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In this paper, a nonlinear problem corresponding to a simplified Oldroyd-B model without convective terms is considered. Assuming the domain to be a convex polygon, existence of a solution is proved for small relaxation times. Continuous piecewise linear finite elements together with a Galerkin Least Square (GLS) method are studied for solving this problem. Existence and a priori error estimates are established using a Newton-chord fixed point theorem, a posteriori error estimates are also derived. An Elast

We develop a discretization and solution technique for elliptic problems whose solutions may present strong variations, singularities, boundary layers and oscillations in localized regions. We start with a coarse finite element discretization with a mesh s ...

The free surface flow of an Oldroyd-B viscoelastic fluid is considered, following A. Bonito, M. Picasso, and M. Laso (2006)[1]. When removing a term in the extra-stress constitutive relation, the description of an elastic incompressible solid is obtained, ...

A space–time adaptive method is presented for the numerical simulation of mass transport in electroosmotic and pressure-driven microflows in two space dimensions. The method uses finite elements with large aspect ratio, which allows the electroosmotic flow ...

An efficient adaptive algorithm is presented for a stationary regularized Stefan problem in 2D. The adaptive criteria relies upon a posteriori estimates based on the residual equation. Since the problem we are studying is a non-linear diffusion-convection problem, these error estimates are relatively crude in the sense that the constant relating the true error to the error indicator is unknown. Thus, instead of trying to build a mesh such that the true error is below a given tolerance, the local error indic

Due to climatic change, many Alpine glaciers have significantly retreated during the last century. In this study we perform the numerical simulation of the temporal and spatial change of Rhonegletscher, Swiss Alps, from 1874 to 2007, and from 2007 to 2100. ...

A posteriori error estimates are derived for a nonlinear parabolic problem arising from the isothermal solidification of a binary alloy. Space discretization with continuous, piecewise linear finite elements is considered. The L-2 in time H-1 in space error is bounded above and below by an error estimator based on the equation residual. Numerical results show that the effectivity index is close to one. An adaptive finite element algorithm is proposed and a solutal. dendrite is computed. (C) 2002 Elsevier Sc

A priori and a posteriori error estimates are presented for nonlinear diffusion-convection problems when using the classical Streamline Upwind Petrov-Galerkin (SUPG) scheme and numerical integration. For this purpose, an abstract framework is developed. A priori estimates are derived in the H-1 and L(2) norms and the error is bounded above and below by an estimator based on the equation residual. An adaptive algorithm requiring the generation of successive Delaunay triangulations is proposed and numerical r

Differential relationships between velocity and stress are derived from the kinetic theory of polymeric liquids. The Fokker-Planck equation corresponding to the so-called dumbbell theory for dilute solutions of polymers is considered. A Chapman-Enskog expansion for time-dependent, nonhomogeneous flows is proposed when the elastic character of the fluid is small, and the results included in the book of R. Bird, C. Curtiss, R. Armstrong, and O. Hassager [ Dynamics of Polymeric Liquids, Vol. 2, Kinetic Theory,

Three methods based on the three-dimensional shallow ice approximation of glacier flow are devised that infer a glacier's subglacial topography from the observation of its time-evolving surface and mass balance. The quasi-stationary inverse method relying ...

The motion of a two-dimensional glacier is considered. At each time step, given the shape of the glacier, ice is modelled as an incompressible non-Newtonian fluid and a non-linear elliptic problem has to be solved to obtain the horizontal velocity field. Then, the upper surface of the glacier is updated by solving a transport equation. Finite element techniques are used to compute the velocity field whereas the transport equation is solved using a Lax-Wendroff scheme. Numerical results are compared to exper

Stabilized finite elements on strongly anisotropic meshes are considered. The design of the stability coefficients is addressed for both the advection-diffusion and the Stokes problems when using continuous piecewise linear finite elements on triangles. Using the polar decomposition of the Jacobian of the a. ne mapping from the reference triangle to the current one, K, and from a priori error estimates, a new definition of the stability coefficients is proposed. Our analysis shows that these coefficients do

A space-time adaptive algorithm is presented to solve the incompressible Navier-Stokes equations. Time discretization is performed with the BDF2 method while continuous, piecewise linear anisotropic finite elements are used for the space discretization. Th ...

