Work

Investigating the significance of flatness defects in the origin of hysteresis in flag flutter

Year: 2025

Type: article

Abstract: Flag flutter frequently features a marked difference between the onset speed of flutter and the speed below which flutter stops. The hysteresis tends to be especially large in experiments as opposed to simulations. This phenomenon has been ascribed to inherent imperfections of flatness in experimental samples, which are thought to inhibit the onset of flutter but have a lesser effect once a flag is already fluttering. In this work, we present an experimental confirmation for this explanation through motion tracking. We also visualize the wake to assess the potential contribution of discrete vortex shedding to hysteresis. We then mould our understanding of the mechanism of bistability and additional observations on flag flutter into a novel, observation-based, semiempirical model for flag flutter in the form of a single ordinary differential equation. Despite its simplicity, the model successfully reproduces key features of the physical system such as bistability, sudden transitions between non-fluttering and fluttering states, amplitude growth and frequency growth.

Source: Journal of Fluid Mechanics

DOI: 10.1017/jfm.2025.10692

Authors: Holger Mettelsiefen, Sunetra Sarkar, Vrishank Raghav

Institutions: Auburn University, Indian Institute of Technology Madras

Language: English

Topic: Fluid Dynamics and Vibration Analysis

Subfield: Computational Mechanics

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,550

Funders: National Science Foundation, Auburn University, Division of Chemical, Bioengineering, Environmental, and Transport Systems