Andrew
I did think about paravanes on a single ship as you suggest but thought
that we could avoid the drag of the paravane by making two systems as
long as the paravane that you would have chosen, joining them together
and throwing away the two paravanes. Two boats is OK if the wake is
twice as wide but I want bubbles coming from the full length.
I think that the limitation on vessel separation might the the pumping
power so I was keen to pump for both ends.
I would not like to have to pump down to 10 metres because of the extra
pumping energy.
Michael Hayes
The boats will sail best on a beam sea slightly on the quarter but may
sometimes need to get to windward. Flettner rotors can go directly
into reverse just by changing the direction of spin. Wing sails can go
directly into reverse by a pitch change. Thanks for the numbers on
bubble size.
Mike MacCracken
I would prefer to start cloud modification field trials on soggy islands
like the Faeroes but would be happy to do experiments on conventional
ships provided that we can go to different sorts of places and do not
mess up the air with our exhaust. I understand that some research
vessels have specially clean fuel.
I an not so happy about conventional ships for bubble release because
the wake will be rather narrow. However if the bubbles gave a drag
reduction everything would change. They would all want to use it. We
would have to develop short lived bubbles of face excessive cooling.
Would this need a higher coal use?
Stephen
Emeritus Professor of Engineering Design
Institute for Energy Systems
School of Engineering
Mayfield Road
University of Edinburgh EH9 3JL
Scotland
Tel +44 131 650 5704
Mobile 07795 203 195
www.see.ed.ac.uk/~shs
On 27/04/2011 15:50, Mike MacCracken wrote:
Another approach to the bubble generation effort, and one Russell has
suggested, is to take advantage of existing ships (of order 1000 to
10,000 commercial ships at sea on a given day) and to put bubble
generators on them---perhaps doing so in a way that reduces their hull
friction to make up for power of bubble generation. Indeed, lifetime
matters, but that depends a good bit on bubble size, and extrapolating
from big bubbles in a present ship's wake must be done cautiously.
Using commercial ships is also an approach that could be used for CCN
generation as well, again depending on lifetime, etc. Indeed, there
are areas where no ships go very often, but commercial ships would
seem a fine starting approach.
Mike
On 4/27/11 10:14 AM, "Michael Hayes" <[email protected]> wrote:
Thank you both for the insight.
Yes, I do now recall the dual boat tether concept and I have some
working back ground in towing a long array of gear. From a pilot's
point of view, I can see an advantage of the dual boat/tether over
the towed array. In that, turning would be easier as well as being
able to "lay out" a broader path than a towed array.
The need for a sail boat to tack back and forth into the wind does
seem challenging with a tether between the 2 boats. But, I can see
how a spring line rigging could adjust for any lag between boats
in that type of maneuver. The symmetrical hull concept is
interesting in that I have never considered a sail boat being able
to "immediately" reverse direction.
I personally would like to play with the idea of modifying the
bright water injectors along the tether to act as a "bow truster"
type of directional control for the tether. That may help in
overall control of the configuration.
The recommended bubble diameter is .002mm. I can only see
ultrasound providing that type size for a high throughput
operation. I believe a table top experiment can possibly be done
using the parts from an off the self ultrasonic humidifier and
deep well pump. Measuring such small bubbles is something I have
not studied yet.
I did read in the paper Dr. Caldeira offered of observations of
long lived bubbles through possible contamination of a natural
surfactant film. Yet, I don't think the nature of the surfactant
was mentioned. I refer to the first page 2nd section
https://docs.google.com/viewer?a=v&pid=forums&srcid=MDE0NTY3NTk0NzY2MTMxMzQ4MjEBMDA1OTY0NDQ3MDgzNzU0NTIwODkBQkFOTGtUaWtZQ0pLSmJ2UzFRdFAzbmFrTHZkUTl3ay1kd0FAbWFpbC5nbWFpbC5jb20BNAE&pli=1
<https://docs.google.com/viewer?a=v&pid=forums&srcid=MDE0NTY3NTk0NzY2MTMxMzQ4MjEBMDA1OTY0NDQ3MDgzNzU0NTIwODkBQkFOTGtUaWtZQ0pLSmJ2UzFRdFAzbmFrTHZkUTl3ay1kd0FAbWFpbC5nbWFpbC5jb20BNAE&pli=1>
Well, again, thank you both for the feed back. I will spend more
time thinking about this.
