Archivo Digital UPM: No conditions. Results ordered -Date Deposited. 2022-01-26T23:58:38ZEPrintshttps://oa.upm.es/style/images/logo-archivo-digital.pnghttps://oa.upm.es/2012-10-03T10:15:35Z2014-09-22T10:51:40Zhttps://oa.upm.es/id/eprint/11753This item is in the repository with the URL: https://oa.upm.es/id/eprint/117532012-10-03T10:15:35ZNumerical simulation of the evolution of viscous rotating dropsIn this contribution we simulate numerically the evolution of a viscous fluid drop rotating about a fixed axis at constant angular velocity ? or constant angular momentum L, surrounded by another viscous fluid. The problem is considered in the limit of large Ekman number and small Reynolds number. In the lecture we will describe the numerical method we have used to solve the PDE system that describes the evolution of the drop (3D boundary element method). We will also present the results we have obtained, paying special attention to the stability/instability of the equilibrium shapes.Marco Antonio FontelosVíctor García GarridoUltano Kindelan Bustelo2011-08-01T08:42:39Z2014-09-29T18:13:27Zhttps://oa.upm.es/id/eprint/8646This item is in the repository with the URL: https://oa.upm.es/id/eprint/86462011-08-01T08:42:39ZADER schemes for linear advection - diffusion problems with nonlinear source term using several flux reconstructionsThe aim of this work is to compare the behaviour of the use of different flux reconstruction techniques when solving advection-diffusion problems with nonlinear source terms in fully saturated porous media. High order schemes are
developed within the finite volume ADER framework (see for example [4]) to-gether with a suitable spatial reconstruction method. For the sake of efficiency,
advective and diffusive part are decoupled, using a different reconstruction technique for each case.
The advective part is solved by means of WENO spatial reconstruction (see for example [1]) together with different intercell numerical fluxes such as GFORCE, FORCE, WAF with a limiter function [2] and Rusanov ones. On
the other hand, the diffusive part and the nonlinear source term are solved using conservative centred spatial reconstruction, with a sixth degree polynomial.
In order to get the intercell flux reconstruction for the diffusive part, a simple
arithmetic mean of right and left fluxes is used. Nevertheless, to solve the source term is involved a Gaussian quadrature.
A comparison of the use of different numerical fluxes for several selected test cases - which involve advective, diffusive and nonlinear source term - is shown.
In order to test its accuracy a convergence rates study has been carried out, considering smooth initial solutions, getting up to sixth order of accuracy.
Finally, other results have been obtained for problems involving non-smooth
solutions, such as sharp advancing fronts (see reference [1, 3]). Although, as expected, accuracy orders are not fulfilled due to the sharp gradients, the error norms are quite small. For these problems, it is analyzed and compared the behavior of the different intercell flux reconstructions considered in this work.
Especially good results are achieved for the second order TVD WAF scheme with limiter function.
Ricardo Castedo Ruizricardo.castedo@upm.esArturo Hidalgo Lópezarturo.hidalgo@upm.es2011-08-01T08:20:54Z2014-09-29T18:13:48Zhttps://oa.upm.es/id/eprint/8655This item is in the repository with the URL: https://oa.upm.es/id/eprint/86552011-08-01T08:20:54ZEsquemas WENO de alto orden en volúmenes finitos
aplicados a problemas de convección-reacción-difusión.En este artículo se trata de construir esquemas numéricos de orden arbitrario
para la resolución de problemas que involucren mecanismos de convección-reacción-difusión
en 1D. En los esquemas numéricos utilizados, se ha empleado para la reconstrucción temporal el método ADER, que constituye una reciente aproximación para
la reconstrucción de alto orden de esquemas en volúmenes finitos (ver [5]).
