20t Per 5-8 Ab Thi oce and flui stru axi flow inv onl Ele sim A m obs pro amp dam Int The inv the Geo Flo occ und eno clas hav sho are any Figu and Ov har On ind obj freq cre th Australasian rth, Australia 8 December 201 bstract is paper investi ean renewable d tidal stream en id-elastic insta ucture results in s. The use of ws has receive vestigation exam ly, covering p ectrical eddy cu mulate the powe maximum pow served at the ovided an imp plitude and fr mping. roduction e subject of flu vestigated for it work by Du an oola [4]. ow-induced osc cur when an el der conditions w ough to decay ssified into tw ving its own s ould be noted th not independen y given time [14 ure 1. Flow-indu d Armandei [7]) er the past deca rvesting potenti e of the FIV m duced vibration ect in a flow ca quencies. A f ated and imple Fluid Mechanic 16 Tors i S igated the poten energy mecha nergy. The tors ability. Steady n oscillatory ro this mechanism ed very little mined the perf plate aspect ra urrent damping er take-off or en wer extraction e lowest aspect proved underst requency are a uid flow-induce ts detrimental e nd Sun [5], Tho illations are th lastic restrained when the struc the motion [ wo types, reson sub-classificatio hat the basic ty nt, and there m 4]. uced oscillations ade, the marine al of flow-indu mechanism prop ns (VIV). The auses the structu ew groups of emented device cs Conference i onal Gal l School of Me University o ntial of torsiona anism to harve sional galloping uniform fluid otational motion m to harvest th attention to d ormance of fla atios ranging f g was applied nergy harvesting fficiency of a m ratio trialled. tanding of ho affected by the ed vibration (FI effects on mari orsen et al. [16] e vibrations of d structure is e ctural damping [17]. These os nance and insta ons, as shown ypes of flow-ind ay be more than flow chart (adap e current and ti uced vibration h posed for this shedding of ure to vibrate at researchers h es which are ab l oping Ma B. Stappen echanical, M of Wollongon al galloping as st marine curr g phenomenon i d flow past n around a cent he energy in flu date. The pres at plate structu from 0.4 to 1 to the system g from the devi modest 5.1% w The study a ow the respon e power take- IV) has long be ine structures ( ] and Bokaian a f an object, wh excited by a fl is not signific scillations can ability, with ea n in Figure 1. duced oscillatio n one occurring pted from Fernan dal stream ener has been explor purpose is vor vortices from t one of its natu have successfu ble to harvest arine Cur nbelt and A aterials and g, New Sout an rent is a the tral uid ent ures 1.5. to ice. was also nse -off een (e.g and ich ow ant be ach It ons g at ndes rgy red. rtex an ural ully the en Jo Al en re [1 sp un be [7 ex Ga flo su tra oc tra (p de ro ga so In tor os re thr thr co po Ad di ran wi Fig ph Th tor en wa of r rent Ene . D. Johnsto Mechatronic th Wales, 252 nergy for power ohnstone and St lso of growing nergy extraction strained structu 0, 11] for exam plitter-plates w niform flow. To een examined re , 8], provided xperimentation w alloping can be ow induced vib ustained manne anslating or to ccurs when the ansverse (perp arallel to fluid efined as the o tate on a hinged alloping, requir oft galloping, wh n their study rsional gallopi scillatory motio duced velocitie resholds (see F reshold reduce onstant extrem osition, provide dditionally, Fer splacement am nge. Only sligh ith increasing re gure 2. Torsi henomenological he present pape rsional gallopin nergy. The fun as examined w ff (PTO) dampin rgy Extr a one c Engineering 22, Australia r generation fro appenbelt [11] g interest in the n is the gallop ure. In the stud mple, translatio was employed o a far lesser de ecently. The stu numerical ana with an associa e defined as a hy bration which c er in a single orsional motio structure unde pendicular to d flow), or bo oscillatory moti d axis [9]. It ca ing an external hich is self-init of low-head ing, Fernandes ons were only p es, having we Figure 2). No os d velocity and me deflection o ed an upper rnandes and Arm mplitude and ht increases in r educed velocity ional galloping modelling (adapt er continues the ng to harvest damental case with particular fo ng and plate asp action g a om VIV (e.g. B and Liu et al. [ e field of flow ping instability ies by Johnston onal galloping to extract en egree, torsional udies by Fernan alysis of torsio ated energy harv ydrodynamic in causes a structu degree of fre on [17]. Trans ergoes oscillati fluid flow) oth [17]. Tors ion when the s an be further def l influence to s iating [13]. hydropower e s and Armand produced over ell defined min scillations were static instabili of the object limit to the g mandei [7] note response frequ response ampli y. g amplitude p ted from Fernand e investigation marine curren of flat plate t ocus on the eff pect ratios. Bernitsas et al. 12]). w-induced vibra y of an elastic ne and Stappen of a cylinder w nergy from ste l galloping has ndes and Arman onal galloping vesting device. nstability; a typ ure to oscillate eedom in eithe slational gallop ons which may [15], longitud sional galloping structure is fre fined as either h start the motion extraction thro dei [7] found a certain rang nima and max e observed belo ity, consisting from its neu galloping moti ed a fairly cons uency across itude was obser predictions thro des and Armandei of the potentia t and tidal str torsional gallop fect of power ta [2], ation cally nbelt with eady also ndei and pe of in a er a ping y be dinal g is e to hard n, or ough that e of xima ow a of a utral ons. stant this rved ough i [7]) al of eam ping ake-
esent investigrformance of flios (L/D) rangievious investiga
experimentatiothough strictly, te misalignmenf-initiate the ga
gure 3. Experimen
dy current damwer take-off or gnets were arration, they trave
parating the comgenerated in t
ween a magnetoduce a reactivetion, proportione Eddy currentmper [6]. As thereased, the amo
creases exponealled, correlatine linear PTO dm the prior stud
ure 4. Experimendy current magnet
e torsional stifough a pair of
m. This allowetem. The array c transferred t
duction, and protput was estimance velocity) us
urrent condition32.5m long 1
gation examinlat plate structuing from 0.4 toations (e.g. [7])on was alignethis represents
nt or perturbatioalloping.
