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Kirti Chandra Sahu

Bio: Kirti Chandra Sahu is an academic researcher from Indian Institute of Technology, Hyderabad. The author has contributed to research in topics: Open-channel flow & Reynolds number. The author has an hindex of 26, co-authored 142 publications receiving 2581 citations. Previous affiliations of Kirti Chandra Sahu include Imperial College London & Indian Institutes of Technology.


Papers
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TL;DR: It is reported that the dynamics is fully three-dimensional, and provide a broad canvas of behaviour patterns, and a perfect correlation between large shape asymmetry and path instability is established.
Abstract: The beauty and complexity of the shapes and dynamics of bubbles rising in liquid have fascinated scientists for centuries. Here we perform simulations on an initially spherical bubble starting from rest. We report that the dynamics is fully three-dimensional, and provide a broad canvas of behaviour patterns. Our phase plot in the Galilei-Eotvos plane shows five distinct regimes with sharply defined boundaries. Two symmetry-loss regimes are found: one with minor asymmetry restricted to a flapping skirt; and another with marked shape evolution. A perfect correlation between large shape asymmetry and path instability is established. In regimes corresponding to peripheral breakup and toroid formation, the dynamics is unsteady. A new kind of breakup, into a bulb-shaped bubble and a few satellite drops is found at low Morton numbers. The findings are of fundamental and practical relevance. It is hoped that experimenters will be motivated to check our predictions.

213 citations

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TL;DR: In this article, a review highlights the profound and unexpected ways in which viscosity varying in space and time can affect flow and the most striking manifestations are through alterations of flow stability, as established in model shear flows and industrial applications.
Abstract: This review highlights the profound and unexpected ways in which viscosity varying in space and time can affect flow. The most striking manifestations are through alterations of flow stability, as established in model shear flows and industrial applications. Future studies are needed to address the important effect of viscosity stratification in such diverse environments as Earth's core, the Sun, blood vessels, and the re-entry of spacecraft.

191 citations

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TL;DR: In this article, the stability of miscible two-fluid flow in a horizontal channel is examined, where flow dynamics are governed by the continuity and Navier-Stokes equations coupled to a convective-diffusion equation for the concentration of the more viscous fluid through a concentration-dependent viscosity.
Abstract: The stability of miscible two-fluid flow in a horizontal channel is examined. The flow dynamics are governed by the continuity and Navier–Stokes equations coupled to a convective-diffusion equation for the concentration of the more viscous fluid through a concentration-dependent viscosity. Our analysis of the flow in the linear regime delineates the presence of convective and absolute instabilities and identifies the vertical gradients of viscosity perturbations as the main destabilizing influence in agreement with previous work. Our transient numerical simulations demonstrate the development of complex dynamics in the nonlinear regime, characterized by roll-up phenomena and intense convective mixing; these become pronounced with increasing flow rate and viscosity ratio, as well as weak diffusion.

100 citations

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TL;DR: In this paper, the linear stability characteristics of pressure-driven two-layer channel flow are considered, wherein a Newtonian fluid layer overlies a layer of a Herschel-Bulkley fluid.
Abstract: The linear stability characteristics of pressure-driven two-layer channel flow are considered, wherein a Newtonian fluid layer overlies a layer of a Herschel-Bulkley fluid. A pair of coupled Orr-Sommerfeld eigenvalue equations are derived and solved using an efficient spectral collocation method for cases in which unyielded regions are absent. An asymptotic analysis is also carried out in the long-wave limit, the results of which are in excellent agreement with the numerical predictions. Our analytical and numerical results indicate that increasing the dimensionless yield stress, prior to the formation of unyielded plugs below the interface, is destabilizing. Increasing the shear-thinning tendency of the lower fluid is stabilizing.

87 citations

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11 Apr 2014-Langmuir
TL;DR: This work uses lubrication theory to derive an evolution equation for the interface that accounts for capillarity and thermocapillarity, and simulates the spreading of droplets of fluids whose surface tension-temperature curves exhibit a turning point.
Abstract: We study the thermocapillary-driven spreading of a droplet on a nonuniformly heated substrate for fluids associated with a non-monotonic dependence of the surface tension on temperature. We use lubrication theory to derive an evolution equation for the interface that accounts for capillarity and thermocapillarity. The contact line singularity is relieved by using a slip model and a Cox-Voinov relation; the latter features equilibrium contact angles that vary depending on the substrate wettability, which, in turn, is linked to the local temperature. We simulate the spreading of droplets of fluids whose surface tension-temperature curves exhibit a turning point. For cases wherein these turning points correspond to minima, and when these minima are located within the droplet, then thermocapillary stresses drive rapid spreading away from the minima. This gives rise to a significant acceleration of the spreading whose characteristics resemble those associated with the "superspreading" of droplets on hydrophobic substrates. No such behavior is observed for cases in which the turning point corresponds to a surface tension maximum.

80 citations


Cited by
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1,242 citations

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01 Jan 2006

1,095 citations

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01 Jan 2006
TL;DR: The mysterious rattleback and its fluid counterpart:Developments in shear instabilities(Patrick Huerre,Falling clouds+Elisabeth Guazzelli)LEcotectural fluid mechanics%Herbert Huppert )
Abstract: 流体力学杂志“Journal of Fluid Mechanics”由剑桥大学教授George Batchelor在1956年5月创办,在国际流体力学界享有很高的学术声望,被公认为是流体力学最著名的学术刊物之一,2005年的影响因子为2.061,雄居同类期刊之首.在它创刊50周年之际,2006年5月JFM出版了第554卷的纪念特刊,其中刊登了现任主编(美国西北大学S.H.Davis教授和英国剑桥大学T.J.Pedley教授)合写的述评:“Editorial:JFM at50”,以JFM为背景,从独特的视角对近50年来流体力学的发展进行了简明的回顾和展望,并归纳了一系列非常有启发性的有趣统计数字.2006年7月21日在剑桥大学应用数学和理论物理研究所(DAMTP)举行了创刊50周年的庆祝会.下午2点,JFM的新老编辑和来宾会聚一堂,Pedley教授致开幕词,其后是5个精彩的报告:The mysterious rattleback and its fluid counterpart(Keith Moffatt),Developments in shear instabilities(Patrick Huerre),Falling clouds(Elisabeth Guazzelli),Ecotectural fluid mechanics(Paul Linden),The success of JFM(Herbert Huppert),最后由Davis教授致闭幕词.

644 citations

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TL;DR: In this paper, the authors distill the salient advances of recent origin, particularly those that challenge textbook orthodoxy, and highlight some of the outstanding questions, such as the extent of the logarithmic overlap layer, the universality or otherwise of the principal model parameters, and the scaling of mean flow and Reynolds stresses.
Abstract: Wall-bounded turbulent flows at high Reynolds numbers have become an increasingly active area of research in recent years. Many challenges remain in theory, scaling, physical understanding, experimental techniques, and numerical simulations. In this paper we distill the salient advances of recent origin, particularly those that challenge textbook orthodoxy. Some of the outstanding questions, such as the extent of the logarithmic overlap layer, the universality or otherwise of the principal model parameters such as the von Karman “constant,” the parametrization of roughness effects, and the scaling of mean flow and Reynolds stresses, are highlighted. Research avenues that may provide answers to these questions, notably the improvement of measuring techniques and the construction of new facilities, are identified. We also highlight aspects where differences of opinion persist, with the expectation that this discussion might mark the beginning of their resolution.

643 citations

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01 Jan 2004

611 citations