Hi Sebastian

Thanks for the ideas.

When i use the equation with a cd of 0.001 (laminar flat plate) or 0.005 (turbulent flat plate) ive got high velocities of 70 m/s or 30 m/s. Both are unrealistic. Nevertheless the Bernoulli Equation makes much more sense (totally forget that one).

You could set P1 to 0 and v1 to Zero (or your free stream Velocity) and P2 to F*A

then calculate v2.

Setting P1 and/ or v1 to 0 leads to numerical problems. I solved it this way with P1 = Atmospheric pressure, v1 = 0.2 m/s (assumption, doesnt really matter), r*g*h is on both term 0 (no height difference). Since the fluid will get accelerated P2 must be smaller than P1. So the energie of the force goes into the velocity term increasing it, thus decreasing P2 by the amount of the force F/A. Ive got 2.2m/s for the velocity which could be possible.

I working on a validation case for calculating Draught Rating correctly. H Koskela1*and J Heikkinen https://www.irbnet.de/daten/iconda/CIB7276.pdf

I basically try to recreate the office room in the paper. So far i have problem getting the right velocity at the vicinity of the diffusor (it is just not good documented)

On the left picture (the green datapoints are from simscale)

Regards David