What is the force exerted on a flat roofed building by wind pressure?

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Homework Help Overview

The problem involves calculating the force exerted on a flat roofed building by wind pressure, given specific parameters such as wind density, speed, roof height, and area. The context is rooted in fluid dynamics, particularly the application of Bernoulli's equation.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the pressure difference between the moving air outside and the still air inside the building. There are inquiries about how to calculate this pressure difference using the dimensions of the roof and the Bernoulli equation.

Discussion Status

Some participants are exploring the relationship between the pressure difference and the dimensions of the roof, while others are attempting to clarify the application of Bernoulli's equation in this context. Guidance has been offered regarding the need to consider the stationary air inside versus the moving air outside.

Contextual Notes

There is an assumption that the thickness of the roof is negligible, which may affect the calculations. The discussion also highlights a lack of understanding regarding the application of Bernoulli's equation and its implications for the problem at hand.

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Homework Statement



"Wind (density=1.29kgm^-3) blows over a flat roofed building of height 20m at 12ms^-1.The area of he roof is 100m^2.What is the magnitude and direction of the force exerted on the roof if the pressure difference between inside and outside is due solely to the fact that the inside air is still?Assume laminar flow."


Homework Equations



Im really stumped with this Q, I have scanned the net and it seems to involve the Bernoulli Eqn , however, i don't really understand what's occurring, any help appreciated.





The Attempt at a Solution

 
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If you assume that the thickness of the roof is negligible, what's the pressure of the air just outside the roof, where the air is flowing? And the pressure inside where the air is stationary? So, what's the force due to the pressure difference?
 
thats the thing, i undererstand where the pressure difference comes from, but not how to calculate it based on the dimensions of the roof?...
 
The dimensions of the roof is needed to calculate the force due to the pressure difference. You need to use Bernoulli's equation to calculate the pressure difference. (Hint: The air inside is stationary, while outside, it's moving.)
 

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