Due to the proprietary nature and costs associated with developing realistic car models, automotive aerodynamic simulations are often run on generic car models such as the so-called Ahmed body or the Ahmed body. The problem is that these generic models are a little too generic to provide anything other than the most basic insights into flow behavior.
Luckily, a more advanced car model by the name of DrivAer was introduced in 2011 to help bridge the gap between simulation and production.
The difficulty is that the preprocessing stage of CFD simulations is still a bit of a chore, especially when it comes to creating water-tight meshes that are suitable for CFD simulation.
However, this week, CFD meshing software company Creative Fields announced that it had successfully completed an incompressible turbulent flow simulation around the DrivAermodel using a combination of its own CF-MESH+ software and OpenFOAM.
Creative Fields’ CF-MESH+ software is a fully automated and easy-to-use CFD meshing solution that features superior capabilities for mesh generation in arbitrary complex geometries.
The software was used to automatically generate a volume mesh around the DrivAer vehicle from a few simple specifications. Then, the car geometry was split into different sections, and different mesh refinement levels were set for each section to allow feature edges to be automatically generated in between the sections. This procedure allows for finer geometry features to be created in the meshing process.
After adding boundary layers to the volume and around the car geometry, the CF-MESH+ meshing process created a Cartesian volume mesh comprising 25 million cells, with 96 percent of those cells being hexahedral.
The automatically generated mesh had no sudden cell size change. Every cell size change was resolved gradually, regardless of its position (further from the car geometry or in the boundary layer), which had a positive impact on the stability of the calculation and its convergence.
After the meshing process was complete, the mesh was imported into OpenFOAM, where it was successfully simulated with the simpleFoam solver and k-ω SST turbulent model. The simulation reached convergence after just 400 iterations, when a quasi-steady solution was reached.
“We are proud of yet another successful case where CF-MESH+ has proven an excellent companion to OpenFOAM when it comes to automotive aerodynamics. Advanced boundary layer generation capabilities and the ability to control the layer thickness in the first cell near the wall make CF-MESH+ an ideal candidate for mesh generation in external aerodynamics simulations,” said Mario Baburic, managing director at Creative Fields.
If you’d like to see more of what is new in the latest release of CF-MESH+ (v2.2.2), then you can read all about it right here.
Or, if you’d like to try out CF-MESH+ to help solve your own meshing woes, then you can get your hands on a free trial over at the this link.