University project: Multihull wave making drag

[marshmat]

In general the length will be the main factor in transverse wave cancellation... but I would note that an asymmetrical hull with a very flat inboard surface would likely not produce as much of a wave between the hulls as a symmetrical hull would. Just a thought.....
On CFD: I'm most familiar with Fluent (and not very, at that...); generally, CFD is great at comparison but poor at absolutes. That is, for two hulls, the ratio of any given parameter for one hull to the same parameter for the other will turn out very close to what it is in reality... but the actual values of those parameters will probably both be wrong by a bit. So it's great as a comparison tool, but is no substitute for a tank or a real hull in performance prediction.

[Leo Lazauskas]

Originally Posted by marshmat

In general the length will be the main factor in transverse wave cancellation... but I would note that an asymmetrical hull with a very flat inboard surface would likely not produce as much of a wave between the hulls as a symmetrical hull would. Just a thought.....

It's possible, but I've never seen any good experimental results demonstrating it. It's not clear that there is any significant resistance reduction by using flat inboard surfaces, especially after induced drag is included in the total resistance.

Prof. Ernie Tuck at the University of Adelaide recently gave a paper on this topic. The paper is at:

http://internal.maths.adelaide.edu.a...s/vortex04.pdf

What he found (and I have verified numerically as well) is that asymmetric demihulls might be beneficial if the demihulls are not at their optimum spacing for a particular speed. If the demihulls are located near their optimum position, it is unlikely that you can reduce the drag by using asymmetric demihulls, or by using toe-in or toe out.

Regards,
Leo.