Table 1 Theoretical predicted frequencies of natural vibration in different modes, βh and βα are determined by boundary condition at two ends of a belt and vibration mode number, ε is related to the maximum normalized bending deformation amplitude Cv/L.

From: Flutter Phenomenon in Flow Driven Energy Harvester–A Unified Theoretical Model for “Stiff” and “Flexible” Materials

Material

Bending fh0

Torsion fα0

“stiff” belt

“flexible” belt with small deformation

“flexible” blet with large deformation