Boundary and initial conditions
Solving the set of Eqs. (1.16) – (1.17) requires initial and boundary
conditions for e 1 and e 2.
The material coordinate system, see Eq. (1.2), used in the expression
model is illustrated in Figure 3. With this ω -coordinate, both
boundaries are stationary. The position of the cloth at ω = 0 is
denoted by Γ 1, while that of the piston atω = Ω is denoted by Γ 2.