A computational formulation for constrained solid and liquid membranes considering isogeometric finite elements

TL;DR

This paper introduces a geometrically exact membrane formulation using isogeometric finite elements that accurately models both solid and liquid membranes, avoiding local coordinate transformations and improving accuracy especially for liquid membranes.

Contribution

It presents a novel membrane formulation based on curvilinear coordinates and isogeometric elements, enabling stable modeling of liquid membranes with enhanced accuracy.

Findings

Isogeometric elements outperform standard Lagrange elements in accuracy.

The formulation effectively models membranes with various constraints.

Liquid membrane modeling benefits significantly from the proposed approach.

Abstract

A geometrically exact membrane formulation is presented that is based on curvilinear coordinates and isogeometric finite elements, and is suitable for both solid and liquid membranes. The curvilinear coordinate system is used to describe both the theory and the finite element equations of the membrane. In the latter case this avoids the use of local cartesian coordinates at the element level. Consequently, no transformation of derivatives is required. The formulation considers a split of the in-plane and out-of-plane membrane contributions, which allows the construction of a stable formulation for liquid membranes with constant surface tension. The proposed membrane formulation is general, and accounts for dead and live loading, as well as enclosed volume, area, and contact constraints. The new formulation is illustrated by several challenging examples, considering linear and quadratic Lagrange elements, as well as isogeometric elements based on quadratic NURBS and cubic T-splines. It is seen that the isogeometric elements are much more accurate than standard Lagrange elements. The gain is especially large for the liquid membrane formulation since it depends explicitly on the surface curvature.