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Sustained drag reduction in a turbulent flow using a low-temperature Leidenfrost surface
Dhananjai Saranadhi1, Dayong Chen2, Justin A Kleingartner2
1Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science Advances
|October 21, 2016
Summary
Active heating of superhydrophobic surfaces creates a stable vapor layer, significantly reducing skin friction drag by 80-90% in water vehicles. This Leidenfrost state offers a promising method for efficient drag reduction.
Area of Science:
- Fluid Dynamics
- Surface Science
- Tribology
Background:
- Skin friction drag is a major component of total drag for aquatic vehicles at high Reynolds numbers.
- Superhydrophobic surfaces offer potential for drag reduction via slip boundary conditions, but trapped air layers (plastrons) are unstable.
- Instability of plastrons is caused by hydrostatic pressure and turbulent fluctuations.
Purpose of the Study:
- To investigate the use of active heating to create a stable vapor layer on superhydrophobic surfaces.
- To achieve significant skin friction drag reduction using a Leidenfrost state.
- To characterize the hydrodynamics and vapor layer thickness.
Main Methods:
- Utilized active heating on a superhydrophobic surface within a custom Taylor-Couette apparatus.
- Generated a stable vapor layer (Leidenfrost state) at low superheat temperatures.
- Measured skin friction drag reduction and derived boundary layer and slip theory.
Main Results:
- Achieved 80-90% skin friction drag reduction compared to unheated superhydrophobic surfaces.
- Observed drag reduction for Reynolds numbers in the range of 26,100 to 52,000.
- Determined a plastron thickness of 44 ± 11 μm, consistent with Leidenfrost conditions.
Conclusions:
- Active heating can stabilize vapor layers on superhydrophobic surfaces, enabling significant drag reduction.
- The Leidenfrost state provides a robust slip boundary condition for reducing skin friction drag.
- This method shows promise for enhancing the efficiency of water vehicles.
Keywords:
Skin friction draglow-temperature Leidenfrost effectslip boundary conditionsuperhydrophobic surfacesustained drag reductionturbulent Taylor-Couette flowMore Related Videos
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