184 research outputs found
On the Trace Operator for Functions of Bounded -Variation
In this paper, we consider the space of
functions of bounded -variation. For a given first order linear
homogeneous differential operator with constant coefficients , this
is the space of --functions such that the
distributional differential expression is a finite (vectorial)
Radon measure. We show that for Lipschitz domains ,
-functions have an -trace
if and only if is -elliptic (or, equivalently, if the
kernel of is finite dimensional). The existence of an
-trace was previously only known for the special cases
that coincides either with the full or the symmetric gradient of
the function (and hence covered the special cases or
). As a main novelty, we do not use the fundamental theorem of
calculus to construct the trace operator (an approach which is only available
in the - and -setting) but rather compare projections
onto the nullspace as we approach the boundary. As a sample application, we
study the Dirichlet problem for quasiconvex variational functionals with linear
growth depending on
Finite element approximation of steady flows of incompressible fluids with implicit power-law-like rheology
We develop the analysis of finite element approximations of implicit power-law-like models for viscous incompressible fluids. The Cauchy stress and the symmetric part of the velocity gradient in the class of models under consideration are related by a, possibly multi–valued, maximal monotone -graph, with . Using a variety of weak compactness techniques, including Chacon’s biting lemma and Young measures, we show that a subsequence of the sequence of finite element solutions converges to a weak solution of the problem as the finite element discretization parameter tends to 0. A key new technical tool in our analysis is a finite element counterpart of the Acerbi–Fusco Lipschitz truncation of Sobolev functions
Convergence Analysis for a Finite Element Approximation of a Steady Model for Electrorheological Fluids
In this paper we study the finite element approximation of systems of
-Stokes type, where is a (non constant) given function of
the space variables. We derive --in some cases optimal-- error estimates for
finite element approximation of the velocity and of the pressure, in a suitable
functional setting
Unconditional stability of semi-implicit discretizations of singular flows
A popular and efficient discretization of evolutions involving the singular
-Laplace operator is based on a factorization of the differential operator
into a linear part which is treated implicitly and a regularized singular
factor which is treated explicitly. It is shown that an unconditional energy
stability property for this semi-implicit time stepping strategy holds. Related
error estimates depend critically on a required regularization parameter.
Numerical experiments reveal reduced experimental convergence rates for smaller
regularization parameters and thereby confirm that this dependence cannot be
avoided in general.Comment: 21 pages, 8 figure
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