The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Yumino Hayase - One of the best experts on this subject based on the ideXlab platform.
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response to comment on surface switching of Rotating Fluid in a cylinder phys Fluids 19 069101 2007
Physics of Fluids, 2007Co-Authors: Toshiyuki Suzuki, Makoto Iima, Yumino HayaseAbstract:In our Letter [T. Suzuki, M. Iima, and Y. Hayase, “Surface switching of Rotating Fluid in a cylinder,” Phys. Fluids 18, 101701 (2006)], we reported a surface switching phenomenon of Fluid in a cylinder driven by the endwall rotation. In the Comment by Vatistas [G. Vatistas, “Comment on ‘Surface switching of Rotating Fluid in a cylinder',” Phys. Fluids 19, 069101 (2007)], the author claims that a periodic sloshing phenomenon reported by Vatistas in 1990 is the same phenomenon as the surface switching. We clarify the difference between these phenomena in terms of the parameters, the phenomena, the boundary condition, and the physical mechanism.
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surface switching of Rotating Fluid in a cylinder
Physics of Fluids, 2006Co-Authors: Toshiyuki Suzuki, Makoto Iima, Yumino HayaseAbstract:We study the surface shape of water in an open cylinder driven by constant rotation of the bottom. Around the critical Reynolds number for the laminar-turbulent transition, the surface deformation, which is of the order of the container size, shows an aperiodic switching phenomenon between an axisymmetric shape and a nonaxisymmetric shape. The axisymmetric shape is observed as a steady state when the Reynolds number is smaller than that in the switching region, while the nonaxisymmetric shape is observed as a (quasi-) periodic state in which the surface rotates at almost constant angular velocity when the Reynolds number is larger than that in the switching region. A detailed analysis for the surface shape suggests that the flow with the nonaxisymmetric shape is turbulent.
Keke Zhang - One of the best experts on this subject based on the ideXlab platform.
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on the gravitational fields of maclaurin spheroid models of Rotating Fluid planets
The Astrophysical Journal, 2013Co-Authors: Dali Kong, Keke Zhang, Gerald SchubertAbstract:Hubbard recently derived an important iterative equation for calculating the gravitational coefficients of a Maclaurin spheroid that does not require an expansion in a small distortion parameter. We show that this iterative equation, which is based on an incomplete solution of the Poisson equation, diverges when the distortion parameter is not sufficiently small. We derive a new iterative equation that is based on a complete solution of the Poisson equation and, hence, always converges when calculating the gravitational coefficients of a Maclaurin spheroid.
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asymptotic solutions of differential rotation driven by convection in rapidly Rotating Fluid spheres with the non slip boundary condition
Geophysical and Astrophysical Fluid Dynamics, 2012Co-Authors: Xinhao Liao, Keke ZhangAbstract:A strong Coriolis force in a rapidly Rotating planet and star not only enforces two-dimensionality of Fluid motion driven by thermal instabilities but also generates strong differential rotation even in the vicinity of the onset of instabilities. We derive an asymptotic solution describing convection-driven differential rotation in Rotating, self-gravitating Boussinesq Fluid spheres with the no-slip boundary condition, taking into account full spherical curvature and being valid for asymptotically small Ekman numbers. For the purpose of validating the asymptotic solution, the corresponding numerical analysis valid for large or small Ekman numbers is also carried out, showing a satisfactory agreement between the asymptotic and numerical solutions.
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a new legendre type polynomial and its application to geostrophic flow in Rotating Fluid spheres
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2010Co-Authors: Xinhao Liao, Keke ZhangAbstract:In rapidly Rotating spheres, the whole Fluid column, extending from the southern to northern spherical boundary along the rotation axis, moves like a single Fluid element, which is usually referred to as geostrophic flow. A new Legendre-type polynomial is discovered in undertaking the asymptotic analysis of geostrophic flow in spherical geometry. Three essential properties characterize the new polynomial: (i) it is a function of r and theta but takes a single argument (r sin theta), which is restricted by 0 <= r <= 1 and 0 <= theta = pi, where (r, theta, phi) denote spherical polar coordinates with theta = 0 at the rotation axis; (ii) it is odd and vanishes at the axis of rotation theta = 0, and (iii) it is defined within-and orthogonal over-the full sphere. As an example of its application, we employ the new polynomial in the asymptotic analysis of forced geostrophic flows in Rotating Fluid spheres for small Ekman and Rossby numbers. Fully numerical analysis of the same problem is also carried out, showing satisfactory agreement between the asymptotic solution and the numerical solution.
