The characteristic length,
, for computing the
critical time step, referring back to
図 1, is defined by:
(1)
(2)
(3)
When the orthogonalized mode of the hourglass perturbation formulation is used, the
characteristic length is defined as:
(4)
(5)
(6)
Where,
is the shell membrane hourglass coefficient and
is the shell out of plane hourglass coefficient, as mentioned
in Hourglass Modes.