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Fluid Flow over an object

11 REPLIES 11
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Message 1 of 12
sfitzgerald2
1073 Views, 11 Replies

Fluid Flow over an object

Hello, 

 

So as the title of my message states, I'm trying to look at the flow of fluid (specifically water) over an object in Autodesk CFD. I've gone through tutorials and looked at other people's examples, but for some reason I still can't get it to work. I've made a virtual flow tank and have placed my object inside of it. I set the material for the object (say abs molded) then set the material for the flow tank (sea water liquid phase). I've placed the flow rate and so forth but for some reason I'm getting an error message stating that "The density of the working fluid is less than or equal to 0". I've gone back and chekd all the data, I've checked the environment data as well and it all seems squared away. Does anyone know what I'm doing wrong? 

 

-Cheers

11 REPLIES 11
Message 2 of 12
harm
in reply to: sfitzgerald2

Hello there, I have exact the same problem, is somthing wrong with setup?

Message 3 of 12
Royce_adsk
in reply to: sfitzgerald2

Hi Sam,

 

What you are running into is actually a known issue.  

 

What I would suggest as a workaround is to create a new material with the same material properties as our Sea Water (Liquid phase), but change the 'Phase' property to 'Variation Method: Vapor Pressure' with a value of 0 instead of the linked Vapor Material.

 

Does that allow your model to work successfully?

 

Thanks,

Royce



Royce.Abel
Technical Support Manager

Message 4 of 12
harm
in reply to: Royce_adsk

Hello, I tried this but it did not solve the problem

Message 5 of 12
aaronlevine
in reply to: sfitzgerald2

Hi,

 

I'm having the same problem. Any idea why this is happening, Royce?

 

Aaron

Message 6 of 12
Jon.Wilde
in reply to: aaronlevine

Have either of you tried launching from CAD and setting it up again? We have seen this work also.

Message 7 of 12
samfitz17
in reply to: sfitzgerald2

No I have no tried that yet. I'll go and see if that works tomorrow. Do you know if there are any good video tutorials? I'm trying to simulate flow over hydrofoils and as I've said before, I'm running into some problems. 

Message 8 of 12
Jon.Wilde
in reply to: samfitz17

Hi,

 

If you have been through the tutorials I would have thought you have most of the knowledge you will need for this.

 

I suggest you consider running in 2D in possible. The more mesh we have with external aero models the better, and utilising the 2D approach can be of great benefit, more mesh, lower runtime.

It would also be worth using Advection Scheme 5 and mesh adaption too.

 

Other than the density issue, are you finding other problems?

Message 9 of 12

Was this issue ever solved? I'm having the same problem.  I was able to run all the tutorials, but when I try my own problem (sea water buoyant flow and convection), I get "The density of the working fluid is less than or equal to 0".

Message 10 of 12
Jon.Wilde
in reply to: g_wheeler2001

Hi,

Did you try launching from CAD and setting the model up again? This was the only workaround I found to work reliably.
What version of CFD are you running?

Kind regards,
Jon
Message 11 of 12
travward
in reply to: Jon.Wilde

Jon, What do you mean by launching from CAD? You mean from inventor? I'm running 2013 and getting this issue. I was told it was an universal issue and that the only fix was to upgrade..

Message 12 of 12
Jon.Wilde
in reply to: travward

Yes, I mean to start from Inventor and launch again into CFD. Perhaps an upgrade is the only solution but I have also seen the problem simply disappear when starting again from scratch like this.

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