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Relaminarization by Steady Modification of the Streamwise Velocity Profile in a Pipe.
J Kühnen1, D Scarselli1, M Schaner1
1Institute of Science and Technology Austria (IST Austria), Am Campus 1, 3400 Klosterneuburg, Austria.
Flow, Turbulence and Combustion
|August 3, 2018
Summary
Simple pipe modifications can fully collapse turbulence, causing relaminarization. This flow control method reduces skin friction by 3.4x at Reynolds numbers up to 6000.
Area of Science:
- Fluid dynamics
- Turbulence control
Background:
- Turbulence in pipe flow leads to significant energy loss.
- Controlling turbulence is crucial for improving efficiency in various engineering applications.
Purpose of the Study:
- To investigate methods for inducing turbulence collapse and relaminarization in pipe flow.
- To analyze the effectiveness of flow modification devices in reducing skin friction.
Main Methods:
- Utilizing a stationary obstacle and an annular fluid injection device to alter velocity profiles.
- Employing stereoscopic particle image velocimetry (PIV) for flow visualization and measurement downstream of the devices.
Main Results:
- Achieved complete relaminarization up to Reynolds numbers of 6000.
- Observed a 3.4-fold reduction in skin friction due to relaminarization.
- Demonstrated transient relaminarization and local drag reduction at higher Reynolds numbers.
Conclusions:
- A simple modification of the streamwise velocity profile can induce significant turbulence reduction and relaminarization.
- The observed relaminarization is linked to a weakened near-wall turbulence production cycle.
- Flow control strategies show potential for substantial drag reduction in pipe flows.
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