An improved Yasutomi correlation for viscosity at high pressure

The Yasutomi temperature–pressure–viscosity correlation is attractive for elastohydrodynamic lubrication analysis because it does not require an equation of state for the liquid. However, the original Yasutomi correlation suffers from the appearance of a zero in the function describing the pressure dependence of the relative free volume thermal expansivity. When the original correlation is employed, a liquid with a high inflection pressure lacks the inflection in the predicted pressure–viscosity behavior and a liquid with a low inflection pressure is predicted to have two inflections. A new function removes these concerns and provides improved precision without the need for an equation of state. The improved function gives a more faithful representation of viscosity at even low pressures.