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Cavitation and Surface Vessels - 10/26/2020 12:17:52 AM

ProdigyofMilitaryPride

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From what I gathered, cavitation in real life can damage the propellers of ships. Is that true for the surface ships and subs in this game as well? I ask because it seems the safest speed for big surface ships like aircraft carriers can only go 8 knots without cavitating.

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RE: Cavitation and Surface Vessels - 10/26/2020 1:13:38 AM

stww2

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I have no idea what happens in real life, but cavitation in CMO will not cause any damage to the platforms cavitating. It will, however, make the cavitating platform much easier to detect on passive sonar.

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RE: Cavitation and Surface Vessels - 10/26/2020 1:16:07 AM

ProdigyofMilitaryPride

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Thanks, stww2.

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RE: Cavitation and Surface Vessels - 10/26/2020 1:43:42 AM

Rory Noonan

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The forces involved in cavitation are actually quite impressive so it doesn't surprise me that cavitation causes damage to props over time. I would be surprised if they had a significant impact on performance in the timeline of a typical Command scenario though.

Detection by passive sonar, on the other hand, is vastly easier if the target is cavitating. This is expressly modelled in Command; and we also provide an AI option to avoid cavitation for this reason.

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RE: Cavitation and Surface Vessels - 10/26/2020 1:49:04 AM

pbrowne

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Well the topic is on cavitation and surface vessels, but I have a question on cavitation, pump jet propulsion and submarines. Pump jet propulsion can significantly reduce cavitation and acoustic signature (link 2) and is being planned for use in large submarines such as the Australian Attack class Short Fin Barracuda SSG (link 1 and link 2) and the US Virginia class SSN. The Attack class is not scheduled to be phased in until 2030. China is also apparently developing rim-driven pump jet propulsion in their new Type 095 SSN.

Is there any modelling of pump jet propulsion in CMO to take account of this type of propulsion, especially in regard to virtually eliminated cavitation and reduced noise signature? E.g. for the current the Virginia, Astute, Triomphant and Borei class subs?

< Message edited by pbrowne -- 10/26/2020 6:13:42 AM >

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RE: Cavitation and Surface Vessels - 10/26/2020 8:55:34 PM

Parel803

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I think in real life cavitation has effect.
Your' NoCav speed goes down until there is hardly any,
Your' speed goes down 1 to 2 knots, in the end it can go up till 5 knots,
Due to vibrations it can damage you're propellor shafts and gear casing more noise, sonars like that.
with regards GJ

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RE: Cavitation and Surface Vessels - 10/26/2020 9:30:18 PM

thewood1

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quote:

ORIGINAL: Parel803

I think in real life cavitation has effect.
Your' NoCav speed goes down until there is hardly any,
Your' speed goes down 1 to 2 knots, in the end it can go up till 5 knots,
Due to vibrations it can damage you're propellor shafts and gear casing more noise, sonars like that.
with regards GJ

I don't think there is an argument about cavitation causing damage to props. The question is over what period of time will a typical ship see damage from cavitation that effects performance. Does it have an effect over hours, days, weeks, etc.?

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RE: Cavitation and Surface Vessels - 10/26/2020 10:04:46 PM

Dimitris

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quote:

ORIGINAL: pbrowne
Is there any modelling of pump jet propulsion in CMO to take account of this type of propulsion, especially in regard to virtually eliminated cavitation and reduced noise signature? E.g. for the current the Virginia, Astute, Triomphant and Borei class subs?

Yes, there is. It doesn't quite eliminate cavitation, but it does significantly raise the speed (per given depth) at which it starts happening. Shrouded propulsors are also quieter for a given speed and offer a slight advantage in acceleration.

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RE: Cavitation and Surface Vessels - 10/26/2020 10:18:48 PM

BeirutDude

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We had to take the prop off the USS Iwo Jima (LPH-2) in Metro Shipyards, Portsmouth, VA and it looked very much like those pictures. During high speed runs (above 15 knots

) she would shake like a wet dog and in the aft portion of the ship you could feel the cavitation bubbles slap the blades! The other interesting part of that was the rudder pin needed to be replaced. They had to cut through three decks to get it out with a huge tripod crane and it was a huge Clevis Pin!

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RE: Cavitation and Surface Vessels - 10/26/2020 11:18:17 PM

HalfLifeExpert

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Yeah I think damaged is caused to propellers, but it would be over a rather long period of time, far longer than the average scope of any CMO scenario.

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RE: Cavitation and Surface Vessels - 10/26/2020 11:27:18 PM

BeirutDude

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It takes years but a lot depends upon the blade of the prop. The old Iwo Jima just had a regular commercial merchant vessel type prop so it was pitted within a few years. They replaced it in 1982 and again in 1985. More efficiently designed props on Burkes, and that, have much longer lives, but yes, it won't occur in a CMO scenario...

...not even one designed by me!

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RE: Cavitation and Surface Vessels - 10/27/2020 3:22:15 AM

magi

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quote:

ORIGINAL: BeirutDude

We had to take the prop off the USS Iwo Jima (LPH-2) in Metro Shipyards, Portsmouth, VA and it looked very much like those pictures. During high speed runs (above 15 knots ) she would shake like a wet dog and in the aft portion of the ship you could feel the cavitation bubbles slap the blades! The other interesting part of that was the rudder pin needed to be replaced. They had to cut through three decks to get it out with a huge tripod crane and it was a huge Clevis Pin!

very interesting.......

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RE: Cavitation and Surface Vessels - 10/27/2020 7:30:20 AM

Parel803

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Dear Wood, than I misread the first question and apologize for my interpetation of the english language.
with regards

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