Drag Reduction in Turbulent Flows over Super-hydrophobic Micro/nano Structured Biomimetic Surfaces Usman Bin Shahid, PI: Anne-Marie Kietzig Department of Chemical Engineering McGill University, Montreal, Canada Superhydrophobicity is attributed to both surface structure and surface chemistry. Surface structuring increases the possible hydrophobicity of a surface beyond what is attainable due to surface chemistry alone. Investigations on the influence of surface structure and hydrophobicity on hydrodynamic drag indicate significant slip enhancements and hence hydrodynamic drag reductions. The Experimental Setup Calculations Calculations for Flow Rates Dimensions /mm Kinematic Viscosity of H 2 O (m 2 /s) D H /mm Velocity range Laminar Flow (mm/s) Flow Rates (mL/min) Width Height Min Max Min Max 38.1 7.9 1.004E-06 13.1 0.77 153.4 13.8 2771 2.5 0.7 1.1 9.18 1835.9 0.96 192.7 12.0 1.2 2.2 4.60 920.3 3.98 795.1 5.0 1.4 2.2 4.59 917.9 1.93 385.5 (Left to right) Micro-channel, Peristaltic Pump, Pressure transducers *∆ = 2 2 Acknowledgement ∆ – Pressure drop – Fluid density V – Velocity of the flow f – Friction factor L – Length of channel D H – Hydraulic diameter Understanding the influence of the surface on the drag-reduction by measuring the inlet/outlet pressure difference *Blevins R D 1984 Applied Fluid Dynamics Handbook (New York: Van Nostrand-Reinhold) Authors would like to thank McGill University for funding this project through the SURE Programme. I would like to also thank Mohammad Bajmmal (grad student) for his contribution in helping set up the transducers and its circuit. Also Anjishnu Sarkar and Jorge Lehr (grad students) for their time and suggestions for the micro-channel design. 5 mm 1.4 mm 23 cm Introduction Objective The objective is to design a setup to be able to measure pressure drop across such surfaces and consequently characterize them with regard to their potential in reducing drag. Surfaces with enhanced drag reduction are inspired by the Biomimicry of shark skin Design Workplan Future Prospects Factors considered while designing the channel: • Set Bench Mark with Other Researches Similar D H (hydraulic diameter) sought Lengths manipulated to give same D H • Surfaces Geometrics Limitations Stages allow a 5 x 5 mm x-y range Time constraint to make surfaces • Entrance Length for Fully Developed Laminar/Turbulent Flows Empirical equations allowed for an estimate 60mm of developing length factored in design • Pump Selection Very small flow rates (range of 1 – 12mL/min) Accuracy of ±2 mL/min Controllable flow rates • Pressure Transducers Range 0-10 kPa Accuracy 0.25% (FS) Circuit for Signal Amplification Signal Calibration and conversion through LabView This channel has been designed to measure the inlet/outlet pressure difference. Further calibration will be carried on in a future project. The design‘s flexibility and transparent nature allows for flow visualization by tracer experiments, and measurements over different surfaces like hydrophobic and hydrophilic. A) 3d Model for Channel. B) Amplification Circuit