As for me, modeling consists in building a model, mathematical or not, to establish predictions in a given field. In NDE, the modeling of a specific phenomenon can therefore predict the outcome of experience in the field of validity of the model.

The simulation is the practical implementation (computing) of the model. This implementation is therefore accompanied by a discretization of the model (whether finite elements or integral methods) and therefore with further approximations to modeling.

In other words, the simulation is the representation of a real phenomenon, based on an underlying theoretical model, itself valid in a bounded domain.

I hope this will help.