Drag reduction of wake flow by shear-driven rotation

Area of Science:

• Fluid Dynamics
• Aerodynamics
• Hydrodynamics

Background:

• Drag and lift forces significantly impact the efficiency of immersed bodies in fluid flow.
• Traditional methods for reducing these forces often involve complex external mechanisms or surface modifications.
• Understanding fluid-structure interactions is crucial for optimizing performance in various engineering applications.

Purpose of the Study:

• To propose and investigate a novel control strategy for reducing drag and lift on immersed bodies.
• To explore the potential of self-induced rotation of cylinders driven by fluid flow.
• To elucidate the underlying mechanism responsible for drag reduction in this system.

Main Methods:

• Numerical simulations or experimental setups involving two side-by-side arranged cylinders.
• Analysis of shear stress distribution on cylinder surfaces to induce rotation.
• Measurement and comparison of drag and lift coefficients for rotating versus stationary cylinders.
• Investigation of the flow field and pressure distribution around the rotating cylinders.

Main Results:

• The proposed strategy successfully drives immersed bodies (cylinders) to rotate using the fluid flow itself.
• Significant reductions in both drag and lift coefficients were observed compared to stationary cylinder systems.
• The self-rotation generates moving fluid-solid boundaries, altering the flow dynamics.
• A pressure-recovery effect, induced by the rotating surfaces, was identified as the primary drag-reduction mechanism.

Conclusions:

• Self-rotation of immersed bodies driven by fluid flow offers an effective method for drag and lift reduction.
• This approach provides an alternative to conventional drag reduction techniques.
• The identified pressure-recovery effect is key to the enhanced performance of this novel control strategy.