in instructions for Challenge 7, we have
Initial Solution: Vz=6 m/s
Boundary Condition - inlet: Vz=23 m/s
Should't they be equal to 23m/s ?
Boundary Conditions - Outlet: averaged static pressure imposed.
Should we specify it as "Cartesian - Static pressure imposed" or as "Cylindrical - Static pressure imposed" (we used cylindrical for the Inlet)?
I see in the demo video that Cartesian is used.
Question 1, also Vt is different, 1m/s in initial solution, 3 m/s in boundary conditions. Shall we use 3 overall?
to question 1: Please use as initial solution the lower value with 6 m/s (and 1m/s for vt). This is on purpose. In general it is a good idea to be as close as possible to the final expected flow field. In practice the geometry is complex and we need to find a good compromise. For this particular case 23m/s would be a very suitable initial solution for the smaller pat of the pipe. In the larger part of the pipe a much lower value is more suitable. In general it is more robust for the simulation, if we choose as initial solution a value, which is rather on the lower side. For some applications it even make sense to initialize the domain with 0m/s.
To question 2: You can choose either of these. We can do this because we specify a constant value. Here it does not matter, if we specify in the cartesian system the constant value or in the cylindrical system the constant value. But your thought is right!