TITLE:
Drag Coefficient of a Non-Convex Polygonal Plate during Free Fall
AUTHORS:
Yoshihiro Kubota, Yuhei Endo
KEYWORDS:
Drag Coefficients, Freefall, Image Analysis, Non-Convex Polygonal Plate, Unsteady Motion, Vortex Formation
JOURNAL NAME:
Journal of Flow Control, Measurement & Visualization,
Vol.11 No.1,
December
21,
2022
ABSTRACT: Waterside creatures or aquatic organisms use a fin or web to generate a thrustforce. These fins or webs have a non-convex section, referred to as a non-convexshape. We investigate the drag force acting on a non-convex plate during unsteady motion. We perform the experiment in a water tank during free fall. We fabricate the non-convex plate by cutting isosceles triangles from the side of a convex hexagonal plate. The base angle of the triangle is between 0° to 45°. The base angle is 0 indicates the convex hexagonal thin plate. We estimate the drag coefficient with the force balance acting on the model based on the image analysis technique. The results indicate that increasing the base angle by more than 30° increased the drag coefficient. The drag coefficient during unsteady motion changed with the growth of the vortex behind the model. The vortex has small vortices in the shear layer, which is related to the Kelvin-Helmholtz instabilities.