Browsing by Author "Sánchez Umbría, Juan"

A comparison of highorder time integrators for highly supercritical thermal convection in rotating spherical shells
Garcia Gonzalez, Ferran; Net Marcé, Marta; Sánchez Umbría, Juan (20140110)
Article
Restricted access  publisher's policyThe efficiency of implicit and semiimplicit time integration codes based on backward differentiation and extrapolation formulas for the solution of the threedimensional Boussinesq thermal convection equations in rotating ... 
A comparison of highorder time integrators for thermal convection in rotating spherical shells
García González, Fernando; Net Marcé, Marta; GarciaArchilla, Bosco; Sánchez Umbría, Juan (20101001)
Article
Open AccessA numerical study of several time integration methods for solving the threedimensional Boussinesq thermal convection equations in rotating spherical shells is presented. Implicit and semiimplicit time integration ... 
Antisymmetric polar modes of thermal convection in rotating spherical fluid shells at high Taylor numbers
García González, Fernando; Net Marcé, Marta; Sánchez Umbría, Juan (20081103)
Article
Open AccessThe onset of thermal convection in a rotating spherical shell of intermediate radius ratio ¼ 0:4 is studied numerically for Taylor numbers Ta 1011 and the Prandtl number of the liquid sodium ( ¼ 0:01). For the first ... 
A parallel algorithm for the computation of invariant tori in largescale dissipative systems
Sánchez Umbría, Juan; Net Marcé, Marta (201306)
Article
Restricted access  publisher's policyA parallelizable algorithm to compute invariant tori of highdimensional dissipative systems, obtained upon discretization of PDEs is presented. The size of the set of equations to be solved is only a small multiple of the ... 
Computation of azimuthal waves and their stability in thermal convection in rotating spherical shells with application to the study of a doubleHopf bifurcation
Sánchez Umbría, Juan; García González, Fernando; Net Marcé, Marta (20130322)
Article
Open AccessA methodology to compute azimuthal waves, appearing in thermal convection of a pure fluid contained in a rotating spherical shell, and to study their stability is presented. It is based on continuation, NewtonKrylov, and ... 
Continuation and stability of convective modulated rotating waves in spherical shells
García González, Fernando; Net Marcé, Marta; Sánchez Umbría, Juan (20160101)
Article
Open AccessModulated rotating waves (MRW), bifurcated from the thermalRossby waves that arise at the onset of convection of a fluid contained in a rotating spherical shell, and their stability, are studied. For this purpose, ... 
Continuation of bifurcations of cycles in dissipative PDEs
Sánchez Umbría, Juan; Net Marcé, Marta (2015)
Conference report
Open AccessA new efficient methodology for the continuation of the codimensionone bifurcations of periodic orbits, including pitchfork bifurcations present in reflectionsymmetric systems, has been developed. It is based on the ... 
Continuation of bifurcations of periodic orbits for largescale systems
Net Marcé, Marta; Sánchez Umbría, Juan (20150101)
Article
Open AccessA methodology to track bifurcations of periodic orbits in largescale dissipative systems depending on two parameters is presented. It is based on the application of iterative NewtonKrylov techniques to extended systems. ... 
Critical torsional modes of convection in rotating fluid spheres at high Taylor numbers
Sánchez Umbría, Juan; García González, Fernando; Net Marcé, Marta (20160215)
Article
Open AccessA numerical study of the onset of convection in rotating internally heated selfgravitating fluid spheres is presented. The exploration of the stability of the conduction state versus the Taylor and Prandtl numbers supplies ... 
Estudio comparativo de la eficiencia de diversos integradores para la simulación numérica de la convección térmica en geometría esférica y rotación
García González, Fernando; Net Marcé, Marta; GarciaArchilla, Bosco; Sánchez Umbría, Juan (2010)
Conference report
Open AccessThe efficiency of implicit and semiimplicit time integration codes based on bac kward differentiation and extrapolation formulae for the solution of the threedimensio nal Boussinesq thermal convection equations in ... 
Exponential versus IMEX highorder time integrators for thermal convection in rotating spherical shells
Garcia Gonzalez, Ferran; Bonaventura, Luca; Net Marcé, Marta; Sánchez Umbría, Juan (20140124)
Article
Open AccessWe assess the accuracy and efficiency of several exponential time integration methods coupled to a spectral discretization of the threedimensional Boussinesq thermal convection equations in rotating spherical shells. ... 
