Dear all,

I have suffered a simple problem now.

I simulate a simple pipe flow with a pipe length of 1m, diameter of 0.4m, and a roughness height of 0.0005m.

The inlet velcoity is 0.2533m/s.

The pressure loss what Fluent gets is 1.58e-3 m(unit with water high).

But the pressure loss gotten by Darcy equation is 1.53e-4 m.

So big different between the CFD and tranditional method.

Could anyone can advise me??

Thank you very much.

Andy

What are your inlet and outlet boundary conditions, and how do these compare to the assumptions in the method of hand calculation? Have you a flat velocity profile and an outlet, ot are you using twu developed flow profiles? DOes the correlation allow for flow development? What is your y+ and are you accurately modelling what happens at the wall. Have you static as well as frictional losses to account for? What if you create a 10m long pipe and look atthe pressure loss between 8 and 9m. Are you sure that the roughness is inputted correctly and that you have converted it to mm in the correlation?