Traditionally, accurate testing of brake system performance requires a physical prototype for conducting extensive road or wind tunnel tests. In these tests, the brake disc is heated by braking through single or multiple braking cycles to a high temperature level. The subsequent cool-down time is measured. If the maximum temperature level exceeds the allowed range or the cooling rate is not sufficient, aerodynamic changes are the main option to improve the cooling performance. This kind of physical testing can be done only in a late design stage, when a prototype exists. In earlier design stages, the brake disc can be tested only on a test bench, but this is not representative of the actual vehicle. The brake system operates in an environment with extremely complex turbulent flow, with interaction between underbody
, underhood flows, and rotating wheels. Visualizing and understanding this complex flow in detail is essential in order to assess adjustments to the geometry of the brake system — but this is virtually impossible to do with any kind of physical testing. Clearly, brake cooling must be analyzed with a simulation tool early in the design cycle.
Brake disks get very hot quickly, and their temperature is a function of the complex interaction between conduction, radiation, and convective cooling to the surrounding air. Any simulation must be able to accurately predict this interaction in an easy-to-use way. Furthermore, the all-important cooldown is, by definition, a transient problem occurring on a longer timescale than most fluid simulation tools can handle.