When this quantity is zero throughout a flow, the flow is said to be a potential flow.
The mean square value of this quantity is known as the enstrophy. It can be generated by the entropy gradient associated with a curved shock, and like entropy, disturbances in this quantity travel through fluids at the flow speed, rather than the speed of sound. When this quantity is zero throughout a flow, the flow is said to be a potential flow. The surface integral of this quantity over a surface bounded by a closed curve equals the circulation about that curve. Equal to twice the local angular velocity, FTP name this quantity given by the curl of the velocity in a fluid.
The mean square value of this quantity is known as the enstrophy.
{vorticity}