29 Aug 2006 15:22:11
TonyW
Bubble line and waves - should there be more?

I noticed watching the coverage at Eton that the bubble line at the
finish dramatically calmed the waves that had built up down the course.


Not sure what they are like to row through but wondered if it was worth
putting in a bubble line every 50-100m to alleviate the cumulative wave
build up in either headwind or tailwind.

Obviously if the bubble line is more disruptive than the waves won't be
a good idea - has anyone tried taking hard strokes through them?



29 Aug 2006 15:36:27
c.anton@blueyonder.co.uk
Re: Bubble line and waves - should there be more?


TonyW wrote:
> I noticed watching the coverage at Eton that the bubble line at the
> finish dramatically calmed the waves that had built up down the course.
>
>
> Not sure what they are like to row through but wondered if it was worth
> putting in a bubble line every 50-100m to alleviate the cumulative wave
> build up in either headwind or tailwind.
>
> Obviously if the bubble line is more disruptive than the waves won't be
> a good idea - has anyone tried taking hard strokes through them?

We've discussed this before here. Try doing a Google search



30 Aug 2006 01:18:25
TonyW
Re: Bubble line and waves - should there be more?

Thanks for the tip. Have just read discussion from 2004.

Still interested to know if it really is disruptive to row through the
bubble line or not. Obviously will increase blade slip but not sure
how much.

Also thought there was an interesting suggestion that you could turn
off the bubble lines 30 seconds before the crews approached. Could
then turn them on again once last crew gone past and before next race.




c.anton@blueyonder.co.uk wrote:
> TonyW wrote:
> > I noticed watching the coverage at Eton that the bubble line at the
> > finish dramatically calmed the waves that had built up down the course.
> >
> >
> > Not sure what they are like to row through but wondered if it was worth
> > putting in a bubble line every 50-100m to alleviate the cumulative wave
> > build up in either headwind or tailwind.
> >
> > Obviously if the bubble line is more disruptive than the waves won't be
> > a good idea - has anyone tried taking hard strokes through them?
>
> We've discussed this before here. Try doing a Google search



30 Aug 2006 10:56:22
ollie
Re: Bubble line and waves - should there be more?

IT seems like a good idea to me. Most 2000 metre courses suffer from
this problem to some extent and even a moderate breeze can produce
pretty uncomfortable conditions as it did last weekend.
Alternatively - rain always flattens the water rather effectively. What
about rigging up sprinklers suspended on a cable across the course
every few hundred metres. This would have the advantage of not changing
the properties of the water below the surface.

Ollie

TonyW wrote:
> Thanks for the tip. Have just read discussion from 2004.
>
> Still interested to know if it really is disruptive to row through the
> bubble line or not. Obviously will increase blade slip but not sure
> how much.
>
> Also thought there was an interesting suggestion that you could turn
> off the bubble lines 30 seconds before the crews approached. Could
> then turn them on again once last crew gone past and before next race.
>
>
>
>
> c.anton@blueyonder.co.uk wrote:
> > TonyW wrote:
> > > I noticed watching the coverage at Eton that the bubble line at the
> > > finish dramatically calmed the waves that had built up down the course.
> > >
> > >
> > > Not sure what they are like to row through but wondered if it was worth
> > > putting in a bubble line every 50-100m to alleviate the cumulative wave
> > > build up in either headwind or tailwind.
> > >
> > > Obviously if the bubble line is more disruptive than the waves won't be
> > > a good idea - has anyone tried taking hard strokes through them?
> >
> > We've discussed this before here. Try doing a Google search



30 Aug 2006 22:28:59
Henry Law
Re: Bubble line and waves - should there be more?

c.anton@blueyonder.co.uk wrote:

> We've discussed this before here. Try doing a Google search

OK, I've read that with some interest but I'm still confused.

The way some of the posts on that thread are phrased it's as if the
bubble lines were there for some _other_ purpose than to calm the waves,
but that people had observed the calming effect. Is that so, and if so
for what original purpose were the bubbles introduced? I could see the
effect on the TV and wondered what on earth it was. Even cleaned the
screen just in case :-)

--

Henry Law < >< Manchester, England


30 Aug 2006 23:30:54
Carl Douglas
Re: Bubble line and waves - should there be more?

Henry Law wrote:
> c.anton@blueyonder.co.uk wrote:
>
>> We've discussed this before here. Try doing a Google search
>
>
> OK, I've read that with some interest but I'm still confused.
>
> The way some of the posts on that thread are phrased it's as if the
> bubble lines were there for some _other_ purpose than to calm the waves,
> but that people had observed the calming effect. Is that so, and if so
> for what original purpose were the bubbles introduced? I could see the
> effect on the TV and wondered what on earth it was. Even cleaned the
> screen just in case :-)
>