We present a shape optimization algorithm to estimate the ice thickness distribution within a two-dimensional, non-sliding mountain glacier, given a transient surface geometry and a mass-balance distribution. The approach is based on the minimization of th ...

We compute solutions of solutal phase-field models for dendritic growth of an isothermal binary alloy using anisotropic mesh refinement techniques. The adaptive strategy is based on anisotropic a posteriori estimators using a superconvergent recovery technique in the form of the Zienkiewicz-Zhu error estimator. The phase-field model contains an anisotropic strongly nonlinear second order operator modelling the dendritic branches; this strong nonlinearity is included in the a posteriori error estimators by u

The anisotropic error indicator presented in [M. Picasso, Comm. Numer. Methods Engrg., 19 (2003), pp. 13-23.] in the frame of the Laplace equation is extended to elliptic and parabolic problems. Our error indicator is derived using the anisotropic interpolation estimates of [L. Formaggia and S. Perotto, Numer. Math., 89 (2001), pp. 641-667; L. Formaggia and S. Perotto, Numer. Math., (2002), DOI 10.1007/s002110200415], together with a Zienkiewicz-Zhu error estimator to approach the error gradient. A numerica

We present a numerical model for the approximation of multiphase flows with free surfaces and strong interfacial effects. The model relies on the multiphase incompressible Navier-Stokes equations, and includes surface tension effects on the interfaces betw ...

Unlike in continuum approaches, time-dependent micro--macro calculations have been performed up to now almost exclusively using a simple explicit time marching algorithm, the exception being the pioneering work by Somasi and Khomami [J. Non-Newtonian Fluid Mech. 93 (2000) 339] whose iteration of a semi-implicit algorithm is equivalent to a fully implicit formulation. The use of explicit time integration puts explicit micro-macro methods at a disadvantage, since they lack the desirable stability of fully imp

Numerical simulation in aluminum production envolves many different topics, this paper is dedicated to some aspects of two of them. In the first part, a numerical approach for the computation of the motion of the fluids in an electrolitic cell is presented ...

The framework of Formaggia and Perotto (Numerische Mathematik 2001; 89:641-667) is considered to derive a new anisotropic error indicator for a Laplace problem in the energy norm. The matrix containing the error gradient is approached using a Zienkiewicz-Zhu error estimator. A numerical study of the effectivity index is proposed for anisotropic unstructured meshes, showing that our indicator is sharp. An anisotropic adaptive algorithm is implemented, aiming at controlling the estimated relative error. Copyr

Marco Picasso

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Existence, a priori and a posteriori error estimates for a nonlinear three-field problem arising from Oldroyd-B viscoelastic flows

Multiscale algorithm with patches of finite elements

From the free surface flow of a viscoelastic fluid towards the elastic deformation of a solid

Adaptive finite elements with large aspect ratio for electroosmotic and pressure-driven microflows

An Adaptive Finite-Element Algorithm for a 2-Dimensional Stationary Stefan-Like Problem

Numerical simulation of Rhonegletscher from 1874 to 2100

A posteriori error estimates and adaptive finite elements for a nonlinear parabolic problem related to solidification

Error estimates and adaptive finite elements for nonlinear diffusion-convection problems

Viscoelastic fluid models derived from kinetic equations for polymers

Bedrock topography reconstruction of glaciers from surface topography and mass-balance data

Numerical simulation of the motion of a two-dimensional glacier

Stabilized finite elements on anisotropic meshes: A priori error estimates for the advection-diffusion and the Stokes problems

An adaptive space-time algorithm for the incompressible Navier-Stokes equations

Estimating the ice thickness of mountain glaciers with a shape optimization algorithm using surface topography and mass-balance

Anisotropic, adaptive finite elements for the computation of a solutal dendrite

Anisotropic error indicator based on Zienkiewicz-Zhu error estimator: Application to elliptic and parabolic problems

A cut-cell method for the numerical simulation of 3D multiphase flows with strong interfacial effects

Implicit micro-macro methods

Scientific Computing For Aluminum Production

Numerical study of the effectivity index for an anisotropic error indicator based on Zienkiewicz-Zhu error estimator