Drag Reduction in Turbulent Flows over Super .Drag Reduction in Turbulent Flows over Super-hydrophobic

Drag Reduction in Turbulent Flows over Super .Drag Reduction in Turbulent Flows over Super-hydrophobic

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  • 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

    H2O (m2/s)

    DH /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

    DH 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 DH (hydraulic diameter) sought

    Lengths manipulated to give same DH

    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 designs 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