Hull Optimization Bubbles and Resistance

BUBBLE SWEEPDOWN AND RESISTANCE R/V HULL OPTIMIZATION

PROPRIETARY INFORMATION A TRADITION OF INNOVATION Since 1958: ▪ Long client relationships ▪ Consistent delivery of effective bespoke solutions ▪ Specializing in Research Vessel optimization

Ocean Naval Marine Electrical Production Marine Civil Noise Control Engineering/ Architecture Engineering Engineering Engineering Construction Engineering Analysis

Regional Class Research Vessel, procured by OSU, funded by NSF

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION COMMITTED TO THE OCEAN INDUSTRY Areas of Service: • Ocean Energy • Oceanographic Research • Commercial Shipping • Civil Infrastructure • Marine Construction • Passenger Transportation • Aerospace & Defense • Regulatory Development

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION HULL DESIGN Owners requirements: • Science capabilities, speed, etc. Hull size constraints: • Draft, length, beam Several considerations during design: • Volume where needed to fit equipment, fuel, and people • Displacement to float at correct draft • Stability • Minimizing resistance • Acoustic survey performance – Mostly limited to research vessels

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION MULTIBEAM INSTALLATION AND RESISTANCE

Acoustic Resistance Performance Flush installation Good Best Plough Fairing Better Increased Gondola Best Highest

Improves Increased with depth appendage and drag separation from hull

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION OPTIMIZING GONDOLAS AND PLOWS • Addresses many acoustic performance issues • Gondolas – Typically around a 5-10% hit on resistance – With a gondola the hull shape is less important for bubble sweepdown • Don’t neglect sweepdown considerations • But can weigh more towards resistance benefits – Gondolas will increase draft a minimum of 0.6m and up to 1.5m • Plows – Typically around a 2-5% hit on resistance – Hull shape still important for bubble sweepdown – Plows typically increase draft up to 0.6m

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION OPTIMIZING FOR FLUSH INSTALLATION Flush Installation • Evaluate streamlines in CFD • Optimization of hull • Goal of lower resistance – Typically achieve 10-20% reduction • Priority is lowering the streamline that crosses the transducer

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION BULBOUS BOWS Pros • Decrease resistance • Can be used to improve bubble streamlines Cons • Could increase bubble formation

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION HULL BUBBLE REDUCTION

Wave generated bubbles: Seastate Hull generated bubbles • Study examined bubble generation of three hull shapes, including the Pourquoi pas?1 Finer bow sections with plumb reverse bows • Produced fewer bubbles Above waterline hull shape • Don’t want to throw water in front of hull • Bow flare – Improves pitch amplitude – Throws more water 1. Bachar Mallat, Grégory Germain, Benoit Gaurier, Philippe Druault, Jean- Yves Billard. Experimental study of the bubble sweep-down phenomenon on three bow designs. Ocean Engineering, Elsevier, 2018, 148, pp.361-375. <10.1016/j.oceaneng.2017.11.041>.

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION TRANSDUCER BUBBLE STUDY: TEAM

Glosten • Tim Leach, Director of Engineering - Research Vessel Naval Architect • Justin Morgan, Ocean Engineering Lead - Hull Form Analysis • Ken FitzGerald, Oceanographer/Ocean Engineer - Project Manager IntelliSense Marine • Kari Walker, Oceanographer - Project Manager • Robert Hagg, Senior Multibeam Technician - Data Collection • John Hughes Clarke, U. of New Hampshire - Multibeam Bubble Analysis Xiamen University, R/V Tan Kah Kee • Haili Wang, Marine Operations Director • Xuewen Wu, Chief Marine Technician • Ruoting Chen, Marine Technical Analyst Marine Operators • IRSO • UNOLS • ERVO • Others

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION TRANSDUCER BUBBLE STUDY

Primary Impacts of Bubble Sweepdown • Transient effect intermittently masks the arrays RV Investigator EM710 + EM122 • Presents as abrupt bottom mis-tracking (bad bathymetry) AGOR-27/28 • Anomalous low echo strength (bad backscatter) EM710 + EM122 – For seabed backscatter studies of the material on the seabed (not just the bathymetry) RV Bat Galim – Degraded backscatter strength obscures material properties EM2040 + EM302 – Starts at a much lower seastate threshold.

