How does surface size affect wind pressure on a sail boat?

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Discussion Overview

The discussion revolves around how surface size affects wind pressure on a sailboat, with a specific focus on calculating the pressure exerted by wind on large surfaces, such as sails and wind turbine blades. Participants explore theoretical frameworks and equations relevant to this topic.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant inquires about the pressure exerted by a 10 mph wind on a 12,000 sq.mt. surface and seeks methods to adjust calculations based on changing parameters.
  • Another participant suggests using Bernoulli's equation to calculate stagnation pressure at the specified wind speed.
  • A different participant notes that the effect of wind pressure depends on the type of surface; for sails, deformation can lead to a zero wind velocity on the surface, while rigid surfaces will deflect wind, invoking Newton's 2nd law.
  • The same participant emphasizes that wind pressure values can vary with wind direction, boat speed, and air compression.
  • A later reply clarifies that the original question may have been misleading due to the comparison between sails and wind turbine blades, which do not deform like sails but also do not behave like rigid walls.
  • The participant with the wind turbine asks how to adjust wind speed to maintain the same pressure if the surface area is decreased.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of Bernoulli's principle versus Newton's laws depending on the surface type, indicating that multiple competing views remain regarding the effects of surface characteristics on wind pressure.

Contextual Notes

Participants acknowledge the complexity of the problem, including factors such as surface deformation, wind direction, and air compression, which may not have been fully addressed in their initial statements.

Who May Find This Useful

This discussion may be of interest to those involved in sailboat design, wind energy applications, or anyone studying fluid dynamics and the effects of wind on various surfaces.

jacques dichi
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Hi forumers,

I've got a question,and of course all proper answers are welcome,
I think however a sailboat designer/engineer would quickly know
what I'm talking about.
I'd like to know what is the pressure/push of a 10 mph (16 km/h)
wind on 12,000 sq.mt. surface ,and how to figure this out if I change
the parameters ?
Thks. & Happy Easter
J.D.
 
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You can use Bernoulli's equation to calculate the stagnation pressure at that wind speed.
 
Thk. u Russ for yr. reply I'll try bernoulli as suggested - if he fails me - I'll come back to u
 
Hey,

It depends on the surface you are talking about. If it is a sail, then it can deform so that the velocity of the wind is practically zero on the sail surface. So Bernoulli's principle would hold good. But if it is a rigid surface, the wind will get deflected and the force is based on Newton's 2nd law. Besides, this value also changes with the direction of wind and speed of the boat(or surface) and compression of air.
Do let me know if you want a general equation for the same :)
 
sci-phy said:
Hey,

It depends on the surface you are talking about. If it is a sail, then it can deform so that the velocity of the wind is practically zero on the sail surface. So Bernoulli's principle would hold good. But if it is a rigid surface, the wind will get deflected and the force is based on Newton's 2nd law. Besides, this value also changes with the direction of wind and speed of the boat(or surface) and compression of air.
Do let me know if you want a general equation for the same :)

thks. for your answer. - I think according to it I might have misled a few people with the phrasing of the question or my comparison - sorry for that.
What I have is a 120m. span 3 wing wind turbine -approx. 12,000 m^2 surface - it does not deform like a sail and it is not rigid like a wall although when rotating it could be considered as such - and a 10 mph wind.
If I decrease the surface,how have I got to increase the wind in order to obtain the same "pressure/push" ?
Pls. bear with me,
Thks.
 

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