Por otro lado, para la reconstrucción espacial de los polinomios de orden arbitrario,
utilizaremos el método WENO [3]. En lo que se refiere a la obtención de flujos en las
interfases entre volúmenes, en esta comunicación se utilizan diversas formas de obtener
el flujo convectivo, como son G-FORCE [2, 3], RUSANOV [1], WAF-TVD (ver por
ejemplo [2, 3]); y el difusivo, con una media aritmética de los flujos a izquierda y
derecha de cada interfase (ver [4]). Además se comparan sus comportamientos en
algunos casos test
Ricardo Castedo Ruizricardo.castedo@upm.esArturo Hidalgo Lópezarturo.hidalgo@upm.es2011-06-22T10:46:43Z2016-04-20T16:40:09Zhttps://oa.upm.es/id/eprint/7548This item is in the repository with the URL: https://oa.upm.es/id/eprint/75482011-06-22T10:46:43ZNumerical simulation of the shape of charged drops over a solid surface.In this work we study the static shape of charged drops of a conducting fluid placed over a solid substrate, surrounded by a gas, and in absence of gravitational forces. The problem can be posed, since Gauss, in a variational setting consisting of obtaining the configurations of a given mass of fluid that minimize (or in general make extremal) a certain energy involving the areas of the solid-liquid interface and of the liquid-gas interface, as well as the electric capacity of the drop. In [6] we have found, as a function of two parameters, Young's angle θY and the potential at the drop's surface V0, the axisymmetric minimizers of the energy. In the same article we have also described their shape and showed the existence of symmetry-breaking bifurcations such that, for given values of θY and V0, configurations for which the axial symmetry is lost are energetically more favorable than axially symmetric configurations. We have proved the existence of such bifurcations in the limits of very flat and almost spherical equilibrium shapes. In this work we study all other cases numerically. When dealing with radially perturbed equilibrium shapes we lose the axially symmetric properties and need to do a full three-dimensional approximation in order to compute area and capacity and hence the energy. We use a boundary element method that we have already implemented in [3] to compute the surface charge density. From the surface charge density we can obtain the capacity of the body. One conclusion of this study is that axisymmetric drops cannot spread indefinitely by introducing sufficient amount of electric charges, but can reach only a limiting (saturation) size, after which the axial symmetry would be lost and finger-like shapes energetically preferredMarco Antonio FontelosUltano Kindelan Bustelo2011-01-19T09:53:05Z2016-04-20T14:28:21Zhttps://oa.upm.es/id/eprint/5741This item is in the repository with the URL: https://oa.upm.es/id/eprint/57412011-01-19T09:53:05ZMathematical description of the hydrodynamic regimes of an asymptotic model for two-phase flow arising in PFBC boilers.Two-phase systems where a dense phase of small particles is fluidized with a gas flow appear in many industrial applications, among which the fluidized bed combustors are probably the most important. A homogenization technique allows us to formulate the mathematical model in form of the compressible Navier-Stokes system type with some particularities: 1) the volumetric fraction of the dense phase (analogous to the density in the Navier-Stokes equations) may vanish, 2) the constitutive viscosity law may depend in a nonlinear form on this density, 3) the source term is nonlinear and coupled with state equations involving drag forces and hydrodynamic pressure, and 4) the state equation for the collision pressure of dense phase blows up for finite values of the density. We develop a rigorous theory for a special kind of solutions we call stationary clouds. Such solutions exist only under restrictions on the geometry of combustor and on the boundary conditions that usually meet in engineering applications. In return, these solutions have a stationary one-dimensional structure very simple and, from them, it is possible to reconstruct much of the dynamics of the whole system, responding to most of the practical issues of interest. Finally, we study the linear stability for the trivial solutions corresponding to uniform fluidized states injecting plane wave perturbations in our equations. Depending on the parameters of the equations of state describing the collisions between solid particles, hydrodynamic pressure, and the values of blowing boundary condition, we can draw detailed abacus separating stable regions of unstable regions where bubbles appear. Then, we use the dispersion relations of this multidimensional linearized model, combined with the stationary phase theorem, to approach the profiles and the evolution of the bubbles appearing in unstable regimes, and verify that the obtained results adjust to the observations.Santiago de Vicente CuencaGonzalo GalianoJulián VelascoJose Miguel Arostegui2010-08-04T06:56:16Z2016-04-20T13:21:33Zhttps://oa.upm.es/id/eprint/3950This item is in the repository with the URL: https://oa.upm.es/id/eprint/39502010-08-04T06:56:16ZFractales en las WEBS de Redes SocialesMediante esta exposición se pretende presentar que el comportamiento de los perfiles de los individuos de una red social pudiera seguir un comportamiento de tipo fractal.Jesús Pedro de Vicente Buenojesuspedrodevicente@hotmail.com2010-05-24T11:26:22Z2016-04-20T12:40:12Zhttps://oa.upm.es/id/eprint/3113This item is in the repository with the URL: https://oa.upm.es/id/eprint/31132010-05-24T11:26:22ZEvolution of neutral and charged drops in an electric fieldWe study the evolution of drops of a very viscous and conducting fluid under the influence of an external electric field. The drops may be neutral or may be charged with some amount of electric charge. If both the external electric field and total drop charge are sufficiently small, then prolate spherical shapes develop according to Taylor’s observations. For sufficiently large charge and/or external field a selfsimilar cone-like singularity develops in a mechanism different from Taylor’s prediction. The opening semiangle of the cones both for uncharged and charged drops in a constant electric field is typically around 300.Marco Antonio FontelosUltano Kindelan Bustelo