COLORADO SPRINGS, CO (CIC/NAFEMS 2104) - The mesh is critical to the speed and accuracy of a CFD analysis. Make too coarse of a mesh of your control volume and results near abrupt shape changes will not be accurate. Make too fine a mesh over the whole volume and the analysis will take forever. You could do a couple of runs to determine zones each corresponding to to different sizes of elements. Or you could get Converge to refine the mesh for you -- and I'll bet Converge will be faster.
Converge solves combustion problems with CFD using a mesh that refines itself on the fly
(picture from Convergent Science site)
It's so fast that it can solve rapidly changing volumes such as those occurring in combustion chambers of engines, where the dyamimic shape of the flame must be modeled and accounted for. If that's not impressive enough, it can calculate and adapt meshes in supersonic shock waves from jets.
Converge utilizes what it calls Adaptive Mesh Refinement (AMR) to reduce the size of elements in critical areas. Because AMR is coupled with the solver, it refines the mesh during the analysis. You don't have to wait a couple hours to see problem in the results and rerun it. You set the level of refinement before the run. One level means the elements are reduced in length by a half, two levels and the elements are halved again, and so on.
On the Fly Mesh Refinement
You start with a coarse mesh:
Coase mesh to start... (picture from Convergent Science site)
Converge takes one look at your rather amateurish mesh and decides to start splitting up elements in areas that seem to need it, either around abrupt changes in geometry or where there is a large delta in your critical variable, in this case velocity of gas. The color changes indicate analyis has already begun.
Converge is already starting to refine the mesh in critical areas...(picture from Convergent Science site)
The control volume mesh will keep refining itself after successive runs until it reaches a preset limit. Here is a highly refined mesh after multiple runs. Note the relatively small size of elements in the narrow passage around the valve and a velocity profile suggests a more accurate solution.
Converge will keep refinining the mesh (picture from Convergent Science site)
Founded in Caterpillar
Converge had its beginnings in Caterpillar, where it was used by the construction vehicle maker to model the chemical reactions in their engines. Converge spun out of Caterpillar and can do general purpose CFD analysis, where there is non-reactive fluids and external volumes (example: flow over a wing section).
"AMR is most suited to transient solutions," says Rob Kaczmarek, Converge's director of sales and marketing, meaning the types of volumes that would change quickly. "We're seeing about 4 times faster than our competition in run time alone -- and that's not even including the time saved by not having to create a mesh!" He names ANSYS and CD-adapco as competitors. Rob claims Converge holds its own with most steady state problems.
Easy to Use Templates
You can set up Converge with templates so users who may not be savvy with CFD can answer a few questions and get results. Converge can be 'bought' as needed, for a project, for example. It will work on the Rescale platform, which does its calculations on HPC, so you don't even have to have a monster workstation.
Clearly, this is not your father's CFD.
For more information
Convergent Scienes website http://www.convergecfd.com/