Innovative Ship and Offshore Plant Design

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1 Lecture Note of Innovative Ship and Offshore Plant Design Innovative Ship and Offshore Plant Design Part I. Ship Design h. 6 esistance Prediction Spring 017 Myung-Il oh Department of Naval rchitecture and Ocean Engineering Seoul National University 1 ontents h. 1 Introduction to Ship Design h. Design Equations h. 3 Design Model h. 4 Deadweight arrier and Volume arrier h. 5 reeboard alculation h. 6 esistance Prediction h. 7 Propeller and Main Engine Selection h. 8 Hull orm Design h. 9 General rrangement (G/ Design h. 10 Structural Design h. 11 Outfitting Design 1

2 h. 6 esistance Prediction 1. Object of esistance Prediction. Decomposition of esistance and Methods of esistance Prediction 3. esistance Prediction by Holtrop-Mennen s Method 4. esistance Prediction by Holtrop-Mennen s Method for a 3,700 EU ontainer arrier 3 1. Object of esistance Prediction 4

3 Object of esistance Prediction (1/3 L = s + o+ m 1.6 L (1 DsL ( D ol NM eview eight Estimation: Method 4 m here are few data available for estimation of the NM at the early design stage. hus, NM can be roughly estimated by dmiralty formula. ad : dmiralty coefficient V dmiralty formula: N f (, V s s : Speed of ship [knots] : Displacement [ton] N: equired power for service speed N V N V N /3 3 s /3 3 s ad 1 Define ad. N ad is called dmiralty coefficient. However, NM should be estimated more accurately based on the prediction of resistance and propulsion power. 5 Object of esistance Prediction (/3 Goal: Estimation of NM t first, we have to predict total calm-water resistance of a ship. Ship speed (V s otal calm-water resistance ( (v DHP hen, by using the propulsive efficiency, shaft, and sea margin, required propulsive power can be estimated. Propeller Propeller Shaft HP Diesel engine 6 3

4 Object of esistance Prediction (3/3 EHP (Effective Horse Power EHP ( v V DHP (Delivered Horse Power EHP DHP HP N (Normal ontinuous ating Sea Margin N HP(1 100 ( : ransmission efficiency DM (Derated Maximum ontinuous ating N DM Engine Margin s (In calm water ( : Propulsive efficiency DHP D D OH D O : Open water efficiency H : Hull efficiency : elative rotative efficiency HP (rake Horse Power NM (Nominal Maximum ontinuous ating DM NM Derating rate esistance Prediction Propeller Efficiency hrust deduction and wake (due to additional resistance by propeller Hull-propeller interaction Engine Selection Engine Data 7. Decomposition of esistance and Methods of esistance Prediction 8 4

5 Definition of esistance Ship speed (V s otal calm-water resistance ( (v esistance he resistance of a ship at a given speed is the force required to tow the ship at that speed in smooth water, assuming no interference from the towing ship. his total resistance is made up of a number of different components, which are caused by a variety of factors and which interact one with the other in an extremely complicated way. * SNME, Principles of Naval rchitecture esistance, Propulsion and Vibration, Vol., ypes of esistance In order to deal with the question more simply, it is usual to consider the total calm water resistance as being made up of four main components. (a rictional resistance, due to the motion of the hull through a viscous fluid. (b ave(-making resistance, due to the energy that must be supplied continuously by the ship to the wave system created on the surface of the water. (c Eddy(-making resistance, due to the energy carried away by eddies shed from the hull or appendages. Local eddying will occur behind appendages such as bossings, shafts and shaft struts, and from stern frames and rudders if these items are not properly streamlined and aligned with the flow. (d ir resistance experienced by the above-water part of the main hull and the superstructures due to the motion of the ship through the air. * SNME, Principles of Naval rchitecture esistance, Propulsion and Vibration, Vol.,

