1. Air cushion overview

We'll call an air cushion any system consisting of a layer of air creating pressure forces on the opposite faces of two objects. Generally speaking, one of the surfaces belongs to the object being supported, while the other belongs to a support.

The cavity between the two surfaces is called the cushion's containment chamber, while the contours of the opposing surfaces, where the fluid film escapes, are called the trailing edge. The thickness of this film at the trailing edge is calledthe trailing height.

We note that, unlike the fluid bearing, the air cushion has the following properties:

• its bearing surface is not a priori rectified and, in reality, the aim is to adapt the trailing edge to this surface;

• air viscosity generally plays no role;

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