where IT is the turbulent intensity and
LT is the turbulence length scale.
A value of 10−3 (
0.1%) is a low turbulent intensity
IT. Good wind tunnels can produce values as low as
5·
10−4 (
0.05%). Fully turbulent flows usually have intensities between
0.05 (
5%) and
0.1 (
10%).
The turbulence length scale LT is a measure of the size of the eddies that are not resolved. For free-stream flows these are typically very small (on the order of centimeters). The length scale cannot be zero, however, because that would imply infinite dissipation. Use
Table 4-5 as a guideline when specifying
LT (
Ref. 3) where
lw is the wall distance, and
