sail aerodynamics

Discussion in 'Hydrodynamics and Aerodynamics' started by Guest, Mar 21, 2002.

  1. brian eiland
    Joined: Jun 2002
    Posts: 4,920
    Likes: 173, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Suppression of Vortex Shedding from a Cylinder

    Sorry Daiquiri, have gotten back to you on those spiltter plate sketches yet.

    But here is an interesting little piece I became acquainted with thru a link on Sailing Anarchy
    http://www.nda.ac.jp/~nhajime/english/research3.html
    Suppression of Vortex Shedding from a Cylinder, 1) Effect of cylindrical rings
     
  2. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 246, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Interesting article, thanks.
    I've been ignoring that particular method of vortex-shedding supression.
     
  3. tspeer
    Joined: Feb 2002
    Posts: 2,268
    Likes: 236, Points: 63, Legacy Rep: 1673
    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    There are a vast number of devices and methods that have been investigated with regard to suppressing the vortices from circular cylinders. The attached paper compares the effectiveness of many of them. In particular, look at Figure 30. Whether you get a reduction in drag from any device depends very much on the Reynolds number range at which the cylinder is operating. The devices are mainly of benefit for subcritical speeds.

    These results may be applicable to a bare mast. However, I don't think any of them apply to a mast with a mainsail set, because of the effect of the mainsail on the wake of the mast.
     
  4. brian eiland
    Joined: Jun 2002
    Posts: 4,920
    Likes: 173, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    As I understand it a mast with the mainsail attached does not require drag suppression?
     
  5. Rurudyne
    Joined: Mar 2014
    Posts: 1,145
    Likes: 33, Points: 48, Legacy Rep: 155
    Location: North Texas

    Rurudyne Senior Member

    Okay, a quick random question.

    If I understand the claim made about vortex reduction correctly, and the implications of the post you are responding to, does it seem that the main benefit would be when the sail is underpowered and still flapping in the wind a bit from turbulence from the mast BEFORE the sail can take up the wake.

    IOW, taking what tspeer said at face value would there be benefit in light winds?

    Moreover, what about sails that overlap the mast rather than sit squarely in its wake like a Bermuda rig might be said to be: squad sails, junk rig, etc? Wouldn't these benefit in all wind conditions?

    Dealing with Reynolds numbers is precise, but not the same ease for the reader as someone saying "in a XX MPH wind with a mast of Y" diameter..."
     
  6. brian eiland
    Joined: Jun 2002
    Posts: 4,920
    Likes: 173, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

  7. BobBill
    Joined: Oct 2009
    Posts: 728
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    Brian, probably, IMHO...

    You guys are way ahead of this dodger on this topic but I keep lurking and schlepping around here, hoping osmosis works...

    What I have come to believe in is the idea the drives much computer coding in last few decades, namely, if a person can think it, it can or will be done...

    Might take some time etc, but it is possible. Years ago I figured the "wing" sail was too spendy, unwieldy and inconvenient...meaning it would eventually give way to a "soft wing" that would be easier to use an so on. Same with foils.

    The need, not the want seems the driving force so I would say, if the need is paramount, it will happen...eventually.
     
  8. brian eiland
    Joined: Jun 2002
    Posts: 4,920
    Likes: 173, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Mastfoil aero, very little response

    Bob, I was disappointed that I got very little (if any) response to some postings I made about the aerodynamics of Chris While's new Mastfoil concept(s)
    ....this page & a few others: http://www.boatdesign.net/forums/hydrodynamics-aerodynamics/sail-aerodynamics-457-53.html#post765907
     
  9. BobBill
    Joined: Oct 2009
    Posts: 728
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    Brian, I understand. I try, but not remotely qualified...so I lurk and say nothing. It all helps though, so do not feel low. You are appreciated by this dodger swab.
     
  10. Skyak
    Joined: Jul 2012
    Posts: 1,194
    Likes: 25, Points: 38, Legacy Rep: 152
    Location: United States

    Skyak Senior Member

    Brian, the answer is yes, but...

    See the AC thread.
     
  11. brian eiland
    Joined: Jun 2002
    Posts: 4,920
    Likes: 173, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    I discovered this video on the AC subject thread, so I'm unsure of what you are referring me to it for my question about soft sail usage?
    They appear to be using it on the hard surface of the wing
     
  12. Skyak
    Joined: Jul 2012
    Posts: 1,194
    Likes: 25, Points: 38, Legacy Rep: 152
    Location: United States

    Skyak Senior Member

    You asked the same question on the AC thread and I answered -post 599

    "The answer is yes of course. You could address durability issues by locating circuits along (on) a batten.

    The big problem is getting a payoff. The AC solid wing can reproduce shape with extreme accuracy... your soft sail can not so the sensors would just be lots more data to deal with continuously. You don't know or control your sail shape accurately enough to make use of pressure data. A better use of your tech budget would be to use 3D cameras to record and reproduce sail shape.

    The aerodynamics class class I took had a lab, and the most interesting and informative sensor IMHO was a tiny microphone on a stick that was used to measure boundary layer thickness. Other than boundary layer development, aerodynamics is a known. Tiny mics are dirt cheap compared to MEM pressure sensors."

    pressure sensor example -looks capable and easy to use.

    http://www.newark.com/stmicroelectr...=81605889141&gclid=CMD-op3c_c4CFQwyaQodZyYERQ
     
  13. brian eiland
    Joined: Jun 2002
    Posts: 4,920
    Likes: 173, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Sorry Skyak, I posted that message/question of mine before I saw your reply over on the other subject thread.

    This new age of electronics and miniature detection devices looks as though one might even find a way to mount these sensors right on total soft (non-battened) sail materials.

    I was assuming the possibility of making/monitoring these measurements on new sails that might hold their flying shape reasonably consistently once they were 'full and drawing' in a particular setting or rig configuration.

    Then perhaps these real time figures could be compared to the CFD and other computer generated figures.
     
  14. Skyak
    Joined: Jul 2012
    Posts: 1,194
    Likes: 25, Points: 38, Legacy Rep: 152
    Location: United States

    Skyak Senior Member

    As I said, the problem is in the control. For a sail I am saying that you would be much better off using optical capture of the sail shape and a microphone to measure boundary layer development. Pressure is the curvature of the flow, which is the boundary layer, which follows the sail shape -until it doesn't. If you know how the flow does and does not follow the sail you have everything.
     

  15. Doug Halsey
    Joined: Feb 2007
    Posts: 426
    Likes: 113, Points: 53, Legacy Rep: 160
    Location: California, USA

    Doug Halsey Senior Member

    The pressure distributions could give you valuable information, even if you don't know the shape. (Just like telltales can, only better.)

    If your boat had real-time displays, they could help you continuously with sail trim and camber & twist adjustments.

    And even without the real-time displays, the data hold all sorts of clues to help you evaluate your performance.
     
Loading...
Similar Threads
  1. Mikko Brummer
    Replies:
    52
    Views:
    2,038
  2. Grunf
    Replies:
    12
    Views:
    991
  3. wesley Sherman
    Replies:
    10
    Views:
    658
  4. Federico Ferretti
    Replies:
    3
    Views:
    1,039
  5. schakel
    Replies:
    4
    Views:
    1,016
  6. Yull
    Replies:
    10
    Views:
    1,266
  7. Manfred.pech
    Replies:
    7
    Views:
    1,536
  8. andysailor
    Replies:
    4
    Views:
    1,139
  9. CocoonCruisers
    Replies:
    75
    Views:
    6,695
  10. mustafaumu sarac
    Replies:
    25
    Views:
    1,506
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.