AVS 57th International Symposium & Exhibition
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP5
Development of Boundary Layer in the Flowing Water on the Solid Surface with Various Wettability

Tuesday, October 19, 2010, 6:00 pm, Room Southwest Exhibit Hall

Session: Surface Science Poster Session
Presenter: M. Sakai, Kanagawa Academy of Science and Technology, Japan
Authors: M. Sakai, Kanagawa Academy of Science and Technology, Japan
M. Nishimura, Tokyo Institute of Technology, Japan
T. Furuta, Tokyo Institute of Technology, Japan
A. Nakajima, Tokyo Institute of Technology, Japan
A. Fujishima, Tokyo University of Science, Japan
Correspondent: Click to Email
Recently, the importance of controlling wettability on the solid surface is recognized in various industries. Superhydrophobic surfaces with water contact angles exceeding 150° are currently the subject of great interest and intensive study. Superhydrophobic coatings that produce rough surfaces at the micro- and nanoscale level with low surface energies have been prepared by several methods. On the other hands, highly hydrophilic surface is obtainable, when the photocatalyst TiO2 is irradiated by ultraviolet light. In the current paper, we evaluated friction drag of water on various surfaces including these surfaces. The amount of friction drag was evaluated by the static pressure during flowing in the tubes coated by various materials. Compared to Darcy-Weisbach’s equation, a superhydrophobic coating and highly hydrophilic coating decreased the friction drag of the flowing under the condition of small Reynolds number. However, a highly hydrophilic coating contributed significantly to the reduction of friction drag, when Reynolds number is large. Moreover, the velocity gradient of the flowing water in the tube was measured by particle image velocimetry (PIV). The development of boundary layer depended on the wettability in the tubes, when the flowing was the same in the flow rate. The mechanism was discussed from the viewpoints of fluid mechanics and surface materials science.