Scope and method of study. The purpose of this study is to quantify the magnitude of induced drag force that results from a flexible material (flag) fluttering in air stream versus a stiff panel vane with identical dimensions. Wind tunnel experiments were performed to assess component lift and drag forces on both flexible and rigid vanes. Furthermore, a qualitative and quantitative analysis describing flutter modes are supported from waveform data including: frequency, phase, wavelength, and amplitude.; Findings and conclusions. As a result of flutter motion, centrifugal forces induce in-plane tension in the fabric. This tension acts to "flatten" the flag thereby opposing the fluid pressure forces which generate the out-of-plane curvature (motion). This dynamically induced tension is felt at the attachment point as increased drag force, above and beyond the magnitude of skin friction drag. (Abstract shortened by UMI.)
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