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Author Topic: FROTHING AND WAVING...  (Read 3632 times)

rathikrishna

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FROTHING AND WAVING...
« on: January 18, 2011, 06:11:23 AM »

Good morning Friends...last night i was watching TV, the History Channel,was about container ships.i saw many tugs there, to pull the ship at harbor.so i saw a marvellous scene around the tugs..it was a heavy frothing and waving all around the tugs along with heavy bubbling...Friends..as i do not have any much idea in marine engineering, i do not know how this phenomena happens..my doubt is this...how can we produce a good frothing and bubbling around our crafts...?  is it possible..?  if so it will be more realistic in an action..please advice me...its a kind request...Rachu
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boneash

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Re: FROTHING AND WAVING...
« Reply #1 on: January 18, 2011, 10:21:08 PM »

Hi Rachu

I think this will explain the frothing !!!

This is THE  preferred multi directional propulsion drive particularly for tugs.

http://www.voithturbo.com/545950.htm

Rod
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john s 2

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Re: FROTHING AND WAVING...
« Reply #2 on: January 18, 2011, 10:29:30 PM »

Thanks for posting Explains what i did not know. John.
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Umi_Ryuzuki

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Re: FROTHING AND WAVING...
« Reply #3 on: January 19, 2011, 03:29:48 AM »

That link does not explain frothing, so much as it diagrams one style of propeller.

The frothing is typically due to "Cavitation".

http://en.wikipedia.org/wiki/Cavitation

This is kind of intersting once they get the timing strobe syncronized.

http://www.youtube.com/watch?v=mQvbispmUF4

 :-)

To create frothing due to cavitation a propeller just has to spin faster than it can
move, or move water in any direction.

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tigertiger

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Re: FROTHING AND WAVING...
« Reply #4 on: January 19, 2011, 03:54:50 AM »

Some frothing and waving is possible, but in modelling we cannot scale down wind or water.

The water molecules are, by scale, much larger. I read somewhere that the model in water is like a real ship would be floating in oil.
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rathikrishna

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Re: FROTHING AND WAVING...
« Reply #5 on: January 19, 2011, 04:47:09 AM »

Ahh..great..Friends how informative all you are...hai...and thanks for the links and advices, from this discussion i hope i can find a way to reproduce frothing and bubbles around our crafts...with great hope..so we must continue for further...
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rathikrishna

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Re: FROTHING AND WAVING...
« Reply #6 on: January 19, 2011, 11:00:17 AM »

Friends..is it possible to make froth and bubbling by fixing a low pitched prop at high speed...? any advice..?
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john s 2

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Re: FROTHING AND WAVING...
« Reply #7 on: January 19, 2011, 12:21:43 PM »

Just a thought. But could an air pump be used to blow out air under the boat ? So simulatng cavitation. John.
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Liverbudgie

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Re: FROTHING AND WAVING...
« Reply #8 on: January 19, 2011, 02:50:57 PM »


It is a popular misconception that when we see a large amount of broken water or foam under the stern of a tug or most other vessels, it is an indication of "cavitaion", it is not. What we are seeing, to all intents and purposes, is the water being "aerated" . "Cavitation" with regard to a ships propeller, is a completely different animal and occurs when a propeller is turning at high speed, this can and does, form a vacuum which collapses with such force that the surface of the blade is pitted and eventually weakened.

The propellers fitted to tugs and to virtually all merchant ships do not turn at anything like the speed required for this to happen. When a tug for instance increases to full power, the amount of water which the propeller moves is quite enormous and some is directed to the surface and forms, what is in effect, an action similar that of a wave breaking on the shore line, hence the foam and frothing.

This is but a brief simplistic explanation to what is a very complex subject, for more detailed information go to Google.

There have been many experiment at simulating this on a model in the past but have not nor will they succeed to many great extent, for the reasons already given. Though on second thoughts a combination of blown air and washing up liquid might work reasonably well but, I doubt very much if Miss Krishna or her dear Ma, would welcome that in their pond.

But donít let that stop you from experimenting for you are a remarkable person and a breath of fresh air. I hope all your desires and wishes come to fruition, if they donít however, Iím sure you will find many suitors here who will be only to willing to indulge you.

