Crazy Ivan maneuver in Red Storm Rising

[ngatimozart]

Flow noise is white noise (all frequencies), but the percentage of the high frequency component increases with the speed. Total signal strength is proportional to the 4th power of the speed, but machinery noise generally exceeds hull noise as long as the flow is laminar.

Also above a certain speed, depending on geometries, the flow changes from laminar flow (low noise) to turbulent flow (noisy and damps incoming signals). In fact the flow regime on can be different on different parts of the sub’s hull, which can make the correct location of the sonar transducers critical for maximum sensitivity as speed increases.

This is the same as airflow around a building or even a leaf. If you want to understand it any fluid mechanics book or any book on climatology that deals in air flows will help you. Same with geology. A basic book on sedimentology should have a good explanation of laminar flows and turbidity.

 

[gf0012-aust]

This is the same as airflow around a building or even a leaf. If you want to understand it any fluid mechanics book or any book on climatology that deals in air flows will help you. Same with geology. A basic book on sedimentology should have a good explanation of laminar flows and turbidity.

I've re[eatedly saif in here and on other forums, aerodynamics and fluid dynamics are kissing cousins.

some of the concepts I dealt with on wind turbine technology for acoustic straking are almost identical to what you face on a sub...

 

[ngatimozart]

I've re[eatedly saif in here and on other forums, aerodynamics and fluid dynamics are kissing cousins.

some of the concepts I dealt with on wind turbine technology for acoustic straking are almost identical to what you face on a sub...

My apologies mate. I hadn't seen your remarks per se. I studied climatology and some geology hence the links. I have found this a very interesting thread and am a fan of Tom Clancy so I do know the two works of fiction in question. If I may comment on some of the WWII IJN subs, they built some large ones and as well as mounting aircraft some mounted 6 inch guns. I also read somewhere that the Kreigsmarine had some pretty advanced U boat designs on the board and / or under development at the end of WWII.

 

[My2Cents]

This is the same as airflow around a building or even a leaf. If you want to understand it any fluid mechanics book or any book on climatology that deals in air flows will help you. Same with geology. A basic book on sedimentology should have a good explanation of laminar flows and turbidity.

I've re[eatedly saif in here and on other forums, aerodynamics and fluid dynamics are kissing cousins.

some of the concepts I dealt with on wind turbine technology for acoustic straking are almost identical to what you face on a sub...

Aerodynamics is a subset of fluid dynamics. They are not ‘kissing cousins’ but offspring and family.

While there are similarities between air and water flows, remember that you are comparing a low density, low viscosity, compressible, flow to a high density, medium viscosity, relatively incompressible, flow. You really need a good understanding of both and especially the scaling laws before trying too hard to apply knowledge from one area to the other. Critical concepts like Mach numbers and cavitation do not translate from one to the other. :argue

 

[ngatimozart]

Aerodynamics is a subset of fluid dynamics. They are not ‘kissing cousins’ but offspring and family.

While there are similarities between air and water flows, remember that you are comparing a low density, low viscosity, compressible, flow to a high density, medium viscosity, relatively incompressible, flow. You really need a good understanding of both and especially the scaling laws before trying too hard to apply knowledge from one area to the other. Critical concepts like Mach numbers and cavitation do not translate from one to the other. :argue

That's true, in that case if people are real keen then I would suggest searching out works on lava flow rates etc. The viscosity will be different but it might be a closer analogy than atmospheric air. Mind you, there should be a lot of work in the open literature on the mechanics of water flow characteristics, that could be analogous to a generic submarines' movement through the oggy.

 

[gf0012-aust]

Aerodynamics is a subset of fluid dynamics. They are not ‘kissing cousins’ but offspring and family.

