Without simulation, how can we calculate and prove the difference in resistance between the bow and

Without simulation, how can we calculate and prove the difference in resistance between the bow and stern shapes of different ships? Is there any empirical formula that can be used?
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For some reason, I haven't been able to log in to this website for over a month.
I particularly like the atmosphere of free discussion on this website. Due to special reasons, I couldn't log in to this website in time. And those technical forums discussing ships and waterborne structures? I can share my thoughts that I can't express and discuss them with everyone.

 

Hi @sun
Holtrop and Mennen have different stern shapes implemented in their resistance prediction method, take a look on it there are several (revised) versions out there on the internet. You could study how the different stern shapes affect the total resistance when all other parameters stay the same.
However, it might be difficult or very subjective which stern shape gets which value. Good luck, let us know the results of your investigation.

 

I concur with mc_rash. There was a large amount of primary investigation in the late 19th through mid 20th centuries specifically addressing this question. By the mid 1950's optimum shapes had been decided for all the major speed-length regimes and are used in most powering predictions today.
FWIW, as was stated, there is no way to "prove" a difference without full scale trials or systemic model tests.

 

Thank you!
I need to find systematic materials to study the ship drag calculation method proposed by Holtrop and Mennen. Where can I find several (revised) versions?

 

We want to build a rescue vessel that needs to have both speed and flexibility (rotation performance).
I indeed haven't mastered comprehensive experiments or systematic model testing, and thus have no way to "prove" the differences.

 

If you are asking elementary questions, designing a rescue vessel is likely above you skill level. Those vessels operate at the most extreme conditions. The usual models for normal use barely apply.

 

sun's initial question isn't an elementary question at all, although it may have a difficult answer, granted, and I can't imagine why asking that question would make him unfit to design a rescue vessel. While I agree that such vessels operate in very extreme conditions (like many other vessels), I don't understand why traditional models or traditional naval architecture calculations barely can't be applied to them. Any clarification on this matter would be welcome. Thank you.

 

And I bet you want want it to be planing also.... That SoR is a very different requirement than a typical 'ship' as you asked about in the original post. You are first going to have to be clear on a size of "rescue vessel".... it could be anything from a 24' MWB to a hospital ship.
But given the PRC Coast Guard's in ineptitude lately, I can see why they would need an internet elicitation for a maneuverable rescue vessel.

 

The U.S. Coast Guard had an RFP out to replace the four 52' MLB(S) class surf capable rescue boats operating out of Gray's Harbor, Cape Disappointment, Yaquina Bay, and Coos Bay. The contract was awarded to Rozema Boat Works, Inc. of Mount Vernon, Washington on September 30. (Didn't design it in-house, darn it.)

 

We have had a model ship for a long time. It hasn't been used for many years, but both the hull and the power system are in good condition. Recently, I suddenly wanted to make use of it, but I also felt that this type of ship might not be the fastest. How can I provide the most intuitive data to prove it to undergraduate students? Especially for these students who will be working on ships after graduation, it is impossible to conduct real-time simulation and experiments. How can we inspire them to study theoretical knowledge during their school years? They must be made aware that the knowledge in textbooks can be put to use.

We always need innovative designs. Even laymen can innovate. Do we have to always view problems with a professional perspective? Or rely on AI?