[jiejie]

Dear foamers

I am currently trying to validate the twoPhaseEulerFoam solver using the case from Becker et al. (1994) Gas-liquid flow in bubble columns and loop reactors Part II Comparison of detailed experiments and flow simulations. In brief, the flat bubble column is 0.5 m wide (x), 2 m high (y) and 0.08 m deep (z) with liquid filled up to 1.5 m in the vertical direction. A gas sparger positioned 0.15 m from the left wall is used to introduce an airflow of 1.6 L/min. The circular sparger with a diameter of 40 mm is modelled as a square inlet of 40 mm x 40 mm for the convenience. The equivalent inlet air velocity is calculated as 0.0167 m/s with a gas volume fraction of 1.

I found some validation results done using ANSYS CFX by Chakraborty et al. (2009) CFD simulation on influence of superficial gas velocity, column size, sparger arrangement and taper angle on hydrodynamics of the column flotation cell. In this paper, the grid used is 50 x 150 x 20 in the x, y and z directions,r respectively. I used same grid resolution for the calculation using twoPhaseEulerFoam with air/water interface at y = 1.5 m, but the computed oscillation period is approximately 51 s (see Fig A. Time series data for vertical liquid velocity) compared to the reported oscillation period of 41 s (See Fig. 7 in Becker et al. and Fig. 3 in Chakraborty et al.). I also refined the grid to 125 x 250 x 20, which resulted an oscillation period of 44 s (see Fig B.). However, I found the time series data for the vertical liquid velocity calculated using OpenFOAM are quite different from the data in Becker et al. (1994) and Chakraborty et al. (2009). The maximum peaks in the OpenFOAM results are much sharper.

I modified the tutorial bubble column RAS case with the following changes:

1. alpha.air: using setFields to initialise water phase up to y = 1.5 m and alpha.air is uniform 1 at the Inlet.

2. p: fixed value; uniform 1e5; at Outlet and zeroGradient at Inlet and Walls

3. p_rgh: prghPressure; value uniform 1e5 at Outlet and zeroGradient at Inl;et and Walls

4. T.air and T.water: fixedValue; uniform 300 at Inlet and Outlet, zeroGradient at Walls

5. U.air: fixedValue; uniform (0 0.01667 0) at Inlet, fixedValue; unifrom (0 0.000667 0) at Outlet and noSlip at Walls

I used mixturekEpsilon RAS model with drag, lift and virtual mass forces. I found the oscillation period can be over-predicted by upto 15 s if the lift force is ignored.

I am wondering if anyone tried to validate the twoPhaseEulerFoam and had similar problem. I would also like to further validate the case using the solver with LES.

Kind regards,
Jie

[jiejie]

I think this tread should be moved to "OpenFOAM Verification & Validation".

Thanks

[meshman]

duplicated message

[meshman]

duplicated message

[meshman]

I tried to do this validation case using the OpenFOAM, however, it does not work (the error occurred at the time step ~ 28s).
If you share your case file, it will be very helpful to my research progress.
Thank you!

Originally Posted by jiejie

Dear foamers

I am currently trying to validate the twoPhaseEulerFoam solver using the case from Becker et al. (1994) Gas-liquid flow in bubble columns and loop reactors Part II Comparison of detailed experiments and flow simulations. In brief, the flat bubble column is 0.5 m wide (x), 2 m high (y) and 0.08 m deep (z) with liquid filled up to 1.5 m in the vertical direction. A gas sparger positioned 0.15 m from the left wall is used to introduce an airflow of 1.6 L/min. The circular sparger with a diameter of 40 mm is modelled as a square inlet of 40 mm x 40 mm for the convenience. The equivalent inlet air velocity is calculated as 0.0167 m/s with a gas volume fraction of 1.

I found some validation results done using ANSYS CFX by Chakraborty et al. (2009) CFD simulation on influence of superficial gas velocity, column size, sparger arrangement and taper angle on hydrodynamics of the column flotation cell. In this paper, the grid used is 50 x 150 x 20 in the x, y and z directions,r respectively. I used same grid resolution for the calculation using twoPhaseEulerFoam with air/water interface at y = 1.5 m, but the computed oscillation period is approximately 51 s (see Fig A. Time series data for vertical liquid velocity) compared to the reported oscillation period of 41 s (See Fig. 7 in Becker et al. and Fig. 3 in Chakraborty et al.). I also refined the grid to 125 x 250 x 20, which resulted an oscillation period of 44 s (see Fig B.). However, I found the time series data for the vertical liquid velocity calculated using OpenFOAM are quite different from the data in Becker et al. (1994) and Chakraborty et al. (2009). The maximum peaks in the OpenFOAM results are much sharper.

I modified the tutorial bubble column RAS case with the following changes:

1. alpha.air: using setFields to initialise water phase up to y = 1.5 m and alpha.air is uniform 1 at the Inlet.

2. p: fixed value; uniform 1e5; at Outlet and zeroGradient at Inlet and Walls

3. p_rgh: prghPressure; value uniform 1e5 at Outlet and zeroGradient at Inl;et and Walls

4. T.air and T.water: fixedValue; uniform 300 at Inlet and Outlet, zeroGradient at Walls

5. U.air: fixedValue; uniform (0 0.01667 0) at Inlet, fixedValue; unifrom (0 0.000667 0) at Outlet and noSlip at Walls

I used mixturekEpsilon RAS model with drag, lift and virtual mass forces. I found the oscillation period can be over-predicted by upto 15 s if the lift force is ignored.

I am wondering if anyone tried to validate the twoPhaseEulerFoam and had similar problem. I would also like to further validate the case using the solver with LES.

Kind regards,
Jie