Hello,

I've been struggling with a school project for some time now.

I need to find out the speed at wich a tank is draining to make a model out of it (in simulink). The model will show a x-t graph, x being the height of the water in the tank.

The flow is laminar, but the lenght of the exittube is significant enough to enduce friciton.

A basic model that i made can already account for the diameter of the exittube, but not yet for it's lenght (and thus friction).

When i tried implementing formulas for head loss the model didn't work as i had hoped. I think i might be using the wrong (combinations) of formulas.

I hope someone can help me with finding out the problem i'm facing here. In calculating the speed of the waterlevel i used the following formulas:

- Bernoulli's equation (with head loss added on the right side of the equation)

- v2=sqrt(2gh)

- P2=density*g*h

- Head loss = f*L/D*(v_{average}/2g)

- Friction factor = 64/Re

- Re = (density*v_{average}*diameter)/viscosity

- v_{average} = (dP*D^2)/(32*viscosity*L)

Thank you kindly for your response.

Greetings,

Teun

**Edited by Student2001, 16 February 2020 - 01:52 PM.**