hull model testing

[wardd]

i was thinking weights and balance and loading and to get an idea of how it would behave , rolling etc?

[Leo Lazauskas]

Originally Posted by ancient kayaker

Is it practical to determine the skin-friction separately by performing a fully immersed (submerged) test then adjusting the surface results to isolate the wave resistance, since they scale differently?

If so, then the effect of the support structure can be eliminated from a submerged test by weighting a model to float stem up and releasing it at the bottom of a tall tank, noting it's speed at different bouyancies. The effect of the submerged deck can be removed by cutting off the top of model at the waterline and attaching a duplicate to it as a mirror image.

It's probably not a good method because (among others):
1. You wont get the same type of separation near the stern, and you might get unusual flow separation at the bow. Hence there might be some very odd form drag effects.
2. Skin-friction depends mostly on the wetted surface area.
3. There are some interactions between the waves on the hull and the boundary layer for surface-piercing vessels, so skin-friction is not exactly proportional to surface area. Remember: it's Froude's "Hypothesis", not Froude's "Law
"

The idea of a double body is used in some analytical treatments (albeit in a different way), so your proposal is not a completely silly idea.

Leo.

[MikeJohns]

Leo
I'm sorry, I missed your posts here for some reason the boat design email didn't flag any reply.

Thanks for your effort it's appreciated.

I have seen studies on brash ice but not oil, it may have been one of the early ship science reports but unfortunantely it's too escoteric for me to have filed it anywhere. The Baltic coutires naval research would be very likely have material in this line.

Cheers

[Joakim]

Originally Posted by Leo Lazauskas

And now a question for you...
I have been working on the resistance of ships travelling
through a surface layer of ice slush. Have you seen any
experimental results for that kind of thing, or for ships travelling
through oil-slicks?

Yes I have seen some results and I have even seen the experiments a few times at the ice model basin near by: http://www.stxeurope.com/businessare...logy/services/

Unfortunately I don't have anything I could show you nor did I find any reports from the internet.