On Wed, Apr 27, 2011 at 5:29 AM, Andrew Lockley
<[email protected]> wrote:
Stephen,
This technology is already used for towing hydrophone
streamers in geophys, but it doesn't work quite like you
suggest. There's no need for two boats, and instead there's a
paid of towed hydrofoils behind one boat, with the support
line tensioned between them. The low mass of the hydrofoils
means that there's no real shock on the cable in rough seas.
The bubble generators would be strung out on streamers behind
this towed line.
The bubbles would be distributed by a number of 'birds' which
are depth-set from the control room - just like the
hydrophones are currently.
To get good saturation with bubbles, I suggest that they'd
need to be delivered at a variety of depths - but whether
that's worth doing depends of course on the lifetime. No use
dropping them ten metres down if they don't last long enough
to mix or rise.
A
On 27 April 2011 13:05, Stephen Salter <[email protected]> wrote:
Hi All
Michael Hayes asks about how bubbles could be deployed.
One possibility would be for a pair of wind-driven vessels
to sail side by side at, say, a kilometre separation,
attached to each other by a buoyant, streamlined tether.
The chord of the tether would be about 100 mm. In plan it
would form a catenary with a generous bulge to reduce the
tensile load. The nose of tether would contain a strong
Kevlar or carbon tension member. Behind this would be a
number of high-pressure air-lines taking very well
filtered air from each vessel to a porous strip near the
nose of the foil section and running the full length. The
drag of the tether would be reduced by the bubble layer
on the underside.
The tether would have to be elastic enough to follow the
curvature of the wave slope. In most sea states this is
surprisingly low but elasticity can be increased by
running the tensile member in a series of S shapes.
The vessels need power but could generate this in the same
way as suggested for the cloud albedo project. Indeed it
would not be difficult to design a dual purpose vessel
which would change mode according to cloud conditions. It
would be convenient if the vessels were symmetrical fore
and aft so that they could tack by going into reverse.
The design does need information on bubble life and the
best bubble diameter and I would be most grateful for any
advice on this matter.
Michael mentions the Dracone project. I worked on this in
a very junior capacity in 1960 but a kilometre wide bubble
wake would be cheaper if the bubbles can last long enough
and less of a risk than a Dracone that got loose.
Stephen
Emeritus Professor of Engineering Design
Institute for Energy Systems
School of Engineering
Mayfield Road
University of Edinburgh EH9 3JL
Scotland
Tel +44 131 650 5704 <tel:%2B44%20131%20650%205704>
Mobile 07795 203 195 <tel:07795%20203%20195>
www.see.ed.ac.uk/~shs <http://www.see.ed.ac.uk/~shs
<http://www.see.ed.ac.uk/%7Eshs>>
On 26/04/2011 23 <tel:26%2F04%2F2011%2023> :21, Michael
Hayes wrote:
Please help me understand the mechanics of Bright
Water deployment. I have spent many months living on
the Bering Sea (in winter) and have piloted 150ft
fishing vessels in that area for countless hours. I
have watched the sea continually produce white caps
for as far as I could see for days and weeks at a
time. How can a practical, cost effective and
meaningful use of bright water be deployed which comes
even close to .0001 percent of the natural production
of white caps? The energy and equipment needed to
cover any meaningful amount of the sea is difficult
for me to comprehend. Outfitting fishing fleets with
the needed equipment and paying the boat owners to run
the gear is possible. But, we are only talking about a
bright water wake which lasts for only a short
distance...at best.
Designing autonomous platforms specifically for the
mission may be possible, but, one storm could beach
every single platform within a few hours. Who and how
will they be collected and sent back out? This, from a
seaman's point of view, is difficult to see as being
practical. I have studied the concept though what has
been offered here and through other links. The
mechanical challenge of producing such small bubbles
is interesting and I have even spent time thinking
through the possible use high throughput ultrasonic
injectors. But, I still come back to the questions of;
1) how can bright water be practically deployed? 2)
How can the investment be justified when the wide area
effect is so tenuous? 3) Would not reflective large
surface rafts provide a more cost effective long term
overall result?
There is the option of a reflective form of the
Dracone Barge as a useful way to deploy large area
ocean surface SRM.
"http://en.wikipedia.org/wiki/Dracone_barge.
If such barges were deployed in large numbers a large
area rafting system could be secured in needed areas
and moved as the season changes. With small
desalinization pods attached, we could have not just
have low cost/long term/flexible ocean surface SRM but
a nice supply of needed fresh water. Sell the fresh
water and buy more bags!!!!
I ask your help in understanding how bright water can
be a competitive form of SRM.
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
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