6 Dimensional nalysis (1/4 Example Model propeller test model propeller test real-ship propeller Dimensional nalysis Dimensional analysis is essentially a means of utilizing a partial knowledge of a problem when the details are too obscure to permit an exact analysis. It has the enormous advantage of requiring for its application a knowledge only of the variables which govern the result. Dimensional solutions do not yield numerical answers, but they provide the form of the answer so that every experiment can be used to the fullest advantage in determining a general empirical solution. * SNME, Principles of Naval rchitecture esistance, Propulsion and Vibration, Vol., Dimensional nalysis (/4 Example Model test in a towing tank Model test pplication of dimensional analysis to a ship o apply it to the flow around ships and the corresponding resistance, it is necessary to know only upon what variables the latter depends. pplying dimensional analysis to the ship resistance problem, the resistance could depend upon the following: a b c d e f V L g p (a Speed, V 3 (b Size of body, which may be represented ML/ M / L L/ L M / L by the linear dimension, L. e f (c Density of fluid, ρ (mass per unit volume L/ M / L (d Viscosity of fluid, μ d e f VL gl p (e cceleration due to gravity, g V L f V V (f Pressure per unit area in fluid, p non-dimensional term * SNME, Principles of Naval rchitecture esistance, Propulsion and Vibration, Vol., 1988 Design ship * M: Mass, L: Length, : ime a b c d 1 6

7 Dimensional nalysis (3/4 It is assumed that the resistance can now be written in terms of unknown powers of these variables : VL gl p f,, 1/ V L V V riting for / and remembering that for similar shapes the wetted surface S is proportional to L, the equation may be written: VL gl p f,, 1/ SV V V he 1 st term is the eynolds number n. he nd term is related to the roude number n. he 3 rd term is the avitation number σ o. he left-hand side of the equation is a non-dimensional resistance coefficient. Equation states in effect that if all the parameters on the right-hand side have the same values for two geometrically similar but different sized bodies, the flow patterns will be similar and the value of 1/SV will be the same for each. * SNME, Principles of Naval rchitecture esistance, Propulsion and Vibration, Vol., Dimensional nalysis (4/4 Dimensionless number derived by dimensional analysis to a ship VL, gl, p f 1/SV V V * Dimensional Homogeneity Dimensional analysis rests on the basic principle that every equation which expresses a physical relationship must be dimensionally homogeneous. Dimensionless Number: n (eynolds Number n (roude Number VL n n V gl non-dimensional term : dimensionless number that gives a measure of the ratio of inertial forces to viscous forces V: characteristic velocity of the ship L: length of the ship at the waterline level : kinematic viscosity V: characteristic velocity of the ship L: length of the ship at the waterline level g: acceleration due to gravity : In 10 degree seawater, 1.35X10-6 In 15 degree seawater, 10-6 : dimensionless number comparing inertial and gravitational forces * avitation number: dimensionless number used in flow calculations. It expresses the relationship between the difference of a local absolute pressure from the vapor pressure and the kinetic energy per volume, and is used to characterize the potential of the flow to cavitate. * SNME, Principles of Naval rchitecture 14 7

8 Decomposition of esistance (1/3 n (eynolds Number : VL n n (roude Number : n V gl he concept of resistance decomposition helps in designing the hull form as the designer can focus on how to influence individual resistance components. esistance decomposition by roude otal resistance ( = rictional resistance ( + esidual resistance ( + Model-ship correlation resistance ( esistance decomposition by Hughes otal resistance ( = Viscous resistance ( V + ave resistance ( 15 Decomposition of esistance (/3 roude : = + +, Hughes : = V + rictional resistance prediction method rictional resistance is assumed to be a function of the eynolds number. rictional resistance ( : he frictional resistance is usually predicted taking the resistance of an equivalent flat plate of the same area and length as follows : 1/ SV he 1957 I (International owing ank ommittee line is expressed by the formula: (log n : density of sea water= 1.05 (Mg/m3 : frictional resistance coefficient V [ m / s] : characteristic velocity of the ship S[ m ] : wetted surface VL n (eynolds Number : 3-dimensionalized form using the form factor Viscous resistance ( v : V k 1 k : form factor : model-ship correlation factor 16 8

9 Decomposition of esistance (3/3 ave resistance prediction method he ship creates a typical wave system which contributes to the total resistance. or fast, slender ships this component dominates. In addition, there are breaking waves at the bow which dominate for slow, full hulls, but may also be considerable for fast ships. he interaction of various wave systems is complicated leading to non-monotonous function of the wave resistance coefficient w. he wave resistance depends strongly on the local shape. f ( L /, /,,, L Example ave resistance formula in the method of Holtrop-Mennen g m m d 1 5exp{ 1 n 4 cos( n } b n ave breaking 5% ave pattern 5% Viscous pressure anker (16 knots 15% orm effect on friction 5% oughness 10% lat plate friction 60% o-o (1 knots 10% 30% 7.50%.50% 10% 40% av e resistance Viscous resistance esistance Prediction by Holtrop-Mennen s Method 18 9

