INTRODUCTION

This Item extends the scope of ESDU 84031 (Derivation 4) to the analysis of bearings under conditions for which the flow in the lubricating film is not laminar. Such superlaminar conditions can arise at high surface speed or if the lubricant is of very low viscosity.

The flow regime is largely determined by the Reynolds number but the onset of turbulence does not occur at a precisely predictable value of the Reynolds number and the transition is likely to feature a regular vortex pattern before random turbulence is encountered.

The presence of vortices and/or turbulence results in increased power loss and, generally, higher operating temperature than that predicted by laminar flow theory. For design purposes the influence of both regular vortices and random turbulence is similar and the treatment in this Item may be used for superlaminar flow in general.