Preliminary study on the hysteresis in flutter amplitude of flexible membranes

A flexible membrane submerged in a fluid stream may exhibit self-excited oscillations, a phenomenon of interest for various engineering applications. Membrane flutter can be harnessed, for instance, to generate turbulence in channel flow to increase heat transfer or mixing. In other cases, membrane flutter is undesirable, for example, in prosthetic heart valves. Except for slender flexible membranes, the onset of flutter and the return to the steady state occur at different freestream velocities. This hysteresis has not yet been completely understood. The present study uses stereophotogrammetry to track the motion of a rectangular sheet in a low-speed wind tunnel in three dimensions with a high temporal resolution; the reaction forces at the mounting are measured simultaneously. The airspeed is gradually increased beyond the onset of flutter, and then reduced until the membrane stops moving. An airspeed-dependent modal analysis of the motion is performed and correlated with the reaction forces. The evolution of the amplitudes of the relevant modes gives new insight into the hysteresis phenomenon.

The authors acknowledge the support from the National Science Foundation under Grant No. 2145189 monitored by Dr. Ronald Joslin.