5. Towards a digital platform

When several scales are involved, the simulation is broken down into different levels, each representing a different scale. To coordinate the levels, engineers use :

• or top-down approaches. They begin by simulating the overall behavior of an aircraft and use the results to determine the boundary conditions applied on the lower levels;

• or bottom-up approaches. In the latter case, the results of fine simulations are used to build models of coarse-scale behavior.

There are many different multi-scale methodologies, all based on the same fundamental principle: simulate each phenomenon at the most appropriate scale. To achieve this, they have two key points: the first is to distinguish between different scales in modeling and simulation, and the second is to model the relationships...