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asymptotic and numerical solutions of the initial value problem in Rotating planetary Fluid cores
Geophysical Journal International, 2010Co-Authors: Xinhao Liao, Keke ZhangAbstract:P>An initial state of Fluid motion in planetary cores or atmospheres, excited, for example, by the giant impact of an asteroid or an earthquake and then damped by viscous dissipation, decays towards the state of rigid-body rotation. The process of how the initial state approaches the final state, the initial value problem, is investigated both analytically and numerically for Rotating Fluid spheres. We derive an explicit asymptotic expression for the time-dependent solution of the initial value problem valid for an asymptotically small Ekman number E. We also perform a fully numerical analysis to simulate time-dependent solutions of the initial value problem for a small value of E. Comparison between the asymptotic solution and the corresponding numerical simulation shows a satisfactory quantitative agreement. For the purpose of illustrating why spherical geometry represents an intricate and exceptional case, we also briefly discuss the initial value problem in a Rotating Fluid channel. Geophysical and planetary physical implications of the result are also discussed.
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on viscous decay factors for spherical inertial modes in Rotating planetary Fluid cores comparison between asymptotic and numerical analysis
Physics of the Earth and Planetary Interiors, 2008Co-Authors: Xinhao Liao, Keke ZhangAbstract:The initial value problem of how an initial state of Fluid motion, excited by earthquake or tide and then damped by viscous dissipation, decays toward the state of rigid-body rotation is considered for rapidly Rotating Fluid spheres like planetary Fluid cores. An essential element in an asymptotic time-dependent solution for the initial value problem is the viscous decay factors for spherical inertial modes. We derive an analytical expression for the viscous decay factors valid for a broad range of the inertial modes that are required for an asymptotic solution of the initial value problem at an arbitrarily small but fixed Ekman number. We also perform fully numerical analysis to compute the viscous decay factors for several selected inertial modes, showing a quantitative agreement between the asymptotic and numerical analysis. It is argued that the correct viscous decay factors cannot be derived using an asymptotic expansion based on the half powers of a small Ekman number. (C) 2008 Elsevier B.V. All rights reserved.
Toshiyuki Suzuki - One of the best experts on this subject based on the ideXlab platform.
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response to comment on surface switching of Rotating Fluid in a cylinder phys Fluids 19 069101 2007
Physics of Fluids, 2007Co-Authors: Toshiyuki Suzuki, Makoto Iima, Yumino HayaseAbstract:In our Letter [T. Suzuki, M. Iima, and Y. Hayase, “Surface switching of Rotating Fluid in a cylinder,” Phys. Fluids 18, 101701 (2006)], we reported a surface switching phenomenon of Fluid in a cylinder driven by the endwall rotation. In the Comment by Vatistas [G. Vatistas, “Comment on ‘Surface switching of Rotating Fluid in a cylinder',” Phys. Fluids 19, 069101 (2007)], the author claims that a periodic sloshing phenomenon reported by Vatistas in 1990 is the same phenomenon as the surface switching. We clarify the difference between these phenomena in terms of the parameters, the phenomena, the boundary condition, and the physical mechanism.
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surface switching of Rotating Fluid in a cylinder
Physics of Fluids, 2006Co-Authors: Toshiyuki Suzuki, Makoto Iima, Yumino HayaseAbstract:We study the surface shape of water in an open cylinder driven by constant rotation of the bottom. Around the critical Reynolds number for the laminar-turbulent transition, the surface deformation, which is of the order of the container size, shows an aperiodic switching phenomenon between an axisymmetric shape and a nonaxisymmetric shape. The axisymmetric shape is observed as a steady state when the Reynolds number is smaller than that in the switching region, while the nonaxisymmetric shape is observed as a (quasi-) periodic state in which the surface rotates at almost constant angular velocity when the Reynolds number is larger than that in the switching region. A detailed analysis for the surface shape suggests that the flow with the nonaxisymmetric shape is turbulent.
Gordon I Ogilvie - One of the best experts on this subject based on the ideXlab platform.
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tidal dissipation in Rotating Fluid bodies the presence of a magnetic field
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Yufeng Lin, Gordon I OgilvieAbstract:We investigate effects of the presence of a magnetic field on tidal dissipation in Rotating Fluid bodies. We consider a simplified model consisting of a rigid core and a Fluid envelope, permeated by a background magnetic field (either a dipolar field or a uniform axial field). The wavelike tidal responses in the Fluid layer are in the form of magnetic-Coriolis waves, which are restored by both the Coriolis force and the Lorentz force. Energy dissipation occurs through viscous damping and Ohmic damping of these waves. Our numerical results show that the tidal dissipation can be dominated by Ohmic damping even with a weak magnetic field. The presence of a magnetic field smooths out the complicated frequency-dependence of the dissipation rate, and broadens the frequency spectrum of the dissipation rate, depending on the strength of the background magnetic field. However, the frequency-averaged dissipation is independent of the strength and structure of the magnetic field, and of the dissipative parameters, in the approximation that the wave-like response is driven only by the Coriolis force acting on the non-wavelike tidal flow. Indeed, the frequency-averaged dissipation quantity is in good agreement with previous analytical results in the absence of magnetic fields. Our results suggest that the frequency-averaged tidal dissipation of the wavelike perturbations is insensitive to detailed damping mechanisms and dissipative properties.
