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Dear all,

When I select Nikuradse law for bed friction, What should be the unit of the friction coefficient? My grain size is 0.689mm, So should I give 0.689 as the friction coefficient? or Do I have to change the unit to metre? i.e. 0.689 divided by 1000?

Thank you.

Hello,

For the Nikuradse law, you have to provide the roughness height ks expressed in meters. Usually, you have the following relationship:
ks ~ 3*D50 ~ 30*z0

I hope it helps.

Regards,
Laurent

Dear Leballeur,

Thank you for your answer. Now I can understand it.

Hope the simulation goes well.