Introduction

This document is a methodology guide: its purpose is to expose readers to Simcenter Amesim's capabilities in the domain of co-simulation with CFD software. It is not a user guide, since these capabilities don't rely on a feature set built specifically for CFD co-simulation; instead it shows possible applications and benefits of 1D/3D CFD co-simulation and how to achieve them.

Simulation is an increasingly intrinsic part of the industrial design cycle, saving time and money and shortening design/production cycles.

The V-Cycle model of system design

The design process of mechatronic systems (e.g. machine tools) follows the well-known V-Cycle: top-down design steps (left side of the V) combined with bottom-up validation steps (right side). Simulation software fits this model, with different levels of modeling needed at different steps. Four levels of modeling are typically distinguished:

• Signal level — block-diagram approach; still the most popular for system modeling, especially control design. Scales to whole-system assembly of equations, but lacks a defined architecture and standard connection rules, making complex systems hard to build this way.
• System level — models based on ODEs (Ordinary Differential Equations) or DAEs (Differential Algebraic Equations), with defined architecture and standard connection rules (this is Simcenter Amesim's native modeling level).
• Geometric level — well suited for detailed results on a specific part of a system, but very CPU-time consuming (hours to days per run), making it impractical to model a complete system including all parts to get system-level energy efficiency results. Another difficulty: geometric-level models are harder to reuse/scale across a full system study.
• (A fourth level is referenced in the source table of modeling approaches but the on-page table itself renders as a figure, not extractable text.)

Why 1D/3D CFD co-simulation

Because the Geometric (3D CFD) level is CPU-costly and hard to scale to full-system studies, while the System (1D) level is fast but coarser for local flow phenomena, Simcenter Amesim's positioning is to co-simulate: couple 1D system-level models with 3D CFD software so each domain is represented at the appropriate level of detail — fast system-level dynamics from Amesim, detailed local flow behavior from the CFD tool — within a single coupled run.

Figure references in the source (Fig. 1: Simcenter Amesim in relation to other CFD software; Fig. 2: V-Cycle model; Fig. 3: Signal vs System levels — Electro-Hydraulic Actuator example; Fig. 4: Geometric vs System levels — Piping system example) illustrate these comparisons visually and are not reproducible as text.