Mass Flow Inlet - Unrealistic Inlet Velocity

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mesakca posted this 01 June 2020

Hi

My problem is an ozonation column. Ozone is introduced from the bottom of a cylinder through a sparger. Cylinder has 6 cm diameter and filled with water with 80 cm height.

I have defined my inlet boundary condition as mass flow inlet.

My ozone flow rate is 1 L/min which corresponds to 3.28e-05 kg/s of ozone at my experimental conditions. I set my slip velocity specification method to volume fraction and assigned value of 0.5, which is the porosity of sparger.

However, at the initialization section, my ozone Z velocity is assigned to 0.00589 m/s. I have checked, and this corresponds to the velocity as if there is no sparger and ozone is introduced directly from the bottom.

Do you have any idea how to fix this? Should i change the ozone Z velocity at the initialization according to sparger pore size or something? Or could there be any other way to fix this?

Thank you, best regards.

 

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rwoolhou posted this 01 June 2020

What volume fraction of ozone enters through the inlet? Do you mean the ozone flow is wrong after running the model or the initialisation value is wrong?

mesakca posted this 01 June 2020

thank you for the response.

only ozone is introduced from the bottom (actually ozone + oxygen but 99.9% ozone mass fraction of mixture). water is stationary in the cylinder. initialization value is wrong.

also, i ran the model, and ozone velocity reported in the post processing is wrong as well. pore size of sparger is 10 um and i have observed the gas velocity in the cylinder. both initialization and ozone velocity after running the model is very unrealistic.

 

mesakca posted this 02 June 2020

hi

i have also noticed that; at the mass flow inlet, i have set slip velocity specification method is volume fraction. and when i change the volume fraction, ozone Z-velocity at the solution initialization section doesn't change?

is this normal?

 

abenhadj posted this 02 June 2020

post pictures of boundary condition.

Best regards, Amine

mesakca posted this 02 June 2020

and finally this is the initialization

abenhadj posted this 02 June 2020

Does the velocity corredponds to 2 times the mass flow of the phase devided by area devided by density?

Best regards, Amine

abenhadj posted this 02 June 2020

Always recompute from inlet the initialization and report area weighted average of the velocity after couple of itérations

Best regards, Amine

mesakca posted this 02 June 2020

no, it is not. actually, velocity corresponds to flow rate divided by area, as if there is no porosity. in other words not two times the mass flow but mass flow divided by area divided by phase density

mesakca posted this 02 June 2020

i will do that. thank you.

mesakca posted this 5 weeks ago

Always recompute from inlet the initialization and report area weighted average of the velocity after couple of itérations

i couldnt figure out how i will do that. can you give some more detail please.

Thank you.

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