10 ypes of Ship esistance Evaluation Methods Ship resistance evaluation methods raditional and standard series methods egression based methods Direct model test omputational luid Dynamics (D aylor yre Lap uf m Keller Harvald S series SSP series Series 60 oaster series Scott Holtrop & Mennen D extrapolation 3D extrapolation dvanced Navier-Stokes Solution capabilities or 3D flow around ships * John arlton, Marine Propellers and Propulsion, 3 rd Edition, Elsevier, esistance estimation by Holtrop-Mennen s Method - eason why a statistical method is presented at the initial design stage of a ship (1/ Model est for the basis ship Model est for the design ship? asis ship Design ship s the resistance of a full-scale ship cannot be measured directly, our knowledge about the resistance of ships comes from model tests. However, at the initial design stage of a ship, the model for the design ship is not provided. urthermore, the design ship and the basis ship are not preserved geometrical similarity. 0 10

11 esistance estimation by Holtrop-Mennen s Method - eason why a statistical method is presented at the initial design stage of a ship (/ herefore, a statistical method was presented for the determination of the required propulsive power at the initial design stage. his method was developed through a regression analysis of random model experiments and full-scale data. Many naval architects use the method, generally in the form presented in 1984 and find it gives acceptable results although it has to said that a number of the formula seem very complicated and the physics behind them are not at all clear, (a not infrequent corollary of regression analysis. * Holtrop and Mennen's method, which was originally presented in the Journal of International Shipbuilding Progress, Vol. 5 (Oct. 1978, revised in Vol. 9 (July 198 and again in N.S.M.. Publication 769 (1984 and in a paper presented to SMSSH'88 (October 1988, meets all criteria with formulae derived by regression analysis from the considerable data bank of the Netherlands Ship Model asin being provided for every variable. 1 ormula Proposed by Holtrop & Mennen 1 rictional resistance 3 ppendage resistance 5 dditional pressure resistance of bulbous bow near the water surface 7 Model-ship correlation resistance ( 1 PP otal resistance orm factor of the hull 4 ave resistance 6 dditional pressure resistance due to immersed transom immersion L 11

12 esistance Prediction by Holtrop-Mennen s Method for a 3,700 EU ontainer arrier 3 esistance Prediction by Holtrop and Mennen s Method Example 3,700 EU ontainer arrier Main Dimension L O L P L L mld D mld d /s (design / scantling Deadweight (design / scantling 57.4 m 45.4 m 39.6 m 3. m 19.3 m 10.1 / 1.5 m 34,400 / 50,00 M(metric ton ransverse bulb area enter of bulb area above keel line ransom area etted area appendages Stern shape parameter Propeller diameter Number of propeller blades learance propeller with keel line 15. m 5.5 m 0 m m V-shaped 7.7 m m Displacement Volume at d 49,65.7 m 3 L % aft of 1/L P Midship section coefficient ( M aterplane are coefficient ( apacity ontainer on deck / in hold,174 EU / 1,565 EU allast water 13,800 m 3 Heavy fuel oil 6,00 m 3 Main Engine & Speed M / E type Sulzer 784 M (HP ⅹ rpm 38,570 ⅹ10 N (HP ⅹ rpm 34,710 ⅹ98.5 Service speed at N (d, 15% SM.5 knots (at 11.5 m at 30,185 HP DO at N 103. M ruising range 0,000 N.M Others omplement (rew 30 Person 4 1

13 rictional esistance (1/3 ( 1 PP 3,700 EU ontainer arrier V L L v.5 knots 39.6 m : oefficient of frictional resistance (I 1957 friction formula (log n n n V L is based on the waterline length (L L Example EU N arrier V LL n (log (log.3310 n rictional esistance (/3 ( 1 PP 1 V S bh S : etted surface area of the bare hull bh : ransverse bulb area Definition of [L ]: he cross sectional area (full section port and starboard at the fore perpendicular. here the water lines are rounded so as to terminate on the fore perpendicular is measured by continuing the area curve forward to the perpendicular, ignoring the final rounding (eference: I. rea h P ase line 6 13

