Wind Pressure (Dynamic)
The pressure a moving airmass exerts on a surface such as a wall or roof.
Formula
Variables
Example
A 40 m/s hurricane gust exerts ~1 kPa on a wall
How it works
This formula estimates the pressure a moving flow of air can produce when it is brought to rest against a surface. The key idea is that faster wind carries more kinetic energy, and that energy shows up as a larger force per unit area when the air is forced to slow down or change direction. The dependence on the square of wind speed means that doubling the wind speed makes the pressure about four times larger, which is why strong gusts can increase loads so dramatically.
When to use it
Use this when you need a quick estimate of wind loading on buildings, signs, roofs, or other exposed surfaces. It is also useful in meteorology and engineering for comparing the effect of different wind speeds on structural stress.
Worked example, step by step
Suppose a gust reaches 25 m/s and the air density is 1.225 kg/m^3. P = 1/2 × ρ × v^2 P = 1/2 × 1.225 × (25)^2 P = 0.6125 × 625 P = 382.8125 Pa P ≈ 383 Pa So the dynamic wind pressure is about 3.8 × 10^2 Pa, or 0.383 kPa.
Common mistakes to avoid
- Using wind speed in km/h instead of m/s without converting first
- Forgetting that the speed is squared, which causes a large under- or overestimate
- Treating this as the total force rather than pressure; to get force, multiply by area
Did You Know?
Because pressure scales with v², doubling the wind speed quadruples the force on a building.
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