A simple model for Taylor flow induced contact angle hysteresis and capillary pressure inside mini/micro-scale capillary tubes

A simple mathematical model is developed to describe the Taylor flow induced contact angle hysteresis and capillary pressure inside mini/micro-scale capillary tubes. The effect of contact angle hysteresis on the capillary pressure is taken into account. Results show that both of the equilibrium contact angle (ECA) and capillary number significantly affect the contact angle hysteresis and capillary pressure. The non-monotonic variations of contact angle hysteresis and capillary pressure as a function of ECA at different capillary number are observed and there exist maximum values for both of them. At a low capillary number (<10(-3)), the variation of capillary pressure is small and approximately independent of the ECA for moderately partial wetting surface. Besides, it is found that the impact of contact angle hysteresis on the capillary pressure should be considered even at a small value (such as less than 10 degrees) for a low capillary number. (C) 2014 Elsevier Ltd. All rights reserved.