ntal apparatus ske
mping was applienergy harvest
anged so that wersed a thick almponents (see the conductor wtic field and thee force which nal to velocity t damper therefe distance betwount of magnetentially. An airng to a dampindamping distingdies by Fernand
ntal apparatus mtic damper
ffness of the rof linear springs ed variation ofof magnets in r
torque from thovided the powated from meassing a non-con
ns were simulat1m1m cross-sned the torsures only, coveo 1.5. This ran). The plate need with the ts a case of hardons in the flow
etch
ied to the systeting from the d
with galloping mluminium disc Figures 3 and when there is e conductor. Thacts in the oppin accordance
fore behaves asween the magnetic flux cut by tr-gap range ofg ratio range oguishes the predes and Armand
mounted on the to
otational systemworking on an
f the natural relative motionhe shaft throu
wer take-off damurements of ro
ntact magnetic r
ted by towing tsection tank. Tsional gallopiering plate aspnge is larger theutral position towing directi
d galloping, minwere sufficient
em to simulate device. A seriesmotions of the twith a set air-g4). Eddy currea relative moti
hese eddy curreposite directionwith Lenz's Las a linear viscot and conductorthe conductor df 1 to 7mm wof 0.033 to 0.2esent investigatidei [7].
owing carriage w
m was controln adjustable levfrequency of
n to the aluminiuugh eddy currmping. The powtary position (arotary encoder
test The ing
pect han for on. nor t to
the s of test gap ents ion
ents n of aw. ous r is
disc was 36. ion
with
led ver the um rent wer and on
thafo
Thdenusuexan
Ta
Reno(Daft
Re
A mgahigtraosinratga
Fig0.5
Fig
Thantretorslico
e shaft and dforementioned a
he structural daetermined to beumber range of ubcritical regimxtraction studiend ranges are sp
Parameter Aspect ratio raPlate width (DStructural damReduced velocReynolds numPTO damping
able 1. Experimen
educed velocitormalised by thD). Only runs fter the initial tr
esults and Di
sample timeeasured is pres
alloping did nogher aspect ratiansitioned direscillations aroustability as thetio plates 1.2 an
alloping under a
gure 5. Galloping575 m/s)
gure 6. Amplitud
he amplitude rend 0.8 are dispend lines have rsional gallopinightly with redonclusions by F
damping torquealuminium disc
amping ratio ine 2.5% throughall experimenta
me than previs (e.g. [7]). Th
pecified in Tabl
ange (AR) D) mping ratio city range (Ur)
mber range ratio range (ζ)
ntal parameter va
ty (Ur) valuehe still water nwhere steady ansient respons
iscussion
series of thsented in Figu
ot occur in all cios and PTO dactly from a tra
und a constant reduced velocnd 1.5 exhibitedany condition tr
g response time s
de response; AR =
esponse plots foplayed in Figurbeen fitted to ng response am
duced velocity. Fernandes and
e using a torq.
n the experimenh free decay teation covered aious torsional he experimentae 1.
Value 0.4 - 1.5 0.30 m 0.025 1.8 - 3.5 5.77 x 100.036-0.3
lues
s presented inatural frequencstate oscillation
se, were include
he torsional gure 5. This steacases trialled. amping, the respansient instabilplate deflectio
city increased. Td no signs of sterialled.
eries sample; AR
= 0.4
or the plates wires 6 and 7 reeach PTO dammplitude is obThis result is cArmandei [7]
que sensor on
ntal apparatus ests. The Reyna larger range of
galloping eneal parameter va
04 – 2.45 x 105
300
in this paper cy and plate wns were observed in the analys
galloping respoady state torsioParticularly at
ponse motion olity (small uneon angle) to stThe highest aspeady state torsio
= 0.8, ζ = 0.036,
th aspect ratiosespectively. Lin
mping data set. bserved to increconsistent with]. Also discern
the
was olds f the ergy
alues
are width
ved, sis.
onse onal t the often even tatic pect onal
, U =
s 0.4 near The ease
h the nible
fromoveredobsinflresp
Figu
As galnotasp
Figu
Figu
The(ϴm
sumcordamconasp
m Figures 6 aner which gallopduced velocitiesserved at highluence of the PTponse region to
ure 7. Amplitude
expected, the loping oscillatited that the ospect ratio.
ure 8. Frequency
ure 9. Frequency
e galloping remax), frequencymmarised in Tarrespond to themping. There nclusions regarpect ratio on the
nd 7 is the limping occurs. Ns below those pher reduced veTO damping ap
o a higher reduc
response; AR = 0
higher the PTon frequency (scillation frequ
response; AR = 0
response; AR = 0
educed velocity (f) and normable 2. Lower e lower plate is insufficient rding the effece torsional gallo
mited range of rNo oscillations plotted and statelocities. The ppears to be to sced velocity ran
0.8
O damping ratsee Figures 8 a
uency increased
0.4
0.8
ty range, oscimalised frequefrequency osciaspect ratios data to draw
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