Cavitation, as I understand it, is manifested as tiny bubbles in a liquid generated by sudden pressure changes. There are traces of vapor inside but the bubbles but the pressure is very low, nearly a vacuum. Surface tension and external pressure cause the bubbles to implode immediately after they form. The pressures and temperatures that result can in some circumstances be extreme enough even generate tiny bursts of light, and the shockwaves produced can be very destructive on a microscopic scale. Of course, after you generate a couple zillion of those little bubbles, large amounts of adjacent materials can be torn into microscopic pieces, which is why cavitation is such a concern.
Crazy Ivan maneuver in Red Storm Rising
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that sounds fair and I think you misunderstood what I meant, water vapor out of the air, condensing, forming droplets on the item. The droplets may stay as such or form a larger mass, air bubbles then forming within the droplet or liquid mass may cause cavitation under the right environment, even though the medium is primarily air
but as I said, I'm a pleb, with no training or real experience in fluid dynamics and could well have the wrong end of the stick, as it was a guess with a question mark
but as I said, I'm a pleb, with no training or real experience in fluid dynamics and could well have the wrong end of the stick, as it was a guess with a question mark
and I've worked on 3 sub classes as well as been involved with wind turbine developments, including one co-funded by the USN because of the similarity of effect on wind turbine cavitation to propulsion cavitation
you've had someone else who's also been involved with wind turbines say similar things.
it is fundamentally irrelevant what you think if the industry uses the term to describe what happens when blades runaway.
seriously, get over it. you are obviously not interested in the fact that its a term used in wind turbine engineering. you're keen on the argument.
I'm not. as said before. I'm done here.
OK.
The water droplets condense on the surface. Next you need an energy input to cause the bubbles to form (Note: These are not air filled bubbles but water vapor filled bubbles. Air has to escape for a bubble to collapse. A water vapor bubble will collapse if the vapor condenses, or the vapor will condense when the bubble is collapsed by other forces.), a blast of ultrasonic sound energy should do the job nicely. But a problem occurs in the next step -- when the bubbles collapse the shockwaves acts in all direction rupturing the surface tension that holds the droplet together and propelling a portion of the droplet mass outward away from the cavitation bubble. The droplet would then need to be reformed before the next cavitation bubble can form.
So, yes it could happen. In fact there is at least industrial process that uses ultrasonics to knock water droplets off a surface which may be exploit this mechanism. :hehe
one of the more bizarre side effects has been surface pitting, and in extreme cases, delamination of the blade. pitting on a prop on a sub will actually trigger material failure, and that was one of the early problems for Collins due to a combination of materials science issues and blade design. Problem solved by the USN, ironically with the Swedes complaining about IP issues even though it was their engineering and design solution which caused the problem in the first place. go figure
the japanese are quite enthusiastic about developing carbon fibre or compound material solutions for both marine propellors and wind turbines blades as the pitting and/or delamination effect is reduced substantially.
there have been some mules made of pump jets and pods using carbon fibre blades but none in production because they're almost horrifically expensive.
one of the worst examples I have seen was in India, and eventually identified as a supply problem. ie they had a 3 bladed upwind turbine where 1 of the blades was sourced from another supplier - basically it was asking for trouble. At about 26rpm the blades ranaway due to controller failure, the mismatch in blade weight and dimensions triggered a significant oscilation problem.. end result, delamination, bearing failure, main shaft failure and blade strike. $3m worth of dead turbine.
Surface pitting is also an issue with plane props as well, to a point where you check the blades for such damage in your pre flight checks
there's some interesting designs coming out of germany, denmark and the US to move away from traditional 3 blade turbines.Surface pitting is also an issue with plane props as well, to a point where you check the blades for such damage in your pre flight checks
one of the new wind turbine concepts is basically a pump jet - it even looks like a jet turbine,
shrouded designs are working out to be one of the ways to deal with energy bleed and cavitation side effects in runaway conditions... controllers fail, components fail, so mitigating against it is always the grail.
it ticks off one of the ugly boxes in the safety hazard checks... as long as the shroud doesn't suffer in a catastrophic event as well...
Wow these must look pretty. A 100ft high and wide shrouded turbine. Certainly ticking the ugly box.
They should instead put the whole turbine thing underground and put up a big aircollecting and focusing shroud which can change its shape depending on conditions to maximise its effectiveness. All the whirlling bits can be underground. Im pretty sure Dune series suggested something like this.
If a controller fails, then the building can deform to limit airflow. And if it fails it doesn't have a 100ft high turbine shattering bits through the countryside.