I'd argue more than that, again we used some of the cavitation management constructs used in subs to manage acoustics onj downwind turbines. IN fact in inbe instance we used basically the same program to deal with blind spots - eg sub sail, turbine mast. the straking solution we used for one sub masy solution was used on a specific turbine where the flow conditions were similar

While there are similarities between air and water flows, remember that you are comparing a low density, low viscosity, compressible, flow to a high density, medium viscosity, relatively incompressible, flow. You really need a good understanding of both and especially the scaling laws before trying too hard to apply knowledge from one area to the other. Critical concepts like Mach numbers and cavitation do not translate from one to the other. :argue

my last contract on subs overseas included wind turbine engineers who were bought in to deal with cavitation management. on my last major wind turbine development (in germany in 2007) included some french maritime engineers who had come from working on the Rubis...

we regularly cross referenced data and material on low revolution cavitation constructs from vawts as well as hawts becaise both had relevance in sub platforms as well as torpedo designs. the smartest new generation propulsion system I've seen for torpedos was gased on some wind engineering work done out of wind engineering teams based at Frauhoffer.

conceptually it's more than family - it's incestuous

 

[My2Cents]

I'd argue more than that, again we used some of the cavitation management constructs used in subs to manage acoustics onj downwind turbines. IN fact in inbe instance we used basically the same program to deal with blind spots - eg sub sail, turbine mast. the straking solution we used for one sub masy solution was used on a specific turbine where the flow conditions were similar

my last contract on subs overseas included wind turbine engineers who were bought in to deal with cavitation management. on my last major wind turbine development (in germany in 2007) included some french maritime engineers who had come from working on the Rubis...

we regularly cross referenced data and material on low revolution cavitation constructs from vawts as well as hawts becaise both had relevance in sub platforms as well as torpedo designs. the smartest new generation propulsion system I've seen for torpedos was gased on some wind engineering work done out of wind engineering teams based at Frauhoffer.

You are talking about turbulent flow, not cavitation. Cavitation is a phenomena unique to liquids, it cannot occur in a gas. :rel

Cavitation is caused by the formation and collapse of gas bubbles in a liquid under high shear. The collapse of the bubbles is extremely violent and destructive, generating momentary pressure on the order of several thousand psi, water jets at near sonic velocities, temperatures over 1000 degrees, and even bursts of light. Though the effects are individually very small, over time they are extremely destructive to nearby surfaces (i.e. the surface that generated them). :rel

conceptually it's more than family - it's incestuous

Hardly, it is not even unusual. :coffee

 

[jack412]

cant poor laminar flow also cause cavitation ?
I seem to recall something about the sail on the collins causing cav problems with the prop

 

[gf0012-aust]

cant poor laminar flow also cause cavitation ?
I seem to recall something about the sail on the collins causing cav problems with the prop

it can and does.

we've actually witnessed material degradation on some surfaces due to flow irregularity and long term impact.

there's substantial evidence of props physically collapsing

we used to see it in some of the wind turbine designs where a side effect of "runaway" cavitation was delamination of the blades.

we had a test design on a USN site in California where the turbine was absolutely destroyed when the buffetting triggered delamination, then blade strike. it sheered the main shaft which was 900mm thick.

 

[gf0012-aust]

You are talking about turbulent flow, not cavitation. Cavitation is a phenomena unique to liquids, it cannot occur in a gas. :rel

and yet every wind turbine technician I ever dealt with knows about cavitation issues on turbines which are obviously pushing air and not fluid.

every turbine tech with even a basic understanding of effect knows what happens when the tips of the blade go supersonic. blade failure is usually due to cavitation issues which in a worst case scenario trigger strike conditions.

we used "cavitation" to describe various effects in both wind turbine developments and in sub management. It is a common term in both industries describing similar effects even if the medium is different.

 

[ngatimozart]

You are talking about turbulent flow, not cavitation. Cavitation is a phenomena unique to liquids, it cannot occur in a gas. :rel

Actually gases are just another form of a liquid so they behave in very similar fashions. It's just the difference in density which defines them and if you look at it from a quantum physics point, they are one and the same again being defined, in this case, by the spatial relationship between each atom and sub atomic particle. What we actually perceive as solid, e.g., the chair we are sitting in etc., is not actually so when viewed at a particle scale. Matter is just a manifestation of energy and gases, liquids, solids, and metallic liquids are just how we define these manifestations.

