How to analysis to two types wall roughness analysis

[dragonjo]

Hi. I am the first person to start Autodesk CFD.

We would like to simulate CFD analysis for the dam spillway use to wall roughness(WR) for concrete(WR=0.1cm) and soil(WR=10cm) as boundary conditions.

However, apply two fluids of Autodesk CFD analysis, Autodesk CFD show the following message(in Korean).

I want to know if the meaning of the generated message is an error or a warning.

Also, I would like to know if there is a proper analysis method because the analysis time of Autodesk CFD with two fluids is too much(if the message’s meaning is warning)

Thank you for your kind comments.

[Xiaojin.Zhang]

Hello @dragonjo ,

Welcome to the forum. CFD has the ability to handle multiple fluids in one model. But the different fluid materials cannot contact one another. Different fluids need to be separated by solids or voids.

[dragonjo]

Hi Xiaojin.Zhang and thanks you for your answer.

But I have the other questions.

We have been received reporting documents about DAM CFD with Flow 3D and Ansys CFD. And they usally used to different Wall Roughness.

So, your answer is meaning that Autodesk CFD's limitation or all CFD solutions limitation?

Does we have to use different solid with difference Wall roughness for effect Wall Roughness analysis?

[Anonymous]

how many elements do you have in your final grid?

[sohan.kumar.thiruvakkadu · Accepted solution]

Hi @dragonjo 

There is a way to do mixing of fluid using Scalar Analysis(just to let you know, which is a bit different scenario/Boundary conditions/Material definition and not what you ask here)

But the mixing of multiple fluid materials as you require in this particular scenario cannot be done in Autodesk CFD. 

As you say in your previous comment. Yes, you can specify different wall roughness's to different solids and perform the analysis to see the fluid reaction accordingly when it flow though those solids.

Bear in mind that the roughness will only affect the pressure results. A K-epsilon turbulence model is to be used and be sure to Off the Intelligent Wall Formulation or-else the wall function will overwrite wall roughness parameters and will give poor results. 

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