Henry - rowing never thinks about improving conditions for rowers, even
less so for that final stroke. The bubble line is to indicate the
finish, because that nice yellow line you saw painted across the water
on the TV screen needs too much maintenance in real life. ;)

Rows of bubbles acroos the course every hundred metres or so would tend
to reduce the effect of wind-fetch on waves, but might cause
difficulties for those whose blades landed in them. Bubbles all the way
down teh course, apart from costing a fortune on air compression, might
sink every boat by reducing the mean density of the water.

Now a purely technical query, in case anyone knows: do they use a
compressor (e.g. taking it up to 100psi/7bar) to blow the bubble line,
or a regenerative blower (putting out ~15psi/1bar)? The lower pressure
ought to be plenty, & would yield a considerable energy saving.

Cheers -
Carl

--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)


30 Aug 2006 23:51:55
mpruscoe
Re: Bubble line and waves - should there be more?

Carl Douglas wrote:
> Now a purely technical query, in case anyone knows: do they use a
> compressor (e.g. taking it up to 100psi/7bar) to blow the bubble line,
> or a regenerative blower (putting out ~15psi/1bar)? The lower pressure
> ought to be plenty, & would yield a considerable energy saving.
>

After talking to the volunteers on the adjacent checkpoint about the
smell (from the compressor, a nearby generator and the cesspit), I
looked over the screen to see where it was, and it looked like a common
building site compressor to me, but I didn't look too closely.


30 Aug 2006 16:10:59
Teaplant
Re: Bubble line and waves - should there be more?


the bubbles (presumably) wouldn't have to run across the course. Some
benefit ought to be seen if the pipes ran along the line of lane marker
buoys. In this case, the pipes would obviously need to be longer (if
fed from just the ends) with enormous compressors but the blade
slip/turbulence caused by rowing over the bubbles might provide a neat
reminder/incentive to get back in the middle of your lane!

Get rid of the buoys entirely then!

I expect that it is best if the line of bubbles is perpendicular to the
wind velocity, but if the wind behaved itself we wouldn't be discussing
this.

Teaplant



31 Aug 2006 00:30:35
John Mulholland
Re: Bubble line and waves - should there be more?

"Carl Douglas" <carl@carldouglas.co.uk > wrote in message
news:ed53j2$ouq$1$8300dec7@news.demon.co.uk...
<snip >
> Now a purely technical query, in case anyone knows: do they use a
> compressor (e.g. taking it up to 100psi/7bar) to blow the bubble line, or
> a regenerative blower (putting out ~15psi/1bar)? The lower pressure ought
> to be plenty, & would yield a considerable energy saving.
>
> Cheers -
> Carl
>


I thought they had enough volunteers to get them to do five minutes each,
blowing into the tube. Pollution-free unless the volunteers have halitosis!

--
John Mulholland




31 Aug 2006 16:13:54
Walter Martindale
Re: Bubble line and waves - should there be more?

John Mulholland wrote:

>
> I thought they had enough volunteers to get them to do five minutes each,
> blowing into the tube. Pollution-free unless the volunteers have halitosis!
>
You mean it's not a direct feed from Parliament? 8-)
W


31 Aug 2006 17:52:32
Martin Gill
Re: Bubble line and waves - should there be more?


"TonyW" <anthony_d_ward@hotmail.com > wrote in message
news:1156890131.507828.14740@h48g2000cwc.googlegroups.com...
>I noticed watching the coverage at Eton that the bubble line at the
> finish dramatically calmed the waves that had built up down the course.
>
>
> Not sure what they are like to row through but wondered if it was worth
> putting in a bubble line every 50-100m to alleviate the cumulative wave
> build up in either headwind or tailwind.
>
> Obviously if the bubble line is more disruptive than the waves won't be
> a good idea - has anyone tried taking hard strokes through them?

Whilst the water directly at the bubble line was calm, this was at the
expense of the water immediately before the line, where the waves simply
piled up to a very significant level, requiring the bubbles to be turned off
at times.

As Carl says later, intermediate lines would break up the long distances and
reduce wind fetch, but would similarly create localised, if smaller, walls
of water to contend with.





