CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

Rayleigh number and rate of fluid rise due to natural convection in a pipe / duct?

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Search this Thread Display Modes
Old   July 6, 2013, 14:50
Default Rayleigh number and rate of fluid rise due to natural convection in a pipe / duct?
New Member
Join Date: Jan 2010
Posts: 28
Rep Power: 16
bzz77 is on a distinguished road
I have calculated densities for the liquid and solid parts of a substance that has partly melted. The liquid and solid would be at the same temperature.

I would like to do a simple calculation of approximately how long the chocolate would take to rise under natural convection (due to buoyancy). Could anyone please suggest a good way to do this?

I was under the impression that this would be very simple--that I should calculate a Rayeigh number. But after searching extensively online, I realize that I'm very confused. There are various ways to calculate the Rayleigh number and it doesn't actually provide velocity anyway. I guess I would want to use a Rayleigh number for an enclosed duct / cylinder, but I can't find one. I realize this is probably a silly question, but if anyone could point me in the right direction, I would be very grateful.

The reason I want to do all this is that when I change certain conditions under which my density calculations are run, the liquid - solid density contrast changes. So for some conditions, rise should be faster. I want to demonstrate how velocity / rise time can be affected by changing density contrast, when all other parameters remain the same.
bzz77 is offline   Reply With Quote


buoyancy, buoyant flow, convection, rayleigh number

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
CFX fails to calculate a diffuser pipe flow shenying0710 CFX 7 March 26, 2013 04:13
Natural Convection Boundary Conditions, tips or advise needed ! Logan Page ANSYS 0 September 27, 2010 18:44
air bubble is disappear increasing time using vof xujjun CFX 9 June 9, 2009 07:59

All times are GMT -4. The time now is 10:03.