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Possibility to mix Fluid Flows ?

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05-20-2013 03:24 AM

Hi, 

 

im Using Autodesk Simulation CFD 2013 and im wondering if it is it stil not possible to mix two different fluids ?

I am trying to simulate the mixing between methane and hydrogen with defined vol flows.

the help says the following: 

 

  • For mixing, an alternative (approximate) strategy is to use a general scalar boundary condition, and vary the fluid properties (density and viscosity) with the scalar concentration.

what does that exactly mean ? density or viscosity cant be changed, even when trying two similar fluids with different colors set, the error of impossible mixing is given.

is there a possibility to visualize a mixing between the 2 gases with different vol - oder massflows ? 

or is there maybe a method to simply visualize gas mixing in a certain geometry ? 

 

thank you very much for you help.

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Re: Possibility to mix Fluid Flows ?

05-20-2013 11:18 AM in reply to: Henka85

Scalar mixing is for mixing to similar fluids (2 gases, or 2 liquids) not for mixing a liquid and a gas.

 

Scalar Mixing  - if you follow the Wiki analysis guidelines, is done by assigning 1 fluid material to the whole domain. This material will have a density (and viscosity if you like) that varies with resepect to scalar, rather than varying with respect to temperature.

 

This will allow us to get an understanding of mixing of 2 constant property gases to mix within a domain.

If you assign 2 different fluids to the domain you will get an error because that is not how we would setup a scalar model and that form of material assignment is not supported.

 

 

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Re: Possibility to mix Fluid Flows ?

05-20-2013 02:11 PM in reply to: apolo.vanderberg

hi and thanks for your reply.

i followed the exact helddesk guideline but i cant access the filed of meterial properties to vary the desity conditions or desity variation method, it is always grey (unusable) even tho the scenario settings have been set to variable.

 

the step when to "Assign a single material to the vessel, but modify the density as a function of scalar." just doesnt work for me. density variation method is always unusable in material conditions. 

in my case methane and hydrogen are in gaseous state, but i set both dfd generated volume parts to the same material "methane". also setting both to a liquid doenst allow to change density conditions. 

 

is there  a thing im doing wrong here ?

 

thanks.

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Re: Possibility to mix Fluid Flows ?

05-20-2013 02:16 PM in reply to: Henka85
Yes, what you are having problems with is you cannot change the material properties while it is in the Default database. Once you edit the material, change to My Materials and then you can modify any of the parameters.
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Re: Possibility to mix Fluid Flows ?

03-27-2014 07:10 AM in reply to: apolo.vanderberg

I apologize to open this thread back up, but I noticed that there is a mention of a Wiki analysis for mixing two fluids. Could you provide a link or reference for how to find that?

I'm looking to create a simulation and optimize the blending of two fluids, and I think a walk through would help quite a bit.

 

Thanks

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Re: Possibility to mix Fluid Flows ?

03-27-2014 07:55 AM in reply to: gduelfer
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Re: Possibility to mix Fluid Flows ?

03-27-2014 07:57 AM in reply to: OmkarJ

Perfect, appreciate the help.

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Re: Possibility to mix Fluid Flows ?

06-02-2014 08:19 PM in reply to: apolo.vanderberg

Is there a possibility that mulit fluid mixing will be added to the CFD capabilities in the near future? eg. two fluid bodies?

 

Regards,

Daniel

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Re: Possibility to mix Fluid Flows ?

06-03-2014 04:18 AM in reply to: dhalls001

If you followed this thread we are discussing mixing two fluids (air + CO2, or two different liquids)

This is done via a scalar analysis