The modeling of any physical system requires intimate knowledge of the physical processes involved. The engineer must decide what processes are to be modeled and how detailed an analysis is required.
Approximations made in the modeling process can greatly alter the calculated dynamic behavior.
Therefore, each simplifying assumption must be justified. The procedure in each case involves writing the conservation equations that describe the physical phenomena of interest and putting these into state form. When appropriate, the finite difference technique is used to convert distributed parameter systems into a lumped parameter description of the system. The modeling process is iterative in that one repeatedly refines the computational models to reflect the current level of understanding. Some of these ideas are expounded in the case studies treated here.