Vibration in ships

Everything... absoloutly everything. From the Old Man's thunder box to the boiler suit dhobie engine including the galley spud basher, not to mention the clankie bits to make it move which will include the prop, worn shaft bearings, and large 'coastal hostesses' paying an in-port visit... it goes on forever, which item of engineering scrap are you particularly worried about?

As stated, just about everything, wind, from the ships motion in the water, the waves as the ship moves through them (pitch and roll), machinery (engines, shaft turning, auxiliary machinery, reduction gears, generators), you name it.

Yeah, everything. OK, only most things, I'm not sure the hostesses are large enough.

You need to put some transducers on the hull or deck plating and measure the vibration. Do a fourier transform analysis to isolate the larger harmonic frequencies. Then start looking for repetitive motions that have the same frequencies, e.g prop rotation speed, engine speed, any generators, etc. That should let you figure out what is making the major contributions to the vibrations.

I would not ask about the frequency of vibration of the hostesses unless you want a black eye....

Hostess vibration frequency would probably be between once a day and 3-4 times an hour.

Not that I would know...

I was thinking more of the higher frequency signal from a single hostess event. I wonder if we could predict amplitude? Maybe I don't want to know.

Not mentioned specifically, but blowers used for air circulation also is potentially a big provider of noise and vibration throughout most any given ship.

Vibration in ships IS a big issue and some companies spend a lot of cash on vibration analysis, mainly to pinpoint projected downtimes of machinery through failure, or preventive maintenance programmes. Ship's these days tend to be built of thin plate high tensile steel, as opposed to the thick plate 'good' stuff of forty years ago or more that were very difficult to turn rusty, as an example. These days on a ship say a 25 000ton RO/RO you can stand on the after deck and feel the anchor go down the hawse pipe... and I wasn't kidding about the spud basher. The bottom line here is that you get what you pay for, shipbuilders build to a price (like most jobs), and if you want cheap that's what you get, and as much vibration as you can only nightmarishly dream of.

They aren't going to be able to get rid of the vibration as long as they are ran by machinery.

Yes the Battleships of old had hulls that were as thick as the largest gun size and for a battleship that was 16". They still had vibrations. Submarine sonar technicians are able to identify a ship just by the vibrations because each ship has its own unique vibration signature. With the new ships having thin hulls, just passing through the water is going to produce vibration and because of the light construction of the ships the crew is going to feel it a lot more.

I served on the last true cruiser in the United States Navy the USS LONG BEACH CGN-9, when we did high speed testing it vibrated and it was of thick hull construction.

Later I served on minesweepers in the Arabian Gulf, they were made of wood and they didn't vibrate so much.

md ajkhan, your original question was what causes vibration in ships...

What is undocumented and is of as much importance especially if you're going into the design of machinery and equipment, is what are the effects of vibration in ships. There's a huge amount of related and anecdotal information that has never been recorded that ships' staff have had to deal with over the years... and it's endless.