# Methane through a pipe

Hello, i would like to simulate the shifting of methane gas in a 500 km pipe in order to determine the loss of pressure, i have uploaded a model thanks to onshape but the lenght of the latter is limited to 100 m, in that case, how can i get around the problem ?

thanks a lot

Sorry for the delayed response, just saw that you posted it in the Projects section.

So about the dimensions, SimScale supports models that do not exceed any dimension by more than 50000 meters, you can try to scale it down and work with that. Regarding the pressure loss you can use a result control item and use Area Average and choose two surfaces - in your case inlet and outlet - to visualize the pressure drop in the post-processing plot. Hope that makes sense, let me know if you have any further questions.

Best,

Jousef

Hello, i want to do a simulation of methane gas in a pipe in order to determine the loss of pressure in it. However, i have faced two main problems:
1-Although methane gas is compressible, is an incompressible simualtion possible in a good approximation ?
2-Iâ€™d like to set a roughness height number for my simulation (initialy 0), however simscale refuse to fix the number chosen (roughness of steel around 0,2 mm 0,008) and stay at 0. Why ? and how can i modify it ?

1. Thatâ€™s correct, you would have to perform a compressible flow simulation - however compressible simulations are not very â€ścooperativeâ€ť in terms of convergence but I think there can be a way to achieve a solution. @Get_Barried & @anirudh2821998, want to add some ideas here?

2. Please share the project, will check this out. You should be able to change the roughness height

Cheers,

Jousef

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This depends on what youâ€™re trying to find out. If you are looking for pressure losses that occur in the bends and angles of pipes, then yes incompressible is enough. If instead you are looking for overall pressure losses that say dependent on other less flow related losses (not sure about this, ani can probably chime in) then compressible may be more appropriate though I would think that the increase in accruacy would not be worth the hassle.

So do define exactly what you are looking for at where.

Cheers.

Regards,
Barry

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Thanks for your replies, this is what iâ€™ve done 500 m pipe with incompressible fluid, iâ€™ve still tried to modify the roughness height but it stays at 0 .
Moreover, if i want to do the same simulation with compressible fluid, should i change features ? or i just take the same simulation but with a compressible fluid ?

I have tried different numbers and all workâ€¦thatâ€™s odd. CFD Squad, can you also please try to modify the number and see if it works for you?

Just creat a new simulation of type compressible and keep your settings in the first iteration. I am quite sure that we need to make adaptions anyway

Best,

Jousef

Finaly, i can change the roughness height but i cannot set a number under 1 m wich is problematic because the roughness of steel is around 0,045 mm (0,000045 m), iâ€™ve even tried in inches but the problem is the same, what can i do ?

Hey @theotoilette!

Please use a dot as the delimiter and not a comma as you are trying to do. This is an issue I will immediately report, there should be a message saying that a comma is not allowed. Let me know if that helped!

Best,

Jousef