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Lennart J. Schulze

Publications and source records attributed to Lennart J. Schulze.

3 recordsLinked to original sources

Globally Adaptive and Locally Regular Point Discretization of Implicit Surface Geometries

Point discretization of implicitly defined curved surfaces is required throughout computer-aided design, engineering analysis, and scientific computing. These applications often impose that surfaces are sampled with local regularity and global curvature adaptivity for unambiguous geometry representation. Finding a numerically well-conditioned point discretization, however, is not trivial, even for simple analytic surfaces. We present an algorithm for finding near-optimal surface point distributions governed by a prescribed resolution field on a curved surface. The algorithm works by approximately minimizing a global potential over local point-point interactions. We leverage a high-order meshfree level-set method to implicitly describe the surface and to perform all required projections without additional surface-attractive forces. To accelerate convergence, the algorithm dynamically fuses and inserts points where a local excess or lack is detected, for which it introduces an integral support measure. We test the proposed algorithm on a variety of shapes, ranging from parametric to non-parametric surfaces. We find point discretizations with different curvature adaptivity and low deviation from the prescribed target spacing. In all cases, the presented algorithm rapidly and robustly converges to the final number and distribution of surface points.

cs.CE↗

A meshfree solver for coupled bulk-surface problems with self-organizing surface geometry

In many systems, the interaction between a deformable surface or interface and the surrounding bulk fluid is coupled with intrinsic spatiotemporal dynamics within the moving surface. Examples include tumor growth, biological tissue morphogenesis, cardiac mechanics, multi-phase surfactant chemistry, additive manufacturing, clothing wear-and-tear, and reactive combustion flows. Solving such problems requires both geometric computing algorithms to track and resolve the surface and numerical methods to solve the coupled governing equations in the surface and the surrounding bulk phase. Here, we present a fully meshfree numerical solver for such coupled bulk-surface problems with deformable interfaces. The presented solver tracks the surface implicitly, solving for the dynamic surface geometry based on stress balance coupled to surrounding fluid phases. We show convergence for a mass-conserving case on a growing sphere and solve bulk-surface problems with incompressible Navier-Stokes fluids coupled to in-surface nonlinear reaction-diffusion dynamics. Finally, we show a model of biological morphogenesis, solving simultaneously for the dynamic surface shape and the fields on the curved surface with two-way coupling.

cs.CE↗

A high-order fully Lagrangian particle level-set method for dynamic surfaces

We present a fully Lagrangian particle level-set method based on high-order polynomial regression. This enables closest-point redistancing without requiring a regular Cartesian mesh, relaxing the need for particle-mesh interpolation. Instead, we perform level-set redistancing directly on irregularly distributed particles by polynomial regression in a Newton-Lagrange basis on a set of unisolvent nodes. We demonstrate that the resulting particle closest-point (PCP) redistancing achieves high-order accuracy for 2D and 3D geometries discretized on highly irregular particle distributions and has better robustness against particle distortion than regression in a monomial basis. Further, we show convergence in a classic level-set benchmark case involving ill-conditioned particle distributions, and we present an application to an oscillating droplet simulation in multi-phase flow.

cs.CE↗