Cavitation, papers and my other stuff
 

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

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.

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?

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

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..

Cavitation simulation procedures using Fluent
 

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

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

Cavitation simulation in Fluent
 

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

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

Thank you so much Daniele!!

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!!

any ideas?