>




31 Aug 2006 12:39:55
TonyW
Re: Bubble line and waves - should there be more?

I have no pretensions to having any expertise in these matters so I
could be completely wrong! However, I don't understand that - how
could a line of bubbles cause a build up of waves that had not even yet
reached the bubble line? Presumably, for any sort of effect like that
to occur there would have to be some interference/ bounce back when the
waves hit the bubble line (like when waves hit a wall). Does that
really happen?

Martin Gill wrote:
> "TonyW" <anthony_d_ward@hotmail.com> wrote in message
> news:1156890131.507828.14740@h48g2000cwc.googlegroups.com...
> >I noticed watching the coverage at Eton that the bubble line at the
> > finish dramatically calmed the waves that had built up down the course.
> >
> >
> > Not sure what they are like to row through but wondered if it was worth
> > putting in a bubble line every 50-100m to alleviate the cumulative wave
> > build up in either headwind or tailwind.
> >
> > Obviously if the bubble line is more disruptive than the waves won't be
> > a good idea - has anyone tried taking hard strokes through them?
>
> Whilst the water directly at the bubble line was calm, this was at the
> expense of the water immediately before the line, where the waves simply
> piled up to a very significant level, requiring the bubbles to be turned off
> at times.
>
> As Carl says later, intermediate lines would break up the long distances and
> reduce wind fetch, but would similarly create localised, if smaller, walls
> of water to contend with.
>
>
>
>
>
> >



31 Aug 2006 21:34:13
Carl Douglas
Re: Bubble line and waves - should there be more?

TonyW wrote:

> Martin Gill wrote:
>
>>"TonyW" <anthony_d_ward@hotmail.com> wrote in message
>>news:1156890131.507828.14740@h48g2000cwc.googlegroups.com...
>>
>>>I noticed watching the coverage at Eton that the bubble line at the
>>>finish dramatically calmed the waves that had built up down the course.
>>>
>>>
>>>Not sure what they are like to row through but wondered if it was worth
>>>putting in a bubble line every 50-100m to alleviate the cumulative wave
>>>build up in either headwind or tailwind.
>>>
>>>Obviously if the bubble line is more disruptive than the waves won't be
>>>a good idea - has anyone tried taking hard strokes through them?
>>
>>Whilst the water directly at the bubble line was calm, this was at the
>>expense of the water immediately before the line, where the waves simply
>>piled up to a very significant level, requiring the bubbles to be turned off
>>at times.
>>
>>As Carl says later, intermediate lines would break up the long distances and
>>reduce wind fetch, but would similarly create localised, if smaller, walls
>>of water to contend with.
>>
>>
> I have no pretensions to having any expertise in these matters so I
> could be completely wrong! However, I don't understand that - how
> could a line of bubbles cause a build up of waves that had not even yet
> reached the bubble line? Presumably, for any sort of effect like that
> to occur there would have to be some interference/ bounce back when the
> waves hit the bubble line (like when waves hit a wall). Does that
> really happen?
>

AIUI, the bubble wall alters the physical properties of the fluid medium
(water) in such a way as to enable it to absorb & dissipate wave energy
- which is why the waves at the line of bubbles are much reduced. It
does not, AFAIK, reflect waves. Any appearance that the waves become
steeper just ahead of the line of bubbles is probably an illusion.

Cheers
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)


31 Aug 2006 14:02:21
Rob Collings
Re: Bubble line and waves - should there be more?

Walter Martindale wrote:
> John Mulholland wrote:
>
> >
> > I thought they had enough volunteers to get them to do five minutes each,
> > blowing into the tube. Pollution-free unless the volunteers have halitosis!
> >
> You mean it's not a direct feed from Parliament? 8-)
> W

They tried that, but found that the increase in water temperature
caused too much evaporation and the water got rather shallow...

Rob.



31 Aug 2006 14:12:01
donal.casey@gmail.com
Re: Bubble line and waves - should there be more?

A very effective illusion.

If the bubbles were at 2 metre intervals ie 1000 lines of them...what
would the effect be on race times..is surface tension affected? Is
speed increased or is buoyancy affected causing the boat to travel at a
lower position in the water which counteracts or eliminates any
potential increases in speed.?

