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.

Analysis of cooling of a conducting fluid film of non-uniform thickness on a rotating disk

Abstract: The unsteady thin conducting liquid film of non-uniform thickness on a rotating disk which is cooled axisymmetrically from below has been analysed numerically by solving the evolution equation of the free surface. Transient film profiles for different initial liquid film distributions have been obtained. The results reveal that the thinning process and film planarisation are markedly influenced by the heat dissipating or cooling parameter β, Prandtl number σ and Reynolds number Re.

Theoretical Investigation of Unsteady Squeeze Flow in a Curved Newtonian Squeeze Film

Abstract: The laminar squeeze flow of a viscous incompressible fluid between a flat circular disk and an axisymmetric curved disk of arbitrary shape is investigated theoretically using modified lubrication theory. The characteristics of squeeze film are investigated through inertia and curvature effects on the normal force exerted on the upper curved moving disk described by an exponential function for the sinusoidal squeeze motion. The constant force squeezing state is also examined. It has been observed that the load carrying capacity of the curved squeeze film is strongly influenced by the curvature and inertia effects.

Spinning of a liquid film from a rotating disc in the presence of a magnetic field — a numerical solution

Abstract: A numerical solution is obtained for the development of a conducting fluid film on the surface of a spinning disc, in the presence of a magnetic field applied perpendicular to the disc. A finite-difference method is employed to obtain the solution of Navier-Stokes equations modified to include magnetic forces due to MHD interactions. The combined effects of film inertia, acceleration of the disc and magnetic forces are analysed. The numerical results reveal that the rate of thinning of the fluid film is strongly influenced by the inertial and magnetic forces when the Reynolds number is large and that the existing asymptotic theory by Ray and Dandapat [24] is inadequate for predicting transient film thickness. When the disc has a finite acceleration at the start-up, the magnetic and inertia effects are important even at low Reynolds numbers and the thinning rate is reduced. It is observed that for both low and high Reynolds number flows, the film thickness increases with Hartmann numberM for a fixed time and the rate of depletion is less for largeM than for smallM.

Dynamics and stability of thin liquid films

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.

Viscous flow due to a shrinking sheet

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.

Principles Of Enhanced Heat Transfer

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