Hi,

I'm trying to make a SMath worksheet for calculating flow over weir. The problem is iterative, i.e. when you calculate it "by hand" you have to estimate some values and then check if your estimation is close enough.

Here is my workbook:
suppressed_weir.sm (79 KiB) downloaded 36 time(s).
suppressed_weir.pdf (365 KiB) downloaded 39 time(s).

I tried to solve this problem by using "solve (2)" function, but I'm obviously doing something wrong...

Could anyone help me with this?

Cheers,
Sandro

Wrote

I'm trying to make a SMath worksheet for calculating flow over weir. The problem is iterative, i.e. when you calculate it "by hand" you have to estimate some values and then check if your estimation is close enough.

The masflow rate of a weir is not iterative.
https://www.brighthubengineering.com/hydraulics-civil-engineering/65880-open-channel-flow-measurement-5-the-rectangular-weir/

Wrote

Hi,

I'm trying to make a SMath worksheet for calculating flow over weir. The problem is iterative, i.e. when you calculate it "by hand" you have to estimate some values and then check if your estimation is close enough.

Here is my workbook:

I tried to solve this problem by using "solve (2)" function, but I'm obviously doing something wrong...

Could anyone help me with this?

Cheers,
Sandro

Hope this is enough for you.
Solve can't work with units.
Sometimes it just refuses even without units.
Use roots(), FindRoot(), al_nleqsolve() if it fails.
In this order generally.

Regards.

suppressed_weir1.sm (82 KiB) downloaded 40 time(s).

Wrote

Hope this is enough for you.
Solve can't work with units.
Sometimes it just refuses even without units.
Use roots, FindRoot, al_nleqsolve if it fails.
In this order generally.

Regards.

Thank you, overlord, that works exactly as I wanted!

Wrote

The masflow rate of a weir is not iterative.
https://www.brighthubengineering.com/hydraulics-civil-engineering/65880-open-channel-flow-measurement-5-the-rectangular-weir/

Jean Giraud, I wasn't precise enough. The problem is regarding the flow over weir, not calculation of a flow rate, per se.

Regards,
Sandro

Wrote

Jean Giraud, I wasn't precise enough. The problem is regarding the flow over weir, not calculation of a flow rate, per se.

1. You calculate mas flow rate for: Nozzle, Venturi.
2. You size orifice plate for given nominal mass flow rate
3. You calculate mass flow rate for a given prefabricated weir.
If you have the mass flow rate from another independent device
per say: partially filled pipe ... you can solve/sanity check.
That is pretentious to sanity the established Standard.
Nothing wrong to sanity the Standard, but sanity $$$$
The biggest Venturi I have been involved 8 ft diameter [$$$$$$..]
It needs the pipe full flow, not partially filled.
ISO-5167 goes up 36" diameter.
From the attached document, be more specific.
Cheers ... Jean

Inst_Weir.sm (230 KiB) downloaded 51 time(s).

Wrote

Thank you, overlord, that works exactly as I wanted!

I am glad to help you exactly as you wanted.
Have a nice day, feel free to ask anything.
Someone shall answer your question as your need.

Regards