Hydrodynamical helicity
= Hydrodynamical helicity
{title2=$H_k=\int\mathbf u\cdot\boldsymbol\omega\,dV$}
{wiki}
= Kinetic helicity
{synonym}
= Hydrodynamic helicity
{synonym}
Kinetic helicity measures the alignment and linking of a <velocity field> and its <vorticity>. It is the volume integral of $\mathbf u\cdot\boldsymbol\omega$, with boundary conditions needed for its conservation.
The integral measures linkage and twisting of <vortex lines> through the <velocity> and <vorticity> fields.