Donal
Carl Douglas wrote:
> TonyW wrote:
>
> > Martin Gill wrote:
> >
> >>"TonyW" <anthony_d_ward@hotmail.com> wrote in message
> >>news:1156890131.507828.14740@h48g2000cwc.googlegroups.com...
> >>
> >>>I noticed watching the coverage at Eton that the bubble line at the
> >>>finish dramatically calmed the waves that had built up down the course.
> >>>
> >>>
> >>>Not sure what they are like to row through but wondered if it was worth
> >>>putting in a bubble line every 50-100m to alleviate the cumulative wave
> >>>build up in either headwind or tailwind.
> >>>
> >>>Obviously if the bubble line is more disruptive than the waves won't be
> >>>a good idea - has anyone tried taking hard strokes through them?
> >>
> >>Whilst the water directly at the bubble line was calm, this was at the
> >>expense of the water immediately before the line, where the waves simply
> >>piled up to a very significant level, requiring the bubbles to be turned off
> >>at times.
> >>
> >>As Carl says later, intermediate lines would break up the long distances and
> >>reduce wind fetch, but would similarly create localised, if smaller, walls
> >>of water to contend with.
> >>
> >>
> > I have no pretensions to having any expertise in these matters so I
> > could be completely wrong! However, I don't understand that - how
> > could a line of bubbles cause a build up of waves that had not even yet
> > reached the bubble line? Presumably, for any sort of effect like that
> > to occur there would have to be some interference/ bounce back when the
> > waves hit the bubble line (like when waves hit a wall). Does that
> > really happen?
> >
>
> AIUI, the bubble wall alters the physical properties of the fluid medium
> (water) in such a way as to enable it to absorb & dissipate wave energy
> - which is why the waves at the line of bubbles are much reduced. It
> does not, AFAIK, reflect waves. Any appearance that the waves become
> steeper just ahead of the line of bubbles is probably an illusion.
>
> Cheers
> Carl
> --
> Carl Douglas Racing Shells -
> Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
> Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
> Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
> URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)



31 Aug 2006 14:36:03
KC
Re: Bubble line and waves - should there be more?


Walter Martindale wrote:
> John Mulholland wrote:
>
> >
> > I thought they had enough volunteers to get them to do five minutes each,
> > blowing into the tube. Pollution-free unless the volunteers have halitosis!
> >
> You mean it's not a direct feed from Parliament? 8-)
> W

Walter,

I've read what I'm about to say so many times that I was convinced
everyone was just lying. Plus I rarely drink coffee, even rarer still
drink it in front of the computer. But it's the end of the day and
week and I have a long drive in front of me so I wanted to pre-charge
the caffeine levels...

I just spewed a mist of coffee on my keyboard. Thank you.

-Kieran



31 Aug 2006 14:45:16
KC
Re: Bubble line and waves - should there be more?


donal.casey@gmail.com wrote:
> A very effective illusion.

The waves may be building up, but it has nothing to do with the bubble
line, and everything to do with increasing winds as you go down the
course. Several accounts from competitors said that the water was much
calmer in the first 1000 than in the last 1000, especially the last
500m. The bubbles ablate the waves, making the illusion that the waves
are building up as a result of the bubbles, when in fact the opposite
is true -- the waves dissipate as a result of the bubbles.

> If the bubbles were at 2 metre intervals ie 1000 lines of them...what
> would the effect be on race times..is surface tension affected? Is
> speed increased or is buoyancy affected causing the boat to travel at a
> lower position in the water which counteracts or eliminates any
> potential increases in speed.?

Effective density of the water would be reduced. This would cause (at
least) two things, both of which Carl already mentioned: 1) blade slip
would increase, and 2) boats would sit lower in the water. Both of
these factors would likely cause a slow in boat speed (although #2
maybe not so much since the effective dynamic properties of the water
would be different a lower sitting boat may not have more drag... dunno
-- don't feel like working the math right now (or looking up the
relevant equations as it were)).

Yes surface tension would also drop significantly. Not sure how big a
factor that would be in boat speed though.

-Kieran



01 Sep 2006 00:19:18
Ewoud Dronkert
Re: Bubble line and waves - should there be more?

donal.casey@gmail.com schreef:
> A very effective illusion.

What?

Q: Top-posting.
A: What is the most annoying thing on usenet?

(Closely followed by either quoting all or nothing of the previous post
regardless of at what part of it the reply is directed.)

--
E. Dronkert


01 Sep 2006 00:32:34
Carl Douglas
Re: Bubble line and waves - should there be more?

KC wrote:
<snip >
>
> Yes surface tension would also drop significantly. Not sure how big a
> factor that would be in boat speed though.
>

Errr... no. Surface tension, a feature of the air/water & boat/water
interfaces, would only drop if you added a suitable surfactant. I
didn't think we were contemplating a bubble bath here, although I 'spose
that might give us cleaner finishes ;)

Nor is surface tension relevant to speed. The viscosity & density of
the water, yes, but not its surface tension.

Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)


31 Aug 2006 19:25:29
KC
Re: Bubble line and waves - should there be more?

Carl Douglas wrote:
> KC wrote:
> <snip>
> >
> > Yes surface tension would also drop significantly. Not sure how big a
> > factor that would be in boat speed though.
> >
>
> Errr... no. Surface tension, a feature of the air/water & boat/water
> interfaces, would only drop if you added a suitable surfactant. I
> didn't think we were contemplating a bubble bath here, although I 'spose
> that might give us cleaner finishes ;)
>

Well, the actual surface tension may not change, but I would think some
sort of "effective" surface tension would change, similar to the fact
that the actual density of the water does not change, since the bubbles
mixed in with it are not water, they are air (nor are they even water
vapor as in the case of deep cavitation from submarines, etc.) With
normal calm water you can "float" a pin/needle on the water due to
surface tension. I would bet that with the bubbles, the pin would
sink. Thus, the "effective" surface tension is reduced.

> Nor is surface tension relevant to speed. The viscosity & density of
> the water, yes, but not its surface tension.

Good to know, I suspected as much but wasn't sure.

-Kieran



01 Sep 2006 11:45:06
Carl Douglas
Re: Bubble line and waves - should there be more?

KC wrote:
> Carl Douglas wrote:
>
>>KC wrote:
>><snip>
>>
>>>Yes surface tension would also drop significantly. Not sure how big a
>>>factor that would be in boat speed though.
>>>
>>
>>Errr... no. Surface tension, a feature of the air/water & boat/water
>>interfaces, would only drop if you added a suitable surfactant. I
>>didn't think we were contemplating a bubble bath here, although I 'spose
>>that might give us cleaner finishes ;)
>>
>
>
> Well, the actual surface tension may not change, but I would think some
> sort of "effective" surface tension would change, similar to the fact
> that the actual density of the water does not change, since the bubbles
> mixed in with it are not water, they are air (nor are they even water
> vapor as in the case of deep cavitation from submarines, etc.) With
> normal calm water you can "float" a pin/needle on the water due to
> surface tension. I would bet that with the bubbles, the pin would
> sink. Thus, the "effective" surface tension is reduced.
>
>

The "floating" pin, spider, etc., or the waterproof fabric in the rain,
or the rolling drop of water on dry ground, or the beads of mercury when
you break a thermometer (we used to play with mercury when I was a kid,
but not no more!) are all examples of where surface tension rules.
However, it is all a matter of scale.

At the very small scale, surface tension can be very important, &
surface tension still affects the ease with which a water surface breaks
up, atomises or forms bubbles & foams (as you'd see if detergent were
injected into the bubble curtain, or when oil is spread over a water
surface), but at the normal scale in which we row its effects are
dwarfed by those of viscosity, density & inertia. Thus when we scale to
the situation of a moving boat we find surface tension has no detectable
influence on the resistance to motion of the boat or, the other side of
the picture, the water's movement around the boat.

Over a century ago, Osborne Reynolds demonstrated that you could scale
many fluid flow phenomena purely on the basis of the ratio of dynamic to
viscous forces - which is expressed in the dimensionless Reynolds number
expressed as:
characteristic dimension x velocity x density / viscosity

Reynolds number similarity is still a fundamental basis for directly
comparing fluid flow situations which at first seem entirely different
in character (e.g. air flowing over a wing or sail vs water flowing
around a rudder or oar-blade).

>>Nor is surface tension relevant to speed. The viscosity & density of
>>the water, yes, but not its surface tension.
>
>
> Good to know, I suspected as much but wasn't sure.
>
> -Kieran
>

But if you bubble air through the water you row on, then surface tension
is significant as it strongly affects the formation & density of the
resulting foam & its flow characteristics around the blade.

Water supports a shell because it is sufficiently dense for that crewed
shell to be able to displace a mass of water equal to its own all-up
mass without that level water surface coming so far up the sides that it
flows in (Archimedes, around 2250 years ago). If you immerse a boat in
a foam of ~ 1/3 water density, then you'll sink because the boat has
insufficient volume to displace its own mass of the stuff. So a large
ship can be sunk by passing through a region of water affected by a
submarine gas vent (one of the Bermuda triangle hypotheses). You'll
also encounter the joys of 2-phase flow.

That 2-phase (mixed air/water) situation completely alters the flow
characteristics of the fluid as well as its bulk density. That means
the blade nolonger generates anything like the lift or drag that it did
in solid water. I think a new coaching technique & much different
equipment may then be needed. It could be a whole new sport!

