Cell3
In this simple example of a tight radius pipe bend we show 2 possible Cell3 combinations. The second being slightly more complex in terms of the 3D connectivity.
The Cell3 is essentially an STC solution, a connectivity solution to a complex problem expressed in a higher order iso parametric volume. Once the Cell3 solution has has been found for a particular geometric problem, it has been solved for ever.
Building a high quality hex mesh with this Cell3 method involves re-using a complex connectivity solution over and over again for topologically similar geometries in a fast convenient way.
Another advantage of the Cell3 representation is that the mesh file size and the Cell3 file size are independent. As an example a 50 Mb Cell3 file can store 500,000,000 hex cells. This mesh size can also be changed dynamically whilst the simulation in running.
In this simple case these pipe bends can be combined with some interconnect and tee-intersection Cell3 to form a pipe network such as a manifold.
The mesh for a bent pipe is dependent on the radius of the bend to the pipe diameter.
Since the pipe is symmetric we will use half in this example.
This is the ideal solution for a bent pipe with a large bend radius however it is not the best solution for a tight radius.
This is what the Cell3 looks like. A set of hexahedral curved blocks.
Using the edge curves we now build an individual cell3 volume. The quality of the mesh cells is completely dependent on the cell3 and therefore it is not necessary to work with the cells directly, this saves on storage space and speeds up the process immensely
This Cell3 solution is fine for a large radius turn but the cells are too closely packed on the inside of the turn and consequently too far apart on the outside of the bend. A much better solution is to do this.........
The mesh cell density is now nearly constant around the bend. But this looks a lot more complex to build. Well yes and no. By importing the Cell3 and fitting it to the pipe by scaling, rotating and associating the outer faces with the pipe this mesh can be created in minutes. The internals look like this.
There appears to be a lot of curves but they do all form cell3 Volumes.
The Cell3 with a few volumes. To build cell3 volumes in CheetahSTC all one needs is a set of curves that form logical blocks.The process of converting these to cell3 is completely automated. All that's required is selection of the curves (represented here by gold bars) and press the auto cell3 builder.
This Cell3 can be mirrored and copied within CheetahSTC to build a pipe network. It can also be morphed to fit a wide range of pipe cross sections.