An energy-efficient pathway to turbulent drag reduction.
Ivan Marusic1, Dileep Chandran2, Amirreza Rouhi3
1Dept. of Mechanical Engineering, University of Melbourne, Melbourne, VIC, Australia. imarusic@unimelb.edu.au.
Nature Communications
|October 5, 2021
Summary
Surface oscillations can significantly reduce turbulent skin-friction drag at high Reynolds numbers. A new method using large-scale eddy frequencies offers substantial drag reduction with lower power costs, benefiting transport and energy sectors.
Area of Science:
- Fluid dynamics
- Turbulence control
Background:
- Previous studies suggested skin-friction drag reduction via surface oscillations is limited at higher Reynolds numbers.
- Turbulent flow near surfaces generates significant drag, impacting energy efficiency.
Purpose of the Study:
- To investigate substantial drag reduction using spanwise surface oscillations at high Reynolds numbers.
- To identify and differentiate physical pathways for drag reduction.
- To assess the power cost and Reynolds number dependency of different oscillation strategies.
Main Methods:
- Direct measurements of skin-friction drag reduction using spanwise surface oscillations.
- Experiments conducted at high friction Reynolds numbers up to 12,800.
- Analysis of drag reduction via actuation frequencies related to small-scale and large-scale turbulent eddies.
Main Results:
- Substantial drag reduction (up to 25%) achieved at Reynolds number 6,000 using small-scale eddy actuation, but with high power cost.
- A novel pathway using large-scale eddy actuation yielded 13% drag reduction at Reynolds number 12,800.
- The new pathway demonstrated lower power requirements and showed increasing drag reduction with higher Reynolds numbers.
Conclusions:
- Spanwise surface oscillations are effective for drag reduction even at high Reynolds numbers.
- Actuation targeting large-scale eddies presents a promising, energy-efficient method for drag reduction.
- This research opens avenues for improving fuel efficiency in transportation and enhancing wind turbine performance.
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