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B. Uma

Bio: B. Uma is an academic researcher from University of California, Santa Barbara. The author has contributed to research in topics: Magnetic field & Wavenumber. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

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TL;DR: In this paper, the effects of a magnetic field on the dynamics of a thin nonuniform conducting film of an incompressible viscous fluid on a rotating disk has been considered, and a nonlinear evolution equation describing the shape of the film interface has been derived as a function of space and time and solved numerically.
Abstract: A theoretical analysis of the effects of a magnetic field on the dynamics of a thin nonuniform conducting film of an incompressible viscous fluid on a rotating disk has been considered A nonlinear evolution equation describing the shape of the film interface has been derived as a function of space and time and has been solved numerically The temporal evolution of the free surface of the fluid and the rate of retention of the liquid film on the spinning disk have been obtained for different values of Hartmann number M, evaporative mass flux parameter E, and Reynolds number Re The results show that the relative volume of the fluid retained on the spinning disk is enhanced by the presence of the magnetic field The stability characteristics of the evolution equation have been examined using linear theory For both zero and nonzero values of the nondimensional parameter describing the magnetic field, the results show that (a) the infinitesimal disturbances decay for small wave numbers and are transiently stable for larger wave numbers when there is either no mass transfer or there is evaporation from the film surface, and although the magnitude of the disturbance amplitude is larger when the magnetic field is present, it decays to zero earlier than for the case when the magnetic field is absent, and (b) when absorption is present at the film surface, the film exhibits three different domains of stability: disturbances of small wave numbers decay, disturbances of intermediate wave numbers grow transiently, and those of large wave numbers grow exponentially The range of stable wave numbers increases with increase in Hartmann number

3 citations


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TL;DR: In this paper, the effects of rotation and inertia on the thin-film flow formed by a circular jet impinging on a rotating disk is analyzed theoretically and the location and height of the hydraulic jump are determined subject to the value of the thickness at the edge of the disk, which is established first for a stationary disk based on the capillary length, and then for a rotating disks using existing analyses and measurements in spin coating.
Abstract: The free-surface flow formed by a circular jet impinging on a rotating disk is analysed theoretically. The study explores the effects of rotation and inertia on the thin-film flow. Both boundary-layer height and film thickness are found to diminish with rotation speed. A maximum film thickness develops in the supercritical region, which reflects the competition between the convective and centrifugal effects. Unlike the flow on a stationary disk, an increase in the wall shear stress along the radial direction is predicted, at a rate that strengthens with rotating speed. Our results corroborate well existing measurements. The location and height of the hydraulic jump are determined subject to the value of the thickness at the edge of the disk, which is established first for a stationary disk based on the capillary length, and then for a rotating disk using existing analyses and measurements in spin coating. The case of a stationary is revisited in an effort to predict the location and height of the jump uniquely. The formulated value of the height at the edge of the disk seems to give excellent results for a jet at moderately high flow rate (or low viscosity) where the jump structure is well identifiable in reality.

26 citations

Journal ArticleDOI
TL;DR: This article reviews experimental and modeling methods for determining the critical roles played by the various factors that control nanocarrier drug delivery to vascular endothelial cells.
Abstract: This article reviews experimental and modeling methods for determining the critical roles played by the various factors that control nanocarrier drug delivery to vascular endothelial cells.

19 citations

Journal ArticleDOI
TL;DR: In this article, a dynamic model of the atomizing disc as a spinning Kirchhoff plate is established with moving melt film treated as a moving load on the disc and as an unstable growing wave interacting with the surrounding air outside the disc.
Abstract: Spinning discs with liquid film on the surface have numerous applications in many industrial processes and have attracted a lot of investigations. Centrifugal atomization of metallic melts using a spinning disc is an efficient process for powder production and spray deposition, which is a typical example of a spinning disc interacting with a liquid film. In this paper, the vibration of an atomizing disc excited by a moving melt is analysed and the role of vibration in the disintegration of the melt film on atomizing discs is then investigated. A dynamic model of the atomizing disc as a spinning Kirchhoff plate is established with moving melt film treated as a moving load on the disc and as an unstable growing wave interacting with the surrounding air outside the disc. The powder size is analysed theoretically and then compared with experimental results. It is found that the predicted results agree with the experimental results very well in the film disintegration mode. Furthermore, the influences of the atomizer parameters on the melt break up and powder size are discussed. The control parameters in the centrifugal atomization are identified, which can provide guidance for atomizer designs.

12 citations