Collimator slots in hoses and pipes

https://rawhidefirehose.com/blog/ways-to-prevent-fire-hose-friction-loss/

From your link,I get that turbulence is one cause of friction in the hoses.Would not the collimator slots along the length of the hose remove at least part of this loss from the equation?

Of course hose size,internal friction,etc. are obvious losses.

Turbulence is more subtle.

At certain levels and conditions this might work, but I don't see a consistent positive impact...

https://core.ac.uk/download/pdf/132212339.pdf

The collimator slots do increase the accuracy of the flow meters,but turbulence is a known factor in efficiency loss.It remains to be seen which is the lesser of two evils,to be determined by testing.

Consider a Labrinth dam,for instance.The total of all of the triangles is equal to a longer shoreline dam, in a shorter actual distance span.

There is a pressure drop associated with any flow conditioning device inserted in the pipe. The flow conditioners for turbine meters ensure there is a predictable cross sectional velocity gradient within the pipe, and the turbine meter is designed and calibrated according to this ideal velocity gradient.

Errors in measuring velocity anywhere across the pipe cross section create flow measure errors. Turbulence, in the extreme going to two phase flow, would measure velocity including vapor where the mass component is missing for part of the flow, creating significant flow error. The turbine itself can generate turbulence, because it also has a pressure drop. The design of the turbine assumes a given velocity profile, eliminating a large percentage of the (micro) cavitation created by an obstruction in the pipeline, knowing the liquid pressure, viscosity, temperature, and mass per unit.

The flow conditioner is only effective for maybe 5 pipe diameters beyond the placement.

If you could predict the place in a given pipe line where cavitation or two phase flow might occur, then a flow conditioner could be helpful. Two phase flow is highly disruptive, perhaps dropping pipe flow by 90% in severe cases. However, in a flexible portable conduit such as a fire hose, you could theoretically install so many conditioners that you would restrict the capacity of the line.

I agree with you on the reason for collimator slots prior to a turbine meter,it is in the installation specs,but what I am suggesting is small,perhaps 1 mm or less along the entire length of pipe.

This could be incorporated in the extrusion process of the inner liner of the hose.

It sounds like a wild idea,but who knows the effect unless tested.I do not have access to the proper test equipment now,I am many years retired. At the time I was contracting in the instrumentation field,there was only one certified flow lab,and it was in Rochester,NY(1978) I am sure there are many modern labs now,with the progress of digital instrumentation making measurement more accurate and economical.

Perhaps someone on this forum has such access.

Some effects defy conventional logic or rules,yet they work anyway.

The bumblebee could not fly,according to engineers,too much mass,too little wings,but the bee had not read the analysis.

Years later they discovered that the motion of the wings,in a sort of figure 8 created a vortex that assisted lift.

You can certainly get around the insertion loss by increasing the overall diameter. I would think you could get a good idea of the feasibility with a CFD analysis, way beyond my skill set.

If you could come up with an ultra low loss branch flow tee, that in itself would be a significant achievement.

We do have the technology to manufacture a precision flexible multiple flow channel insert to any length, so the design proof is really all that is left. Bending radius for monolithic construction might be a constraint...

Some elbows and tees are designed as spheres to reduce losses on the turns.

The firefighters here have a selection of nozzles for different purposes.

Normally for bushfires, they want a spray effect and use nozzles appropriate, however they also have some nozzles with collimating effect.

These collimated nozzles create an integrated single stream that has significantly more range than simple open ended nozzles. They use them to reach treetops and across terrain.

The water used here is not necessarily "potable" and could come from creeks or farm dams. The impurities would potentially clog whole lengths of hose when they are most needed.

In town water supplies, we typically have a factor of ten capacity over the firefighting draw rates and they are a factor of ten above peak annual (hourly) demand. As the water supply authority, we upgrade water mains when we see a 10% pressure difference at customer end between static (no demand) and peak demand situation. We are regulated to have 80% of treated water reservoir demand available for firefighting, so domestic usage really only uses the top 20% of reservoir capacity of any use/fill cycle. Firefighters are actually able to "pump the mains" to negative pressure, but I've never seen that done. We are not big city, so 4 hydrants in one street at 15L/sec each is maximum that I've noted.

One needs to understand what <...turbulent flow...> is from the perspective of fluid dynamics. In a round pipe, at Reynolds Numbers greater than about 2300 the regime is turbulent and below that it isn't. In laminar, viscous forces predominate; in turbulent flow, inertial forces overcome the viscous forces.

Reynolds Number is a function of fluid properties, its velocity, and the pipe diameter and has nothing to do with the insertion of a <...Collimator...>. All a <...Collimator...> is doing is evening out the velocity vectors in the pipe so that the effects of elbows, bends, valves, etc. upstream are taken out prior to its passing a flow instrument. Downstream of it, turbulence may well resume, whether it is laminar through the <...Collimator...> or not, and the velocity profile across the pipe is more uniform with respect to radius from the centre of the pipe from what it was upstream. It is this feature that improves the accuracy of the flow instrument.

Anything introduced into the inside of the pipe will increase the pressure drop relative to an empty pipe as it introduces stationary surfaces for the fluid to pass by, introducing friction, which resolve as increased pressure drop. So it simply isn't a correct statement that a <...Collimator...> will <...increase flow and reduce losses...>, as it is not its job to do so; it is there to improve the accuracy of a downstream flowmeter.

The reason that <...Fire hoses are replaced frequently...> by fire authorities is to make sure that in an emergency 100.0% of the available flow is heading towards the fire to put it out, and not around 63% with the rest coming out of leaks that would exacerbate an already time-precious event where lives and property are at stake, and reducing the range of the nozzle on the end of it thereby putting at grater risk the lives of the individuals holding the nozzle, who would have to get closer to the fire to be fully effective.

Fire authorities and operatives don't care about the turbulence of the flow in the pipe. Their job is to bale as much water as is necessary onto the conflagration with the aim of putting it out in the shortest possible time. In such circumstances, as much turbulence as possible is the effect of as much flow as possible, and the pressure drop is what it is and isn't an economic factor in the operation.