Full Scale Measurements and Flow

Analysis on a High Speed Rescue/Patrol

Boat

Hans Jørgen Mørch1

(M), Thomas Larsen1, Erik Mostert2, Karl Marius Norschau3, Gunnar Semb2.

1CFD Marine AS

2Norsafe AS 3Meyer Norschau design

CFD Marine AS • Aim: Be a supplier to the marine industry of services related to

CFD, Computational Fluid Dynamics and contribute to research and new areas of applications for CFD

• 6 employees, of whom 5 do CFD-analysis • CFD code, STAR-CCM+®, 6ps, 900 CPU-core cluster • Abaqus, Fluid Structure Interaction (FSI) • FRIENDSHIP-Framework, optimization • AutoHydro, hydrostatics and stability • SolidWorks, CAD • Research institution within NFR Skattefunn

Race High Speed Boat Operations Forum

Portugal 2015

Leg 1

Leg 2

Leg 3

Leg 4

• Originally from Lorient, France to Lisbon, Portugal • Total distance was 350 nm over three days • Was shortened down due to few participating boats • First day had Hs ≈ 5 m • Measurements were only conducted day 2-3 • Sea states from hindcast data

Norsafe Magnum 850

Boat specifications:

Engine: 2 x 221 kW

Length overall: 8,87 m

Height: 3,2 m

Maximum capacity: 17 persons

Breath overall: 3.27 m

Displacement as tested: 4786-5036 kg

Top speed, OP. crew 47 knots

Seats: Shock mitigating

Measurement System

Maintained Speed in Waves Leg 1-4

Leg 2

Motions and Accelerations Local Accelerations at Seat Positions

Criteria Light Manual Work Limit Vert. Acc RMS FP 0.65 g

Vert. Acc RMS bridge 0.275 g

Roll RMS 6°

Vert. Acc RMS at bridge Max of Crew seats

Vert. Acc RMS forward Max of Forward seats Roll RMS

Leg 2, Sea State appr. Hs 2 m Tp 9

Norsafe GES52 FreeFall Lifeboat Drop height 66.8 m, new world record 03.09.2013

Pitch Rotation Rate Full Scale Test and CFD Analysis

Pressure probes from full-scale measurements at 44 meter drop compared with the average pressure panel from CFD.

CFD Analyses Calm Water and Head Waves, Hs 2m Tp9s

• STAR-CCM+ • VOF model • Overset grid method • 2.8 mill cells • Dt = 0.0025 • Solution time = 120 s • Sim. Time = 100 h • 3DOF: Surge, Heave and Pitch • Thrust force

Calm Water Resistance ( Required Thrust force) and Effective Power

Calm water resistance CW weight 5036 kg CW Red. weight 4786 kg, condition towards end leg 2, head waves ,Hs 2 Tp 9s Available thrust force in waves; linear function through Vref 14.8 m/s (rpm 2500)

Measured rpm 2500

CFD vs Measurements Head Waves Hs 2 m Tp 9 s

Parameter Unit Measurements CFD Tp = 8 CFD Tp = 8,5 CFD Tp = 9 CFD Faster

Trim avg. Dyn. [°] -3.90 -4.91 -4.01 -3.73 -2.85

Trim RMS [°] 2.20 4.09 3.29 2.77 2.55

Acc. Z C.G. RMS [m/s2] 3.25 4.09 2.97 2.27 3.30

Acc. X C.G. RMS [m/s2] 0.58 0.50 0.44 0.39 0.39

Avg. velocity [m/s] 14.20 12.81 13.51 13.79 (12.5) 18.21

Heave RMS [m] 0.38 0.59 0.54 0.51 0.51

Maximum average panel pressures vs design pressures

CFD ISO, cat B Offshore

14.2 m/s 18.3 m/s 14.3 m/s 18.2 m/s

Tp 8.00 8.50 9.00 9.00

Panel

P1 [kPa] 37.723 28.751 19.54 38.53 22.40 32.70

P2 [kPa] 34.374 22.547 13.60 21.75 26.20 36.40

P3 [kPa] 32.866 20.368 11.68 23.41 27.40 36.70

P4 [kPa] 33.31 20.078 11.87 24.74 30.70 39.70

P5 [kPa] 22.718 12.954 10.61 19.64 38.80 48.50

P6 [kPa] 21.947 12.604 11.25 21.14 41.90 51.00

P7 [kPa] 18.591 10.085 10.77 13.46 43.80 52.90

P8 [kPa] 22.142 9.8908 7.12 10.14 45.50 54.90

Planing boat in regular waves – Verification against model tests Fridsma 1969, configuration A, Wave height / Beam = 0.111

-80.0

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

80.0

100.0

0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000

Lambda/H

Phase angles deg

Phi, heave, cfd Phi, pitch, cfd

Phi,heave, m. test Phi, pitch, m. test

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5 6 7

Axi

s Ti

tle

lambda/L

Accelerations (g)

Acc, cg, cfd Acc, bow, cfdAcc, cg, m. test Acc, bow, m. test

Conclusions

• Promising agreement between CFD analysis and measurements in spite of several uncertainties regarding

– Sea state

– Propeller characteristics

– Effect of interceptors

• Motivated to do further work with measurements and CFD / structural analysis – General headings in waves

– Manouvers

• In order to – Optimize the design

– Establish criteria for safe operation