Flow and performance characteristics of a direct drive turbine were studied in a numerical wave tank. The wave period and the rotational speed of the turbine were varied. The maximum power in the waves, PWave=131.68 W/m was obtained at a wave period 2.5 s which corresponded to primary energy conversion of 0.27. On the other hand, water power increased as the wave period increased. Water power was the deciding factor which determined at which wave period the performance was the best. The results indicated that higher energy was available
in both the front guide nozzle and the augmentation channel at the selleck chemical wave period of 3 s. The water power was 32.01 W and the primary energy conversion was 0.36. The power available to the turbine was the highest at 3 s. The results of CFD simulation showed good agreement with the experimental data at the wave period of 2 s. The difference in results was within 3%. The turbine power was always higher at T=3 s for all the turbine speeds. The efficiency increased as the turbine speed increased, it reached a maximum and then decreased. The peak in efficiency
basically indicated that the interaction between the turbine and flow was maximized at this optimum rotational speed. At this speed maximum energy was extracted hence higher turbine power and efficiency. Maximum turbine power of 14 W which corresponds to an efficiency of 55% was obtained at the wave period of 3 s. “
“The motions of marine craft can be uncomfortable, damaging PLX-4720 in vitro and detrimental to successful and safe operation(s) on-board. Not only can physiological, biomechanical and psychological motion responses reduce crew performance and impair ship functionality (Stevens and Parsons, 2002) but the motions can cause undesirable phenomena
to the craft including loss of stability, loss of steering, shipping not water, slamming, cargo damage and decreased propulsion efficiency (Lewis, 1986). In particular, occupants of high speed marine craft, which are typically 6–15 m in length and capable of speeds in excess of 30 knots, are exposed to uncomfortable, non-linear motions that can cause physical and mental fatigue (Lemmer, 1998 and Myers et al., 2008) and chronic and acute injuries (Troesch and Falzarano, 1993, Peterson et al., 1997, Ensign et al., 2000, Bass et al., 2008 and Coats and Stark, 2008). The motion exposures have been reported by Ensign et al. (2000) to cause annoyance, fatigue, sleepiness, discomfort, anxiety, nausea, loss of visual acuity and hand eye coordination, abdominal pain, sprains, torn ligaments, broken ankles and legs, damaged vertebrae and damage to internal organs. The most commonly cited injuries including damage to the lower back, kidneys, neck and bruises on the buttocks and inner thighs (Niekerk and Barnard, 2006). The motions of high speed marine craft have also been reported to reduce cognitive (McMorris et al., 2009) and physical ability (Myers et al., 2011).