The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Javier A. Diez - One of the best experts on this subject based on the ideXlab platform.
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Laplace Pressure-Driven Drop Spreading: Quasi-Self-Similar Solution
Journal of Colloid and Interface Science, 1994Co-Authors: Javier A. Diez, Roberto Gratton, L. P. Thomas, B. M. MarinoAbstract:Abstract We present a hydrodynamic calculation of the spreading of viscous droplets on a smooth rigid horizontal surface, under the condition of complete wetting (spreading parameter S > 0) with the Laplace pressure as the dominant force. The starting point is a Self-Similar Solution reported elsewhere which is modified by the introduction of a very simple boundary condition at the current front, namely a fixed cutoff thickness hc. As the introduction of this new parameter breaks up Self-Similarity, we obtain the complete Solution by pasting successive Self-Similar Solutions, each one corresponding to slightly different ratios hc /h0, where h0 is the thickness at the center of the drop. The results are in excellent agreement with our own and other authors' experimental data, showing that this heuristic model gives the right correction to the original theory.
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self similar Solution of the second kind for a convergent viscous gravity current
Physics of Fluids, 1992Co-Authors: Javier A. Diez, R Gratton, Julio GrattonAbstract:The axisymmetric flow of a very viscous fluid toward a central orifice is studied. In a recent paper, a self‐similar Solution for this problem has been found. The self‐similarity is of the second kind and hence the flow remembers its initial condition only through a nondimensional constant which characterizes it. In this work this convergent flow is studied experimentally (using silicone oils) by measuring the front position and the height profile as a function of time. It is verified that the self‐similar Solution properly describes the flow within a certain interval of the cavity radius, where values are obtained for the similarity exponent δ in agreement (accounting for experimental errors) with the theoretical value 0.762... . The transition to the self‐similar flow is also simulated numerically and numerical values are obtained for the time closure for different initial conditions. These simulations also show the theoretical self‐similar flow after the cavity closure, which is very difficult to observe experimentally.
G X Wu - One of the best experts on this subject based on the ideXlab platform.
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self similar Solution for oblique impact of a water column with sharp front on a wall and its zero inner angle steady limit
Physics of Fluids, 2014Co-Authors: G X WuAbstract:The hydrodynamic problem of a three-dimensional (3D) water column impacting on a solid wall is investigated. The focus is on cases of Self-Similar flow and its related implications in physics. It is demonstrated that limiting process of the Self-Similar flow can become the steady flow. The problem involves a free surface whose shape is unknown and on which the boundary conditions are nonlinear. It is solved through boundary element method (BEM) with quadrilateral elements within an iterative procedure. The application of the BEM to such a problem has some major challenges. During the process, mesh used in the BEM is regularly regenerated to follow the deformation of the free surface and the data in the old mesh are transferred to the new one. Coordinate rotation technique is used to resolve the difficulties caused by the multi-valued free surface, together with the technique for the thin liquid film over the wall surface. Results are provided for the free surface shapes and pressure distributions for perp...
Ramesh Narayan - One of the best experts on this subject based on the ideXlab platform.
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Self-Similar hot accretion on to a spinning neutron star: matching the outer boundary conditions
Monthly Notices of the Royal Astronomical Society, 2003Co-Authors: Ramesh Narayan, Mikhail V MedvedevAbstract:Medvedev & Narayan have described a hot accretion flow on to a spinning neutron star in which the gas viscously brakes the spin of the star. Their Self-Similar Solution has the surprising property that the density, temperature and angular velocity of the gas at any radius are completely independent of the outer boundary conditions. Hence, the Solution cannot be matched to a general external medium. We resolve this paradoxical situation by showing that there is a second Self-Similar Solution which bridges the gap between the original Solution and the external medium. This new Solution has an extra degree of freedom which permits it to match general outer boundary conditions. We confirm the main features of the analytical results with a full numerical Solution.
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self similar hot accretion onto a spinning neutron star matching the outer boundary conditions
arXiv: Astrophysics, 2003Co-Authors: Ramesh Narayan, Mikhail V MedvedevAbstract:Medvedev & Narayan have described a hot accretion flow onto a spinning neutron star in which the gas viscously brakes the spin of the star. Their Self-Similar Solution has the surprising property that the density, temperature and angular velocity of the gas at any radius are completely independent of the outer boundary conditions. Hence, the Solution cannot be matched to a general external medium. We resolve this paradoxical situation by showing that there is a second Self-Similar Solution which bridges the gap between the original Solution and the external medium. This new Solution has an extra degree of freedom which permits it to match general outer boundary conditions. We confirm the main features of the analytical results with a full numerical Solution.
