Let's talk about [old] submarine propeller designs (nothing confidential)

[p7p8]

This is very good! Thank you Kapitan.
I know Udaloy is for ASW with very good hull/bow sonar but i haven't photo of this warship in dry dock.

In this case "size have matter"

Sorry for Off-topic

[Castout]

Originally Posted by FPSchazly

I would not consider that particular Victor-III prop design to be an old design, I would consider this to be an old design (from Alfa):



I am by no means a propeller expert or fluid dynamics voodoo witch doctor, but the design referenced in your first link seems to decrease the pressure along the leading edges of the propeller blade in order to reduce cavitation.

As to the ring around LA props (which may be getting into classified territory ), I imagine it's also there as a form of cavitation reduction to reduce the prop tip cavitation. I read an article a while ago stating that there are three forms of propellor cavitation, and cavitation at the tip is one of them. It's where the blade is rotating the fastest, so tipping over the blades, like with that Victor-III prop, seemingly increases prop area without increasing the speed of the blade as much.

Anyone well-versed in propellers, please feel free to correct my terminology.

Oh so both are meant to reduce cavitation?

I wonder how effective is the Los Angeles propeller design as the ring is very thin......

For the Russian propeller, yes it can be argued it is to reduce cavitation too I guess but at the same time I think it increases the amount of water being pushed by the propeller thus increasing its speed efficiency.

[Kapitan]

If they left these on i wonder how much extra noise there would be ?

especially as this submarine has a top speed of 44.7 knots i could imagine it being like a freight train running past a house and with these left on even louder.





And this is the back end of the K222 project 661 Anchar and still holds the fastest sustained underwater speed record (Alfa could only sprint not sustain)
Considered the predecessor to Charlie I and Alfa this boat had a titanium hull armed with 10 SS-N-7 ASM she like Charlie and Oscar are one shot wonders.

The boat was out of comission in 1988 and scrapped at zerverodorchka in 2010

[speed150mph]

I believe they hit the nail on the head. The ring on the 688 prop is most likely for reducing blade tip cavitation noise at slow to moderate speeds. This feature is what gives the 688 class it's somewhat higher silent speed. The Russians main focus with propeller design was speed first and foremost, and ducting the propellers on the diesel boats like the tango was more for protection when operating in shallow water then silencing. We are only now seeing the use of pump jets coming into Russian designs, such as the Borie and the Yasen-m class subs.

In response to the fella who brought up the Alrosa, she was a test bed for pump jets on diesel electric subs. Now pump jets are very effective at dampening noise and cavitation at moderate speeds, but only have a marginal effectiveness at slow crawling speeds. This makes them rather useless on conventional diesel electrics like the kilo as they are generally quiet enough on battery to avoid detection, and more importantly, they are pretty well forced to operate at slow speeds to have adequate range on their batteries.

As mentioned the pump jet comes into it's own at moderate speeds, which diesel patrol subs hardy ever operate at. The Russians deemed it to not be work the higher costs to install it on the subs for so little reward which is the reason why they didn't continue with it. They no doubt however worked the design into their SSN and SSBN designs, since they can operate at the moderate speeds where pump jets become most efficient without worrying about battery life.

[Aktungbby]

http://americanhistory.si.edu/subs/anglesdangles/taming6.html

The tactical speed of a submarine is that speed at which the submarine is quiet enough to remain undetected while tracking enemy submarines effectively, with sources of self-noise reduced to the point that other submarines and ships can be detected using onboard passive sonar sensors. The the maximum burst speed of a submarine is the highest speed that can be achieved by the submarine's propulsion system, regardless of the self-noise created in the process. In the past, the tactical speed of a submarine was typically significantly less than its burst speed, though in the case of the SSN-21 Seawolf it is said that the tactical speed of 25 knots is a significant fraction of the burst speed of the boat.

https://fas.org/man/dod-101/sys/ship/deep.htm Shrouded propulsors are good; Depth is better! The Best Depth for a submarine to avoid detection by a hull-mounted sonar is conventionally regarded as the Sonic Layer Depth plus 100 meters

[Kapitan]

Originally Posted by speed150mph

I believe they hit the nail on the head. The ring on the 688 prop is most likely for reducing blade tip cavitation noise at slow to moderate speeds. This feature is what gives the 688 class it's somewhat higher silent speed. The Russians main focus with propeller design was speed first and foremost, and ducting the propellers on the diesel boats like the tango was more for protection when operating in shallow water then silencing. We are only now seeing the use of pump jets coming into Russian designs, such as the Borie and the Yasen-m class subs.

In response to the fella who brought up the Alrosa, she was a test bed for pump jets on diesel electric subs. Now pump jets are very effective at dampening noise and cavitation at moderate speeds, but only have a marginal effectiveness at slow crawling speeds. This makes them rather useless on conventional diesel electrics like the kilo as they are generally quiet enough on battery to avoid detection, and more importantly, they are pretty well forced to operate at slow speeds to have adequate range on their batteries.

As mentioned the pump jet comes into it's own at moderate speeds, which diesel patrol subs hardy ever operate at. The Russians deemed it to not be work the higher costs to install it on the subs for so little reward which is the reason why they didn't continue with it. They no doubt however worked the design into their SSN and SSBN designs, since they can operate at the moderate speeds where pump jets become most efficient without worrying about battery life.

Which sounds about right to be honest it doesnt give much reward but on something like borei and yasen it would indeed be a good reward

this post i put the pictures up of the arse end of alrosa

http://www.subsim.com/radioroom/showthread.php?t=229270

[NiceSub]

Originally Posted by FPSchazly

I would not consider that particular Victor-III prop design to be an old design, I would consider this to be an old design (from Alfa):



I am by no means a propeller expert or fluid dynamics voodoo witch doctor, but the design referenced in your first link seems to decrease the pressure along the leading edges of the propeller blade in order to reduce cavitation.

As to the ring around LA props (which may be getting into classified territory ), I imagine it's also there as a form of cavitation reduction to reduce the prop tip cavitation. I read an article a while ago stating that there are three forms of propellor cavitation, and cavitation at the tip is one of them. It's where the blade is rotating the fastest, so tipping over the blades, like with that Victor-III prop, seemingly increases prop area without increasing the speed of the blade as much.

Anyone well-versed in propellers, please feel free to correct my terminology.

What are those small propellers next to the large one? What is their task?

[Castout]

Originally Posted by NiceSub

What are those small propellers next to the large one? What is their task?

That's for extra quiet operation at very low speeds like 1-2 knots I think or not more than 3 knots. They might even use battery to reduce noise but I'm not sure.


@Speed150mph

The thin ring on the 688i might not be effective at high speeds just as you mentioned.

The Russian Typhoon SSBN has very long rings (shrouds) which is to say that they are to prevent cavitation by the propellers' blade tips to higher speeds than on the 688i, probably even to its maximum speed...But the tips of those blades are 'sloppy'. Perhaps because they have those long rings/shrouds and they thought to give the blades maximum push efficiency.

The thing with propellers is that they don't push with equal/uniform force distribution....I guess that's why everyone is building submarines with pump-jet propulsions to have a more uniform force distribution to minimize cavitation...allowing for higher tactical speed.

A more uniform force distribution demands a new innovative way to propel submarines without the use of any propellers or to use much thinner and more numerous blades perhaps not unlike blades in jet engines...

Perhaps, although this is just speculation, a new innovative way to propel submarines can be found by mimicking nature. There's a reason propeller- like propulsion isn't found in nature. It could be because it's not the best way to move around underwater...

Edit:
I googled octopus inspired submarines and found a good link.
http://www.ibtimes.com.au/octopus-in...e-ever-1419803