Turbulent Intensity

Turbulent Intensity

Turbulence Intensity (I) is a dimensionless measure of turbulence strength, defined as the ratio of the standard deviation of wind speed fluctuations to the mean wind speed. It’s expressed as:

$$ I = \frac{u’}{U_{\text{local}}} $$

Where:

  • u′ is the root-mean-square of the turbulent wind speed fluctuations

  • U_local is the local mean wind speed

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Non-linear Relationship with Wind Speed

Turbulence Intensity does not increase linearly with wind speed. This non-linear relationship is due to several factors:

  1. Atmospheric Stability: As wind speed increases, the atmosphere becomes more neutrally stable, which can lead to a decrease in turbulence intensity.
  2. Surface Roughness: The effect of surface roughness on turbulence becomes relatively less significant at higher wind speeds.
  3. Mechanical Turbulence: At very high wind speeds, mechanical turbulence generated by wind shear may become more dominant than thermal turbulence.

Importance of Turbulence Intensity

Understanding Turbulence Intensity is essential for several applications:

  • Wind Energy: High turbulence intensity affects the performance and lifespan of wind turbines.
  • Aviation: Turbulence intensity is crucial for flight safety and planning, as high turbulence can impact aircraft stability and passenger comfort.