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advection dominated accretion a self similar Solution
The Astrophysical Journal, 1994Co-Authors: Ramesh Narayan, Insu YiAbstract:We consider viscous rotating accretion flows in which most of the viscously dissipated energy is stored as entropy rather than being radiated. Such advection-dominated flows may occur when the optical depth is either very small or very large. We obtain a family of Self-Similar Solutions where the temperature of the accreting gas is nearly virial and the flow is quasi-spherical. The gas rotates at much less than the Keplerian angular velocity; therefore, the central stars in such flows will cease to spin up long before they reach the break-up limit. Further, the Bernoulli parameter is positive, implying that advection-dominated flows are susceptible to producing outflows. Convection is likely in many of these flows and, if present, will tend to enhance the above effects. We suggest that advection-dominated accretion may provide an explanation for the slow spin rates of accreting stars and the widespread occurrence of outflows and jets in accreting systems.
F M Kuni - One of the best experts on this subject based on the ideXlab platform.
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self similar Solution of a nonsteady problem of nonisothermal vapor condensation on a droplet growing in a diffusion regime
Journal of Physical Chemistry C, 2008Co-Authors: A P Grinin, Yu G Gor, F M KuniAbstract:This paper presents a mathematically exact Self-Similar Solution to the joint nonsteady problems of vapor diffusion toward a droplet growing in a vapor−gas medium and of removal of heat released by a droplet into a vapor−gas medium during vapor condensation. An equation for the temperature of the droplet is obtained, and it is only at that temperature that the Self-Similar Solution exists. This equation requires the constancy of the droplet temperature and even defines it unambiguously throughout the whole period of the droplet growth. In the case of a strong display of heat effects, when the droplet growth rate decreases significantly, the equation for the temperature of the droplet is solved analytically. It is shown that the obtained temperature fully coincides with the one that settles in the droplet simultaneously with the settlement of its diffusion regime of growth. At the obtained temperature of the droplet, the interrelated nonsteady vapor concentration and temperature profiles of the vapor−gas m...
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self similar Solution of a nonsteady problem of nonisothermal vapour condensation on a droplet growing in diffusion regime
arXiv: Statistical Mechanics, 2008Co-Authors: A P Grinin, Yu G Gor, F M KuniAbstract:This paper presents a mathematically exact Self-Similar Solution to the joint nonsteady problems of vapour diffusion towards a droplet growing in a vapour-gas medium and of removal of heat released by a droplet into a vapour-gas medium during vapour condensation. An equation for the temperature of the droplet is obtained; and it is only at that temperature that the Self-Similar Solution exists. This equation requires the constancy of the droplet temperature and even defines it unambiguously throughout the whole period of the droplet growth. In the case of strong display of heat effects, when the droplet growth rate decreases significantly, the equation for the temperature of the droplet is solved analytically. It is shown that the obtained temperature fully coincides with the one that settles in the droplet simultaneously with the settlement of its diffusion regime of growth. At the obtained temperature of the droplet the interrelated nonsteady vapour concentration and temperature profiles of the vapour-gas medium around the droplet are expressed in terms of initial (prior to the nucleation of the droplet) parameters of the vapour-gas medium. The same parameters are used to formulate the law in accordance with which the droplet is growing in diffusion regime, and also to define the time that passes after the nucleation of the droplet till the settlement of diffusion regime of droplet growth, when the squared radius of the droplet becomes proportionate to time. For the sake of completeness the case of weak display of heat effects is been studied.
Julio Gratton - One of the best experts on this subject based on the ideXlab platform.
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self similar Solution of the second kind for a convergent viscous gravity current
Physics of Fluids, 1992Co-Authors: Javier A. Diez, R Gratton, Julio GrattonAbstract:The axisymmetric flow of a very viscous fluid toward a central orifice is studied. In a recent paper, a self‐similar Solution for this problem has been found. The self‐similarity is of the second kind and hence the flow remembers its initial condition only through a nondimensional constant which characterizes it. In this work this convergent flow is studied experimentally (using silicone oils) by measuring the front position and the height profile as a function of time. It is verified that the self‐similar Solution properly describes the flow within a certain interval of the cavity radius, where values are obtained for the similarity exponent δ in agreement (accounting for experimental errors) with the theoretical value 0.762... . The transition to the self‐similar flow is also simulated numerically and numerical values are obtained for the time closure for different initial conditions. These simulations also show the theoretical self‐similar flow after the cavity closure, which is very difficult to observe experimentally.
