Releasing the pressure: High-order surface flow discretizations via discrete Helmholtz-Hodge decompositions

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Hauptverfasser: Brüers, Tim, Lehrenfeld, Christoph, van Beeck, Tim, Wardetzky, Max
Format: Preprint
Veröffentlicht: 2026
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author Brüers, Tim
Lehrenfeld, Christoph
van Beeck, Tim
Wardetzky, Max
author_facet Brüers, Tim
Lehrenfeld, Christoph
van Beeck, Tim
Wardetzky, Max
contents We present a discrete Helmholtz--Hodge decomposition for H(div)-conforming Brezzi--Douglas--Marini (BDM) finite elements on triangulated surfaces of arbitrary topology. The divergence-free BDM subspace is split L2-orthogonally into rotated gradients of a continuous streamfunction space and a finite-dimensional space of discrete harmonic fields whose dimension equals the first Betti number of the surface. Consequently, any incompressible flow discretized on this subspace can be reformulated with a scalar streamfunction and finitely many harmonic coefficients as the only unknowns. This eliminates the pressure and the saddle-point structure while ensuring exact tangentiality, pointwise divergence-freeness, and pressure-robustness. We present a randomized algorithm for constructing the harmonic basis and discuss implementation aspects including hybridization, efficient treatment of the harmonic unknowns, and pressure reconstruction. Numerical experiments for unsteady surface Navier--Stokes equations on a trefoil knot and a multiply-connected sculpture surface demonstrate the method and illustrate the physical role of the harmonic velocity component.
format Preprint
id arxiv_https___arxiv_org_abs_2603_27714
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Releasing the pressure: High-order surface flow discretizations via discrete Helmholtz-Hodge decompositions
Brüers, Tim
Lehrenfeld, Christoph
van Beeck, Tim
Wardetzky, Max
Numerical Analysis
Differential Geometry
65N30, 76D05, 58A14, 76D07, 76M10, 35Q30, 58J10
We present a discrete Helmholtz--Hodge decomposition for H(div)-conforming Brezzi--Douglas--Marini (BDM) finite elements on triangulated surfaces of arbitrary topology. The divergence-free BDM subspace is split L2-orthogonally into rotated gradients of a continuous streamfunction space and a finite-dimensional space of discrete harmonic fields whose dimension equals the first Betti number of the surface. Consequently, any incompressible flow discretized on this subspace can be reformulated with a scalar streamfunction and finitely many harmonic coefficients as the only unknowns. This eliminates the pressure and the saddle-point structure while ensuring exact tangentiality, pointwise divergence-freeness, and pressure-robustness. We present a randomized algorithm for constructing the harmonic basis and discuss implementation aspects including hybridization, efficient treatment of the harmonic unknowns, and pressure reconstruction. Numerical experiments for unsteady surface Navier--Stokes equations on a trefoil knot and a multiply-connected sculpture surface demonstrate the method and illustrate the physical role of the harmonic velocity component.
title Releasing the pressure: High-order surface flow discretizations via discrete Helmholtz-Hodge decompositions
topic Numerical Analysis
Differential Geometry
65N30, 76D05, 58A14, 76D07, 76M10, 35Q30, 58J10
url https://arxiv.org/abs/2603.27714