2013 Volume 7 Issue 3 Pages 162-176
We conducted an experiment to quantify the increase in efficiency of energy extraction from a constant flow that can be obtained by attaching a pair of tripping wires to an elastically mounted cylinder under influence of vortex-induced vibrations. Free oscillation tests were carried with three different cylinder configurations: smooth, with tripping wires positioned at angular positions equal to 60° and 75°. The Reynolds number varied from 2.9×103 to 2.2×104. We measured the amplitude of oscillation and the output voltage to calculate the power generated and conversion efficiency. The maximum power generation occurred when tripping wires were positioned at 60° and reduced velocity was 12, but only a 2.88% efficiency was achieved at this case. The maximum efficiency obtained was 12.47% and occurred when tripping wires were positioned at 75°, with reduced velocity 6.5. The maximum efficiency with tripping wires attached was about four times larger than the maximum efficiency obtained on smooth cylinder case. The presence of tripping wires also widen the lock-in region and when they were placed at 75° an almost constant power generation was obtained within reduced velocity ranging from 6 to 8.5, meaning that it is possible to design a system that generates the same amount of power even with variations on flow speed.