Cycling helmet
On a helmet, aerodynamics competes with ventilation and weight at the same table. Seeing the drag difference early decides which compromise is affordable.
The decision
Which of these two shells produces less drag at the head angle the rider actually holds.
Setting it up
- Export the shell as STL, with the vents open or closed depending on which pair you are comparing
- Set the speed to race speed; one value is enough, since the comparison is relative anyway
- Run several head angles: a rider does not hold one
- Spalart-Allmaras is the quick answer; SST does better behind the shell where the flow separates
What you see
- Pressure over the shell: the stagnation point and the low pressure regions
- Streamlines, particularly where the flow separates behind the helmet
- A live CD read and the residuals as the run proceeds
The awkward part
A helmet does not float in the air by itself. A run without a head and shoulders does not see the flow the helmet is actually in. Add at least a rough head and shoulders, and keep them identical between the two shapes.
The limit
This is a design-stage tool. Use it to compare shapes against each other and to catch obvious mistakes. For a number that goes to certification, approval or a signature, take the chosen shape to a validated solver or a wind tunnel.
Other analyses
Try it with your own file
Free during the beta. Request a key by e-mail and install it on a Mac running macOS 14 or later on Apple Silicon.
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