## Fluids

#### Cavitation Mass Transfer Issue

Subscriber

Hi,

I have been trying mass transfer from water to vapor due to cavitation using UDF (LINEARIZED_MASS_TRANSFER). Both water and vapor is incompressible. I have introduced sinusoidal frame motion using UDF (ZONE_MOTION) which show sinusoidal pressure profile in my container when mass transfer is turned off and this physically expected. Which means when pressure drops below vapor pressure bubble starts to grow and when pressure increases bubble will collapse. So now if I turn on mass transfer and do the same simulation I get bubble grow when pressure drops but surrounding pressure doesn't increase any more. hence bubble doesn't collapse rather pressure drops to negative absolute pressure. What am I missing? How should I model my case so that after bubble grow I can also see bubble collapse? Thanks.

• Raef.Kobeissi
Subscriber

can you please attach the case. What do you mean by surrounding pressure doesn't increase anymore?

Subscriber

Hello Mr. Raef,

Let me explain in detail what I am trying to do. We have a cuvette of polystyrene (38x10x10 mm) partially filled with water upto 35 mm and rest of the space (3 mm) is filled with air. When we accelerate that cuvette (due to the nature of impact the acceleration profile is sinusoidal) we saw cavitation bubble formed. ( please check the published article to see the videos video). Now since the acceleration is sinusoidal in nature the pressure profile in cuvette is also sinusoidal hence when pressure drops below vapor pressure bubble starts to grow and then when pressure increases bubble starts to collapse. Now when I am turning off the mass transfer between the phases and check the pressure at the bottom of the cuvette I get very good sinusoidal pressure profile. Problem starts when I am turning on the mass transfer between the phases. As soon as pressure drops below vapor pressure I can see nice bubble formation but then the mixture pressure continue to decrease and goes to negative absolute pressure. So bubble never collapse rather elongate (stretched). Please see the detail of the problem.

detail of the domain

pressure profile at the right wall (bottom wall if tilted vertical)

bubble formation

bubble collapse

fluent simulation of absolute pressure at the right wall (bottom wall if tilted vertically)

fluent simulation of bubble grow

bubble stretching due to further pressure drop (negative abs pressure)

fluent simulation of static pressure (operating pressure 101325 pa) at the right wall (bottom wall if tilted vertically)

Subscriber

here is case and data file for both the cases (no_mass_transfer and mass_transfer)

Subscriber

here is case and data file for both the cases (no_mass_transfer and mass_transfer)