A little help please

I've been looking for ANY research on the effect of marine nozzels on small craft without any luck. On a large vessel they seem to produce great gains in in fuel consumption and running speeds Has this technology ever been applied to small craft? (under 8 meter)

Any input would be appreciated

Thanks in advance
Dave

 

Dave,

Does there actually have to be data on smaller vessels? I pressume that when this technique works on larger craft, it also works on smaller craft?!

 

Good question!
But in my limited knowlege, (VERY limited) I think there are different variables involved. Proportions of the boat, hull design ie: strakes and chines which change the laminar flow and are not really applicable on a 100 ton vessel, O.A.L., speed of the prop, ( a couple of rev's vs. 3500+) a smaller craft will plane out, ect.

If I am off base here let me know. I do have a habit of over thinkin'

Dave

 

No. your not overthinking.

I just think the variables you mention are for the biggest part covered in the research on nozzles on larger craft. For example freighter/tug = proportion of the boat and hull design.
Flow into the nozzle is covered for sure, the reason is not important (chines or A-bracket) it's that you can predict there will be a change in the flow!
On the speed of the prop I can tell you that I've seen outboards fitted with nozzles aand it was stated this reduces fuel consumption and improved manouvrability, so that works.
Don't get me wrong, I'm not saying stop looking, I'm just suggesting there might be less to it then you think!

I'll keep my eyes open anyway!!!

 

Thanks Peter

 

Jammer,

Came across these sites:

http://www.poseidon-pde.nl/PDFdocuments/nozzles.pdf
http://www-waterloo.ansys.com/cfx/cases/detail.asp?ID=18


Anything for you?

 

Jammer,
There are two things about nozzles that I have heard. One is that they are efficient only at displacement speeds. The other is that they only function when the prop is turning; that is they have very little steering effect if the wheel is stationary. This is hearsay evidence and someone may be able to contradict me with real data or experience.
Gilbert

 

Peter,

According to the CFX study, they state that "The flow velocity through the nozzle at full scale is higher than at model scale." I realize the study does not specify the the size of the model used, but in other studies, models are in the general proportions of the size that I am questioning.
I guess I'll have to research some "model" studies.


Gibert, thank you for the input. Just raises more questions.