# Comparison of the CFD softwares: Jadim and Fluent with experiments

We will compare the simulations with Fluent and Jadim with the experiments, which are movies of oil and water flow in a certain geometry with and without connectivity.

The valves can not be completely opened in the experiments, therefore we will see if respecting the ratio between the hole area and the total area of the valve will have an impact on the simulations.

 $$\rho_{water} /\rho_{oil}$$ (kg/m3) $$\nu_{water} /\nu_{oil}$$ (Pa.s) $$\sigma_{oil/water}$$ (N/m) 1000; 800 0.001;0.01 0.025

 bottom valve closed bottom valve opened equilibrium time (s) 36.7 19.3

The first simulation is made without ratio for the valves, here is a comparison between the VOF and level set method with the Jadim software.

 $$\rho_{water} /\rho_{oil}$$ (kg/m3) $$\nu_{water} /\nu_{oil}$$ (Pa.s) $$\sigma_{oil/water}$$ (N/m) mesh size (cells) mesh size (m) 1000; 800 0.1;1 0.025 70x88 0.35x0.44
VOF method on the left and Levelset method on the right.

VOF method with fluent (same parameters)

We have increase the viscosity 100 times to avoid numerical diffusion near the interface but the VOF method still present a lot of numerical diffusion and therefore does not show a equal equilibrium at the end: the iso-contour of oil volume fraction value of 0.5 is not at the same height at the end. The level set method does not show numerical diffusion and still has some problem on the wall, this problem comes from the code which is still developing currently at the IMFT and was firstly coded for bubbles.

Therefore we will continue the simulations with the level set method and try a geometry with ratio.

The results comparing fluent and jadim with the VOF method are the same on the flow versus time but fluent shows less numerical diffusion.

# Bottom connected case

In this case, a simulation using level set method with a refine mesh with jadim is realized, for which the geometry is exactly the same with experiments,  the mesh is is refined, and the bottom of the equipment is connected.

Mesh

 $$\rho_{water} /\rho_{oil}$$ (kg/m3) $$\nu_{water} /\nu_{oil}$$ (Pa.s) $$\sigma_{oil/water}$$ (N/m) mesh size (cells) mesh size (m) 1000; 800 0.02;0.2 0.025 280x352 0.35x0.44

Experiment                                                             Simulation with jadim-level set method

In the bottom open case, after the valve opens, the interface moves mainly  due to gravity as well as U tube effect, and finally reaches equilibrium, with the same flow pattern, oil on the top and water on the bottom.  It is observed that the equilibrium time to arrive the final steady state are similar with the experiment and  simulation, despite a difference in viscosity. Also, compared with the fluids movement during the experiment, in which the interfaces of water and oil rises or drops more steady.  With simulation with the method level set in jadim, more dispersed phase appears.

# Bottom blocked case

A simulation with a refine mesh to simulate the experiment bottom blocked case is also conducted.

 $$\rho_{water} /\rho_{oil}$$ (kg/m3) $$\nu_{water} /\nu_{oil}$$ (Pa.s) $$\sigma_{oil/water}$$ (N/m) mesh size (cells) mesh size (m) 1000; 800 0.02;0.2 0.025 280x352 0.35x0.44

Experiment