Flow Visualization of Horseshoe Vortices around a Surface-Mounted Hydrofoil

The horseshoe vortex (HSV) usually induces undesirable effects like noise, vibration, and drag. Therefore, the HSV is not only of academic interest but also a critical engineering issue. We used two high-speed cameras with prolonged exposure time to record the pathlines of the seeding particles illuminated by a continuous-wave laser. These particle pathlines constitute a very clear visualization of flow structures, especially vortical structures, i.e. vortices. Next, we used this PIV-based flow visualization technique to study the kinematics of HSV associated with a surface-mounted NACA66 hydrofoil for a Reynolds number of 8,820 (based on the maximum thickness of the hydrofoil and the free-stream velocity).

We observed six kinematic patterns of HSV, and measured the occurrence probability for each pattern: (i) steady (17%), (ii) amalgamating (26%), (iii) breakaway (31%), (iv) transition (12%), (v) random (8%), and (vi) roll-up (6%). The naming and definitions of patterns (i) to (v) are adopted from Younis et al [1]. We also found that the HSV adjacent to the hydrofoil surface rises as it extends downstream.

Subjects

Coherent structure

Flow visualization

Horseshoe vortex

Kinematic pattern

DDC Class

600: Technik

Lizenz

http://rightsstatements.org/vocab/InC/1.0/

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paper_0059_file_0405_Flow_Visualization_of_Horseshoe_Vortices_around_a_Surface_Mounte.pdf

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1.89 MB

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Flow Visualization of Horseshoe Vortices around a Surface-Mounted Hydrofoil