  We establish a method to trace the Lagrangian evolution of extended objects
consisting of a multicomponent scalar field in terms of a numerical calculation
of field equations in three dimensional Eulerian meshes. We apply our method to
the cosmological evolution of global strings and evaluate the energy density,
peculiar velocity, Lorentz factor, formation rate of loops, and emission rate
of Nambu-Goldstone (NG) bosons. We confirm the scaling behavior with a number
of long strings per horizon volume smaller than the case of local strings by a
factor of $\sim$ 10. The strategy and the method established here are
applicable to a variety of fields in physics.
