The criterion for calculating fluid friction bearings is the condition under which the thickness of the gap between the surfaces in relative motion is not less than a certain specified allowable value.
For semi-fluid friction bearings, a similar criterion is formulated as a requirement in relation to the operating temperature of the bearing: it must be less than allowed for a given type of oil.
Liquid friction bearings are calculated by solving the Reynolds equation and the equilibrium equation. In this case, the fluid flow in the gap is considered to be laminar.
The method for calculating a bearing operating under conditions of semi-fluid friction is based on the study of the process of heat release during friction and the solution of heat transfer equations.