They should instead put the whole turbine thing underground and put up a big aircollecting and focusing shroud which can change its shape depending on conditions to maximise its effectiveness. All the whirlling bits can be underground. Im pretty sure Dune series suggested something like this.
If a controller fails, then the building can deform to limit airflow. And if it fails it doesn't have a 100ft high turbine shattering bits through the countryside.
Costs and complexities you don't need. You still have to meet an energy budget as well as a financial budget. You would lose energy from the air flow as it passed through the ducting to the underground shroud due to attenuation. That is friction with the ducting as the air passed through would reduce the air velocity hence it's energy. Secondly the costs of building an underground complex would make such a project uneconomic.
Wookie and I worked on a project concept a few years back where this was what we intended to do.
stillborn, for a number of reasons as outlined by our kiwi mate ngatimozart preceeding this...
i was a child when i first watched Hunt for Red October, since then somehow crazy ivan got into my lingo and i use it from time to time. Unfortunately people around me don't understand it most of the times.
However recently i saw a few tv shows which used the phrase to my delight. Most recent one i remember was in an episode of Ncis where Dinozzo mentions it ( don't recall the episode number, sorry)
Do any of you use Crazy ivan as a phrase? Or heard people use it at everyday conversations.
However recently i saw a few tv shows which used the phrase to my delight. Most recent one i remember was in an episode of Ncis where Dinozzo mentions it ( don't recall the episode number, sorry)
Do any of you use Crazy ivan as a phrase? Or heard people use it at everyday conversations.
SOP for driving in most 3rd world countries.
Dinozzo would have mentioned it in NCIS because of his film mania. No I don't hear it used in conversations. Even when I was in the pussers (RNZN) I didn't really hear it used, but then I never served on the frigates so didn't have anything to do with ASW.
SOP for driving in Christchurch too. Green light go. Yellow light go faster. Red light go real fast.SOP for driving in most 3rd world countries.
oldsailor58
New Member
1) zigzag not helpful against acoustic weapons
2) acelerate to speed where passive sonar not effective, go to a course to achieve maximum change of bearing to contact, then slow till passive contact regained. continue until target localized
I believe zigzaging randomly is useful for a surface ship if an attacking sub use passive sensor only. Even if you use homing torpedo, you still need to bring that torpedo close enough to the target for the homing head to effectively track the target. Submarine use Time Bearings Interval Chart to plot target bearings at certain time interval relative to own ship movements. I think it was called something else in the western navy but i don't remember what. random Zigzaging target make it more difficult to plot an accurate target location and movement information and may provoke the attacking submarine to come to periscope depth, coming closer to the target or in a rare occasion, use their active suite, both will increase their vulnerabilities.
localhost127
Member
has there ever been any experimentation regarding some device at the bow of a ship that would in essence create a wake much like that at the bow but 180* out of phase such that the bow wave combined destructively out-of-phase with the wake at the stern of the ship?
i realize this would be a static device determined by a particular speed (unless it were somehow designed to be dynamic based on speed of the vessel) - but just random thought.
has there been any such experiments? or maybe wrt submarines?
i realize this would be a static device determined by a particular speed (unless it were somehow designed to be dynamic based on speed of the vessel) - but just random thought.
has there been any such experiments? or maybe wrt submarines?
its basically done on modern cruiseliners
there are 3 types of harmonic triggers that contribute to a surface vessels overall harmonics. bow shape (bulb length and shape) , (absolute) hull length and stern design. all 3 have to work in sympathy otherwise the vessel can end up slow porpoising....Apart from some other stabilisation mods (gyro, dead weight pendulums etc...) it also assists in managing ship roll
oldsailor58
New Member
well the attacking sub just needs to localize the target enough to determine if it is within weapon range and that the target will be in the torpedo search zone when it gets there.
i taught SUBMARINE TIME BEARING PLOTTING AND ANALYSIS in the mid 1970s. still don't know what can be discussed about what i taught.
the old sailor
There is a well established maxim in subs, the crow community and special forces that even if you do know that you shouldn't say anything even if others are waxing lyrical.
if you have prior exp it would be useful to contact myself, the webmaster or any other mods with some detail so that we can establish credentials
oldsailor58
New Member
have contacted webmaster. i am retired from the us navy. was an instructor at a submarine tactical training command. have seen some of what i taught talked about on a navy.mil webpage. still to this day(have been away from sub community since 1979) not sure what can even be hinted at. and yes i remember, even commenting in a round about manner can verify information.