  A flexible sheet in uniform parallel flow is studied in order to quantify its
fluid dynamic drag and fluid-elastic stability characteristics. An experimental
campaign is undertaken that involves a cantilevered sheet in air flow
characterised by Reynolds numbers of order R=10^4-10^6. The properties of the
sheet include: constant mass per unit area; small but finite flexural rigidity;
varying aspect ratios from within the range 0.43<l/L<1, where L and l denote
the length and width respectively; and tension applied at the trailing edge.
The unique aspect of the present work is an investigation into the influence of
in-plane tension on both the fluid drag and fluid-elastic stability of the
sheet. In the absence of tension, the configuration resembles a flag and the
drag coefficient is observed to decrease with increasing aspect ratio and
Reynolds number. In the presence of tension, the fluid drag is significantly
reduced in the region below the critical flow velocity at which convected wave
instabilities appear. This critical flow velocity can be increased through the
moderate application of in-plane tension. Under lateral tension, the drag of
the sheet is given to good approximation by the turbulent boundary layer drag
law for a flat plate. Once stability is lost, however, the drag coefficient
increases rapidly with Reynolds number due to convected waves travelling over
the sheet's surface.
