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DTU Olie og Gas
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these sudden huge
wave
s
. in 2012, a maersk oil employee photographed a high breaking
wave
on the tyra platform in the danish section of the north
sea
. ?for such a dramatic
wave
type to occur out in the open
sea
was com- pletely unexpected. and it raised the question: were the platforms designed to withstand these extreme
wave
s
?? asks professor christos ?omas geor- gakis from the department of engi- neering at aarhus university. a potential threat ?e episodes resulted in a number of further investigations. ?maersk oil launched a major pro- ject to map the impacts from breaking
wave
s
. ?e focus was mainly on the platforms in the tyra field which had sunk with time, so that the distance from the surface of the
sea
to the plat- forms was reduced. ?e overall con- clusion was that the
wave
s
could po- tentially pose a threat, and that more re
sea
rch in the area was needed,? he says. ?at was the reason for establishing the re
sea
rch project ?extreme
wave
s
?, which is a joint project by dhrtc and aarhus university with the part- ners dtu mechanical engineering, dtu wind, dhi, and maersk oil. test facilities at
sea
?e project aims to develop an im- proved model for the loads which off- shore structures are exposed to, to de- velop a technology that can measure
wave
impacts, and, finally, to improve the collection, processing, and com- parison of data. ?initially, we are focusing on eval- uating the importance of a number of fundamental assumptions. how- ever, it is our hope that the project will grow, and that we get to understand the impact of
wave
s
better, among other things by establishing an inshore experimental centre,? says christos ?omas georgakis. most of the existing knowledge about breaking
wave
s
and their impact comes from experimental
wave
pools around the world. ?e problem is that the natural spatial and environmental conditions cannot be replicated exactly. ?a typical
wave
pool is 50 cm deep and has artificially created
wave
s
. when simulating
sea
depths of 45 metres, the scale is 1:90. however, we know for a fact that there are scaling effects, and a test centre on a scale of 1:10 would be very useful for being able to assess the errors from these scaling effects,? he says. whether the test centre will be es- tablished and where it might be situ- ated is still unknown. however, chris- tos ?omas georgakis is in no doubt about the potential benefits. ?if we build a test centre with a wa- ter depth of 5?6 metres, we can meas- ure the interaction between
wave
s
and structures on a scale that is not 1:90, but 1:8 or 1:9 instead. and for every extreme
wave
that we register in the north
sea
, we can probably register 10,000 corresponding
wave
s
at a depth of 5 metres close to the shore. ?is will give us much more accurate data about the impact of extreme
wave
s
,? he says. ?e ?draupner
wave
? ? a single, monster
wave
that was measured on the norwegian platform of the same name on new year?s day in 1995 ? confirmed the existence of extreme
wave
s
, which until then had been regarded as almost mythical. source: dmi
wave
height (m) time (s) 20 15 10 5 0 -5 -10 0 100 200 300 400 500 600 ?e project 'extreme
wave
s
' aims to develop an improved model for the loads which offshore structures are exposed to. photo: maersk oil 30 dhrtc 2016
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