[mateus]

Hello everybody,

I'm not very active on CFD Online since about 2005 but people still contact me frequently regarding cavitation, cavitation erosion, bubble dynamics and other stuff I did in back then. That's why I set-up a web page where you can find all my papers and a youtube channel with some movies of simulations and experiments from different fields that I did.

I hope you'll find it useful. If you have any questions please contact me!

www2.arnes.si/~mdula/

http://www.youtube.com/channel/UCMHR...tAYzQp5zg/feed

Best regards,
Mateus

[samir_1]

Hi ,

I am using Fluent to simulate steady and unsteady turbulent flow around marine propeller. Please could you help me to know cavitation simulation steps in fluent.

Best regards.

[ghost82]

Hi Matevz,
thank you very much for the material, I appreciate very much.
I see that you have successfully simulated ultrasonic transducers with fluent, by setting a sinusoidal position of the horn tip, am I right?..I will further investigate in it.
If you can, can you upload "Dynamics of attached cavitation at an ultrasonic horn tip" somewhere?
Again, thank you.

Daniele

EDIT: do you confirm that in the article "Numerical Simulation of a Near-Wall Bubble Collapse in an Ultrasonic Field" b should be 2*10^-8 and not -2*10^-8?

[ghost82]

Hi!
I'm having some trouble in trying to reproduce a similar simulation to that of Matevz, in paper "Numerical Simulation of a Near-Wall Bubble Collapse in an Ultrasonic Field".

Attached is my case: a 2ddp axisymmetric simulation in which all the bottom wall moves changing its position sinusoidally.

At the first time I set a constant density for the liquid, so liquid was incompressible and I wasn't able to view the pressure wave propagation..

I think that this is related to liquid compressibility, so I wrote an udf to take into account this aspect.

Interno and bottomwall are rigid bodies, outlet is stationary.

I set a velocity profile which reproduce the x coordinate movement:
x=a*sin(2*pi*f*t)
a=0,2 micron, f=33000 Hz

Bottom wall starts to move when it is at its lowest position.

However, with liquid compressibility I have divergence in amg solver
I played with urf and v-w-c cycle, flexible, but I continue to receive amg divergence..

Any help please?

Thank you!

Daniele

[ghost82]

I think I solved my problem
My operating pressure point was attached to the bottom wall and this created the amg divergence error..now the pressure wave seems to propagate..

[samir_1]

Hello Daniel,

I am simulating flow cavitation around marine propeller, but i don't have idea about the procedure on Fluent. Please can you help me to know procedures of cavitation simulaton using Fluent.

Thanks

Samir

[ghost82]

Hi Samir,
you have to use the mixture model (under multiphase tab) and choose 2 material (ex: water liquid and water vapor); then under phase tab-->interaction-->mass you have to enable cavitation.
If your propeller rotates I think you have to use rotating frames, but I'm not expert in these simulations..maybe someone else can provide more information.

See this tut for cavitation in a nozzle:
http://hpce.iitm.ac.in/website/Manua...f/tg/tut18.pdf

Daniele

[samir_1]

Hi Daniel,

Thank you so much for your message,
Just want to tell that i used the tutorial that you have send it to me before, and it doesn't work. For the non cavitating cas, i found good results, but in the cavitating case, i think i have problems and don't know where exactly.

Please Daniel, can you send me your email to show you the steps (my case using fluent)

Thank you again

Samir

[ghost82]

ok Samir,
check your private messages, I'm sending my email.
I will check your case and see if I can be of any help..

Daniele

[samir_1]

Thank you so much Daniele!!

[ndabir]

Hi all,

I am modeling the water vapor bubble collapse phenomenon inside water close to a wall. The initial pressure inside bubble is 3000 Pa and the ambient pressure is 1 atm. I assume both phases as compressible and use VOF model. I can see the bubble contraction but after some time, I see very small pressures (around 1 Pa) below the bubble close to solid wall. then After some time I get the "floating point exception" and "AMG solver divergence" errors.
I have attached a picture of pressure contours between the bubble boundary and close to wall. The blue parts correspond to small pressures of 1 Pa.

Any idea what should I do? Is it reasonable to have such small pressures below the bubble? I use "simple" method and PRESTO! and first order upwind for others.
Please help I am really in trouble!!

[ndabir]

any ideas?