UV grafting process for synthetic drag reduction of biomimetic riblet surfaces

Abstract

Skin–friction drag accounts for a large portion of resistance encountered by water‐based vehicles, such as ships and submarines. Developing drag reduction methods to improve drag reduction performance has drawn worldwide attention recently. UV‐induced polymerization has been investigated as a way to graft the drag reduction agent PAM on to a PVC substrate with a biomimetic riblet surface. The effects of AM concentration and irradiation time on the grafting rate were explored to determine optimal grafting parameters. UV grafting polymerization was clarified by comparing the peak absorption variation of the infrared spectrum before and after grafting. The PAM thin film grafted on riblet surface was measured approximately 10 µm in thickness. A rotating disk apparatus was built to measure the synthetic drag reduction performance. The drag reduction rate of the grafted PAM riblet surface was tested at approximately 14%, higher than the 6% of the traditional riblet surface. Moreover, the excellent drag reduction performance of grafted PDMS riblet surface lasted for 12 days. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42303.

Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction

“…Smaller dimensionless wavelengths were not helpful for drag reduction. The use of polymer drag reducers or surfactants could also increase the drag reduction rate of the grooves [77][78][79]. The drag reduction rate of a biomimetic riblet surface increased by 6% after grafting the drag reduction agent polyacrylamide [77].…”

“…The use of polymer drag reducers or surfactants could also increase the drag reduction rate of the grooves [77][78][79]. The drag reduction rate of a biomimetic riblet surface increased by 6% after grafting the drag reduction agent polyacrylamide [77]. Table 3 shows several biomimetic shark-skin grooves and maximum drag reduction rates in recent years.…”

“…Table 3 shows several biomimetic shark-skin grooves and maximum drag reduction rates in recent years. increase the drag reduction rate of the grooves [77][78][79]. The drag reduction rate of a biomimetic riblet surface increased by 6% after grafting the drag reduction agent polyacrylamide [77].…”

“…Table 3 shows several biomimetic shark-skin grooves and maximum drag reduction rates in recent years. mimetic riblet surface increased by 6% after grafting the drag reduction agent polyacrylamide [77]. Table 3 shows several biomimetic shark-skin grooves and maximum drag reduction rates in recent years.…”

Drag reduction by herringbone riblet texture in direct numerical simulations of turbulent channel flow

“…With a simplified riblet geometry, a maximum DR of almost 10% has been obtained [5]. In the search for even higher values of DR, many variations on the standard riblet geometries have been investigated [19], such as hierarchical or compound riblets [91], riblets on a spanwise traveling surface wave [47], oscillating riblets [88,37,83], riblets in a wave-like pattern (either in phase [36] or out of phase [69]) and riblets combined with drag-reducing polymers [12]. The rationale behind these alternatives is to further reduce drag by somehow incorporating other drag-reducing methods, such as oscillating walls or polymer addition.…”