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    Project 885: Yasen class

    kvs
    kvs

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    Project 885: Yasen class - Page 40 Empty Re: Project 885: Yasen class

    Post  kvs on Wed Dec 23, 2020 11:15 pm

    Nobody designs properly hydrodynamic shaped submarines like Russia.

    Project 885: Yasen class - Page 40 1920px-SSN774.svg

    Project 885: Yasen class - Page 40 1920px-Graney_class_SSN.svg

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    limb

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    Project 885: Yasen class - Page 40 Empty Re: Project 885: Yasen class

    Post  limb on Thu Dec 24, 2020 9:43 am

    kvs wrote:Nobody designs properly hydrodynamic shaped submarines like Russia.  

    Project 885: Yasen class - Page 40 1920px-SSN774.svg

    Project 885: Yasen class - Page 40 1920px-Graney_class_SSN.svg

    Does hydrodynamic shaping allow reduced cavitation at higher speeds and thus less noise?

    It seems like westerners say only the pumpjet works for reducing high speed noise, which is wierd.
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    walle83

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    Project 885: Yasen class - Page 40 Empty Re: Project 885: Yasen class

    Post  walle83 Yesterday at 2:06 am

    kvs wrote:Nobody designs properly hydrodynamic shaped submarines like Russia.  

    Project 885: Yasen class - Page 40 1920px-SSN774.svg

    Project 885: Yasen class - Page 40 1920px-Graney_class_SSN.svg


    Altough the sail on the Yasen look alot bulkier then on the old Alfa class. Or the Akula for that matter.

    Project 885: Yasen class - Page 40 Yasen10
    Project 885: Yasen class - Page 40 Alfa10
    Project 885: Yasen class - Page 40 Akula10
    kvs
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    Project 885: Yasen class - Page 40 Empty Re: Project 885: Yasen class

    Post  kvs Yesterday at 3:10 am

    The cavitation noise from the propeller (only under full load) is not the only source of noise. The hull pushing through the water
    is another source of longer wavelength noise. This includes turbulence and the deformation (vibration) of the hull. Nothing
    the size of a submarine is a perfectly stiff object. It deforms in all sorts of ways. Long wavelength acoustic detection is
    a real thing in naval warfare.

    So conforming to hydrodynamic "aesthetics" is not superfluous but rather necessary. The US submarine tower is not only ugly,
    it is noisy even if it is shaped like a fin in horizontal section. The sloping contour on the tower of the Russian submarine is not
    a decoration. Also, pushing through water requires a shape that is not like a conic wedge with a taper to a leading point, but the
    reverse with a nearly spherical frontal contact with a trailing shape like a tear drop. The US submarine in the graphic was
    designed by someone barely aware of this detail and they were clearly going for a bullet penetrator shape, which is simply
    the wrong approach. It may not look like much of a difference, but the Devil is in the details. The goal is to reduce the
    disturbance of the flow contours and any transitions generate transients.

    Pump jets are something every fanboi trots out a proof of their vicarious achievement credentials. Pump jets reduce
    the propulsion efficiency and cavitation is only an issue at the limit of propeller rotational speed. Lots of effort is expended
    designing propellers that push the cavitation regime to the high rotation limit. The decision to use a shroud only for the
    missile carrier submarines makes perfect sense. Not hobbling the attack submarines with this feature is the right choice.
    There is a trade off between speed under water and noise reduction. The Borei class has a pump jet and a tower that
    is not shaped with the sort of streamlining as the Yasen class because it mostly crawls around under water and is not
    intended for rapid maneuvers.

    The Yasen-II pump jet is a whole new design that is supposed accommodate a much larger diameter propeller with a shorter
    shroud length. That makes perfect sense to me. The propulsion efficiency goes up with such modifications since shroud
    drag is reduced.

    https://www.popularmechanics.com/military/navy-ships/a13990706/russias-new-missile-submarine-sure-looks-familiar/

    An example of the masturbation common in western coverage of Russia. Clowns teaching Russians about hydrodynamics.
    Recall that Kolmogorov was from Russia and not the USA. To this day nobody has come up with any improvement on
    his unstratified turbulent boundary layer theory. And the people working on coming up with an extension to stratified
    boundary layers for geophysical applications are from Russia as well.


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    Isos
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    Project 885: Yasen class - Page 40 Empty Re: Project 885: Yasen class

    Post  Isos Yesterday at 3:18 am

    I've seen somewhere the best design in terms of noise reduction is the water drop.

    Kilo class is similar to it and thus has the best noise reduction design.

    For the sail it's better not to have it. They can design periscops that raise without the need to put a sail.

    That's the future of SSK IMO.
    Big_Gazza
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    Project 885: Yasen class - Page 40 Empty Re: Project 885: Yasen class

    Post  Big_Gazza Yesterday at 5:07 am

    limb wrote:Does hydrodynamic shaping allow reduced cavitation at higher speeds and thus less noise?

    Cavitation doesn't occur at all if you operate at a sufficient depth as water pressure is high enough to ensure that screw rotations doesn't result in regions having an absolute lower than water vapour pressure at the prevailing temperature.  Cavitation is also less of a factor in cold water as the vapour pressure is proportional to water temperature - Russian boats running deep in polar seas are much less affected than USN boats (or Chinese) running in shallow depths in warmer pacific waters.

    Don't expect the budweiser-swilling NASCAR-watching NRA members over at The Drivel to understand any of this however.  They just want to read yee-haa inducing feel-good nonsense while they wave their flags and stroke their inadequate weiners.. Twisted Evil

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