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-   -   Simulating buoyancy (http://www.cfd-online.com/Forums/floefd-floworks-flotherm/27176-simulating-buoyancy.html)

Shay June 29, 2008 10:42

Simulating buoyancy
 
I have a question. Can you simulate buoyancy at cosmos floworks 2008? I've got an assembly and i want to put it in water and see if it will float and if it floats than how deep will it sink in the water.

Thanks in advance, Shay

Vik Vedantham July 2, 2008 10:30

Re: Simulating buoyancy
 
As far as I know, FloWorks does not support Free Surface problems (where the interaction is between a gas and a liquid in the same control volume). In other words, the boundary layer interface between air and water in your assembly cannot be simulated. Thus, capturing the buoyancy and the sunk portion of the assembly might not be feasible.

FloWorks is excellent if the assembly is surrounded by similar fluids (multiple liquids or multiple gases), or even if a liquid and gas are separated into different volumes.

One potential workaround (that is up for debate, though) is modeling Air as a liquid of very low density, or modeling Water as a gas of very high density.

Best Regards,

Vik Vedantham.


Nick July 7, 2008 11:07

Re: Simulating buoyancy
 
I had a question about modelling air as a liquid about the time EFD.Lab ver6 just came out. The problem then (and possibly still is) was that there the solver doesn't like differences in density of more than 10x.

But that doesn't really answer Shay's question. My suggestion is to work out the answer basically on the back of an envelope. Work out how much water must be displaced for the object to float and then manually take cuts through the model to see how far up the water will go.


Rajesh Thombre August 2, 2008 03:43

Re: Simulating buoyancy
 
Can you simulate buoyancy induced flow through a vertical pipe. The incompressible fluid is intially steady and at rest at some initial temperature Tf. The heat is supplied to the pipe from outside.

Thanking you

Rajesh

Bill McEachern September 22, 2008 16:54

Re: Simulating buoyancy
 
Come on guys - this is a very basic hydro statics problem and is simple to do with any 3D solid CAD tool if not a bit tedious - just line up the CofG withthe centre of bouyancy of hte displaced liquid and make sure the displaced volume of liquid has the same wt. as the object. Simple sink and trim and you do not need a fluid code - that is taking an excavator when a spoon would do.


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