Boundary Layer Texture?

[Leo Lazauskas]

Originally Posted by LyndonJ

Query probably my physics is flawed but the way I immediately think of this is....

Isn't the energy in the creation of the wave in the first place?
Whether they cancel out or not subsequently has little to do with wave making resistance since you don't get the energy back when the waves cancel.

You make a low wash vessel but how does cancelling a subsequently generated wave make the vessel more efficient. Whether its in the near or the far field.

You need to interfere with the wave creation in the first instance as in bulbous ships bows.

You could also think of the stern "surfing" the wave created at the bow, and thereby getting a bit of a free "ride".

Without mathematics you are stuck with fairly sloppy descriptions like that from me. I hope someone else here can describe it better than I can.

Good luck!
Leo.

[ancient kayaker]

Random thoughts on air injection:

I assume it works by modifying the effective viscosity of the water. I'd expect it to be less effective on a slow moving displacement hull because the bubbles take the shortest route to the surface. If a displacement hull is moving very quickly then wave effect has more effect than viscosity so there is little benefit to be had.

It would be reasonable to expect that a planing boat would do better. However, designers of really fast hydroplanes might not want it - I suspect they employ suction to achieve gees on tight turns and the last thing they want is air under the hull.

Air injection is not the same as the introduction of air to aid "unsticking" which requires larger quantities of air not little bubbles. It is also not related to the surface texture of a golf ball which, I understand, creates lift from the ball's spin and makes the "slice" predictable rather than random for improved range and accuracy.

Those are random thoughts which seem reasonable but may not be correct.

Small bubbles are going to persist longer than larger ones, which should be helpful. Rather than experimenting with direct air injection, I wonder if a foam can be used which is first created within the boat and then injected under it. An additive would probably help which would be environmentally undesirable, but perhaps acceptable in the context of a speed record or a military vessel at combat speed.