39 research outputs found
Simulation of a Hard-Spherocylinder Liquid Crystal with the pe
The pe physics engine is validated through the simulation of a liquid crystal
model system consisting of hard spherocylinders. For this purpose we evaluate
several characteristic parameters of this system, namely the nematic order
parameter, the pressure, and the Frank elastic constants. We compare these to
the values reported in literature and find a very good agreement, which
demonstrates that the pe physics engine can accurately treat such densely
packed particle systems. Simultaneously we are able to examine the influence of
finite size effects, especially on the evaluation of the Frank elastic
constants, as we are far less restricted in system size than earlier
simulations
Dynamic Load Balancing Techniques for Particulate Flow Simulations
Parallel multiphysics simulations often suffer from load imbalances
originating from the applied coupling of algorithms with spatially and
temporally varying workloads. It is thus desirable to minimize these imbalances
to reduce the time to solution and to better utilize the available hardware
resources. Taking particulate flows as an illustrating example application, we
present and evaluate load balancing techniques that tackle this challenging
task. This involves a load estimation step in which the currently generated
workload is predicted. We describe in detail how such a workload estimator can
be developed. In a second step, load distribution strategies like space-filling
curves or graph partitioning are applied to dynamically distribute the load
among the available processes. To compare and analyze their performance, we
employ these techniques to a benchmark scenario and observe a reduction of the
load imbalances by almost a factor of four. This results in a decrease of the
overall runtime by 14% for space-filling curves
Differential-Algebraic Equations and Beyond: From Smooth to Nonsmooth Constrained Dynamical Systems
The present article presents a summarizing view at differential-algebraic
equations (DAEs) and analyzes how new application fields and corresponding
mathematical models lead to innovations both in theory and in numerical
analysis for this problem class. Recent numerical methods for nonsmooth
dynamical systems subject to unilateral contact and friction illustrate the
topicality of this development.Comment: Preprint of Book Chapte