Research on variation of static contact angle in incomplete wetting system and modeling method

[Display omitted] •The contact angle in capillary is generally greater than 0° and multivalued.•The model of solid-liquid static contact angle considers the meniscus surface of liquid.•The paper constructs incomplete wettability system contact angle model that could accurately predict the contact angle.•The prediction error of the contact angle is less than 3% by using the prediction model of the paper.•Experimental conclusions will play an important guiding role in research field of contact angle. The solid-liquid contact angle which reflects the wettability of solid-liquid system is determined by the physical nature of solid-liquid medium and environmental factors. Through experiments we discovered that the value of contact angle in capillary is generally greater than 0° and multivalued. In addition, the experiments show that as the tube diameter increases, the equivalent height of liquid meniscus increases; as the liquid column height increases, the equivalent height of liquid meniscus decreases. In order to build the solid-liquid static contact angle model of incomplete wetting system, we established the equivalent height function with the capillary diameter as the independent variable. Furthermore, the contact angle model was constructed based on the Jurin formula. The experiments indicated that the model was coincident with the experimental data, what is more, the forecast errors of the contact angle were less than 3%. The model had higher prediction precision compared with that of Jurin or Rayleigh formula. Meanwhile, the reasonability of the modeling method and the practicability of the model are also verified by the paper.