This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.

Resource Abstract

Multi-Body Dynamics (MBD) software has been used to investigate the dynamic behavior of the mechanical systems since the early 1980s. Since that time MBD software has continually added capabilities to simulate related physics and/or numerical methods, such as control system modeling, linear and nonlinear flexible bodies, Design of Experiments (DOE), and system-level optimization. Starting a bit more recently, Computational Fluid Dynamics (CFD) has been used to understand the characteristics of fluid flow, including the distribution of fluid pressure.

While the operation of many products includes the combination of moving mechanical assemblies and fluids, co-simulations could not be done because the two different simulation domains could not be properly coupled because of technical reasons. For example, traditional CFD uses a mesh-based computational approach, while the changing configurations of the MBD mechanical system causes continual changes of the available volume for the fluid. Another consideration was the proper exchange of forces and momentum between the fluid and the moving components.

This presentation explains how a particle-based CFD method, the so-called MPS (Moving Particle Semi-implicit) method can be used with MBD software. The MPS method is a formulation for modeling fluid dynamics for uncompressible fluids, using a Lagrangian approach. In contrast with conventional CFD methods that require meshes, the MPS method models fluids using particles. This approach allows for easy modeling of the free surfaces of fluids and for modeling multiple fluid types together, along with the boundaries between these fluids. As a result, the MPS method provides a remarkable advantage in simulation of free surface flows and complex boundary geometries. Since this method doesn’t use a mesh, co-simulation with MBD works well.

In this presentation, a new and strong coupling method between MBD and CFD will be introduced, together with several industry case studies. The highest interest in the automotive industry has been observed in two areas. The first is the interaction between the lubricating fluid and the moving mechanical components in transmissions and axles. The second is the simulation of fluid flow in the undercarriage and the engine compartment of a vehicle. Given the higher voltages that are present in hybrid and electrical vehicles, it is important to understand the distribution of water as the vehicle operates in roads with puddles.