Support-Free Measurements of Aerodynamic Characteristics of Axial Circular Cylinders with Fineness Ratio from 0.50 to 0.75

In this study, aerodynamic characteristics of axial circular cylinders having the fineness ratio (length to diameter, $L/D)$ of 0.50, 0.67 and 0.75 were measured using the 1-m Magnetic Suspension and Balance System (MSBS) in the Low-Turbulence Wind Tunnel at Tohoku Univ. The MSBS supports and controls the model using magnetic forces. All the tests were conducted at \textit{Re }$=$ 100,000 and the models were aligned with the free stream. The results of force measurements show that the drag decreases gradually in the $L/D$ range from 0.50 to 0.75 and connects continuously to the data for higher fineness ratios. This indicates that a local maximum of the drag does not exist in this range. The previous studies show that, for axial circular cylinders having $L/D$ from 1.0 to 2.0, the drag measured using a MSBS differs substantially from the value measured with sting support, however this study shows that a circular cylinder of $L/D =$ 0.50 has a drag close to that measured with sting support. This suggests that the influence of support interference is significant when a shear layer separated from the leading edge reattaches on the body or interacts near the base, but is insignificant when a separated shear layer is away from the base area.