 O 4 ) reduced the wear rate and stabilized the friction coefficient at 30 and 35 m/s. Finally, crack deflection and branching at the interface between the composite and Cu layers improved the flexural strength of the layered composites. The fractography analysis indicates a quasi-cleavage intergranular fracture in the composite layer and a purely ductile fracture in the Cu layer.
08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …
Abstract: The phase-field method has become an important and extremely versatile technique for simulating microstructure evolution at the mesoscale. Thanks to the diffuse-interface approach, it allows us to study the evolution of arbitrary complex grain morphologies without any presumption on their shape or mutual distribution. It is also straightforward to account for different thermodynamic driving forces for microstructure evolution, such as bulk and interfacial energy, elastic energy and electric or magnetic energy, and the effect of different transport processes, such as mass diffusion, heat conduction and convection. The purpose of the paper is to give an introduction to the phase-field modeling technique. The concept of diffuse interfaces, the phase-field variables, the thermodynamic driving force for microstructure evolution and the kinetic phase-field equations are introduced. Furthermore, common techniques for parameter determination and numerical solution of the equations are discussed. To show the variety in phase-field models, different model formulations are exploited, depending on which is most common or most illustrative.
18 Oct 2011-Soft Matter
Abstract: The term superhydrophilicity is only 11–12 years old and was introduced just after the explosion of research on superhydrophobic surfaces, in response to the demand for surfaces and coatings with exceptionally strong affinity to water. The definition of superhydrophilic substrates has not been clarified yet, and unrestricted use of this term to hydrophilic surfaces has stirred controversy in the last few years in the surface chemistry community. In this review, we take a close look into major definitions of hydrophilic surfaces used in the past, before we review the physics behind the superhydrophilic phenomenon and make recommendation on defining superhydrophilic surfaces and coatings. We also review chemical and physical methods used in the fabrication of substrates on surfaces of which water spreads completely. Several applications of superhydrophilic surfaces, including examples from the authors' own research, conclude this review.
01 Aug 2009-Current Opinion in Colloid and Interface Science
Abstract: This paper provides a review of superhydrophobicity and related phenomena (superoleophobicity, omniphobicity, self-cleaning) induced by surface micro- and nanostructuring. The classical approaches to superhydrophobicity using the Young, Wenzel, and Cassie–Baxter models for the contact angle (CA) are presented. After that, the issues that are beyond the Wenzel and Cassie–Baxter theories are discussed, such as multiscale effects, 1D vs. 2D interactions, the effects of contact line, size of roughness details, curvature, and CA hysteresis dependence on roughness. New potential applications of superhydrophobicity are reviewed, such as new ways of energy transition, antifouling, and environment-friendly manufacturing.
04 Mar 2008-Langmuir
Abstract: Most of the artificial superhydrophobic surfaces that have been fabricated to date are not biodegradable, renewable, or mechanically flexible and are often expensive, which limits their potential applications. In contrast, cellulose, a biodegradable, renewable, flexible, inexpensive, biopolymer which is abundantly present in nature, satisfies all the above requirements, but it is not superhydrophobic. Superhydrophobicity on cellulose paper was obtained by domain-selective etching of amorphous portions of the cellulose in an oxygen plasma and subsequently coating the etched surface with a thin fluorocarbon film deposited via plasma-enhanced chemical vapor deposition using pentafluoroethane as a precursor. Variation of plasma treatment yielded two types of superhydrophobicity : "roll-off" (contact angle (CA), 166.7 degrees +/- 0.9 degrees ; CA hysteresis, 3.4 degrees +/- 0.1 degrees ) and "sticky" (CA, 144.8 degrees +/- 5.7 degrees ; CA hysteresis, 79.1 degrees +/- 15.8 degrees ) near superhydrophobicity. The nanometer scale roughness obtained by delineating the internal roughness of each fiber and the micrometer scale roughness which is inherent to a cellulose paper surface are robust when compared to roughened structures created by traditional polymer grafting, nanoparticle deposition, or other artificial means.
Author's H-index: 19