The Brake Disk Cooling

The brake disk cooling is evalueted by two sensors which can be installed on the inner and outer side of the disk, or on the same side of the disk as it is shown in the picture.

The two sensors measure the tangential velocity on the surface of the rotating disk.
Their ferquency response is very high, therefore a good spatial resolution is achieved.
Furthermore, as the measurements are repeated for each rotation of the wheel, the time-averaged velocity and the standarad deviation can be computed in each point.

All that gives a clear indication of the flow that can cool the brake disk.

An example of Tangential Velocity on the rotating disk surface in two different car set up is shown below.

In the following picture the tangential velocity (as a percentage of the wheel rotation velocity) on the inner side of the brake disk is plotted vs. the angular position of the disk itself.

After mounting a spoiler in front of the wheel (h=100mm) the average tangential velocity decreases. Note how the velocity angular distribution changes after applying the spoiler: in the downstream zone (about 180 deg.) the disk ventilation is reduced, while in the lower part of the disk (about 270 deg.) the disk ventilation is increased.