RV Discovery Imaging Bubble Sweepdown: Near-transducer EM710 + EM122 acoustic scattering RV Falkor • Viable from any R/V equipped with 2x water column EM710 + EM302 logging multibeams*

RV Tan Kah Kee EM710 + EM122 TAGS-60-66 EM2040 + EM712 + EM124

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION PROPRIETARY INFORMATION R/V HULL OPTIMIZATION IMPACT OF BUBBLE SWEEPDOWN MBWC analysis – John E. Hughes Clarke, CCOM/UNH NE BACKSCATTERBATHYMETRY

SW NW

Typical deep water regional survey – multiple azimuths Duration: several days as seastate modulates (RV Okeanos Explorer EX1303, EM302 – 5000m)

A compromising seastate An acceptable seastate

1: reduced swath (continuous noise) 2: corrupted swath (transient) PROPRIETARY INFORMATION TRANSDUCER BUBBLE STUDY: METHODS

Primary Contributors to Poor Multibeam Data • RMS roll/pitch/heave/yaw perturbations and spectrums 56.2 dB • Acoustic noise levels – averages from BISTs (built-in- self-tests). 51.5 dB • Environmental conditions (usually waves and wind speed and direction) 65.7 dB Octagonal Survey Observations 54.1 dB • RMS roll/pitch/heave/yaw perturbations • Acoustic noise levels – averages from BISTs (built-in- self-tests). • Supporting Environmental data (usually wind speed and 58.4 dB direction) Performance 53.9 dB • Vessels perform worse going into the sea 57.5 dB – Swath width notably drops • Why the effect is so intermittent? – Transient events 50.6 dB

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION TRANSDUCER BUBBLE STUDY: METHODS

Investigating the transients • Why exactly during that ping? • Motion statistics (RMS and spectra) provide an indicator of the mean conditions Vessel motion periods of enhanced activity Maximum motion • Are these the clear causes of No impact? bubble sweepdown? Worst impact • No simple wave-motion to Minimal motion? bubble sweep relationship

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION TRANSDUCER BUBBLE STUDY: METHODS

Deep-water Ping Cycle ~ 4-5 km of water

• Nadir beam echo arrives 5-7 +7 seconds after transmission Roll • Vessel moving through sequence of wave periods -7 • When is the bubble +5 sweepdown happening? Pitch – rise – top – fall - bottom of wave cycle? • Logged water column of the -5 12 kHz system provides +2 some clues Heave

-2 10-25 seconds

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION TRANSDUCER BUBBLE STUDY: METHODS

SonarMode Imaging of Bubbles EM2040 + EM302 122 Tx 30+ x 710 Tx within single EM122 Tx-Rx cycle 122 Tx

~ 10-25 second EM122 Receive Time Window

EM122 Water Column EM710 Water Column 0-5000m 0-50m Update ~10-15 seconds Update ~0.4 sec

MBWC analysis – John E. Hughes Clarke, CCOM/UNH

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION TRANSDUCER BUBBLE STUDY: PRELIMINARY RESULTS Head Seas • Primary issue • Not a surprise Hull bubbles VS breaking wave bubbles • Forward looking sonar for seastate generated bubbles More data loss with bubbles during transmit 1. Transmit ping is blocked by bubbles 2. Triggers multibeam auto adjustments 3. Beam narrows and ping frequency increases – Ping frequency approaches vessel pitch frequency – Helpful or harmful synchronizing with vessel motion?

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION TRANSDUCER BUBBLE STUDY: NEXT STEPS

Transducer Bubble Study Phase 2 • TKK – more data in more sea states • Similar datasets from another vessel • Compare vessels of different designs

Engineering Implementation • Get more data from more vessels • Forward looking sonar: Seastate generated bubbles • Compare results for different hull types • CFD Study: Best measures for hull design or retrofit

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION DESIGN CONSIDERATIONS & QUESTIONS Vessel overall size • Larger vessels tend to move less • Look at climatology to see if possible to avoid predominant wave length Hull shape • Is it better to have narrower hull shape that pitches more, but with less acceleration or to try and limit pitch? Gondola • Recommend to increase performance • What resistance gains can we achieve from a multipart hull optimization including the gondola? • What resistance and draft gains can we achieve with a “retractable” gondola?

PROPRIETARY INFORMATION R/V HULL OPTIMIZATION ACKNOWLEDGEMENTS

• Xiamen University - ship time for this study • John Hughes Clarke - multibeam methods discussion • Marine Techs and Oceanographers Xuewen Wu, Ruoting Chen, Kari Walker, Rob Hagg • IRSO - encouraging this presentation

Ken FitzGerald [email protected] For further information on the study or vessel design, please Tim Leach contact us. [email protected] Office: +1 206-624-7850

PROPRIETARY INFORMATION