 

[My2Cents]

it can and does.

we've actually witnessed material degradation on some surfaces due to flow irregularity and long term impact.

there's substantial evidence of props physically collapsing

we used to see it in some of the wind turbine designs where a side effect of "runaway" cavitation was delamination of the blades.

we had a test design on a USN site in California where the turbine was absolutely destroyed when the buffetting triggered delamination, then blade strike. it sheered the main shaft which was 900mm thick.

and yet every wind turbine technician I ever dealt with knows about cavitation issues on turbines which are obviously pushing air and not fluid.

every turbine tech with even a basic understanding of effect knows what happens when the tips of the blade go supersonic. blade failure is usually due to cavitation issues which in a worst case scenario trigger strike conditions.

we used "cavitation" to describe various effects in both wind turbine developments and in sub management. It is a common term in both industries describing similar effects even if the medium is different.

We are obviously having a problem here with the same word being used to describe different phenomena. This is a description for cavitation in a liquid:

Cavitation is caused by the formation and collapse of gas bubbles in a liquid under high shear. The collapse of the bubbles is extremely violent and destructive, generating momentary pressure on the order of several thousand psi, water jets at near sonic velocities, temperatures over 1000 degrees, and even bursts of light. Though the effects are individually very small, over time they are extremely destructive to nearby surfaces (i.e. the surface that generated them).

Could you please post a more detailed description for the phenomena referred to as cavitation when dealing with wind turbines?

 

[My2Cents]

Actually gases are just another form of a liquid so they behave in very similar fashions. It's just the difference in density which defines them and if you look at it from a quantum physics point, they are one and the same again being defined, in this case, by the spatial relationship between each atom and sub atomic particle. What we actually perceive as solid, e.g., the chair we are sitting in etc., is not actually so when viewed at a particle scale. Matter is just a manifestation of energy and gases, liquids, solids, and metallic liquids are just how we define these manifestations.

Solid, liquid, gas, and plasma are the 4 phases of matter based on the bulk properties, of which density is only one. Gasses are not liquids, but gasses and liquids, as well as plasma, are classified as fluids.

Your appeal to quantum mechanics in your support is just sophistry. :flame

 

[gf0012-aust]

We are obviously having a problem here with the same word being used to describe different phenomena. This is a description for cavitation in a liquid:

Could you please post a more detailed description for the phenomena referred to as cavitation when dealing with wind turbines?

example 1 http://pia.sagepub.com/content/221/2/219.full.pdf
the article refers to a marine tidal turbine. the blade technology used is similar to some small german HAWT designs. in this case one of the common effects is tip vortex. on a traditional 3 blade downwind turbine this will trigger if the blades "runaway" due to a faulty controller, be it speed or pitch management.

example 2 Honeywell turbines sheath the blades, similar to what we do with submarine pumpjets, again to help direct energy bleed away from the tips and to stop tip cavitation generation at high speeds.

example 3 the infinity blade as developed by Windwandler is designed to deal with cavitation issues on wind turbines.

 

[aussienscale]

Would have to agree with GF here, having worked in the Wind Turbine & Solar tech industry, cavitations does not only occur in fluids (water) it happens to turbines, also happens to props on planes as well, ask any pilot and they will tell you what happens when it cavitates and stalls. Same things that happens to wind turbines, boat props etc. It is not unique to subs

 

[Bonza]

Your appeal to quantum mechanics in your support is just sophistry. :flame

Accusing people of deceit really isn't necessary. People are being courteous with you, even if they don't agree with your position, why not return the favour.

