Bundeswehr Technical Centre for Ships and Naval … - WTD71 - Underwater... · Bundeswehr Technical Centre for Ships and Naval Weapons, WTD 71 Naval Technology and Research Research

Bundeswehr Technical Centre for Ships and Naval Weapons,

Naval Technology and ResearchWTD 71

Research Department for Underwater Acoustics and Geophysics

Underwater acoustic measurements at FINO3

Complete German project title:„Untersuchung der räumlichen und zeitlichen Variabilität des Schallfeldes bei

FINO3 mit gleichzeitiger Erfassung der Anwesenheit von Schweinswalen“

Sponsored byPrincipal

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WTD 71 - FWGFINO Conference, Oct. 30th 2013 2

Project goals

- Investigation of the spatial and temporal variability of the underwater sound-field in the vicinity of an offshore wind-farm (here primarily DanTysk)

- Identification of factors affecting the estimation accuracy and relevance of single point measurements and predictions (thereby providing input for a refinement of the measurement instructions by BSH)

- Assessment of the local population of harbor porpoises at FINO3 and of the possible dependence of the population on the variable sound field; comparison of acoustic and optical systems

(www.dantysk.de)

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Offshore wind-farm construction

SeaFox 5 with a steel monopile

SeaFox 5 at DanTysk

FINO3 at the western borderof DanTysk

Photo taken by Dr. E. Philipp, Vattenfall

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Instrumentation

1) C-PODs for the acoustic detection of harbour porpoises

- several deployments since May 2012 (before official project start)

2) Video camera on FINO3 platform for optical detection of porpoises - fully operational since end of Juni 2013

3) Underwater acoustic hydrophone chain

- installed at FINO3 in September 2013

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Detektion of porpoises with C-PODs

C-POD: commercial system commonly used to detect the click sounds made by harbor porpoises (and other mammals)

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Some challenges

Surface markerfor C-PODs(distance to FINO3 about 200m)

Surface markerfor recovery line

- Five recoveries from May 2012 til now

- 3 out of 5 with damages (cut steel cables, missing floats, dragged by 1.5km)

- But C-PODs survived

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Results so far: porpoise positive minutes (dpmin)

Upper C-POD Lower C-POD

(CET)

Seasonal variation 2012 Peak in summer (max. herring) 2013 Peak in winter (max. sand-eel)

Sun

rise

Sun

set

Hourly variation Sand-eels in water-column during day-time, but hidden in sea-floor at night

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Video camera system

- First installed in April 2013 (testing and improvement necessary)

- Fully operational since June 2013; resolution 2592 x 1936 pixel

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Video camera: further work

1.) On the basis of C-POD acoustic detection manual check for the presence of porpoises

2.) If successful, investigation of possibility for automatic detection by use of an algorithm

3.) Clearly, conditions of sea-state and visibility need to be taken into account

4.) Work for later: comparison with acoustic recordings in hydrophone chain

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Likely porpoise sightings

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Underwater acoustic measurement system

Requirements on system:

a) several hydrophones distributed vertically in the water column from top to bottom

b) measurement of pile driving noise and ambient noise

c) measurement of click noises made by porpoises (centered at about 130khz)

d) sufficient distance to FINO3 (to avoid contamination by FINO3 self noise)

e) possibility for remote control (via satellite internet connection), large data storage, system recovery in case of power outages and/system crashes

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Underwater acoustic measurement system

Present configuration (forhigh seas)

- only 6 hydrophones; near surface hydrophone omitted

- better resistance against mechanical strain by waves

Good weather (summer) configuration:

- either a longer hydrophone chain

- or additional hydrophone with extra cable to pressure housing

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Acoustic measurement system, wet part

Hydrophone chain (RESON TC4014-5)

400m power and fibreoptics cable to FINO3

Electronics housing

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Acoustic measurement system, dry part

Electronics housing, insideData storage and acquisitioncontrol on FINO3

UPS system

Isolatingtransformer

NAS (32 TB, 18 TB RAID )

Camera-system(BOX-PC, 2 x NAS a 4 TB)

- Tasler LTT24- max. sampling freq. 500 kHz- 24 Bit analog-to-digital

- possible data rate for us: 7 channels at 250 kHz each (9 TByte in about 2 weeks)

Ethernet-power switch

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Sample acoustic data

Acoustic signal from piling work at a distance of 11.2km from FINO3.

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Sample acoustic data: single hit

Signal recorded from a single hit at a distance to FINO3 of about 11.2 km.

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Summary

Instrumentation:

- The most important components have been put into in operation; the most tricky system (hydrophone chain) is running smoothly since mid-September (and has survived yesterday's storm!)

- there is room for improvement: improved data storage, second camera for covering a larger area, some tidying up of the rack installation

Data analysis:

- C-POD data are being analyzed as they come in; comparison with optical data has begun, first acoustic recording have just arrived in the lab

- Measurement of piling noise has priority at the moment (there are 9 more piles)

Caveat (as consequence of late project start)

The hydrophone chain will have to stay at FINO3 during the winter

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WTD71/FWG:

MzB(k) Stollergrund

FuE FH Kiel GmbH

Baltic Taucher

DW-ShipConsult

Thanks to the many people involved

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... and also thanks to 4 days of decent weather

5. & 6. Sept: Transit and constructionon Helgoland

7. & 8. Sept: deployment of tower, C-POD, AMAR-buoy, transmission experiments

8. to 11. Sept: bad weather

12. & 13. Sept: Connection to FINO3,start of system, use ofadditional recording system

14. Sept: Recovery of recording system andAMAR-buoy, afterwards bad weather => termination of sea trial

Other measurements and plenty of repairs

Documents

Bundeswehr Technical Centre for Ships and Naval … - WTD71 - Underwater... · Bundeswehr Technical Centre for Ships and Naval Weapons, WTD 71 Naval Technology and Research Research