Integration methods used

Hold inputs constant

Integration methods

This section is appropriate reading for those who are interested in the numerical algorithms employed by Simcenter Amesim.

Some simulation software packages give you a menu of integration algorithms from which you are invited to make a choice. Even for a specialist numerical analyst, given a newly constructed system, it is difficult to make an informed selection. The problem is made much more difficult because the characteristics of the equations governing the system may change in the course of the simulation. This often happens at discontinuity points. Just before the discontinuity algorithm A might be very suitable. After the discontinuity it is very unsuitable and algorithm B is much better. It is unreasonable to expect the user to recognize this fact, stop the simulation at this point and restart with a different integration algorithm. In practice what often happens is that an integration algorithm is used which is unsuitable for at least part of the simulation. This may lead to very long run times.

The Simcenter Amesim integrators provided can be divided into two types:

• variable step, variable order methods with control of errors,

• fixed step, fixed order methods with no error control.

The standard Simcenter Amesim integrator uses a collection of 17 variable step variable order methods. These are very robust and flexible. They are capable of adapting to a wide variety of problems. Most of the time you will be using these methods.