Turbulence

 

Turbulent eddy dissipation rate is estimated using an algorithm developed by Sand (Sand et al. 1976), based on earlier work described in MacCready (1962).  The approach is based on the spectral properties of homogeneous turbulence in the inertial subrange.  Basically a Fast-Fourier transform of the high-resolution true air speed record is fit to the spectral form expected for homogeneous isotropic turbulence and the result used to infer the eddy dissipation rate. As with the vertical wind calculation, the turbulent eddy dissipation rate calculation is valid only in straight-and-level non-accelerating flight.

 

 

 

 

Pilot-observed short-term airspeed fluctuations also can be qualitatively correlated with turbulence characteristics. Sand (1976) gives an empirical correlation between airspeed fluctuations on few-seconds time scale and pilot-reported turbulence intensity in aircraft of the weight and speed class of the T-28:  Light  2.5 – 7.5 m s^-1; Moderate 7.5 – 12.5 m s^-1; and  Severe  > 12.5 m s^-1.