An OpenFOAM-based electro-hydrodynamical model

In this work we present an OpenFOAM-based electro-hydrodynamics model. We have incorporated Gauss’s Law and a free charge transport equation in an existing Volume-Of-Fluid model delivered with OpenFOAM. With the model it is possible to simulate the interaction of a fluid-fluid interface with an electric field, using perfect dielectric liquids as well as conductive liquids. Our implementation is validated using two approaches; first off, we simulate two vertically stacked liquids subjected to an electric field. The potential distribution is compared to the analytical result and a good comparison is found, using either a combination of two perfect dielectric liquids and a dielectric and a conductive liquid. For the latter case, we also find a good agreement with the theoretical relation for the surface charges. Secondly, we have simulated an artificial charge bump in a conductive liquid, and verify the charge transport equation by comparing the decay of the charge over time. Again, a good agreement with theory is found. Finally, we present a test case where we break up a droplet in an electric field. With that, we have shown to have a reliable EHD implementation in the OpenFOAM framework. For our future goal to simulate electrowetting phenomena, we require the electric field distribution in a coupled solid phase as well; we will use the current EHD model and extend it to a multi-region solver to include those effects.