Formula for two adjacent weirs

[TimBL]

I am looking at a flow control/flow splitting device using two weirs set at different levels and adjacent to each other in the same stream. Flow volumes are large max 450l/s. Any ready formulas out there for calculating the head or flow for this arragement?

 

[saxon]

Timbl, When you say "weir" what kind of weir? Each type has it's own flow vs head characteristic. Do a web search for Isco. They are the experts on open channel flow measurement.

Hope this helps.
saxon

 

[rmw]

Cameron's Hydraulic Data has weir formulae for a variety of wier types.

Other threads on this site state where one can get a current or older Cameron versions.

rmw

 

[TimBL]

Some clarifcation the weirs are thin plate weirs. The weirs will be set in the channel side (at 90 degrees to the normal flow) there will be a step between the two weir levels

 

[hacksaw]

sounds like you need a hand book on open channel irrigation

most of the documented weir flow fornulas are for normal flow with known upstream conditions.

 

[katmar]

It all depends on what you want to do. If you want to meter the flows accurately then you must ensure that all the requirements regarding distance from flow disturbances are met, taking into account that each weir is a flow disturbance to the other weir(s).

But if all you want to do is achieve a flow split where +/-15% accuracy is OK then you have got a chance. From what I have seen on weirs the flow disturbance diminishes rapidly with distance, and if you have about 18 inches (450 mm) the weirs will have little effect on each other.

As I have said here several times before - the answer depends on the question, so the question has to be clearly stated if you want a clear answer.

 

[waterexpert]

TimBL,

There are some relevant formulae at:

http://www.seanmoran.co.uk/Water Feature Design.htm

there are also lots of useful tools for this sort of thing (quite a few of them free)at

http://www.lmnoeng.com

Hope this helps

Seán

http://www.seanmoran.co.uk