Integral force acting on a body due to local flow structures

TLDR

The forces on a body moving through a fluid are strongly influenced by local dynamic processes such as flow separation and vortices, and a detailed quantitative understanding of these effects is fundamental for flow analysis and control. This study employs unconventional force expressions based on derivative‑moment transformations to gain better insight into local dynamics. We jointly apply three alternative unconventional force expressions to analyze two numerical solutions of unsteady, viscous circular‑cylinder flows. The results confirm the exactness of the expressions and provide a unified understanding of how each individual flow structure influences the force at its various evolution stages.

Abstract

The forces exerted on a body moving through a fluid depend strongly on the local dynamic processes and structures generated by the body motion, such as flow separation, vortices, etc. A detailed and quantitative understanding of the effects of these processes and structures on the instantaneous overall force characteristics is of fundamental significance, and may improve our capabilities for flow analysis and control. In the present study, some unconventional force expressions based on ‘derivative-moment transformations’, which can have a rich variety of forms for the same flow field, are used to provide better insight into local dynamics. In particular, we apply jointly three alternative unconventional force expressions to analyse two numerical solutions of unsteady and viscous circular-cylinder flows. The results confirm the exactness of the expressions and, more importantly, provide a unified understanding of the specific influence on the force of each individual flow structure at its different evolution stages.