Filtrado transversal adaptativo de varianza constante para la ecualización de canal
Vázquez Grau, Gregorio; Gasull Llampallas, Antoni; Sánchez Umbría, Juan; Oliveras Vergés, Albert (1989)
Conference report
Open AccessThis paper describes the problem of lineal filtering of noisy data under a Maximum Likelihood objective. In this sense, the paper shows that a weighted square error cost function deals and it is necessary to weight the ... 
Mathematical modeling of different molecule removal on online haemodiafiltration. Influence of dialysis duration and infusion flow
Maduell, Francesc; Sánchez Umbría, Juan; Net Marcé, Marta; Gómez, Miquel; González, Josep Maria; Arias, Marta; Rodriguez, Nestor; Rico, N.; Campistol, Josep (20150201)
Article
Restricted access  publisher's policyBackground: In a previous study on a nocturnal, everyotherday online haemodiafiltration scheme, different removal patterns were observed for urea, creatinine, ß2¿microglobulin, myoglobin and prolactin. The aim of this ... 
Numerical bifurcation methods and their application to fluid dynamics: analysis beyond simulation
Dijkstra, Hendrik; Wubs, Fred W.; Cliffe, Andrew K.; Doedel, Eusebius J.; Dragomirescu, Ioana Florica; Eckhardt, Bruno; Gelfgat, Alexander Yu; Hazel, Andrew L.; Lucarini, Valerio; Salinger, Andrew G.; Phipps, Erik T.; Sánchez Umbría, Juan; Schuttelaars, Henk M.; Tuckerman, Laurette S.; Thiele, Uwe (201401)
Article
Restricted access  publisher's policyWe provide an overview of current techniques and typical applications of numerical bifurcation analysis in fluid dynamical problems. Many of these problems are characterized by highdimensional dynamical systems which ... 
Numerical continuation methods for largescale dissipative dynamical systems
Sánchez Umbría, Juan; Net Marcé, Marta (20161122)
Article
Open AccessA tutorial on continuation and bifurcation methods for the analysis of truncated dissipative partial differential equations is presented. It focuses on the computation of equilibria, periodic orbits, their loci of ... 
Numerical simulations of thermal convection in rotating spherical shells under laboratory conditions
García González, Fernando; Sánchez Umbría, Juan; Net Marcé, Marta (20140305)
Article
Restricted access  publisher's policyAn exhaustive study, based on numerical threedimensional simulations, of the Boussinesq thermal convection of a fluid confined in a rotating spherical shell is presented. A moderately low Prandtl number fluid (ro = 0.1) ... 
Numerical study of the onset of thermosolutal convection in rotating spherical shells
Net Marcé, Marta; García González, Fernando; Sánchez Umbría, Juan (20120601)
Article
Open AccessThe influence of an externally enforced compositional gradient on the onset of convection of a mixture of two components in a rotating fluid spherical shell is studied for Ekman numbers E = 10−3 and E = 10−6, Prandtl numbers ... 
On the multiple shooting continuation of periodic orbits by NewtonKrylov methods
Sánchez Umbría, Juan; Net Marcé, Marta (2010)
Article
Restricted access  publisher's policyThe application of the multiple shooting method to the continuation of periodic orbits in largescale dissipative systems is analyzed. A preconditioner for the linear systems which appear in the application of Newton’s ... 
On the onset of low Prandtl number convection in rotating spherical shells: nonslip boundary conditions
Net Marcé, Marta; García González, Fernando; Sánchez Umbría, Juan (20080115)
Article
Open AccessAccurate numerical computations of the onset of thermal convection in wide rotating spherical shells are presented. LowPrandtlnumber (σ) fluids, and nonslip boundary conditions are considered. It is shown that at small ... 
Oscillatory convection in rotating spherical shells: low Prandtl number and nonslip boundary conditions
García González, Fernando; Sánchez Umbría, Juan; Dormy, Emmanuel; Net Marcé, Marta (20151001)
Article
Open AccessA fivedegree model, which reproduces faithfully the sequence of bifurcations and the type of solutions found through numerical simulations of the threedimensional Boussinesq thermal convection equations in rotating ...