A single trilinear prolate spheriod with hydrostatic pressure interpolated quadratically in Xi3 (element based). The pole-zero law defines the incompressible material behaviour of the wall region. A cavity region is defined with a single free node at the top (opening) of the cavity.

The pressure inflated prolate is initially contracted due to the steady-state tension-length-Ca relation against a constant volume constraint in the cavity region. Movement of the top cavity node is restricted (using an 'impedance' parameter) to simulate isovolumic contraction.

Ejection is simulated by reducing the impedance parameter to allow the top cavity node to move out of the cavity.

Created by Martyn Nash 1995
Updated by Martyn Nash Aug 2004