Do waterjets create as much turbulence as props...?

[gotchiguy]

Slightly sciencey question I suppose, however:

I was just tootling around the estuary earlier and the big Condor ferry came past, I followed it out a little bit and sat in its nice a flat wake. It is an accepted fact that following directly in the turbulence of another prop makes yours less efficient, however does the style of the water jet (ie just a moving column of water as opposed to a rotating column of water) negate this effect?

[Starovich]

Props are designed to work in "still" water not turbulent, any disturbance will affect the performance. Incidentally, your hull will be less efficient in any form of turbulent water

[Hightower]

Originally Posted by Starovich

Incidentally, your hull will be less efficient in any form of turbulent water

Any form? Don't race boats have notches sculpted in to their hull to create a kind of foam/bubble turbulence so that it unsticks the hull from the water?

[Starovich]

Originally Posted by Hightower

Any form? Don't race boats have notches sculpted in to their hull to create a kind of foam/bubble turbulence so that it un sticks the hull from the water?

I was talking about running in the wake of another boat,
I would venture that even stepped hulls are not optimized to run under these circumstances.

There is a difference between laminar flow, boundary layers and running in prop wash/jet wash.

[9D280]

Originally Posted by gotchiguy

water jet (ie just a moving column of water

I think you just hit the nail on the head - Is it any worse than motoring against a strong tide, regardless of how the water is moved past you?

[gotchiguy]

Originally Posted by 9D280

I think you just hit the nail on the head - Is it any worse than motoring against a strong tide, regardless of how the water is moved past you?

That's what I was thinking, however surely that water has been through the impeller and a piping system so will be just as turbulent as water from a prop?

[Starovich]

Originally Posted by gotchiguy

That's what I was thinking, however surely that water has been through the impeller and a piping system so will be just as turbulent as water from a prop?

the water is straightened in the out nozzle otherwise it would be wasted thrust.

[Starovich]

Originally Posted by gotchiguy

That's what I was thinking, however surely that water has been through the impeller and a piping system so will be just as turbulent as water from a prop?

the water is straightened in the out nozzle otherwise it would be wasted thrust.

FRom 0:32

[gotchiguy]

Originally Posted by Starovich

the water is straightened in the out nozzle otherwise it would be wasted thrust.

Very interesting, thanks for finding that video. He seems to call them "fixed stator veins". Why are these a benefit & therefore how come it would be wasted thrust without them?

[Starovich]

Originally Posted by gotchiguy

Very interesting, thanks for finding that video. He seems to call them "fixed stator veins". Why are these a benefit & therefore how come it would be wasted thrust without them?

I'm no expert but I would posture any energy that is rotational in nature is not adding to the forward thrust, removing/reducing this will increase the forward thrust.

[Locozodiac]

Props creates higher wake's lateral waves than water jet. When sea is windy and choppy like to enter boats middle wake from behind, it's like riding on top a paved road in which you ride at a much faster rate than on your own.

If wanting to get out need to throttle back to slow down for lateral waves to be reduced in order to cross them sideways adequately and bow doesn't hit, splash or submerge directly against them. Less of an issue if doing same on water jet wakes specially when exiting sideways.

Happy Boating