Also contains definitions of: area viscosity, surface dilatational viscosity
https://doi.org/10.1351/goldbook.S06189
For steady state deformations a surface , and an area viscosity or surface dilatational viscosity can be defined. In a Cartesian system with the x-axis normal to the surface, they are defined by the equations: where is the shear component of the and are the and components of the surface velocity vector, respectively, is the surface area, is the time, and is the difference between the (steady state)
shear viscosity
surface stress
tensor, dynamic surface tension
and the equilibrium surface tension.