ESDU 85028:2010

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.