SimScale CAE Forum

Multi-phase Fluid Domain Wall Thickness

Hello All,

When running a multi phase CFD simulation of fuel in a tank my CAD model is a solid model but when using the multi phase method it creates an internal section on the model for the fluid to move in what is the preset thickness of the walls that sim scale uses.

Thank you,

Hey again Will!

Glad to see you being so active right now :wink: First off, I would suggest not creating new posts unless it is a completely different topic, we could have communicated that in the other chat as well but we can keep it as it is right now.

Would you mind sharing your project with us? This might just be an option issue (external vs. internal fluid flow setting).



Yes here is the project sorry about making another I’m just trying to find the thickness of the tank walls since I did not specify any boundaries for that.

Thanks Much,

Hey @whuaman welcome, I am sure someone else is better to explain this than me, but I am still going to try to make it :slight_smile:

Whenever we perform ‘conventional’ CFD, we either conduct internal or external flow simulations or a combination. What this implies is the following:

Suppose we wish to simulate an internal flow simulation (as in your case), we import a certain geometry and first we will make a mesh of the volume trapped by that imported body. And in reality we do not consider the thickness of the tank wall, just the volume trapped inside the solid body that we imported. We need to specify ourselves what the walls of the body do, are they actual physical walls? Or inlets? Etc. Why do you need the thickness of the walls?

Whenever we simulate external flow, the flow around an object is simulated and hence a mesh around that object is created.

The combination is when we would for example have some propeller inside your tank/vessel, then the flow inside the tank is considered, however at the same time it is the flow around the propeller.

If you could specify what you are trying to achieve, maybe I can help you better.

Kind regards,

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Thank you for the response, I am trying to find the thickness of the tank walls in order to accurately determine the volume of fluid inside of the tank. By your answer it seems that tank walls are infinitesimal and just the surface is considered is this a correct assumption, such that the volume of fluid inside of the tank is equal to volume of the tank itself?

Thanks so much,

Hi @whuaman

It’s still not clear to me about what you want to perform in this simulation.
Is this what you are trying to perform in this simulation?? - To find the thickness of a container so that it can hold the forces exerted by a particular fraction of fluid inside it.


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Hello Ani,

No that’s not exactly what I’m looking for I’m just curious what the actual thickness dimensions imposed by simscale are for any general case such that when I define a fluid subdomain what is the internal boundary simscale fills the fluid to inside of the tank. For example if a perfect cylinder is used with radius of 1 and height of 2 when a fill level of 100% is chosen is the fluid filling the entire volume of the cylinder with zero wall thickness or does simscale fill it to a slightly smaller volume assuming a small wall thickness inside.


Hi @whuaman

When you assign a fluid to any volume, it fills it completely(it’s boundary is the faces of your CAD model) Simscale /or any other simulating platform doesn’t assume any thickness of the wall, it will only work with the CAD model you are feeding to the simulator. I hope that solves your query.


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Yes Thank You!

@anirudh2821998 I fully agree on your answer Ani, thanks for replying and explaining it.

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