[MichaelC]

Hi all,

just looking to see if I can get some help with a current simulation I am working on. I am using CFX to model the intake stroke of an internal combustion engine to analyse the effectiveness of an intake port(currently without the valve geometry for simplicity). So far i have managed to apply the mesh motion technique and the simulation runs until the piston is approximately 75 deg ATDC. At this point i encounter the error of negative volume and highly skewed mesh causing the solver to crash. I have kept the geometry and mesh quite basic as firstly i would like to learn the process and setup and then further refine the geometry and mesh. I have applied a pressure inlet at the intake of the port, and used a wall boundary with "parallel to boundary" mesh motion on the piston/cylinder walls. On the top of the piston I have applied a wall boundary with "specified displacement" mesh motion, where the motion of the piston is defined by an expression named "pistondisp" which relates the displacement of the piston to time, which is determined by the time step in the simulation. I have attached some images which i hope will help with my explanation. Any suggestion would be greatly appreciated.

Port_and_Chamber_TDC.JPG

Port_and_Chamber_MidStrokeJPG.JPG

Mesh.JPG

setup2.JPG

setup1.JPG

[ghorrocks]

This FAQ has tips and how to debug this problem: http://www.cfd-online.com/Wiki/Ansys..._went_wrong.3F

By the way: my PhD thesis used CFX to model internal combustion engines https://opus.lib.uts.edu.au/handle/10453/20133