# Chrono example: CaseFlexibleGate, why the friction coefficient does not affect anything

Hi, I was trying to running the example file: caseflexiblegate. I firstly run the code without any modification. Then the second trial I opened the file "Floating_Materials.xml" and changed the kfric to 1000 times larger. The "Floating_Materials.xml" defines the material properties that is called by the "CaseFlexibleGate_Def.xml".

My question is, when I compare the two simulations, why they are exactly the same? Shouldn't it be different since I have changed the friction coefficient? Does the "fric" means the friction between the fluid and the solid boundary?

Appreciate it!

• They are the same if you do not solve collisions between the objects.

To solve collisions between solid objects, you have to include the "collision" section that will use Chrono

• @Alex Thank you! How about if I am not interested in the interaction between solid objects, instead, I am interested in the contact between fluid and solid boundary? I include the Chrono because I hope it can help me solve the frictional contact between fluid and solid (not sure it can achieve that). I haven't found any other way that can help me introduce friction between fluid and solid.

Appreciate it!

• Hi

Chrono is not meant to be used for that. Here you unfortunately only have the ViscoBound factor to influence it directly in connection with Visco.

Kind regards

• @Asalih3d Hi, thank you for the confirmation! I thought this could be the fact (that chrono frictional contact is only used for solid-solid interactions) but couldn't make sure.

Unfortunately I cannot use the "ViscoBound factor" because the "viscotreatment" was chosen as "constitutive eq.". i.e. in my constitutive model,I have to express the full stress tensor explicitly instead of using the "artificial viscosity" expression, The "artificial viscosity" formulation is too simple to be implemented in my model. Please see the other discussion I created:

In this case, do I still have a way to consider the fluid-solid frictional contact?

Thank you!

• I see, I do not know anything about that :-)

Perhaps someone else can help.

Kind regards