Title page for ETD etd-06102011-124812

Type of Document Master's Thesis
Author Dominic, Justin
URN etd-06102011-124812
Title Experimental Study of Wall Shear Stress Modification by Surface Coating: Pressure Drop Measurements in a Rectangular Channel
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Vlachos, Pavlos P. Committee Chair
Charonko, John J. Committee Co-Chair
Diller, Thomas E. Committee Member
  • boundary layer
  • drag reduction
  • hydrophobicity
  • wetting
Date of Defense 2011-05-31
Availability unrestricted
Presented in this paper are experiments to test the hypothesis that drag reduction is possible over hydrophobic surfaces in the Wenzel state during laminar and turbulent flows. Quantification of surface drag reduction in rectangular channel flow over walls with specific hydrophobic or hydrophilic properties was obtained with pressure drop measurements along the channel for a range of Reynolds numbers between 350 and 5900. Several commercially available materials and coatings were chosen in order to span a range of contact angles between 30° and 135°. The results are within the bounds of the theoretical values calculated with the Colebrook equation, and do not show any reduction in wall shear stress as a function of material properties or surface chemistry. The differences between this experiment and others measuring pressure drop over hydrophobic surfaces is the macro-scale conditions and the hydrophobic surfaces being fully wetted. These experiments are further proof of the importance of a liquid-vapor interface for increasing the shear free area to produce drag reduction.
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