14 rictional esistance (3/3 ( 1 PP 1 V S bh = ρ=1.05 ton/m 3 3,700 EU ontainer arrier L (L L 39.6 m 10.1 m 3. m S : etted surface area of the bare hull bh M P m S L( ( / / bh M M P In this formula, the hull form coefficients are based on the waterline length (L L. Example EU N arrier S L( ( / / bh M M P 39.6( ( ,670.4[ ] m V Sbh 8, [ kn ] 7 orm actor of the are Hull (1/3 ( 1 PP 1k ( / L ( / L ( L/ L 1 14 ( L / ( P ,700 EU ontainer arrier fter body form V-shaped 14 : he prismatic coefficient based on the waterline length stern stern 5 Pram stern with gondola V-shaped sections Normal section shape U-shaped sections Example EU N arrier stern stern ( L 8 14

15 orm actor of the are Hull (/3 ypes of stern V-shaped U-shaped ulbous-shaped Pram with gondola win gondola stern ( ruiser sterned vessels - In the aspect of resistance, V-shaped is better. - In the aspect of propulsive efficiency, U-shaped is better. ( ransom sterned vessels ( ounter sterned vessels 9 orm actor of the are Hull (3/3 ( 1 PP 1k ( / L ( / L ( L/ L 1 14 ( L / ( P =0.89 3,700 EU ontainer arrier L 39.6 m 3. m 10.1 m L : Length of run t early design stage, if L is unknown, it can be obtained by following formula: L / L L /(4 1 P P P L : he longitudinal position of the centre of buoyancy forward of 0.5L as a percentage (% of L. forward : (+, aft : ( p L % (aft Example EU N arrier L L( L / (4 1 P P P 39.6( ( / ( [ m] 1k ( / L ( / L ( L/ L ( L / ( P (3. / 39.6 (10.1/ 39.6 (39.6 / (39.6 / (

16 esistance of ppendages (1/3 ( 1 PP PP 1/ V S PP (1 k eq = ρ=1,05 kg/m 3 3,700 EU ontainer arrier V.5 knots S PP ( 1 k : he wetted area of the appendages : he appendage resistance factor udder behind skeg: 1.5~.0 Hull bossings:.0 udder of single screw ship: 1.3~1.5 Shafts:.0~4.0 win-screw balance rudders:.8 Stabilizer fins:.8 Shaft brackets: 3.0 Dome:.7 Skeg: 1.5~.0 ilge keels: 1.4 Strut bossings: 3.0 he equivalent 1 + k value for a combination of appendages is determined from: (1 k eq S i (1 k S i i ppendages (S PP S i and (1+k I is the wetted area of the appendages and the appendage resistance factor for the i th time m (rudder 135 m (bilge keel Si(1 k i 8.74( (1.4 (1 k eq 1.4 Si PP V SPP (1 k eq ( [ kn] 31 3 esistance of ppendages (/3 Hull appendage onventional twin-screw after body hull form 3 16

17 esistance of ppendages (3/3 Hull appendage skeg win-screw twin-skeg after body hull form 33 4 ave esistance (Low Speed ange (1/5 - Low speed range: n 0. 4 ( 1 PP L = ,700 EU ontainer arrier g m m d 1 5exp{ 1 n 4 cos( n } L 39.6 m 3. m 10.1 m P ( / (90 i E P L % (aft 49,887 m ( / L 7 / L / L 7 : when /L 0.11 : when 0.11 /L 0.5 : when 0.5 /L i : he half angle of entrance in degree E t early design stage, If i E is unknown, it can be obtained by following formula: i 1 89e E ( L / (1 P (1 P 0.05L ( L / (100 / L / L / L3. / ie 189e L 189e { ( L / (1 P (1P 0.05 L ( L / 3 (100 / L { ( / ( ( ( (73.69/3. 3 ( / [deg] ( / (90 i E (10.1/ 3. (

