Author(s)

Yasuhiro Nakahara, Hidemi Yamada

Department of Mechanical and Energy Systems Engineering, Oita University, Oita, Japan.

Various properties of a necklace vortex system formed around a rectangular plate standing vertically on a flat ground wall were investigated by visualizations produced by injecting fluorescent dye into a water channel flow. As a result, it was found that the necklace vortex pattern had three steady systems depending on the Reynolds number Reh, the relative height h/δ of the rectangular plate compared with the laminar boundary layer thickness and the aspect ratio w/h. As it is expected that the aspect ratio of the rectangular plate will typify the projected area configuration of various three-dimensional bodies, the aspect ratio is varied widely from 0.5 to 7.0. The transitional boundaries of Reh and h/δ in the 2-vortex, 4-vortex and 6-vortex systems for each aspect ratio decreased when w/h < 3.0, and increased when w/h ≥ 3.0 as w/h increased. The x-direction length of the main vortex position XV1/h was almost constant when w/h < 3.0, and decreased when w/h ≥ 3.0 as Reh increased. Then, the separation length r1/h increased when w/h < 3.0 and Reh < 1000, and became almost constant when w/h ≥ 3.0 and Reh ≥ 1000 as w/h and Reh increased. Moreover, the increase of r1/h is notably rapid when w/h < 3.0.

Flow Visualization, Necklace Vortex System, Rectangular Plate, Laminar Boundary Layer

Nakahara, Y. and Yamada, H. (2015) Visualization of a Laminar Necklace Vortex System in Front of a Vertical Rectangular Plate on a Ground Wall. Journal of Flow Control, Measurement & Visualization, 3, 75-85. doi: 10.4236/jfcmv.2015.32008.