Modified structure function method

This method performs a regression of the structure function against

$D=a_0+a_1(\delta r_0{)}^{2/3}+a_3((\delta r_0{)}^{2/3}{)}^3$

The last term includes the influence of non-turbulent motions which result in a velocity difference between bins which varies linearly with separation distance and hence contributes to $D(n,\delta )$ as $(\delta r_0{)}^2$

[IMPROVE AND GIVE REFERENCE TO BRIAN'S PAPER]