Report of the Specialist Committee on High Speed Craft Presenter: Giles Thomas, Australia

Committee Membership:

•  Chairman: Yoshiho Ikeda, Japan •  Secretary: Giles Thomas, Australia •  Gregory Grigoropoulos, Greece •  De-Bo Huang, China •  Dominic Hudson, UK •  Kourosh Koushan, Norway •  Gordana Semijalac, Croatia •  Andrey Sverchkov, Russia •  Osman Turan, UK

Committee Meetings:

•  Zagreb, Croatia •  Athens, Greece •  Launceston, Australia •  Osaka, Japan

Terms of Reference:

1. Review and identify numerical and experimental developments for the prediction and behaviour of high-speed craft, especially multi-hull vessels.

2. Identify validation data for new designs appropriate for benchmarking purposes.

3. Review, identify any requirements for changes and update ITTC Recommended Procedures applicable to high-speed craft.

4. Update the ITTC Symbols List for high-speed craft, especially with respect to waterjet propulsion, making the symbols consistent in the procedures for high-speed craft.

Tjx

Review of state of the art •  Last ITTC committees with a

high speed craft focus reported to the 22nd ITTC in 1999: Safety of HSMV and the Model Testing of HSMV.

•  Review limited to developments presented in 2005 to 2010.

•  Main focus on multihull vessels, plus significant work is included for monohulls and novel craft

Review of state of the art •  Seakeeping •  Resistance •  Powering and performance

prediction •  Manoeuvring •  Wave loads including

slamming •  Propulsion •  Vessel generated wash •  WIGs and hydrofoils

Resistance - Numerical •  CFD has made great

progress in recent years. •  Various codes of both

potential and viscous CFD have been developed and applied in many aspects of HSC.

•  Some of these can accommodate complex hull forms and conditions.

Resistance - Numerical •  Some codes capable of 3 to

10% accuracy for resistance, sinkage and trim for mono- and multi-hull HSC. Good simulation of the free surface (breaking waves, wave pattern and wave profile)

•  However many still show considerable discrepancies with experimental tests (26th SNH)

Resistance - Numerical •  Inviscid CFD methods are

now in practical application.

•  Viscous methods are still under rapid development.

•  Systematic large or full-size model tests are needed for both validation and extrapolation.

Resistance - Experiments •  Conducting high quality

experiments of high speed craft is still challenging, e.g. speed, size of model, magnitude of forces.

•  Focus on resistance, control surfaces and drag reduction methods.

Seakeeping - Operability • Key parameter in design of HSC. • Combined with resistance, service economics, etc. in optimisation. • ISO 2631, Part 1 (2003) should be applied for motion sickness • ISO 2631 (2003) may also be used for - Vibration Dose Value calculations - Part 5 applied for lumbar spine ‘equivalent static compressive dose value’

Seakeeping – Numerical Semi-Displacement • Potential flow methods can be applied in most cases. • For multi-hulls must capture interaction effects correctly. • For forward speed effects Green’s function method with forward speed, Rankine source method, 2D+t strip theory, have been applied.

Seakeeping – Numerical Planing craft • Strip theory based on Zarnick(1978) still most commonly applied. • Refinements to transom stern pressures improves results. • RANS-based methods are improving in accuracy but computational time still too long for practical applications & meshing strategy is challenging.

Seakeeping – Full Scale Data • For catamaran RAOs – Davis and Watson (2005) and Fukunaga et al. (2008). • Planing craft – Morch and Hermundstad (2005), Schleicher (2006). • Still a general absence of public domain data.

Seakeeping – Model Experiments • For catamaran RAOs – Molland et al. (2001) & Thomas et al. (2009) provide extensive data-set for NPL and Series 64 derived hulls. • For planing craft – various sources including systematic series experiments by Taunton et al (2011). • Still a lack of benchmark study data meeting ITTC requirements

Wave Loads and Slamming - Experiments •  Segmented hydroelastic

model experiments on wave-piercing catamaran, Thomas et al.

•  Segmented monohulls, Dessi et al. and Ogawa et al.

Wave Loads and Slamming – Full Scale Measurements • Wave-piercing INCAT catamarans USN X-Craft 80m catamaran Visby class corvette • Advances in instrumentation (wave radar) and data acquisition systems (digital network), e.g. Kivimaa and Rantanen (2007)

Wave Loads and Slamming – Slamming • 2d modelling of monohulls e.g. explicit FE code LS-DYNA, CFD, SPH • 3d BEM, Faltinsen & Chezhian • Drop tests for validating numerical codes and investigating effect of hull form on slam loads

Propulsion - Waterjet CFD Rhee & Coleman used a RANS code to calculate the flow field around a high speed monohull bare hull and also with axial-flow waterjets.

Rhee & Coleman 2009

Propulsion - Waterjet Experiments LDV measurement of waterjet nozzle discharge

Donnelly & Gowing 2008

Propulsion - Surface Piercing Propellers Young & Kinnas presented a 3-d low-order BEM for performance prediction of surface-piercing propellers.

Young & Kinnas (2004)

Propulsion - Ventilation Effect for SPP Experimental investigation of partly submerged propellers. Results are relevant for surface piercing propellers, though the geometry used for the investigation is a conventional propeller geometry.

