CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   Main CFD Forum (http://www.cfd-online.com/Forums/main/)
-   -   Multiphase bubble size (http://www.cfd-online.com/Forums/main/63627-multiphase-bubble-size.html)

F/lix April 14, 2009 18:54

Multiphase bubble size
 
Hello all,

I am to model a multiphase simulation of an hydraulic turbine (using CFX 11.0) for the first time. To do so, I have to specify the mean bubble diameter, dm, which I find very hard to estimate, especially since the results seem to be very sensitive to this parameter.

Bubble diameter must somehow be related to existing shear stresses and to the surrounding pressure but I don't know how. The only relation I found uses a secret constant parameter "k" multiplying the whole equation and I have no idea of it's order of magnitude, so it's useless.

Does anyone of you have had good experiences modelling bubbles ? How do you estimate their size ? Some people must use these solver capabilities !

Thanks a lot, any help is welcome

Felix

F/lix April 16, 2009 17:17

No one has ever tried multiphase in hydro turbines ? :confused:

A_Lyaskin April 17, 2009 12:43

I remember I've seen some estimations for simple flows (like pipe flows) - I'll try to find a book later.

BTW, CFX also has MUSIG model, which allow you to specify bubble size distribution instead of just one fixed size.

A_Lyaskin April 17, 2009 14:24

So the book is "Bubbles, Drops and Particles" by R.Clift, J.R.Grace and M.E.Weber. I'll try to look for other publications - I remember I've seen experimental data for bubble size distribution in pumps, which is more or less similar to your case of hydro turbine

F/lix April 17, 2009 14:46

Thanks a lot, I'll try to find the book and have a look at it. The MUSIG model looks interesting but I am still stuck with the distribution size estimation. Specifying a distribution must be more adequate though...

Felix


All times are GMT -4. The time now is 20:20.