Simulation 1 : High viscosities

In this first simulation, oil, gas and water viscosities are multiplied by 100. Indeed, increasing viscosity values should allows Jadim to avoid convergence issues and to reduced numerical diffusion.

The table below recaps the main caracteristics of the simulation:

  Physical properties Velocity inlet Time step Scheme Order Time simulated Quantity of N2 injected
Fluent Viscosities x100 0.1 m/s 10-4 Second Order 2.5 sec 6.25.10-3 m²
Jadim Viscosities x100 0.1 m/s max. 10-4 Second Order 2.5 sec 6.25.10-3 m²

This simulation is carried out for a velocity of 0.1 m/s, 1m/s and 10 m/s. In term of convergence, CPU time and accuracy of the results, the velocity of 1 m/s appeared to be the suitable velocity for this case, for bth Fluent and Jadim simulations. Therefore, the simulations presented in this page have been carried out with a velocity of 1 m/s. 

 

The inlet is characterized by a gas Reynolds Number of 260 at the inlet. Therefore, the gas jet at the inlet is not turbulent.

If a flow Reynold Number in the domain  is complicated   to calculate, velocities in function of time can be  observed. In  both Jadim and Fluent  simulations,  flow  velocity  does  not exceed 7 m/s. The picture  on the   right shows the velocity field at 1.5 sec with Jadim.

Thus, it is relevant to conclude that the flow  is laminar and  that turbulence models are not needed.

 

 

The two videos below show the same case simulated with Fluent and Jadim. As explained previoulsy, gas is injected on the lower right side of the domain, and the outlet is situated on the middle left side. The physical time simulated is 2.5 seconds, which correpond to an injection of %47 of gas i the domain.

Simulation carried out with JADIM

 

Simulation carried out with Fluent

In the videos, if befferent local flow features can be observed, the global flow in the domain has the same behaviour with Fluent and Jadim. Moreover, the phenomenon of numerical diffusion is not too important and the position of the norrow gas interface is accurate. From the observation of these videos, Jadim seems to handle the three-phase flow simulation and the results seem accurate and relevant.

In order to confirm these observations, macroscopic data of interest are analyzed with the matlab post-treatment. The figure below represents the evolution of oil, water and gas volume fraction in the domain in function of a dimentionless time. Results of Fluent and Jadim simulations are compared.

The first observation is that for both simulations, oil and water volume fraction decrease as gas volume fraction increase, which corresponds to the injection of gas and the disparition of oil and water into the outlet.

Secondly, it shows that no gas injected have left the domain after an injection of 74% of nitrogen. Indeed, the evolution of the gas volume fraction is a  linear curve with represents a constant evolution in the domain.

Finally, oil, pushed by water, starts to leave the domain after an injection of 14% of gas and at the end of the simulation, after an injection of 47% of gas, 52.7% of oil wedged remains in the domain.

The results obtained with Jadim and Fluent are similar: the same amount of oil has left the domain at the end and the evolution of phases repartition is similar during this period of time. These results confirm that  Jadim predicts well flow features in a case of   high viscosities.

 

                  

Then, the evolution of the outlet oil flow rate is plotted in function of a dimentionless time.  

When oil starts to leave the domain after 14% of nitrogen injected, the dimentionless oil flow rate reach a maximum of 1. The previous videos show that at the time, only oil goes out of the domain. Theses observations lead to the conclution that flow conservation between the inlet and the outlet is respected.

Moreover, like the evolution of the volume fraction, the comparison of the outlet oil flow rate shows that Jadim and Fluent produce similar results in this case.

                            

Conclusion: If local flow features observed on the videos  have differences in function of the CFD software, the study of macroscopic values of interest shows that in this case, Jadim and Fluent give similar results. Jadim seems to gives more accurate results when it does not have to deal with the small viscosity of nitrogen.