Hydraulics - calculating the size of a water jet & a water splash

[JBFarrell]

Hi,

I'm looking for guidance on calculating the spray of water as it leaves a pipe (Problem A) and also the size of the splash it causes when it hits water a certain distance below the pipe discharge (Problem B). See attached pdf for illustrations.

Problem A: Water is spraying out of a pipe and I want to know how wide the spray of water will be at any distance after it leaves the pipe.
Application: Wastewater Membrane Filtration during the cleaning step when the basin is being filled with water and we want to be sure that the jet of water filling the tank does not hit the membrane fibers.
- Pipe diameter = 10 inches
- Velocity = 6 to 12 ft/sec

Problem B: Water is jetting out of a pipe and I want to know the width and height of the splash it causes when it hits the water.
Application: Drinking water filtration during the backwash step when the backwash water discharges into a trench drain. We want to make sure the trench drain is large enough to prevent water from splashing onto the floor.
- Pipe diameter = 12 inches
- Velocity = 4 to 8 ft/sec

Thank you!

 

[JBFarrell]

Corrected link to illustrations of Problems A and B.

 

[bimr]

For the wastewater application, one should try to minimize the splashing as it will create foam. An inlet chamber is recommended.

An inlet chamber prevents the inflow from directly splashing into the basin and conveying air along with it. The intake structure should be designed with adequate width and depth to limit the maximum approach velocity to 1.5 ft/sec.

For the water application, a covered sump with a depth of around 3 feet should work.

 

[LittleInch]

Try this

https://digitalcommons.usu.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1030&context=ishs

And search fro "unconfined plunging jets"

I think you've got problem B all wrong. A continuous water flow won't create a splash as though you've dropped a large rock into it.

You get air entrainment instead

Problem A is complicated by the fact you have an elbow right in front of the pipe end. You will get all sorts of swirl and turbulence which is difficult to simplify.

There seem to be much better ways to address this by diffusers, flow paths etc

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Thanks for posting that article.

 

[cvg]

suggest following bimr advice. your velocities are much too high. transition to a larger pipe size might help a bit. but to eliminate the splashing and air entrainment, you need to increase your tailwater so the jet is submerged