Hull Optimization of Dolnetter

Ambattuparambil Gopi Nikhil (09NA1008)

Banoth Mothilal (09NA3024)

Contents• Introduction• Vessel Parameters & Hydrostatics• Selection of Fishing Vessel Series• Fairing of bulbs onto hull• Freeboard Check• Analysis of Vessel with bulb-3

– Roll & Pitch– Resistance

• Productive Work• Future Work• References

Dolnetter - Introduction

• Indian Fishing Vessel• Found in coasts of Gujarat & Maharashtra• Travel up to 30 km away from shore• Length = 8-20m• Number of dol nets vary from 1 – 4• Not refrigerated (fishes brought soon after catch)• Lack of sophistication increases difficulty to get

information for research

Previous Work

• Showed reduction in resistance with addition of bulb

• Comparison with different kinds of bulbs• Bulbs – unfaired• Comparison between two different positions

of propeller and shaft

Original Vessel ParametersParameter Value

Displacement 64.533 tVolume 62.959 m^3

Draft to Baseline 1.5 mLwl 16.497 m

Beam wl 5.082 mWSA 86.131 m^2

Max cross sect area 6.067 m^2

Waterplane area 66.372 m^2Cp 0.629Cb 0.501

Cm 0.797Cwp 0.792

Parameter ValueLCB from zero pt 8.25 mLCF from zero pt 7.627 m

KB 0.931 mKG 1.8 m

BMt 1.812 mBMl 17.582 mGMt 2.743 mGMl 18.514 mKMt 2.743 mKMl 18.514 m

Immersion (TPc) 0.68 t/cmMTc 0.708 t.m

Hydrostatics

Selection of Fishing Vessel series

Cb Lwl/B B/T Lwl/vol^1/3 actual0.501 3.246 3.388 4.147

Need for series

• Experimental values for comparing with results to be obtained from SHIPFLOW

• Approximate range of KG Values to go ahead with stability analysis in various loading conditions

Verification of KG Values from ITU• Deadweight requirements:

– Total distance travelled (maximum) 100 km– Speed 7 knots– Time taken 8.1 hours– Fuel Intake (Suzie 100HP) 200g/hp/hr– Total requirement 113 kg– FO Capacity 135 L– LO Capacity 4 L– FW Consumption 20L/person– FW Capacity 160L

• Steel Weight empirical estimation (Watson & Gilligan)19.52 tonnes

Verification of KG Values from ITU

Group Weight (t) VCG LCG

OUFIT 2.50 2.498 5.87

ENGINE 0.42 0.980 10.72

FW 0.16 3.920 10.72

LO 0.00 0.840 10.72

FO 0.11 0.840 9.49

ICE 2.50 2.100 4.95

STEEL 19.52 1.540 8.25

LIGHTWEIGHT 25.22 1.693 7.75

CARGO 40.00 2.240 7.98

TOTAL 65.22 2.028 7.89

Weight Distribution

Counter-checking

Group W% VCG/D% LCG/L%Steel 61.4 59 43Accommodation 0.3 123 35Equipment 8.8 131 40Hatches 1.1 102 64propulsion 3.0 30 19Electrical systems 2.7 59 30Ballast system 3.6 9 50Piping 3.4 57 24Fishing Equipment 4.1 111 15Fish Processing Equipment

6.7 72 32

Miscellaneous 4.8 55 55Total 100 66 40

Typical Fishing Vessel Distribution [6]

Fairing of bulbs on to hull (bulb 1)

Fairing of bulbs on to hull (bulb 2)

Fairing of bulbs on to hull (bulb 3)

Fairing of bulbs on to hull (bulb 4)

Freeboard Check

• Initial Flooding Angle (27.49 deg)• Flooding angle if bulwark kept watertight

(37.23 deg)

• Higher flooding angle has been achieved by assuming water-tightedness of bulwark. This allows the area under GZ curve to reach minimum value as required by the safety standards of the classification societies.

