Influence of surface topology on the wake development behind circular and rectangular cylinders *

Suspension lines of precision airdrop systems are susceptible to galloping instability, resulting in large-amplitude self-sustained vibration and increased drag. The cross section of these suspension lines is typically non-circular and resembles a rectangle with rounded corners. Additionally, the surface is not smooth and is characterized by topological features. As part of an effort to understand the basic characteristics of the flow field around suspension lines, the current work focuses on the wake development and how it is affected by changes in the shape of the cylinder cross section and surface topology. Molecular tagging velocimetry (MTV) is employed to measure the flow velocity field for cylinders with circular and rectangular cross section, each contrasting the influence of prescribed surface topology compared to a smooth surface. Results will be presented for downstream development of the wake in terms of mean and fluctuating streamwise velocity component and wake closure length.