;)
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)


01 Sep 2006 07:07:24
KC
Re: Bubble line and waves - should there be more?


Carl Douglas wrote:
... a treatise on the basics of fluid mechanics and similarity
methodology.

He could have cut it down to:
>
> But if you bubble air through the water you row on, then surface tension
> is significant as it strongly affects the formation & density of the
> resulting foam & its flow characteristics around the blade.
>

Come on, Carl, you know by background and that I'm well aware of
Reynolds' Number, similitude, and most certainly Archimedes' principle!
The above snippet is the only part of that long post that addresses my
comment(s) about surface tension (for which I thank you.) Next time
though, save your self some typing and time! :-)

-Kieran



01 Sep 2006 08:13:46
Re: Bubble line and waves - should there be more?


KC wrote:

> Carl Douglas wrote:
> ... a treatise on the basics of fluid mechanics and similarity
> methodology.
>
> He could have cut it down to:
> >
> > But if you bubble air through the water you row on, then surface tension
> > is significant as it strongly affects the formation & density of the
> > resulting foam & its flow characteristics around the blade.
> >
>
> Come on, Carl, you know by background and that I'm well aware of
> Reynolds' Number, similitude, and most certainly Archimedes' principle!
> The above snippet is the only part of that long post that addresses my
> comment(s) about surface tension (for which I thank you.) Next time
> though, save your self some typing and time! :-)
>
> -Kieran

Well, it made up for this one not being up to the usual standard:
http://groups.google.co.uk/group/rec.sport.rowing/msg/1da77a9be6894116

;o)



01 Sep 2006 19:00:22
Carl Douglas
Re: Bubble line and waves - should there be more?

kdavies@kidare.com wrote:
> KC wrote:
>
>
>>Carl Douglas wrote:
>>... a treatise on the basics of fluid mechanics and similarity
>>methodology.
>>
>>He could have cut it down to:
>>
>>>But if you bubble air through the water you row on, then surface tension
>>>is significant as it strongly affects the formation & density of the
>>>resulting foam & its flow characteristics around the blade.
>>>
>>
>>Come on, Carl, you know by background and that I'm well aware of
>>Reynolds' Number, similitude, and most certainly Archimedes' principle!
>> The above snippet is the only part of that long post that addresses my
>>comment(s) about surface tension (for which I thank you.) Next time
>>though, save your self some typing and time! :-)
>>
>>-Kieran
>
>
> Well, it made up for this one not being up to the usual standard:
> http://groups.google.co.uk/group/rec.sport.rowing/msg/1da77a9be6894116
>
> ;o)
>

Hey Kieran - were I replying for our private benefit, I'd have done so
privately & cut straight to the chase.

But this is a world-wide NG. Not everyone reading will have your (or
even my) grasp of engineering science & some might like to know more,
including the background.

That's why I try to explain things - which may be blindingly obvious to
you & me - in terms which I hope will make sense to those with
non-engineering backgrounds. After all, we do both want our fellow
rowers to know why there may be other ways to row, & that it wasn't all
sorted out by a bunch of classics scholars 150 years ago.

Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)


01 Sep 2006 11:21:08
KC
Re: Bubble line and waves - should there be more?


Carl Douglas wrote:
> kdavies@kidare.com wrote:
> > KC wrote:
> >
> >
> >>Carl Douglas wrote:
> >>... a treatise on the basics of fluid mechanics and similarity
> >>methodology.
> >>
> >>He could have cut it down to:
> >>
> >>>But if you bubble air through the water you row on, then surface tension
> >>>is significant as it strongly affects the formation & density of the
> >>>resulting foam & its flow characteristics around the blade.
> >>>
> >>
> >>Come on, Carl, you know by background and that I'm well aware of
> >>Reynolds' Number, similitude, and most certainly Archimedes' principle!
> >> The above snippet is the only part of that long post that addresses my
> >>comment(s) about surface tension (for which I thank you.) Next time
> >>though, save your self some typing and time! :-)
> >>
> >>-Kieran
> >
> >
> > Well, it made up for this one not being up to the usual standard:
> > http://groups.google.co.uk/group/rec.sport.rowing/msg/1da77a9be6894116
> >
> > ;o)
> >
>
> Hey Kieran - were I replying for our private benefit, I'd have done so
> privately & cut straight to the chase.
>
> But this is a world-wide NG.

Fair 'nuf. :-)

-KC