Hydrodynamics of High Speed Craft Dr. D.A. Hudson, Professor A.F. Molland School of Engineering Sciences, Ship Science, University of Southampton. London Branch RINA 17th March, 2006

Motivation To improve ship design, safety and operation through a better understanding of ship hydrodynamics: Resistance and propulsion Wave wash Ship motions Human factors – very high speed

Components of Design Hull form [calm R, added R, motions] Hydrostatics, stability, damaged stability, flooding Hydrodynamics: resistance and propulsion, motions, steering Structures, materials Machinery: Propulsion and auxiliary outfit Safety, regulations GA Design for operation, safety, production, scrap, environment, sustainability

Resistance components Total Hull Resistance = Viscous + Wave Monohulls Catamarans  and  are hull interaction coefficients

Models Model hull forms Vary hull form Vary separation of hulls Also test as monohull (a) (b)

Wave resistance Wave resistance measurement Wave probes in tank: drive model past Shallow water

Wave resistance Shallow water

Viscous resistance Viscous resistance measurement Total viscous and viscous interaction from viscous wake traverse in tank Viscous interaction from wind tunnel tests and CFD analysis

Viscous resistance

VISCOUS RESISTANCE Viscous resistance

Aerodynamic resistance Wind tunnel tests: generic shapes

Aerodynamic resistance

Wave wash Generated by ship Propagated to shore (with decay) Impact on safety (e.g. beaches, small craft) Impact on environment (coastal erosion, plants, animals, etc.)

Wave wash Need to estimate ship waves: Estimate size of waves at shore Influence of hull form/type Speed Shallow water effects Estimate size of waves at shore Possible limits on wave heights (or energy) Passage plans, shallow water, critical speeds

Wave wash Sub-critical Supercritical

Wave wash WASH

Wave wash Comparison of wave profiles

Wave wash H  y-n n=0.5 transverse n=0.33 diverging n=0.2, 0.4 shallow

Wave wash Critical speed - water depth relationship

Wave wash

Ship motions Pitch, heave, roll, accelerations (yaw, sway, surge) Safety – strength, cargo, crew, passengers Comfort – motion sickness Different limits: strength, comfort, operability Statistics – e.g. RMS values, probabilities of exceedance

Ship motion analysis - overview

Ship motions - models Model hull forms Vary hull form – L=1.6m, L=4.5m Vary separation of hulls – S/L=0.2, 0.4 Vary heading to waves Fn=0.2, 0.53, 0.65, 0.80 Also test as monohull (a) (b)

Ship motions Measurement of motions – model scale NPL 5b, S/L=0.2, Fn=0.65: head seas (180 deg) NPL 5b, S/L=0.4, Fn=0.65: oblique seas (150 deg)

Ship motions Measurement of motions – model scale Southampton water: NPL 5b, S/L=0.2, Fn=0.65

Ship motions Heave measurements 5S, S/L=0.2, oblique seas

Ship motions – theoretical analysis Development of numerical methods Detailed validation of numerical methods What are the choices? 2D strip theory 3D Green’s function (or panel methods) 3D time domain 3D Rankine panel Linear or (partly) non-linear ‘CFD’

Ship motions – numerical methods At Southampton: 2D strip theory - linear 3D Green’s function Zero speed Forward speed 3D time domain Linear (under development) Partly non-linear 3D Rankine panel non-linear (under development) ‘CFD’ – under development 5S, S/L=0.2, 700 panels

Ship motions – head waves 5S, S/L=0.4, head seas 5S, S/L=0.2, head seas

Ship motions – oblique waves 5S, S/L=0.4, head seas 5S, S/L=0.2, head seas

Ship motions Fn=0.0 Fn=0.2 Fn=0.5

Ship motions Detailed investigations into: Numerics of Green’s function – 2 alternative formulations ‘Irregular’ frequencies – removal Transom stern effects Prediction Towing tank

Ship motions - summary For multi-hull craft must account for hull-hull interaction Forward speed Green’s function is promising Correct trends with wave heading …but… Numerically complex Pitch still over-predicted Fn>0.70 need alternative approaches – planing craft

Human Factors Modern small, very high-speed vessels: Fatigue, injury, long-term pain Quantify effects on operator (UCC) Heart rate, blood chemistry, muscle fatigue, oxygen uptake Link to naval architecture attributes Boat design, sea-state, operating manner

Human Factors – model testing WAL/GKN tank – up to 12 m/s Calm water and regular/irregular waves Conventional RIB form at 45kts

Human Factors – Full scale testing Robust measurement system 11 channels accelerations Wave buoy data GPS track Heart-rate of crew Conventional RIB form at 30kts

Human Factors Assisting ‘Team Kali’ Gas turbine propelled wave-piercing RIB Attempt Round Britain <30ft record Kali at 52kts

Summary Resistance – understanding of components Wave wash – operating guidelines Ship motions Experimental and numerical techniques Human factors Experimental techniques Collaboration with sports science Design techniques and operator guidelines

Thanks – and questions? Prof. W.G. Price Prof. P. Temarel Prof. R.A. Shenoi Dr. S.X. Du Dr. E. Ballard Dr. T. Ahmed Dr. P. Bailey Dr. S. Georgoudis Dr. D. Taunton Mr. O. Diken Ms. R. Spink Mr. M. Yuceulug Mr. T. D’Arcy Mr. P. Kingsland Mr. I. House LR – UTC Ms. C. Damecour RNLI - ATP Team ‘Kali’