Structure Function Help

1. Jun 7, 2014

joshmccraney

Hello again pf!

i was wondering if any of you could help me with the intuition for the following structure function:
$$S_{xy}(R) = \overline{\big[v_x (x + R) - v_x(x)\big] \big[v_y(x+R) - v_y(x) \big]}$$
where $v_i$ is the velocity in the $i$ direction, $x$ is distance, and $R$ is a displacement in $x$ ($R$ need not be infinitesimal, and in fact isn't always!). Now this looks something like covariance mixed with a derivative?

can i get any help here?

thanks!!

2. Jul 1, 2014