terminology - In fluid dynamics does $u_x-v_y$ have a name?

I have come across the quantity: $$\frac{\partial u}{\partial x}-\frac{\partial v}{\partial y}$$ of the two dimensional velocity field $(u,v)$. Does this quantity have a name or is it related to any quantity with a name?

Answer

This quantity is called the Stretching deformation. The reference (1) given below says the following about it:

Stretching deformation, $D^{(1)}$, is a measure of the deformation of a fluid element due to compression in one direction and simultaneous dilation in a direction orthogonal (90 degrees) to it.

Here by deformation it seems to be referring directly to a change in shape rather then also including changes in areas. This is because the quantity above is zero when the shape is kept the same but the area varied.

Reference

(1) Mak, M. 2011. Atmospheric Dynamics. Cambridge: Cambridge University Press (page 50 Link to Google Books)