arXiv subjects

Nikolaus. A. Adams

Publications and source records attributed to Nikolaus. A. Adams.

3 recordsLinked to original sources

arXiv2018

A variational-level-set based partitioning method for block-structured meshes

We propose a numerical method for solving block-structured mesh partitioning problems based on the variational level-set method of (Zhao et al., J Comput Phys 127, 1996) which has been widely used in many partitioning problems such as image segmentation and shape optimization. Here, the variational model and its level-set formulation have been simplified that only one single level-set function is evolved. Thus, the numerical implementation becomes simple, and the computational and memory overhead are significantly alleviated, making this method suitable for solving realistic block-structured mesh partitioning problems where a large number of regions is required. We start to verify this method by a range of two-dimensional and three-dimensional uniform mesh partitioning cases. The results agree with the theoretical solutions very well and converge rapidly. More complex cases, including block-structured adaptive mesh partitioning for single-phase and multi-phase multi-resolution simulations, confirm the accuracy, robustness and good convergence property. The measured CPU time shows that this method is efficient for both two-dimensional and three-dimensional realistic partitioning problems in parallel computing. The proposed method has the potential to be extended to solve other partitioning problems by replacing the energy functional.

physics.comp-ph↗

arXiv2017

A conservative sharp-interface method for compressible multi-material flows

In this paper we develop a conservative sharp-interface method dedicated to simulating multiple compressible fluids. Numerical treatments for a cut cell shared by more than two materials are proposed. First, we simplify the interface interaction inside such a cell with a reduced model to avoid explicit interface reconstruction and complex flux calculation. Second, conservation is strictly preserved by an efficient conservation correction procedure for the cut cell. To improve the robustness, a multi-material scale separation model is developed to consistently remove non-resolved interface scales. In addition, the multi-resolution method and local time-stepping scheme are incorporated into the proposed multi-material method to speed up the high-resolution simulations. Various numerical test cases, including the multi-material shock tube problem, inertial confinement fusion implosion, triple-point shock interaction and shock interaction with multi-material bubbles, show that the method is suitable for a wide range of complex compressible multi-material flows.

physics.comp-ph↗

arXiv2017

A consistent analytical formulation for volume-estimation of geometries enclosed by implicitly defined surfaces

We have derived an analytical formulation for estimating the volume of geometries enclosed by implicitly defined surfaces. The novelty of this work is due to two aspects. First we provide a general analytical formulation for all two-dimensional cases, and for elementary three three-dimensional cases by which the volume of general three-dimensional cases can be computed. Second, our method addresses the inconsistency issue due to mesh refinement. It is demonstrated by several two-dimensional and three-dimensional cases that this analytical formulation exhibits 2nd-order accuracy.

math.NA↗