18 ave esistance (Low Speed ange (/5 Meaning of a entrance angle ater plane area ft : ngle of run of waterline ore : ngle of entrance of waterline ( i E i E : he half angle of entrance is the angle of the waterline at the bow in degrees with reference to the center plane but neglecting the local shape at the stem ave esistance (Low Speed ange (3/5 - Low speed range: 0. 4 n d 1 5exp{ 1 n 4 cos( n } g m m ( 1 : parameter which accounts for the reduction of the wave resistance due to the action of a bulbous bow e If there is not bulb, is /{ (0.31 h } PP 3,700 EU ontainer arrier 3. m 10.1 m 10.1 m 15. m h 5.5 m 0 m : ransverse bulb area M h : he position of the centre of the transverse are above the keel line : he forward draft of the ship : parameter which accounts for the reduction of the wave resistance due to the action of a transom stern 5 : he immersed part of the transverse area of the transom /( M at zero speed /{ (0.31 h } /( M (15. /{3.10.1( } e ( e

19 ave esistance (Low Speed ange (4/5 - Low speed range: 0. 4 n d 1 5exp{ 1 n 4 cos( n } g m m ( 1 PP 3,700 EU ontainer arrier m 1/ L / / L / 0 L P P 6. P P 16 : when P 0.8 : when 0.8 P 16 L 39.6 m 10.1 m p ,778 m 3 n 0.44 d 0.9 m e n 1/ ( L / 8.0 /.36 3 : when L / 51 3 : when 51 L / : when L / 1/3 m L/ / L / L16 L 3 / / / / n / m e 0.034n e ave esistance (Low Speed ange (5/5 - Low speed range: 0. 4 n d 1 5exp{ 1 n 4 cos( n } g m m ( 1 L = =1.63 = =1 m 1= d=-0.9 m 4= PP 3,700 EU ontainer arrier P 0.03L / P : when L/ 1 : when 1 L/ L 39.6 m 3. m p ,778 m 3 n L/ P 0.03 L/ / g m d w 1 5exp{ 1 n m4cos( n } exp{ cos( } [ kn] 38 19

20 ave esistance (High Speed ange - High speed range: 0.55 n g m m d 1 5exp{ 1 n 4 cos( n } ( 1 PP 3,700 EU ontainer arrier L 39.6 m In the high speed, the coefficients 1 and m 1 are changed M ( / L ( L / 3. m p ,778 m 3 n 0.44 m ( / L ( / 39 4 ave esistance (Middle Speed ange - Middle speed range: n ( 1 ( (10 4 {( ( }/1.5 atn0.4 n atn0.55 atn0.4 PP 3,700 EU ontainer arrier ( at n ( - at n 0.55 ( at n 0.4 : he wave resistance prediction for n = 0.4 according to the formula in low speed range n 0.44 ( at n 0.55 : he wave resistance prediction for n = 0.55 according to the formula in high speed range 40 0

21 dditional Pressure esistance of ulbous ow near the ater Surface ( 1 PP P e g P ( ni / (1 ni : measure for the emergence of the bow P 0.56 /( 1.5h 3,700 EU ontainer arrier 15. m 10.1 m h 5.5 m V.5 knots g 9.81 m/s ρ 1.05 ton/m 3 ni ni : he roude number based on immersion of bulbous bow V / g( h V P 0.56 / ( 1.5 h / ( V / g( h V ni ( 3 P e ni g/ (1 ni ( / ( e 8.33[ kn] / (9.81(10.1?5.5? ( In the recent research, it is assumed that =0[kN] dditional Pressure esistance of Immersed ransom Immersion ( 1 PP 1/ V 6 3,700 EU ontainer arrier 0 m 0.( n 6 0 : when n 5 : when 5 n g 9.81 m/s 3. m P V.5 knots ρ 1.05 ton/m 3 n V / g /( P 1/ 0[ kn ] V

22 Model-Ship orrelation esistance (1/ ( 1 PP 1/V S total he model-ship correlation resistance is supposed to describe primarily the effect of the hull roughness and the still-air resistance. 3,700 EU ontainer arrier L 39.6 m m V.5 knots ρ 1.05 ton/m 3 S total m ( L L / 7.5 ( / L : when / L : when 0.04< / L 4 / L / L 10.1/ ecause 0.04 /L L L ( / 7.5 ( ( / ( total [ ] V S kn 43 7 Model-Ship orrelation esistance (/ ( 1 PP 3,700 EU ontainer arrier 8.61 kn ( PP 9.59kN kn 0 kn 0 kn kn = ,577.1,, & 1,

