In computational fluid dynamics, incoming flow at open boundaries, or backflow, often yields to unphysical instabilities, already for moderate Reynolds numbers.

Several treatments to overcome these backflow instabilities have been proposed in the literature. However, these approaches have not yet been compared in detail in terms of accuracy in different regimes, in particular due to the difficulty to generate stable reference solutions apart from analytical forms.

The goal of this database is to collect different benchmark problems in order to test and compare different methods for handling incoming flow at open boundaries. The benchmarks are characterized by different backflow regimes (such as full reversal flows or vortices propagating through the open boudary). In order to create a solid basis for further research, the examples are implemented using open source software (such as FreeFem++) and the source code is available in this database

2D Benchmarks

Codes

The FreeFem++ code used to generate the numerical results for the benchmark listed below can be downloaded here (as a single .zip file).
A basic documentation will be available in the near future.
The latest version of FreeFem++ can be downloaded from the FreeFem++ homepage.

Reversed (asymmetric) channel flow

  • Computational meshes (.mesh and .msh), FreeFem input files and values of Neumann load on boundary nodes:
    blood regime, air regime

Flow in a stenotic vessel

  • Computational meshes (.mesh and .msh), FreeFem input files and values of Neumann load on boundary nodes:
    blood regime, air regime