Calculator inputs
Tip: pick a terrain preset first, then refine α and z₀ for your actual site if measured roughness data exists.
Example data table
| Reference speed | Reference height | Hub height | α | z₀ | d | Method | Hub speed | Dynamic pressure |
|---|---|---|---|---|---|---|---|---|
| 6.50 m/s | 10 m | 80 m | 0.16 | 0.05 m | 0.00 m | Average | 9.06 m/s | 49.43 Pa |
Formula used
Vhub = Vref × (Hhub / Href)α
Vhub = Vref × ln[(Hhub - d) / z0] ÷ ln[(Href - d) / z0]
ρ = P ÷ (R × T)
q = 0.5 × ρ × V²
Use the power law when a terrain exponent is already defined by project practice. Use the log law when roughness length and displacement height are known. The average option gives a balanced estimate when both methods are reasonable for early construction planning.
How to use this calculator
- Enter the measured reference wind speed and choose its unit.
- Provide the reference anemometer height and the required hub height.
- Select a terrain preset, then adjust α and z₀ if needed.
- Add displacement height when nearby buildings or tree canopies affect the lower profile.
- Enter temperature and pressure for better density and pressure outputs.
- Choose a final method or use the average for a balanced estimate.
- Press the calculation button and review the result block above the form.
- Download the live results as CSV or PDF for reporting.
Frequently asked questions
1) What does hub-height wind speed mean?
It is the estimated wind speed at the equipment or structural operating elevation. It helps assess lifting limits, turbine exposure, facade loads, and temporary works risk.
2) When should I use the power law?
Use it when your project already applies a known terrain exponent. It is simple, fast, and common for preliminary vertical wind profile estimates.
3) When is the log law better?
Use the log law when roughness length and displacement height are available. It usually reflects boundary-layer behavior more directly near real terrain features.
4) Why does terrain matter so much?
Smooth terrain causes weaker vertical shear, while urban or obstructed terrain creates stronger shear. That changes the speed increase between measurement height and hub height.
5) What is displacement height?
Displacement height represents the effective height of large obstacles, such as dense trees or buildings. It shifts the log profile upward and changes the estimated wind gradient.
6) Why are temperature and pressure included?
They improve the air-density estimate. Air density does not strongly change the hub speed itself, but it directly affects dynamic pressure calculations used in load checks.
7) Can I use this for code compliance?
Use it for screening, comparison, and reporting support. Final compliance should still follow your governing wind standard, project specification, and qualified engineering review.
8) Why compare both methods?
Comparing both methods shows sensitivity to terrain assumptions. A wide gap can signal uncertain site roughness, weak input quality, or the need for project-specific calibration.