AquaBuOY scale 1:10 - Energinet.dk

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The following week on July 28 the Aalborg team observed the model in wave conditions calculated to Hs =0,7 meter with average wave periods of about 3 seconds. The team estimated that the model had problemsas it was observed to be leaning to one side as shown on the photo below.Observation of the float July 28 2007The following inspection on July 30 verified the suspicion as the model was stranded on the beach.Float ashore on July 30 2007It appeared that a structural failure in the upper flange connecting the float to the tube had taken place. Thefloat had tilted to a horizontal position. The connecting fins had cut the mooring lines and the float strandedon the beach. Weeks later the lower part of the tube was also recovered and removed from the beach.9
Results and conclusionThe 1:10 scale project has made it possible to investigate different design solutions with respect toincorporation of power take off system and testing equipment in small scale as well as the design of the endstop by-pass solution for the piston.The practical experience showed that even in the relative small scale the model needed to be handled withgreat care to avoid damage. The PVC material is fragile and sensitive to impact loads and the bolting flangesbetween the sections in the acceleration tube appeared to be relatively weak compared to the overallstrength of the model when placed horizontal for transportation.The placement of ballast in order to obtain the correct metacenter height also showed some difficulty due tothe light weight of the PVC structure. It was finally decided to place the sand ballast in the hull (about 80 kg)to obtain the correct water line. Even though the model was operating vertical in heave when installed – theinitial tilting of the model showed that the sand could move resulting in a sloped angel of the centerline.The installation was very easy and could be carried out within a few hours in calm weather.Following the installation the weather changed and for 2 weeks the waves made it impossible with theavailable transportation means to access the devise. Observations made by AAU after one week showedthat the model was not floating vertical but leaning to one side. After two weeks the lower part of theacceleration tube had broken off – the mooring lines had been cut and the model could be picked up on thebeach.The data handler box with stored measurements appeared empty and data from the experiment could not beretrieved.Concluding and looking back on the experience of this exercise it appears that a number of further initialtasks could have been incorporated to ensure a better performance.ooIn the case of this system initial tests of the structure could probably have revealed if the boltingsections needed further reinforcement – or pretension by wires.Dry test of measuring equipment and data collection system combined with a setup to activate thePower take off on land could probably have provided a better understanding of why no data wasobtained.The main practical experience from the 1:10 scale model tests however has given sufficient confidence inthe operation of the device and the experience and knowledge gained has supported the development of theAquaBuOY i.e. shown areas where a redesign was needed, such as a redesign of the bypass system toallow better support for the piston and at the same time provide sufficient length to incorporate the hoseswithin the length of the acceleration tube.10
Page 1 and 2: AquaBuOY scale 1:10Test in Nissum B
Page 3 and 4: Introduction:This R&D project invol
Page 5 and 6: Scope and ObjectivesooooTo build a
Page 7 and 8: Choice of end-stop solution the by-
Page 9: Methodology used installing of the
Page 13 and 14: 1:50 Scale Experiment HMRC CorkTo v
Page 15: References:[1] Energi från havets

AquaBuOY scale 1:10 - Energinet.dk

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