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non linear evolution of tidally forced inertial waves in Rotating Fluid bodies
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: Adrian J Barker, Benjamin Favier, C Baruteau, Gordon I OgilvieAbstract:We perform one of the first studies into the nonlinear evolution of tidally excited inertial waves in a uniformly Rotating Fluid body, exploring a simplified model of the Fluid envelope of a planet (or the convective envelope of a solar-type star) subject to the gravitational tidal perturbations of an orbiting companion. Our model contains a perfectly rigid spherical core, which is surrounded by an envelope of incompressible uniform density Fluid. The corresponding linear problem was studied in previous papers which this work extends into the nonlinear regime, at moderate Ekman numbers (the ratio of viscous to Coriolis accelerations). By performing high-resolution numerical simulations, using a combination of pseudo-spectral and spectral element methods, we investigate the effects of nonlinearities, which lead to time-dependence of the flow and the corresponding dissipation rate. Angular momentum is deposited non-uniformly, leading to the generation of significant differential rotation in the initially uniformly Rotating Fluid, i.e. the body does not evolve towards synchronism as a simple solid body rotator. This differential rotation modifies the properties of tidally excited inertial waves, changes the dissipative properties of the flow, and eventually becomes unstable to a secondary shear instability provided that the Ekman number is sufficiently small. Our main result is that the inclusion of nonlinearities eventually modifies the flow and the resulting dissipation from what linear calculations would predict, which has important implications for tidal dissipation in Fluid bodies. We finally discuss some limitations of our simplified model, and propose avenues for future research to better understand the tidal evolution of Rotating planets and stars. ; Comment: 17 pages, 17 figures, accepted for publication in MNRAS
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tidal dissipation in Rotating Fluid bodies a simplified model
arXiv: Earth and Planetary Astrophysics, 2009Co-Authors: Gordon I OgilvieAbstract:We study the tidal forcing, propagation and dissipation of linear inertial waves in a Rotating Fluid body. The intentionally simplified model involves a perfectly rigid core surrounded by a deep ocean consisting of a homogeneous incompressible Fluid. Centrifugal effects are neglected, but the Coriolis force is considered in full, and dissipation occurs through viscous or frictional forces. The dissipation rate exhibits a complicated dependence on the tidal frequency and generally increases with the size of the core. In certain intervals of frequency, efficient dissipation is found to occur even for very small values of the coefficient of viscosity or friction. We discuss the results with reference to wave attractors, critical latitudes and other features of the propagation of inertial waves within the Fluid, and comment on their relevance for tidal dissipation in planets and stars.
Makoto Iima - One of the best experts on this subject based on the ideXlab platform.
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response to comment on surface switching of Rotating Fluid in a cylinder phys Fluids 19 069101 2007
Physics of Fluids, 2007Co-Authors: Toshiyuki Suzuki, Makoto Iima, Yumino HayaseAbstract:In our Letter [T. Suzuki, M. Iima, and Y. Hayase, “Surface switching of Rotating Fluid in a cylinder,” Phys. Fluids 18, 101701 (2006)], we reported a surface switching phenomenon of Fluid in a cylinder driven by the endwall rotation. In the Comment by Vatistas [G. Vatistas, “Comment on ‘Surface switching of Rotating Fluid in a cylinder',” Phys. Fluids 19, 069101 (2007)], the author claims that a periodic sloshing phenomenon reported by Vatistas in 1990 is the same phenomenon as the surface switching. We clarify the difference between these phenomena in terms of the parameters, the phenomena, the boundary condition, and the physical mechanism.
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surface switching of Rotating Fluid in a cylinder
Physics of Fluids, 2006Co-Authors: Toshiyuki Suzuki, Makoto Iima, Yumino HayaseAbstract:We study the surface shape of water in an open cylinder driven by constant rotation of the bottom. Around the critical Reynolds number for the laminar-turbulent transition, the surface deformation, which is of the order of the container size, shows an aperiodic switching phenomenon between an axisymmetric shape and a nonaxisymmetric shape. The axisymmetric shape is observed as a steady state when the Reynolds number is smaller than that in the switching region, while the nonaxisymmetric shape is observed as a (quasi-) periodic state in which the surface rotates at almost constant angular velocity when the Reynolds number is larger than that in the switching region. A detailed analysis for the surface shape suggests that the flow with the nonaxisymmetric shape is turbulent.
