# how to consider buoyancy without switching heat transfer on

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 November 26, 2012, 15:41 how to consider buoyancy without switching heat transfer on #1 New Member   Join Date: Jan 2012 Posts: 28 Rep Power: 7 Hi, I am a beginner of cfx. In my simulation, I want to consider buoyancy, but heat transfer. In default setting of buoyancy, the Buoy. Ref. Temp. option cannot left blank. If I specify a temperature here, the simulation type will be switched to heat transfer. Is there anybody can show me how to fit this problem? sorry for that my english is quite poor. Thanks in advance

 November 26, 2012, 17:27 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,805 Rep Power: 107 What is driving the buoyancy in your simulation? Is it temperature gradients, multiphase or multicomponent?

November 27, 2012, 06:13
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 Originally Posted by ghorrocks What is driving the buoyancy in your simulation? Is it temperature gradients, multiphase or multicomponent?
it is independent of temperature, i just want to model the motion of a rigid ball in a container, so i need to consider the buoyancy. thanks ¬¬¬

 November 27, 2012, 06:22 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,805 Rep Power: 107 I see. Can the bouyancy of the rigid body be represented by an external force? Then you do not need to use the buoyancy model in CFX and can turn all that stuff off.

November 27, 2012, 06:25
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 Originally Posted by ghorrocks I see. Can the bouyancy of the rigid body be represented by an external force? Then you do not need to use the buoyancy model in CFX and can turn all that stuff off.
thanks for your guidance, i will have a try¬¬¬many many thanks¬¬

 November 27, 2012, 12:52 #6 Member   anonymous Join Date: Jun 2011 Posts: 58 Rep Power: 8 Please correct me if i'm wrong. But my understanding is that it does not turn on heat transfer. The buoyancy reference temperature is used to get a density difference based off a difference in temperature. i.e. If you have a domain filled with water at 25 C and you apply a reference temperature of 0 C then it would act to create a force on your full domain based off the difference in density of water at 25 C and water at 0 C. It does not apply a heat transfer. In your case, if you only have 1 phase and it fills a container setting the buoyancy ref temperature to the same reference temperature of your fluid (typically default is 25 for both air and water) should be fine and you will be able to apply your gravity force. *note: you can check the reference temperature of the fluid your working with by opening the materials tree menu and clicking on your material. Its a material property of the fluid

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