airVelocityAttenuation

This project implements a sink term applicable to the momentum conservation equation of the multiphase OpenFOAM solvers (interFoam, interIsoFoam), which attenuates velocities in the air phase.

Description

The sink term has the following expression:

$$ \frac{\partial \rho U}{\partial t}+\nabla \cdot \left( \rho U \otimes U \right) -\nabla \cdot \left(2 \rho \nu D \right) + \nabla R_d = -\nabla p + \rho g + \sigma \kappa \nabla \alpha - A_r \rho U f(\alpha) $$

where $A_r$ is the attenuation rate (1/s) and $f$ is a function which has a value of zero in the water fraction, and one in the air fraction:

$$ f(\alpha) = \max(\min(\frac{\alpha_t - \alpha}{\alpha_t}, 1), 0) $$

with $\alpha_t$ being the alpha threshold, bellow which the attenuation is applied.

Getting Started

• Just copy the fvOption file into the constant folder of your simulation.
• The attenuation rate and alpha threshold con be easily changed in the source code.

Example results

Warning

• Always ensure that the sink term doesn't affect the problem solution.
• Artifially limiting the air velocity can lead to increased velocity gradients near the free surface, and hence additional turbulence production in that region.

License

This project is licensed under the MIT License - see the LICENSE.md file for details

Author

Nicolás Diego Badano (https://www.linkedin.com/in/nicolas-diego-badano/)