This hydraulic analogy was obtained in a horizontal channel with a flat transparent bottom. This configuration allows the observation of a pattern of colored stripes placed under the channel and whose image, deformed by the waves appearing on the water surface around the model, reveal the features of the flow, such as the shock and expansion waves attached to the wedge.

Image created by Henri Werlé. Reproduced with permission from his spectacular collection Courants et Couleurs published in 1974 by ONERA, the French Aerospace Lab.