 

[My2Cents]

example 1 http://pia.sagepub.com/content/221/2/219.full.pdf
the article refers to a marine tidal turbine. the blade technology used is similar to some small german HAWT designs. in this case one of the common effects is tip vortex. on a traditional 3 blade downwind turbine this will trigger if the blades "runaway" due to a faulty controller, be it speed or pitch management.

The marine tidal turbine is classic cavitation in a liquid, not a gas.

example 2 Honeywell turbines sheath the blades, similar to what we do with submarine pumpjets, again to help direct energy bleed away from the tips and to stop tip cavitation generation at high speeds.

Air turbines? Water turbines? Steam turbines? What type?
Submarine pumpjets are, again, for liquids not gas. This is not helpful.

example 3 the infinity blade as developed by Windwandler is designed to deal with cavitation issues on wind turbines.

Cannot find any reference to “infinity blade” wind turbine on the internet (except as the name of a fantasy warfare game advertised on several green energy websites).
Found the Windwandler website, but it has no mention of the “infinity blade” or cavitation anywhere.

How about you just describe the physical phenomena that you call cavitation in relation to a wind turbine?

I suspect has happened is that someone years back has just ported over the word from hydraulics to windpower because they did not know what the correct term was for a phenomena when working with air, and it has stuck within the wind turbine community. From what I can glean from your posts I suspect you are referring to the creation of the blade tip vortices, which is something else altogether. :argue

 

[gf0012-aust]

The marine tidal turbine is classic cavitation in a liquid, not a gas.

Air turbines? Water turbines? Steam turbines? What type?
Submarine pumpjets are, again, for liquids not gas. This is not helpful.

Cannot find any reference to “infinity blade” wind turbine on the internet (except as the name of a fantasy warfare game advertised on several green energy websites).
Found the Windwandler website, but it has no mention of the “infinity blade” or cavitation anywhere.

How about you just describe the physical phenomena that you call cavitation in relation to a wind turbine?

I suspect has happened is that someone years back has just ported over the word from hydraulics to windpower because they did not know what the correct term was for a phenomena when working with air, and it has stuck within the wind turbine community. From what I can glean from your posts I suspect you are referring to the creation of the blade tip vortices, which is something else altogether. :argue

Seriously. you're coming across as a pedant.

1) when I was involved with the development of wind turbines it was a typical term used by the engineers. as the original 2 bladed upwind turbine we tested was funded by the USN, and that their engineers used the term (and also happened to be maritime engineers along with the crew from woods hole), and as desigm engineers from Bonus, Suzlon, EHN and Vestas also used the term to describe runaway conditions etc then I'm pretty sure that they also knew what we were talking about.

at this point its irrelevant what you're thinking, feel free to discuss it by yourself.

I'm quite happy to stick by the engineers I worked with and industry in general on this

I'm done with this.

 

[My2Cents]

Seriously. you're coming across as a pedant.

1) when I was involved with the development of wind turbines it was a typical term used by the engineers. as the original 2 bladed upwind turbine we tested was funded by the USN, and that their engineers used the term (and also happened to be maritime engineers along with the crew from woods hole), and as desigm engineers from Bonus, Suzlon, EHN and Vestas also used the term to describe runaway conditions etc then I'm pretty sure that they also knew what we were talking about.

at this point its irrelevant what you're thinking, feel free to discuss it by yourself.

I'm quite happy to stick by the engineers I worked with and industry in general on this

I'm done with this.

.
I am a mechanical engineer with 30 years of experience in liquid and gas flow design, and I have NEVER heard the term heard the term cavitation used to describe a phenomena in a gas flow. I have a professional interest in discovering if there is a potential problem causing phenomena that we are overlooking in our work.

Could you PLEASE explain what cavitation in a gas flow is, what causes it, and what the consequences are?

 

[jack412]

I'm a pleb but perhaps its that there is water vapor in the gas that forms droplets that then go on to cause cavitation problems ?

but it seems the main point is.. a fluid state umbrellas gaseous and liquid states