Usually, when it comes to modeling and simulation, the sequence is simulate first, then build. But that is not always possible, especially in the defense sector where major programs can span decades.
The Bath Iron Works shipyard (BIW, Bath, ME) faced this situation with regard to its ongoing contract to build DDG-51 Arleigh Burke-class guided-missile destroyers. The ships' primary armament is the Aegis missile. The Navy regards the DDG-51 as the most technologically advanced warship in the world. BIW had already been building the ships for years when it decided to start using computer simulations to help streamline the construction processes.