Danyang Zhao

Study on the Hydrophobic Property of Shark-Skin-Inspired Micro-Riblets

This paper aims to characterize the hydrophobic property of shark-skin-inspired riblets with potential engineering applications. Based on the hydrophobic theory, a new hydrophobic model which is consistent with the special structure of shark-skin-inspired micro-riblets was proposed. Then, the contact angles of different droplets were measured by optical contact angle measuring device on the shark-skin-inspired micro-riblets and the smooth surface, respectively. The results show that the surface of micro-riblets possesses obvious hydrophobicity, and the actual contact angles of different droplets residing on the riblets decrease with the increase in the droplet volume. According to the new hydrophobic model and the measurement of contact angle, it was found that the arrangement and structure of the shark-skin-inspired micro-riblets significantly affect the surface hydrophobic property. Using the new hydrophobic model, the prediction error of contact angle can be less than 3% compared with the measured one. The research on hydrophobic property of biomimetic micro-riblets is proved to be necessary and important to well explain drag reduction and microbe-resistant property of micro-riblets.

Numerical simulation and experimental study of polymer micro extrusion flow

The uniformity of polymer melt flow in micro extrusion die determines the quality of products directly. It is the base of extrusion die design. According to rheology testing theory and with the help of capillary rheometer, the reasonable extrusion parameters have been achieved. The comparative micro scale viscosity model is built based on Kelvin-Voigt constitutive equation and the wall slip model is built based on Navier slip law. The extrusion of double-lumen is taken for example. By use of both numerical simulation and orthogonal experiment, the effects of main structure parameters on flow uniformity are studied. The conclusions show that shunting angle affects the uniformity most, then length of center stereotyping part, compression angle and compression ratio. Meanwhile, the best lumen structure parameters are determined. After that, double-lumen catheter die is fabricated by precision machining technology. The results of experiment validate the correctness and validity of numerical simulation for polymer micro extrusion flow.