Experiments with actively pitch-controlled and spring-loaded oscillating foils

Ship propulsion in waves by actively controlled flapping foils

“…On the other hand, selection of extreme forward location of the flapping foil is dangerous from the point of view of intense slamming, especially at high wave conditions, and should be avoided. Similar findings based on experimental research have been reported by Naito and Isshiki [8] and more recently by Bøckmann and Steen [9].…”

“…Belibassakis). useful propulsive thrust, with simultaneous reduction of unwanted responses; see, for example, Rozhdestvensky and Ryzhov [7] for an extensive review, Naito and Isshiki [8] for a review in flapping-bow wings on ship propulsion, and Bøckmann and Steen [9] and Terao and Sakagami [10] for recent experimental research and full-scale applications, respectively. Working in the above direction Belibassakis and Politis [11] proceed by substituting the passive pitching setup by an active pitching control, using a proper control mechanism and a pitch setup algorithm, on the basis of the (known) random motion history of the wing.…”

Experimental study of a wave energy scavenging system onboard autonomous surface vessels (ASVs)

“…This slight backlash made it difficult to investigate the possibility of simultaneous thrust and power generation. Further enhancements in propulsive performance may also be made by changing the pitch spring constant as highlighted by Bockmann et al [19].…”

“…The foils are mounted in two halves either side of the pivot arm and fixed via a shaft that rotates through three bearings that are pressed into the pivot arm, as can be seen in Figure 7. The spring constant can be altered using the same technique used by Bockmann et al in their experiments to test the performance of a flapping foil under passive and active pitch conditions [19], illustrated in Figure 8. A length of spring steel is fixed to the foil rotational shaft either side of the bearing mounting, shown in Figure 7.…”

“…al. [19] By adjusting the height of the vertical mounting and setting the neutral pitch angle of the foil to 18 o relative to the pivot arm, shown in Figure 18 a) and Figure 19 a), the foil depth was set to 0.25m below the waterline. The foils are neutrally buoyant to prevent buoyancy forces or weight from applying a torque to the pivot arm.…”