PISM, A Parallel Ice Sheet Model  stable v2.0.4 committed by Constantine Khrulev on 2022-05-25 12:02:27 -0800

## ◆ secondInvariant_2D()

 static double pism::secondInvariant_2D ( const Vector2 & U_x, const Vector2 & U_y )
inlinestatic

This uses the definition of squared second invariant from Hutter and several others, namely the output is $$D^2 = \frac 1 2 D_{ij} D_{ij}$$ where incompressibility is used to compute $$D_{zz}.$$

This is the approximation of the full second invariant corresponding to the shallow shelf approximation. In particular, we assume that $$u$$ and $$v$$ are depth-independent ( $$u_z = v_z = 0$$) and neglect horizontal derivatives of the vertical velocity ( $$w_x = w_y = 0$$).

Definition at line 44 of file FlowLaw.hh.

References pism::Vector2::u, and pism::Vector2::v.