Anisotropic turbulence

Short definition of Anisotropic turbulence
Anisotropic turbulence is where the fluctuating flow properties have some directional dependence

This is the common definition for Anisotropic turbulence, but other definitions maybe discussed within the wiki.

A state whereby the velocity components and their derivatives are dependent on direction. If this is not the case the turbulence is said to be isotropic.

Taylor makes the statement "That there is a strong tendency to isotropy in turbulent motion has long been known. It has been shown by Townend, for instance, that the average values of the three components of velocity in the central region of a pipe of square section are nearly equal to one another" A natural consequence of this is the large body of work on anisotropy in boundary-layer flows.

However, stratification also influences the degree of isotropy. Taylor then goes on to say "in the atmosphere the same phenomenon has been observed; though, as might be expected, the vertical components are smaller near the ground than the horizontal ones, this inequality decreases with height above the ground."

The Ozmidov Lengthscale is the largest scale for stationary homogeneous isotropic turbulence and is defined [math]\displaystyle{ L_o=\left(\frac{\varepsilon}{N^3}\right)^{1/2} }[/math]. Overturns greater than the Ozmidov lengthscale are partially suppressed by density stratification as defined by buoyancy frequency [math]\displaystyle{ N }[/math] and isotropy is impeded .