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-   -   **Help needed on plume simulation** (http://www.cfd-online.com/Forums/fluent/86386-help-needed-plume-simulation.html)

plk March 21, 2011 16:16

**Help needed on plume simulation**
 
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Here's a basic idea of what I'm trying to do: I am simulating an ocean environment using fluent were there are slightly warmer fluids intruding from the seafloor. Water temperature at the seafloor is 4 deg C. This creates a heat plume in the ocean water. I have a temperature gradient of the water calculated by a udf. Since density changes from surface to seafloor, I also have a udf to calculate density and sound speed from the temperature. Is this necessary to have these udf's for density and sound speed?

Also, pressure changes from surface to seafloor. One question I have is how in Fluent can I get this pressure gradient represented? I would think to apply it to the water face boundary condition as fixed values, but I dont see an option there for pressure.

I have tried running the simulation without the pressure conditions and I dont feel like I am getting a realistic result. The plume, which is originating from an inlet with a temperature of 9 deg C, rises all the way to the top of the model and then proceeds to destroy the temperature gradient that has been established.

Another question I have about this simulation is if you look at the picture attached, the plume is rising into water that is getting warmer as you go up. Is there a reason why the plume is not taking the heat from the surrounding water? What would make sense to me is that the plume would rise to a certain point then start to spread laterally. It wouldnt go all the way to the top of the model.

I am also wondering which type of boundary condition to use for the left and right sides of the model. I have tried symmetry, outflow, and pressure-outlet

Just fyi: the model is using a pressure based solver, using the energy equation, and k-epsilon with full buoyancy effects for the viscous model. Gravity is also turned on with a y value of -9.81

Any help would be greatly appreciated. I am not very familiar with how fluent works. I have just been thrown into it and am learning as I go. Thanks :)


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