LB
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rathikrishna

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Re: FROTHING AND WAVING...
« Reply #9 on: January 20, 2011, 02:18:59 PM »

 Liverbudgie ..thanks for the great guidance...now i am too happy to say you one great thing...i got a thud in my knee, as i rushed my driving ..so last night was almost sleepless...so i turned my dark night in to some research...by last night i found a simple solution to make a good rate of frothing and bubbling on to my crafts...its a simple device...so i will post it soon..but only after my voice clears..now i have a good cold..its intensified now..because i ate two ice creams now...hi..hi...have a nice time..i will be with you all..be in touch...then ample of frothing and bubbling...woooosshhhhh.....hi..hi....god may bless us...rachu
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Liverbudgie

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Re: FROTHING AND WAVING...
« Reply #10 on: January 20, 2011, 02:30:35 PM »

Rachu,

Two ice creams, that will not do your lithe figure or your cold much good will it now!!

LB
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rathikrishna

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Re: FROTHING AND WAVING...
« Reply #11 on: January 20, 2011, 02:42:15 PM »

Hai liver..it was too irrestible..ommm..was so yummy...thats why i told you i will shoot the video of the frother later..now no voice...hi...hi...
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rathikrishna

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Re: FROTHING AND WAVING...
« Reply #12 on: January 20, 2011, 02:44:18 PM »

and also have to post a steam whistle and continuous smoke generator...today was in duty..now way back home..so soo fre..thats why still i am sitting this cafe...hi...hi...
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Arrow5

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Re: FROTHING AND WAVING...
« Reply #13 on: January 20, 2011, 05:49:00 PM »

I`m sure that someone from the film industry could tell us about simulating the foam and froth.  Detergent will provide oversized bubbles I think, perhaps a chemical frother might work, say "Epsom Salts" makes minute bubbles. Is there any other cheap harmless chemicals that could be used. Film effect of wind blown spray was in fact salt grains.
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RRS01

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Re: FROTHING AND WAVING...
« Reply #14 on: January 21, 2011, 02:20:28 AM »

Hi Rachu!  :-)

 How about if You took something like Your contra-rotating propeller with a PVC pipe 'sheath' like I think You did on Your destroyer, but with this as a modification ... You drill some small holes (possibly 3 or 4 rows) across the top of the pipe close to the transom and maybe partially block the end of the pipe, thereby forcing water upward while still allowing water to be moved out the "exhaust" to propel the tug forward ... I'm not sure how "frothy" it would get, but it might work ...  :D

OH, I hope You gave some ice cream to Your baby in Your row boat!  %)  ok2   :-))
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rathikrishna

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Re: FROTHING AND WAVING...
« Reply #15 on: January 21, 2011, 01:06:58 PM »

Hi..hi..thanks for the ice creams...i will post a detailed video of my froth generator soon..sure..it working well and nice...
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tigertiger

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Re: FROTHING AND WAVING...
« Reply #16 on: January 21, 2011, 01:57:51 PM »

RRS01 has given me an idea.

Fish tank pumps have a plastic tube and the end has a kind of diffuser to create aeration. These bubbles are tiny.
I am not sure if the diffuser is a solid block of aerated stone (or similar) or a fine mesh.

Now the big ifs.
If you can get a pump that can blow air at high pressure running on 12v.
If you can place a row of diffusers into the stern below the waterline and link them through a branched pipework.
If the joins in the pipe do not burst due to the high air pressure.
If you can link the pump to an ESC.
Then this dumb solution might work.

Just my thoughts.
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rathikrishna

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Re: FROTHING AND WAVING...
« Reply #17 on: January 22, 2011, 06:19:58 AM »

Yes sure..now i am trying for an even more better one...sure..
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three knots

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Re: FROTHING AND WAVING...
« Reply #18 on: January 23, 2011, 08:21:21 PM »

L B on reas tugs ,the old steam ,applegarth etc ,on the movement given from full ahead to full astern ,the stern would literally lift out of water ,it was the power and the enormous rate as you say the cavitation ,i know because i had to study this ,and i did operate them big triple expansion jobs .a great bit of history almost lost ,but you seem to know a bit ,good on you .
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rathikrishna

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Re: FROTHING AND WAVING...
« Reply #19 on: January 24, 2011, 08:57:55 AM »

will you elaborate this phenomena in simple manner once..? please...?
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