Study on the drag reduction mechanism of spheres with various hydrophobic types

Abstract

In this paper, a 3D hydrophobic model was developed using User-Defined Functions to investigate the flow characteristics and drag reduction mechanism of spheres with various hydrophobic types. The results confirmed that for the fully hydrophobic spheres, the separation point was continuously shifted back and the separation angle was reduced from 57.6° to 29.5° when the dimensionless slip length was increased from 0.02 to 0.1. The length of the recirculation zone was reduced from 1.90D to 0.93D, which was 51% shorter. And the decreasing fluctuation energy made the vortex structure transformed from hairpin-shaped vortices to vortex-ring. In addition, the drag reduction of partial-hydrophobic spheres was closely related to the number and location of the sudden change interfaces.

Keywords

• Slip length
• Sphere
• Hydrophobic
• Drag reduction mechanism
• Vortex structure
• Separation point
• Slip length