83 research outputs found
A Monotone, Second Order Accurate Scheme for Curvature Motion
We present a second order accurate in time numerical scheme for curve
shortening flow in the plane that is unconditionally monotone. It is a variant
of threshold dynamics, a class of algorithms in the spirit of the level set
method that represent interfaces implicitly. The novelty is monotonicity: it is
possible to preserve the comparison principle of the exact evolution while
achieving second order in time consistency. As a consequence of monotonicity,
convergence to the viscosity solution of curve shortening is ensured by
existing theory
Statistical exponential formulas for homogeneous diffusion
Let denote the -homogeneous -Laplacian, for . This paper proves that the unique bounded, continuous viscosity
solution of the Cauchy problem \left\{ \begin{array}{c} u_{t} \ - \ (
\frac{p}{ \, N + p - 2 \, } ) \, \Delta^{1}_{p} u ~ = ~ 0 \quad \mbox{for}
\quad x \in \mathbb{R}^{N}, \quad t > 0 \\ \\ u(\cdot,0) ~ = ~ u_{0} \in BUC(
\mathbb{R}^{N} ) \end{array} \right. is given by the exponential formula
where the statistical operator is defined by with , when and by with , when . Possible extensions to problems with Dirichlet boundary conditions and to
homogeneous diffusion on metric measure spaces are mentioned briefly
Algorithms for Area Preserving Flows
We propose efficient and accurate algorithms for computing certain area preserving geometric motions of curves in the plane, such as area preserving motion by curvature. These schemes are based on a new class of diffusion generated motion algorithms using signed distance functions. In particular, they alternate two very simple and fast operations, namely convolution with the Gaussian kernel and construction of the distance function, to generate the desired geometric flow in an unconditionally stable manner. We present applications of these area preserving flows to large scale simulations of coarsening
An efficient threshold dynamics method for topology optimization for fluids
We propose an efficient threshold dynamics method for topology optimization
for fluids modeled with the Stokes equation. The proposed algorithm is based on
minimization of an objective energy function that consists of the dissipation
power in the fluid and the perimeter approximated by nonlocal energy, subject
to a fluid volume constraint and the incompressibility condition. We show that
the minimization problem can be solved with an iterative scheme in which the
Stokes equation is approximated by a Brinkman equation. The indicator functions
of the fluid-solid regions are then updated according to simple convolutions
followed by a thresholding step. We demonstrate mathematically that the
iterative algorithm has the total energy decaying property. The proposed
algorithm is simple and easy to implement. A simple adaptive time strategy is
also used to accelerate the convergence of the iteration. Extensive numerical
experiments in both two and three dimensions show that the proposed iteration
algorithm converges in much fewer iterations and is more efficient than many
existing methods. In addition, the numerical results show that the algorithm is
very robust and insensitive to the initial guess and the parameters in the
model.Comment: 23 pages, 24 figure
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