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A. Sameen

Bio: A. Sameen is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Reynolds number & Vortex. The author has an hindex of 12, co-authored 44 publications receiving 454 citations. Previous affiliations of A. Sameen include Indian Institute of Science & Jawaharlal Nehru Centre for Advanced Scientific Research.

Papers
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Journal ArticleDOI
01 Jun 2016
TL;DR: In this article, a hybrid finite element-finite volume method was used to solve Navier-Stokes and energy equations for flow past a heated two-dimensional cylinder in the laminar regime.
Abstract: Flow past a heated two-dimensional cylinder in the laminar regime is investigated. A hybrid finite element–finite volume method is used to solve Navier–Stokes and energy equations. The vortex shedd...

5 citations

Journal ArticleDOI
TL;DR: In this article, the combined influence of rarefaction and compressibility on classical Kelvin-Helmholtz instability is investigated with numerical simulations employing the unified gas kinetic scheme, and five different regimes in the Reynolds-Mach-Knudsen number parameter space are identified.
Abstract: The combined influence of rarefaction and compressibility on classical Kelvin-Helmholtz instability is investigated with numerical simulations employing the unified gas kinetic scheme. Five different regimes in the Reynolds-Mach-Knudsen number parameter space are identified. The flow features in various Mach and Knudsen number regimes are examined. Stabilizing action of compressibility leads to suppression of perturbation kinetic energy and vorticity and/or momentum thickness. The suppression due to rarefaction exhibits a different behavior. At high enough Knudsen numbers, even as the perturbation kinetic energy is suppressed, the vorticity and/or momentum thickness grows. The flow physics underlying the contrasting mechanisms of compressibility and rarefaction is highlighted.

4 citations

Journal ArticleDOI
TL;DR: In this article, the structure of vorticity field in compressible mixing layers is studied using direct numerical simulations of temporally evolving mixing layers, and the probability distribution of the inclination angles of the V2V vector with respect to various axes are analyzed.
Abstract: The structure of vorticity field in compressible mixing layers is studied using direct numerical simulations of temporally evolving mixing layers. The probability distribution of the inclination angles of vorticity vector with respect to various axes are analyzed. Spanwise projections of vorticity vectors have a tendency to align at angles -45lsupgol/supg and 135lsupgol/supg with respect to the streamwise direction. On streamwise and transverse planes the projected vorticity vectors tend to align at very small angles with respect to the mean vorticity vector. These distributions are uninfluenced by changes in compressibility. Orientations of vortex filaments which are dominant contributors to the vorticity covariances are also identified. These orientations are independent of the transverse location within the turbulent core. The orientations of the projections of these filaments on to different planes are found out. Compressibility has no effect on the orientation of vorticity vectors contributing most to covariances.

4 citations

Journal ArticleDOI
TL;DR: In this paper, the topology and the dynamics of Vogel-Escudier flow are investigated using a direct numerical simulation of the Navier-Stokes equations in cylindrical coordinates.
Abstract: The topology and the dynamics of Vogel–Escudier flow, which is the flow inside a circular cylinder with a top rotating lid, are presented in this paper. A three-dimensional direct numerical simulation of the Navier–Stokes equations in cylindrical coordinates is used to investigate the flow. Various combinations of Reynolds number and aspect ratio are studied and classified based on the flow topology. The flow is found to exhibit steady axisymmetric, unsteady axisymmetric, rotating azimuthal waves, and weak turbulence regimes. The perturbations found in the system are characteristically different for various flow regimes and are used for the classification of flow. The presence of several modes at high Reynolds number suggests a weak turbulence state, and a Taylor–Gortler type instability wave is found in the sidewall boundary layer.

4 citations


Cited by
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Book ChapterDOI
01 Jan 1997
TL;DR: The boundary layer equations for plane, incompressible, and steady flow are described in this paper, where the boundary layer equation for plane incompressibility is defined in terms of boundary layers.
Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

2,598 citations

Journal ArticleDOI
TL;DR: Key emphasis is given to the physics and structure of the thermal and velocity boundary layers which play a key role for the better understanding of the turbulent transport of heat and momentum in convection at high and very high Rayleigh numbers.
Abstract: Recent experimental, numerical and theoretical advances in turbulent Rayleigh-Benard convection are presented. Particular emphasis is given to the physics and structure of the thermal and velocity boundary layers which play a key role for the better understanding of the turbulent transport of heat and momentum in convection at high and very high Rayleigh numbers. We also discuss important extensions of Rayleigh-Benard convection such as non-Oberbeck-Boussinesq effects and convection with phase changes.

630 citations

Journal ArticleDOI
TL;DR: A review of linear instability analysis of flows over or through complex 2D and 3D geometries is presented in this article, where the authors make a conscious effort to demystify both the tools currently utilized and the jargon employed to describe them, demonstrating the simplicity of the analysis.
Abstract: This article reviews linear instability analysis of flows over or through complex two-dimensional (2D) and 3D geometries. In the three decades since it first appeared in the literature, global instability analysis, based on the solution of the multidimensional eigenvalue and/or initial value problem, is continuously broadening both in scope and in depth. To date it has dealt successfully with a wide range of applications arising in aerospace engineering, physiological flows, food processing, and nuclear-reactor safety. In recent years, nonmodal analysis has complemented the more traditional modal approach and increased knowledge of flow instability physics. Recent highlights delivered by the application of either modal or nonmodal global analysis are briefly discussed. A conscious effort is made to demystify both the tools currently utilized and the jargon employed to describe them, demonstrating the simplicity of the analysis. Hopefully this will provide new impulses for the creation of next-generation algorithms capable of coping with the main open research areas in which step-change progress can be expected by the application of the theory: instability analysis of fully inhomogeneous, 3D flows and control thereof.

599 citations

Journal ArticleDOI
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.

231 citations