Bluff body, frontal dimension: 5.05 cm & 3.81 cm. Eel membrane, length: 45.7 cm & 7.6 cm
(i) Investigated and confirmed the feasibility of harvesting fluid energy via VIV. (ii) Determines that optimal performance occurs at resonance condition
Flapping PVDF membrane: 25.4 cm × 17.78 cm × 457.2 μm
0.378
(i) The use of windward bluff body and mass on the free end of the flapping piezoelement can enhance energy conversion. (ii) Experimentally proves the use of quasi-resonant rectifier can increase the efficiency by a factor of 2.3 compared to a standard full-wave rectifier. (iii) Theoretically confirms the use of AFC/MFC can increase the efficiency by a factor of 25 compared to PVDF
Bluff body frontal dimension: 1.035 cm. Three identical cantilevers: 1.4 × 1.18 × 0.035 cm3
0.0817
(i) The use of piezoelectric bimorph cantilever ensures only the first mode deformation to guarantee no charge cancellation on the surface. (ii) Theoretically proposes the optimal geometry of . (iii) Adjacent cantilevers arrangement enhances output power
Bluff body frontal dimension: 1.035 cm. Nine identical cantilevers (Series 1): 2.2 × 1.18 × 0.035 cm3
0.164
(i) Experimentally validates the optimal geometry of . (ii) Use of stapled piezoelectric layers enhance output power. (iii) Adjacent cantilevers arrangement can further lower the cut-in wind speed down to 8 m/s
Bluff body: 3 cm in dia., 1.2 m in length. Cantilever: 3 × 1.6 × 0.02 cm3
4.72 × 10−6
(i) The driving mechanism of the beam’s oscillation was discovered via CFD as the combined effect of the overpressure resulting from the stagnation region and the suction of the core of another vortex on the opposite side. (ii) The optimal position of the upstream tip of the cantilever was found to along the centerline and at a distance of . (iii) Nonattachment of bluff body and cantilever results in very low output power
Bluff body: 1.98 cm in dia., 20.3 cm in length. Cantilever: 26.7 × 3.25 × 0.0635 cm3
1.47 × 10−3
(i) Attachment of the cylinder on the cantilever tip and use of PZT instead of PVDF greatly enhanced the output power. (ii) Attachment of the cylinder on the cantilever tip reduces the resonance wind speed for maximum power
Bluff body: 2.5 cm in dia., 11 cm in length. Cantilever: 2.86 × 0.63 × 0.25 cm3. Whole plane size: 22.5 × 11 cm2
0.0918
(i) Operational wind speed range is broadened, because the harvester's resonance frequency and its resonance wind speed can be tuned by adjusting the position of the added weight. (ii) Tuning mechanism is not automatic
Bluff body: 2.91 cm in dia., 3.6 cm in length. Cantilever: 3.1 × 1.0 × 0.0202 cm3
1.25 × 10−3
(i) Turbulent flow results in higher output power of harvester than laminar flow. (ii) Turbulence excitation is claimed to be the dominant driving mechanism of the harvester; vortex shedding excitation in the lock-in region gives add-on contribution. (iii) Cantilever and cylinder are in parallel
(i) Can be easily deployed in the pipelines, tire cavities, or machinery by installing a diaphragm on the wall. (ii) Output power is relatively low compared to other devices. (iii) Methods of enhancing power are proposed, for example, optimizing the blockage ratio, adjusting the diaphragm position, and using material with high piezoelectric constants
Two identical bluff bodies: 0.425 cm in base length, 0.218 cm in altitude. PVDF film: 2.5 × 1.3 × 0.0205 cm3
3.70 × 10−6
If more than one sized prototypes were investigated in the reference, the information of dimension and critical wind speeds listed in the table corresponds to the one giving maximum output power. The device volume is approximated without considering the piezoelectric element volume, thus the power density calculated is the conservative estimates showing the upper bound.
