Experimental investigation of energy harvesting behind a bluff body

The effect of base suction on flapping and energy harvesting through the piezoelectric membrane in the wake of a cylindrical bluff body is studied in this paper by carrying out a series of wind tunnel experiments. The effect of S/D (ratio of the distance between the cylinder and membrane to the cylinder diameter), L/D (ratio of the membrane length to the cylinder diameter), and flow speed on the flapping dynamics and energy generation from the polyvinylidene fluoride membrane placed behind the bluff body was studied. Different flapping modes were found from optimal coupling to fully deformed. The flapping motion of the membrane was determined by using a high-speed camera, and an oscilloscope was used for the measurement of the generated voltages. Also, the flapping dynamics and output voltages were extensively studied in the sub and post-critical regions by varying the S/D ratio, L/D ratio, and flow velocity. An increase of 38% in energy harvesting is observed when the piezomembrane was placed at L/D = 1 and S/D = 2 with free stream velocity U = 10 m/s. An increase or decrease in voltages is attributed to the observation that the amount of harvested energy changes by varying the stated parameters. Optimum energy can be harvested by fine-tuning of flow and geometrical parameters and adjusting the piezoelectric flag in the specified range.