One of our Master degree students, Felix Sträubig from Technical University Berlin, evaluates whether the combination of TwinMesh grids and ANSYS CFX simulation are helpful for gear box lubrication analysis. Although there are only first results available yet I found this video quite amazing and therefore decided to share it here in this Blog.

The video shows the oil flow in a simplified three-dimensional gear box geometry. An isosurface for oil volume fraction of 0.5 and the local pressure on the gears and on gear box walls are shown. The rotational speed of the pinion is 150 revolutions per minute for this case.

This gear box lubrication CFD analysis was done in ANSYS CFX using structured hexahedral grids generated by our TwinMesh software for the moving flow volumes, and a moving nodes approach for the mesh movement between and around the gears. In total the entire mesh consists of barely 1.6 million elements. Instead of the moving contact point, the geometry was modeled with a gap of at least 50 µm between both gears so that TwinMesh could distribute the hexahedra as an O-type grid around each gear.

The flow of oil and air was modeled with the homogeneous multiphase model and a free surface model. Both phases are incompressible and isothermal, and the SST turbulence model was used. On a single CPU the whole simulation (three revolutions of the pinion) lasts almost 13 days. Running it in parallel on 8 cores the job requires around two or three days of computation time. Previous 2D simulations showed totally different fluid behavior, so that the consideration of 3D effects is very important. Future model extensions shall include a systematic gap size study, and the detailed examination of the generation of oil films and of the cooling of the gears.

Well done Felix!