60 degrees 90 degrees 120 degrees 160 degrees 180 degrees

200 degrees 220 degrees 240 degrees 260 degrees 295 degrees

Koushan 2006

Manoeuvring •  CFD methods

(RANS solvers) modelled manoeuvring of high-speed craft.

•  Porpoising and transverse instabilities investigated experimentally and numerically, up to very high speeds (Fn = 6.0).

Manoeuvring

•  Improvements in the numerical methods based on semi-empirical corrections based on experiments.

•  Also focus on trimarans and foil-assisted monohulls

Powering & Performance •  Model-scale measurements

compared with full-scale trials and also used for evaluation of numerical methods, e.g. Bhushan et al. (2009) – Athena hullform

•  Effects of the shallow water and spray on monohull drag also investigated.

Vessel Generated Waves •  Important factor for vessel

operations •  Focus on impact of waves on

environment and other water users, e.g. Baltic, Puget Sound, Dutch canals

•  Macfarlane showed good correlation between model experiments and full scale measurements for 24 m cat

WIGs - Numerical Methods •  CFD used for both drag

and longitudinal stability problems.

•  Also more fundamental approaches to investigating control using equations of motion in a simulation, e.g. Grillo et al. (2006) non-linear control model.

WIGs - Experiments •  Model tests using radio

control models are an effective method for testing the performance of WIGs.

•  For example Akimoto et al. (2005, 2007) investigated a canard type model for takeoff from rough seas. measurement equipment such as flight data recorders, GPS and onboard camera.

Benchmark Data Examples of published experimental data include NPL catamaran (Molland et al., 2001), NTUA Series (Grigoropoulos and Loukakis, 2002, Grigoropoulos et al., 2010). Though lack of appropriate benchmark data available in the public domain

i.e. does not include full data on hull form, appendage definitions, displacement and mass distribution, hydrostatics including draft and trim, and loading condition.

Procedures Committee initially reviewed all procedures pertaining to the testing of high speed craft.

Following this and after receiving guidance from the Advisory Council two procedures were reviewed in detail:

•  No. 7.5-02-05-02 Testing and Extrapolation Methods - High Speed Marine Vehicles - Propulsion Test.

•  No. 7.5-02-05-03.3 Testing and Extrapolation Methods - High Speed Marine Vehicles, Waterjets - Uncertainty Analysis - Example for Waterjet Propulsion Test.

No. 7.5-02-05-02 - HSMV Propulsion Test •  Guidance on the appropriate size of model to be used

was clarified, particularly with respect to shallow water effects.

•  Scaling of wake is clarified that the model wake is essentially the same as the full-scale wake for exposed, raked shafts.

•  The method of controlling the flow over the propeller blades should be treated with extreme care.

No. No. 7.5-02-05-03.3 - Uncertainty Analysis - Example for Waterjet Propulsion Test The updating of this procedure focussed on correcting errors in the tables e.g. parameter values and symbols, as well as providing some additional text to aid clarification and explanation.

Symbols

All of the high speed craft procedures were reviewed with respect to symbols.

Changes were required in all three procedures applying to water jets: 7.5-02-05-03.3, 7.5-02-05-03.3 and 7.5-02-05-03.3. This resulted in changes to several equations, tables and diagrams.

Symbols

Two changes were recommended to the ITTC Quality Systems Group with respect to the ITTC Symbols List.

•  A6 [nozzle discharge area] be removed since An [nozzle discharge area] is also defined in the Symbols List and this is the symbol used in all the waterjet procedures.

•  Tjetx [jet thrust] be changed to Tjx [jet thrust] for consistency with all the waterjet procedures: 7.5-02-05-03.3, 7.5-02-05-03.3 and 7.5-02-05-03.3.

Recommendations to the Full Conference

Adopt the updated procedures: •  No. 7.5-02-05-02 Testing and Extrapolation Methods -

High Speed Marine Vehicles - Propulsion Test. •  No. 7.5-02-05-03.1 Testing and Extrapolation Methods -

High Speed Marine Vehicles, Waterjets - Propulsive Performance Prediction.

•  No. 7.5-02-05-03.2 Testing and Extrapolation Methods - High Speed Marine Vehicles, Waterjets - Waterjet System Performance.

Recommendations to the Full Conference

Adopt the updated procedures: • No. 7.5-02-05-03.3 Testing and Extrapolation Methods - High Speed Marine Vehicles, Waterjets - Uncertainty Analysis - Example for Waterjet Propulsion Test. • Update the ITTC List of Symbols in accordance with the committee’s recommendations

Future Work

•  Study of form factors for HSMV, especially those with large transom sterns since 7.5-02-05-01 currently applies a form factor k=0 due to the difficulty of determining the value of the form factor from low speed model tests.

•  Review of current vessel generated wash measurement techniques be undertaken and a procedure developed to cover this experimental work

•  Benchmarking study on catamaran hullform performance in calm water and in waves plus comparative model tests for a modern high-speed monohull at speeds corresponding to Fr =0.4 - 2.5

Discussion and Questions…

Powering & Performance •  Extensive use of

commercial CFD codes made to predict propulsion characteristics high speed ships.

•  Techniques allow hull form, propulsion systems (including waterjets, CRP and SPP) and appendages to be optimised.

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