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R. Usha

Bio: R. Usha is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Reynolds number & Instability. The author has an hindex of 17, co-authored 85 publications receiving 1061 citations. Previous affiliations of R. Usha include University of Hyderabad & Anna University.


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TL;DR: In this paper, an analysis of a pressure driven two-layer Poiseuille flow confined between a rigid wall and a Darcy-Brinkman porous layer is explored, and a linear stability analysis of the conservation laws leads to an Orr-Sommerfeld system to identify the time and length scales of the instabilities.

13 citations

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TL;DR: In this article, the development of a heat conducting fluid film on a rotating disk has been analyzed numerically under the planar interface assumption and the film thickness, the flow characteristics, the temperature distribution and the rate of heat transfer are determined.
Abstract: The development of a heat conducting fluid film on a rotating disk has been analysed numerically under the planar interface assumption and the film thickness, the flow characteristics, the temperature distribution and the rate of heat transfer are determined. The range of validity of the time scales and Reynolds number bounds have been presented for the existing asymptotic solution for film cooling on a rotating disk. The effects of the Reynolds number Re , cooling parameter β and the Prandtl number σ on the variation of film thickness, and temperature distribution have been examined.

13 citations

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TL;DR: In this article, a sphere theorem for non-axisymmetric Stokes' flow outside/inside a shear-free sphere is proved and proved in a special case.

12 citations

Journal ArticleDOI
TL;DR: In this paper, the authors considered the spatio-temporal instability of a viscous two-fluid symmetric flow in a horizontal slippery channel and showed that it is possible to achieve early transition to turbulence by making the channel walls hydrophobic/rough/porous with small permeability, which can be modelled by the Navier-slip condition.

12 citations

Journal ArticleDOI
TL;DR: In this article, a weakly nonlinear stability analysis of thin power-law liquid film flowing down an inclined plane including the phase change effects at the interface has been investigated, and the results show that both the supercritical stability and subcritical instability are possible for condensate, evaporating and isothermal power law liquid film down a inclined plane.
Abstract: Weakly nonlinear stability analysis of thin power-law liquid film flowing down an inclined plane including the phase change effects at the interface has been investigated. A normal mode approach and the method of multiple scales are employed to carry out the linear stability solution and the nonlinear stability solution for the film flow system. The results show that both the supercritical stability and subcritical instability are possible for condensate, evaporating and isothermal power-law liquid film down an inclined plane. The stability characteristics of the power-law liquid film show that isothermal and evaporating films are unstable for any value of power-law index 'n' while there exists a critical value of power-law index 'n' for the case of condensate film above which condensate film flow system is always stable. Thus, the results of the present analysis show that the mass transfer effects play a significant role in modifying the stability characteristics of the non-Newtonian power-law fluid flow system. The condensate (evaporating) power-law fluid film is more stable (unstable) than the isothermal power-law fluid film flowing down an inclined plane.

12 citations


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Journal ArticleDOI
TL;DR: The dynamics and stability of thin liquid films have fascinated scientists over many decades: the observations of regular wave patterns in film flows along a windowpane or along guttering, the patterning of dewetting droplets, and the fingering of viscous flows down a slope are all examples that are familiar in daily life.
Abstract: The dynamics and stability of thin liquid films have fascinated scientists over many decades: the observations of regular wave patterns in film flows down a windowpane or along guttering, the patterning of dewetting droplets, and the fingering of viscous flows down a slope are all examples that are familiar in daily life. Thin film flows occur over a wide range of length scales and are central to numerous areas of engineering, geophysics, and biophysics; these include nanofluidics and microfluidics, coating flows, intensive processing, lava flows, dynamics of continental ice sheets, tear-film rupture, and surfactant replacement therapy. These flows have attracted considerable attention in the literature, which have resulted in many significant developments in experimental, analytical, and numerical research in this area. These include advances in understanding dewetting, thermocapillary- and surfactant-driven films, falling films and films flowing over structured, compliant, and rapidly rotating substrates, and evaporating films as well as those manipulated via use of electric fields to produce nanoscale patterns. These developments are reviewed in this paper and open problems and exciting research avenues in this thriving area of fluid mechanics are also highlighted.

1,226 citations

Journal ArticleDOI
TL;DR: In this paper, the viscous flow induced by a shrinking sheet is studied and its existence and uniqueness are proved. Exact solutions, both numerical and in closed form, are found.
Abstract: The viscous flow induced by a shrinking sheet is studied. Existence and (non)uniqueness are proved. Exact solutions, both numerical and in closed form, are found.

589 citations

01 Jan 2016
TL;DR: The principles of enhanced heat transfer is universally compatible with any devices to read and is available in the book collection an online access to it is set as public so you can get it instantly.
Abstract: Thank you very much for reading principles of enhanced heat transfer. As you may know, people have look numerous times for their chosen books like this principles of enhanced heat transfer, but end up in malicious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they are facing with some infectious bugs inside their desktop computer. principles of enhanced heat transfer is available in our book collection an online access to it is set as public so you can get it instantly. Our books collection spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Merely said, the principles of enhanced heat transfer is universally compatible with any devices to read.

553 citations

01 Jan 1985

384 citations