In the model, the expansion of the exploded wire array was
modeled as an expansion of a cylindrical piston. The Euler
equations for an axially symmetric flow were used in the
Lagrange form. The coordinate in these equations is themass
m(r ) enclosed in a cylindrical layer of a given height at a distance
r from the axis. The mass conservation law for a cylindrical
layer with mass dm and thickness dr reads [24,25]
dm = 2πρrdr, where ρ is the water density. Thus, the coordinate
r (t,m) is defined by the Euler equations as