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

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Presentation on theme: "1 Hydrodynamics of High Speed Craft Dr. D.A. Hudson, Professor A.F. Molland School of Engineering Sciences, Ship Science, University of Southampton. London."— Presentation transcript:

1 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 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 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 4 Resistance components –Total Hull Resistance = Viscous + Wave Monohulls Catamarans and are hull interaction coefficients

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

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

7 7 Wave resistance Shallow water

8 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 9 Viscous resistance

10 10 VISCOUS RESISTANCE Viscous resistance

11 11 Wind tunnel tests: generic shapes AERODYNAMIC RESISTANCE Aerodynamic resistance

12 12 Aerodynamic resistance

13 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 14 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

15 15 Wave wash Sub-critical Supercritical

16 16 WASH Wave wash

17 17 Wave wash Comparison of wave profiles

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

19 19 Critical speed - water depth relationship Wave wash

20 20 Wave wash

21 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 22 Ship motion analysis - overview

23 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 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 25 Ship motions Measurement of motions – model scale Southampton water: NPL 5b, S/L=0.2, Fn=0.65

26 26 Ship motions Heave measurements 5S, S/L=0.2, oblique seas5S, S/L=0.4, oblique seas

27 27 Ship motions – theoretical analysis Development of numerical methods Detailed validation of numerical methods What are the choices? –2D strip theory –3D Greens function (or panel methods) –3D time domain –3D Rankine panel –Linear or (partly) non-linear –CFD

28 28 Ship motions – numerical methods At Southampton: –2D strip theory - linear –3D Greens 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

29 29 Ship motions – head waves 5S, S/L=0.4, head seas5S, S/L=0.2, head seas

30 30 Ship motions – oblique waves 5S, S/L=0.4, head seas5S, S/L=0.2, head seas

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

32 32 Ship motions Detailed investigations into: –Numerics of Greens function – 2 alternative formulations –Irregular frequencies – removal –Transom stern effects Prediction Towing tank

33 33 Ship motions - summary For multi-hull craft must account for hull-hull interaction Forward speed Greens function is promising –Correct trends with wave heading …but… –Numerically complex –Pitch still over-predicted Fn>0.70 need alternative approaches – planing craft

34 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 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 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 37 Human Factors Assisting Team Kali –Gas turbine propelled wave-piercing RIB –Attempt Round Britain <30ft record Kali at 52kts

38 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 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. SpinkMr. M. Yuceulug Mr. T. DArcy Mr. P. Kingsland Mr. I. HouseLR – UTC Ms. C. DamecourRNLI - ATP Team Kali


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