TY  - JOUR
A1  - Höllbacher, Susanne
A1  - Wittum, Gabriel
T1  - Gradient-consistent enrichment of finite element spaces for the DNS of fluid-particle interaction
T2  - Journal of computational physics
N2  - Highlights
• Monolithic scheme for particulate flows preventing an oscillating pressure along the interface.
• The choice of enriching shape functions is driven by the properties of its gradient instead of its value.
• The choice of enriching shape functions inherits a natural stabilization on small cut elements.
Abstract
We present gradient-consistent enriched finite element spaces for the simulation of free particles in a fluid. This involves forces being exchanged between the particles and the fluid at the interface. In an earlier work [23] we derived a monolithic scheme which includes the interaction forces into the Navier-Stokes equations by means of a fictitious domain like strategy. Due to an inexact approximation of the interface oscillations of the pressure along the interface were observed. In multiphase flows oscillations and spurious velocities are a common issue. The surface force term yields a jump in the pressure and therefore the oscillations are usually resolved by extending the spaces on cut elements in order to resolve the discontinuity. For the construction of the enriched spaces proposed in this paper we exploit the Petrov-Galerkin formulation of the vertex-centered finite volume method (PG-FVM), as already investigated in [23]. From the perspective of the finite volume scheme we argue that wrong discrete normal directions at the interface are the origin of the oscillations. The new perspective of normal vectors suggests to look at gradients rather than values of the enriching shape functions. The crucial parameter of the enrichment functions therefore is the gradient of the shape functions and especially the one of the test space. The distinguishing feature of our construction therefore is an enrichment that is based on the choice of shape functions with consistent gradients. These derivations finally yield a fitted scheme for the immersed interface. We further propose a strategy ensuring a well-conditioned system independent of the location of the interface. The enriched spaces can be used within any existing finite element discretization for the Navier-Stokes equation. Our numerical tests were conducted using the PG-FVM. We demonstrate that the enriched spaces are able to eliminate the oscillations.
KW  - Immersed boundary method
KW  - Monolithic scheme
KW  - Enriched finite elements
KW  - Petrov-Galerkin finite volumes
KW  - Spurious pressure
Y1  - 2019
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/77785
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-777850
SN  - 0021-9991
VL  - 401.2020
IS  - 109003
PB  - Elsevier
CY  - Amsterdam
ER  -