Understanding Fluid Film Behavior in Pumps

Achievement date: 

Researchers at the Center for Compact and Efficient Fluid Power (CCEFP) – a National Science Foundation (NSF) Engineering Research Center (ERC) have demonstrated the first successful use of the Cox-Merz rule in predicting friction. The method enables improved understanding of fluid film behavior in pumps.


While the Cox-Merz rule—an analogy between shearing frequency and shearing rate properties—is well established for polymers, the measurement of the steady shear dependence for low viscosity liquids has been an exceedingly challenging task that requires very high pressures to avoid thermal softening from viscous heating.


The friction in highly loaded lubricated contacts is determined mainly by the pressure and shear dependences of viscosity. But progress in reducing friction through the selection of properties has been slow, due to the difficulty of measuring for correlation with chemical structure. CCEFP researchers have found that using high frequency, small-strain techniques provide a simple, easy method to explore friction reduction through intelligent property selection.