Hydrodynamics of High Speed Craft Dr. D.A. Hudson, Professor A.F. Molland School of Engineering Sciences, Ship Science,

1. 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

2. 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

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

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

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

6. Shallow water Wave resistance

7. 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

8. Viscous resistance

9. VISCOUS RESISTANCE Viscous resistance

10. AERODYNAMIC RESISTANCE Aerodynamic resistance Wind tunnel tests: generic shapes

11. Aerodynamic resistance

12. 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.)

13. Wave wash • Need to estimate ship waves: • 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

14. Wave wash Sub-critical Supercritical

15. Wave wash WASH

16. Wave wash Comparison of wave profiles

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

18. Wave wash Critical speed - water depth relationship

19. Wave wash

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

21. Ship motion analysis - overview

22. (a) (b) 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

23. 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)

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

25. Ship motions Heave measurements 5S, S/L=0.2, oblique seas 5S, S/L=0.4, oblique seas

26. 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’

27. 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 • Linear (under development) • non-linear (under development) • ‘CFD’ – under development 5S, S/L=0.2, 700 panels

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

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

30. Ship motions Fn=0.0 Fn=0.2 Fn=0.5

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

32. 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

33. 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

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

35. 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

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

37. 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

38. 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’