Transient calculation

The term transient simulation is especially common for time-dependent simulations of flow fields, temperature fields or magnetic fields where no 2nd order term (mass, acceleration) corresponds in the underlying differential equation. In a FEM simulation of flow fields, temperature fields or magnetic fields, a transient simulation is calculated in the time domain. Thereby, the course of time is processed step by step. A simulation in the frequency domain is not possible, because the differential equation does not contain a 2nd order term.

For simulations of structural mechanics, where the inertia terms are present in the underlying differential equation but are neglected and where, however, there is a time dependence of the stiffnesses and/or the loads, we can speak of a static transient simulation. Example: an exhaust pipe that is heated, i.e. experiences time-dependent thermal strains, but is not excited to vibrate as a result.

In a transient simulation, when discussing gradients, a distinction should be made between the local gradient - i.e. the change in one spatial direction - and the temporal gradient - i.e. the change over time - otherwise there may be misunderstandings.