How to have a constant flow in a spillway?

Ali_gh97 · January 30, 2023, 05:16

hey everyone, I'm modeling flow in a bell mouth (morning glory) spillway and I want a specific flow rate and I can't reach that. for instance I want a 600 m3/s volume flow rate but I can't have it fixed at that number it varies like from 500 to 700 m3/s.
any tip on that?
I have used volume flow rate and specified pressure as boundary conditions and the results were similar.

MSM1985 · January 30, 2023, 07:31

The probable reasons of fluctuating flow values could be:

i) The results might be extracted before steady state. The model finish time should be enough to reach simulations to a steady state.

ii) A finer mesh will definitely increase the accuracy.

iii) Flow measurement should be made where there flow is almost uniform.

Ali_gh97 · January 31, 2023, 15:15

Quote:

Originally Posted by MSM1985

The probable reasons of fluctuating flow values could be:

i) The results might be extracted before steady state. The model finish time should be enough to reach simulations to a steady state.

ii) A finer mesh will definitely increase the accuracy.

iii) Flow measurement should be made where there flow is almost uniform.

Thank you for your time
Yes I do reach steady state and the results are converged as well and I have tried a better mesh but it didn’t get any better

MSM1985 · February 1, 2023, 03:19

While modeling a morning glory spillway as shown in the picture, initial condition is also important. Do not fill pipe completely. Instead give time dependent boundary condition where waterlevel increases from reservoir floor to headwaterlevel. This will prevent spillway from drawing additional water as the mouth of morning glory does not flow full.

Ali_gh97 · February 1, 2023, 05:07

Quote:

Originally Posted by MSM1985

While modeling a morning glory spillway as shown in the picture, initial condition is also important. Do not fill pipe completely. Instead give time dependent boundary condition where waterlevel increases from reservoir floor to headwaterlevel. This will prevent spillway from drawing additional water as the mouth of morning glory does not flow full.

Thank you yes I think I'm gonna use the time dependent BC and see how it goes.
Thank you for your time

January 30, 2023, 05:16	How to have a constant flow in a spillway?	#1
Ali_gh97 New Member Ali Ghafouri Join Date: Jan 2023 Posts: 3 Rep Power: 3	hey everyone, I'm modeling flow in a bell mouth (morning glory) spillway and I want a specific flow rate and I can't reach that. for instance I want a 600 m3/s volume flow rate but I can't have it fixed at that number it varies like from 500 to 700 m3/s. any tip on that? I have used volume flow rate and specified pressure as boundary conditions and the results were similar.

January 30, 2023, 07:31		#2
MSM1985 Member Sehroosh Join Date: Apr 2019 Location: Pakistan Posts: 60 Rep Power: 7	The probable reasons of fluctuating flow values could be: i) The results might be extracted before steady state. The model finish time should be enough to reach simulations to a steady state. ii) A finer mesh will definitely increase the accuracy. iii) Flow measurement should be made where there flow is almost uniform. Ali_gh97 likes this.

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