Sheer Calculation

Sheerrequired ordinate (mm) x

actual ordinate

factor

Factor * reqd ordinate

AP 387.475 0.000 632 1 387.475 632 after half1/6L from AP 172.0389 2.750 412 3 516.11 1236 109.27711/3L from AP 43.3972 5.499 13 3 130.19 39

amidships 0 8.249 1 1 0 11/3L from FP 86.7944 10.998 59 3 260.3832 177

forward half

1/6L from FP 344.0778 13.748 221 3 1032.233 663 -81.4458

FP 774.95 16.497 575 1 774.95 575

Freeboard Check

• Correction for deficiency in shear at forward half 61.08 mmminimum bow height1028.75 mm Loadline 1966 rules

1107.18 mmDNV Fishing vessel rules

1875 mm actual

minimum freeboard loadline 1966200 mm (L = 24 m)50 mm type B61.08 mm shear correction311.08 mm REQUIRED1300 mm actual

Loading Conditions (DNV Fishing Vessel Rules)

• Departure for the fishing grounds with full fuel, fresh water, stores, ice, fishing gear, etc.

• Departure from the fishing grounds with full catch, at maximum draught and no more than 30% fuel, fresh water and stores

• Arrival at home port with full catch and 10% fuel, fresh water and stores remaining

• Arrival at home port with 20% of full catch and 10% fuel, fresh water and stores remaining

• At fishing grounds with maximum catch on deck, hold empty and 50% fuel, fresh water and stores remaining (if consistent with fishing method)

Analysis of Bulb – 3 (Roll & Pitch)• Using Fourier analysis Roll Restoring Coefficients

were found• A33 , B33 ,A44 , B44 were digitized from relevant

graphs (from reference for varied sectional area coefficients (beta values))

• Extracted underwater Hull section at Equilibrium State In all 5 loading conditions

• Using Strip Theory, MATLAB codes were generated for calculation of A33, A44, A55, A35, B33, B44, B55, B35, C33, C44, C55, C35, F33, F44, F55

Formulae for coefficients:

Equations of motion

Roll equation:

(m + A44)ἤ4 + B44ἠ4 + C44′η4 + C44

′′ η43

+ C44″′ η4

5= F44

Pitch Heave coupling equation:

Sample values from MATLAB codes• A33 = 88.98 t• A35 = 256.84 t.m• A44 = 70.71 t.m• A55 = 1712.4 t.m• B33 = 158.49 kNs/m• B35 = 253.89 kNs• B44 = 75.95 kNs• B55 = 3668.5 kNs• C33 = 644.42 kN/m• C35 = 366.76 kN• C44 = 560.84 kN• C55 = 8799.5 kN• k = 0.3 m-1, H = 1.2m• F33 = 305.27 kN• F44 = -129.60 kNm• F55 = -378.82 kNm

Analysis of Bulb – 3 (Resistance)

Analysis of Bulb – 3 (Resistance)

SHIPFLOW HULLSPEED

ITU

Fn V(knots) V(m/s) wave resistance (KN)0.300869 7.463 3.838 1.658 2.519 2.80050.301373 7.475 3.845 1.774 2.538 2.86890.302381 7.500 3.858 1.449 2.592 2.9372

Productive work • MATLAB codes generated for calculating added

mass and damping coefficients can be used to calculate these coefficients for any vessel by inputting sectional properties (area, half-breadth and draft, and position of section w.r.t. ship). Also, the forcing codes can be used to calculate Froude-Krylov forces for respective sections. The elliptical body approximation would be more accurate for similar types of ships as sectional area coefficients are in the range of that of an ellipse (π/4).

Future Work

• Increase accuracy of the MATLAB code (diffraction forces can be taken into account)

• To reinforce results obtained before being faired, further SHIPFLOW analysis can be carried out for other bulbs too. More bulb forms can also be simulated in SHIPFLOW Design to look for better bulb shapes.

• In SHIPFLOW calculations, propeller position can be designed to reduce wake variation.

References• Seakeeping Aspects of Slice Hulls by Stephen B Peffers 1984, Naval

Postgraduate School Monterey, California (MSc Thesis)• A Body Exact Strip Theory Approach To Ship Motion Computations

by Piotr J´ozef Bandyk 2009, University of Michigan (PhD thesis)• Resistance Characteristics of Fishing Boats Series of ITU, Muhsin

Aydin and Aydin Salci, Marine Technology, Vol. 45, No. 4, October 2008, pp. 194–210

• Loadline 1966 rules• DNV Fishing Vessel Rules• Ship Design & Construction Volume 2, Chapter on Fishing Vessels• Analytical Approximation of GZ curve, Gabriele Bulian, Universita

Degli Studi Di Trieste (PhD Thesis)• Sea Loads on Ships and Offshore Structures by O Faltinsen