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. 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

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

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

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

7. Wave resistance
Shallow water

8. 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

9. Viscous resistance

10. VISCOUS RESISTANCE
Viscous resistance

11. Aerodynamic resistance
Wind tunnel tests: generic shapes

12. Aerodynamic resistance

13. 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.)

14. 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

15. Wave wash
Sub-critical
Supercritical

16. Wave wash
WASH

17. Wave wash
Comparison of wave profiles

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

19. Wave wash
Critical speed - water depth relationship

20. Wave wash

21. 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

22. Ship motion analysis - overview

23. 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)

24. 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)

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

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

27. 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’

28. 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

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

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

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

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

33. 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

34. 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

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

36. 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

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

38. 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

39. 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’