Installation manual
Simrad38-7
Mountthetransducerattheforwardpartofthe
hulltominimisetheeffectsfromtheboundary
waterlayer
Whenthevesselforcesitswaythroughthesea,thefriction
betweenthehullandthewatercreatesaboundarylayer.The
thicknessoftheboundarylayerdependsuponvesselspeedand
theroughnessofthehull.Objectsprotrudingfromthehull,and
dentsinthehull,disturbtheowandincreasethethicknessof
theboundarylayer.Theowinthisboundarylayermaybe
laminarorturbulent.Alaminarowisanicelyordered,parallel
movementofthewater.Aturbulentowhasadisorderlypattern,
fullofeddies.Theboundarylayerincreasesinthicknesswhenthe
owgoesfromlaminartoturbulent.Thegurebelowillustrates
theboundarylayerofavesselmovingthroughthewater.
Figure1Boundarywaterlayer
ATurbulentow
BLaminarow
CAirbubblesinthewater
Furthermore,airbubblesintheseawaterarepresseddownbelow
thehullandmixedintotheboundarylayer.Theboundarylayer
isthinunderneaththeforwardpartofthevessel,andincreasesin
thicknessasitmovestowardsaft.Ifthesidesofthehullaresteep,
someoftheairbubblesintheboundarylayermayescapetothe
seasurfacealongthevesselsides.Itisourexperiencethatawide
andatbottom,witharisinganglelessthanaround13degrees,
ispronetogivingairproblemsforthetransducer.Inanycasea
transducerlocationintheforwardpartofthehullispreferredin
ordertominimisetheinuenceoftheboundarylayer.
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130003/D