Given the option, it is often better to create geometry specifically for your Computational Fluid Dynamics (CFD) simulations. It is even better if your CFD system supports geometry creation. Then you can stay within a single integrated simulation environment for your entire task without the need to learn or purchase additional software packages.

Two Flow Volumes Created Ready For CFD Simulation

Of course it helps if your geometry doesn't require manufacturing artifacts (e.g., bolts), at least initially, and you are using CFD early in the concept design phase of your overall design process. With total control over your geometry you can tailor it specifically for simulation. For example, if there is geometric symmetry and likely to be flow symmetry (as in external aerodynamic simulations over cars) then you can produce a half model, which will reduce memory requirements and turnaround time by up to 50%.

Half Model Due To Symmetry

Full ModelHalf model reflected in Y-Axis

Using an integrated analytic geometry engine within your CFD system also ensures that when you create a mesh the actual geometry is used, which then avoids faceted artifacts making it into your simulation results. Further, with access to a true geometry engine, you have the full power of standard geometry operations (e.g., Booleans and extrusions) to efficiently create watertight geometry. During direct geometry creation for CFD you can also avoid features (e.g., slivers, small gaps, and overlaps) that might cause problems for subsequent meshing operations.

Separate Volumes Prior to Boolean Operations

Single Watertight Volume After Boolean Operations

Taking control of your CFD geometry creation also opens the door to automating your simulations through the use of automated scripts. If a series of simulations are likely to be similar, then recording the operations for one CFD simulation in a script can provide an easy way to parameterize and automate a vast array of similar simulations.

Parameterized Rear Slant Angle Script Produces Watertight Half Flow VolumesSlant angles of 25 and 35 degrees shown side-by-side for comparison