Passive Turbulent Boundary Layer Control through 3D-Printed Dolphin Skin

This study examines the efficacy of 3D-printed transverse sinusoidal grooves modeled after the Atlantic bottlenose dolphin (Tursiops truncates) skin to mitigate boundary layer separation as a form of passive flow control, energizing the flow near the wall. A water tunnel generates a tripped turbulent boundary layer across a vertical test plate, and a rotating cylinder induces flow separation by creating an adverse pressure gradient. The dolphin-inspired models are tested in a range of Re values of 10^5 with a constant amplitude(A) of 0.9 mm and varying groove spacings or period (P) from 5 mm to 10 mm in comparison to flow across a smooth plate control group. Models are notated based on the ratio of the amplitude to period, signifying that A/P = 0.18 and A/P = 0.09 areinvestigated. It is hypothesized that the nature-inspired A/P = 0.18 model with smallergroove spacing will better capture the flow and enhance momentum near the wall, therebyreducing boundary layer detachment. An additional parameter of model orientation istested to understand possible effects on passive separation control. Model orientations are termed as either "peak" or "valley" to notate whether incoming turbulent flow first meets arising or falling sine wave. It is further hypothesized that, through a mechanism of secondary flow tripping, the peak orientation will provide an additional increase in momentum close to the wall. Time-resolved digital particle image velocimetry (TR-DPIV) is employed to document the flow behavior and quantify flow separation. The resulting backflow coefficients, boundary layer velocity profiles, Reynolds stresses, turbulent kinetic energies, proper orthogonal decompositions, and streamlines are visualized from the data. It is concluded that both nature-inspired A/P = 0.18 peak and valley orientation present the best results in separation reduction by increasing flow momentum near the wall, while the larger groove spacings for A/P = 0.09 are shown to have a negative effect as the region of flow separation was increased. This result further confirms the hypothesis that the dolphin-inspired grooved geometry is optimized as a passive separation control method. Differences in model capabilities between the A/P = 0.18 peak and valley are slight; however, the A/P = 0.09 cases display more significant differences across flow parameters. In addition, the formation of stable vortices was observed within the grooves for the nature-inspired peak model, which was further verified through a proper orthogonal decomposition analysis.

Grantor dc:publisher

University of Alabama Libraries

Year dc:date.issued

2025

Author dc:creator

• Kodsi, Devin Alexander

Advisor dc:contributor.advisor

• Lang, Amy W

Contributors dc:contributor

• Hubner, James P
• Koh, Amanda S

• Adverse pressure
• Bio-inspired
• Dolphin grooves
• Flow separation

Statement dc:rights

• All rights reserved by the author unless otherwise indicated.

Language dc:language.iso

en_US, English

Dc Identifier Other

1177664

OAI identifier oai:identifier

oai:ir.ua.edu:123456789/17085