Introduction

This brief technical note describes Overview :

• The algorithms used in Simcenter Amesim™ software software to solve or integrate the equations defining a Simcenter Amesim model,

• The reasons for this choice,

• The strategy for progressively upgrading these algorithms.

When models are developed, assumptions and simplifications are made. It is one of the skills of the modeler to decide what these should be. If the detail of the model is very fine, the important variables will be functions of both time and position. Thus a pressure P would be a function of 4 variables

Normally a large grid of nodes is used to cover the 3-dimensional region of solution and a large array of pressure and another variables is stored. The evolution of these variables is governed by systems of partial differential equations. There are specialist packages for solving equations of this type such as those for computational fluid dynamics. Such software is used for detailed analysis of individual components of a system.

However, it is often necessary to simulate a larger engineering system. In this case it is normal to reduce any partial differential equations to ordinary differential equations. This leads to models with either ordinary differential equations (ODEs) or differential algebraic equations (DAEs). Simcenter Amesim belongs to this category of software. An essential feature is the provision of facilities for solving or integrating these ODEs and DAEs.