Library for rigid body interaction with two phase flow. Can also be used in single phase mode by setting alpha field to 1 internally and on boundaries. FloatStepper solves the added mass instability problem by calculating the added mass matrix of the rigid body and exploiting that in the updating of the body motion. With FloatStepper you no longer need outer correctors or acceleration relaxation to stabilise coupling.

floatStepper

floaterMotion (code structure based on sixDoFRigidBodyMotion)

OpenFOAM-v2206 (may compile with later versions as well).

1. Source OpenFOAM-v2206
2. Execute ./Allwmake from FloatStepper main directory

Execute ./Allrun in run/circleFallingIntoWater

Note that case syntax in slightly different from sixDoFRigidBodyMotion cases. In particular:

1. Set application to floatStepper in system/controlDict.

2. Use dynamicFloaterMotionSolversFvMesh in constant/dynamicMeshDict. See examples of usage:

   • run/circleFallingIntoWater/constant/dynamicMeshDict.
   • run/mooredBoxInWaves/constant/dynamicMeshDict.

   Restraints and their syntax is like sixDoFRigidBodyMotion but class names are changed, where "sixDoFRigidBody" is replaced with "floater". Constraints are specified with two vectors e.g.

   • linDirs (1 0 1);
   • rotDirs (0 1 1);

   which means translation only along x- and y-axes and rotation only around the y-axis (default is all DoF's active). The integer parameter MaddUpdateFreq (default 1) determines how often the (computationally expensive) added mass update is done, so setting MaddUpdateFreq e.g. to 3 means that the added mass matrix is only updated evert 3rd time step. Subdictionaries constraints{}, solvers{} and parameters accelerationRelexation and accelerationDamping will not be read or used by FloatStepper.

3. Use floaterVelocity for U on floating object patches. Set slip true; to run with slip boundary condition (default is no-slip).

4. Specify in 0.orig/uniform/floaterMotionState the initial body position, orientation, linear and angular velocity and acceleration.

Johan Roenby, STROMNING APS and Roskilde University

• Henrik Bredmose (conceptualisation)
• Sithik Aliyar (validation and verification)
• Henning Scheufler (code structure)

Please report bugs on the issue tracker of the repository or write to [email protected].

Roenby, Johan, (2023). FloatStepper-v0.0.1 [Computer Software]. Zenodo. https://www.doi.org/10.5281/zenodo.8146516

@software{isoadvector_2023_8146516,
  author       = {isoAdvector},
  title        = {FloatStepper/FloatStepper: FloatStepper},
  month        = jul,
  year         = 2023,
  publisher    = {Zenodo},
  version      = {v0.0.1},
  doi          = {10.5281/zenodo.8146516},
  url          = {https://doi.org/10.5281/zenodo.8146516}
}

• Currently only runs with morphing mesh (not overset mesh).
• Currently only supports a single rigid body.
• Has not been tested with turbulence modelling.
• Currently only runs with isoAdvector (not MULES).
• Plenty of field copying that can probably be avoided to increase efficiency.
• Currently a simple time integration of the 6-DoF equations of motion are hardcoded in the floaterMotion class. The chosen method for Q update guarantees that it stays an orthogonal matrix to machine precission.

Innovation Fund Denmark Grand Solution project FloatStep (8055-00075B).

Independen Research Fund Denmark, InterFlow project (9063-00018B).

This offering is not approved or endorsed by OpenCFD Limited, producer and distributor of the OpenFOAM software via www.openfoam.com, and owner of the OPENFOAM® and OpenCFD® trade marks.