Investigation on superhydrophilic surface with porous structure: Drag reduction or drag increasing

Lei Tang, Zhixiang Zeng, Gang Wang, Eryong Liu, Longyang Li, Qunji Xue

Research output: Contribution to journalArticle (Academic Journal)peer-review

10 Citations (Scopus)


In this paper, different apertures of superhydrophilic porous TiO2 films are fabricated by sol-gel method with PEG2000 additive. The drag reduction effect of the films is investigated through experiment of falling-ball method and FEM simulation. The larger PEG2000 content, the bigger size and the more regular and homogeneous of the pores. The joint action of anatase crystal, hydroxyl groups and water molecules absorbed on the surface and porous structure causes the superhydrophilicity. The resistance test shows that when the addition amount of PEG2000 changes from 0.25 g to 2 g, the drag reduction efficiency increases from − 17.9% to 8.6% and − 16.8% to 9.4% with 12 mm and 25 mm diameter balls. The drag reduction mechanism can be obtained from Finite Element Method simulation. The result shows that vortexes are formed in the pore which can reduce the frictional drag by lowering the velocity gradient and giving a frictional driving force. Meanwhile, an “extra press drag” is formed between the front and back wall. If the degree of friction drag reduction is greater than the degree of press drag increase, the film will show the effect of drag reduction overall.

Original languageEnglish
Pages (from-to)54-63
Number of pages10
JournalSurface and Coatings Technology
Early online date21 Mar 2017
Publication statusPublished - 15 May 2017


  • Drag reduction
  • FEM simulation
  • Porous structure
  • Sol-gel
  • Superhydrophilic TiO film
  • Vortex

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