23 esistance Prediction for a Ship (1/3 Given Model test of the basis ship Model test of the design ship ind alculate esistance of basis ship estimated by Holtrop-Mennen method alculate esistance of design ship estimated by Holtrop-Mennen method 45 esistance Prediction for a Ship (/3 Given alculate Model test of the basis ship,basis,modeltest,design, modeltest,basis,holtrop & Mennen esistance of basis ship estimated by Holtrop-Mennen method,, & 1,557.1 Model test of the design ship,design,holtrop & Mennen ind alculate esistance of design ship estimated by Holtrop-Mennen method 46 3

24 esistance Prediction for a Ship (3/3 Model test of the design ship Given Model test of the basis ship ind alculate alculate esistance of basis ship estimated by Holtrop-Mennen method esistance of design ship estimated by Holtrop-Mennen method 47 esistance Estimation by Holtrop and Mennen s Method - pproximation ormula of the Propeller Efficiency (1/4 1 3 D O H 1 [1/ ( ] k O P k[ (( / / 0.6] (0.731/ nn ( P V(1 w n E , (log O 3 1 t H 0.98 ~ w 0. M DP 15.4 c M: Maximum ontinuous ating N: Normal ontinuous ating HP: rake Horse Power DHP: Delivered Horse Power EHP: Effective Horse Power : otal esistance : ransmission Efficiency D : Propulsive Efficiency O : Propeller Efficiency H : Hull Efficiency : elative otative Efficiency t: hrust Deduction raction w: ake raction 3 1 nm lade = 5 : 1 =1, 3 0. lade = 4 : 1 = (38570[ ] /10[ ] 1 HP rpm 7.936[ m] eware of Unit * : he ratio between a propeller's efficiency attached to a ship ( O, and in open water ( O, that is, = O, / O 1PS = k 1HP = k 48 4

25 esistance Estimation by Holtrop and Mennen s Method - pproximation ormula of the Propeller Efficiency (/4 1 3 M: Maximum ontinuous ating 1 t N: Normal ontinuous ating D O H H, 1 HP: rake Horse Power w DHP: Delivered Horse Power w c 9 V L EHP: Effective Horse Power V c 11 : otal esistance (1 P1 : ransmission Efficiency D : Propulsive Efficiency O : Propeller Efficiency H : Hull Efficiency stern V stern L( : elative otative Efficiency P1 P t: hrust Deduction raction w: ake raction ( ( ( ( c8 S / ( LDP when / 5 c =S(7/ -5/(LD (/ -3 8 P when / 5 c9 c8 when c 8 8 c / ( c -4 8 when c 8 8 c11 / D P when / D P 3 c ( /D when / D P V (1 k L P1 P c S/ ( LD / ( P ( / 3.19 c ( c c ( / D 1.7 P (1 k ( V L ( P1 P 49 esistance Estimation by Holtrop and Mennen s Method - pproximation ormula of the Propeller Efficiency (3/4 1 3 D O H 1 t H, 1 w t 1 1 t t L/ ( P c D / ( stern / (3. ( / ( ( 10 M: Maximum ontinuous ating N: Normal ontinuous ating HP: rake Horse Power DHP: Delivered Horse Power EHP: Effective Horse Power : otal esistance : ransmission Efficiency D : Propulsive Efficiency O : Propeller Efficiency H : Hull Efficiency : elative otative Efficiency t: hrust Deduction raction w: ake raction 1 t H 1 w If number of shaft = 1 c10 / L when L/ > 5. c / ( / L when L/ < 5. c ( L/ / ( 0.05 L E O P ( ( If number of shaft = ( L P/ D P i P * hrust deduction fraction or coefficient (t: dditional resistance on the hull due to the rotation of the propeller 50 5

26 esistance Estimation by Holtrop and Mennen s Method - pproximation ormula of the Propeller Efficiency (4/4 1 3 D O H 1 [1/ ( ] k O [1/ ( ] D OH P M: Maximum ontinuous ating N: Normal ontinuous ating HP: rake Horse Power DHP: Delivered Horse Power EHP: Effective Horse Power : otal esistance : ransmission Efficiency D : Propulsive Efficiency O : Propeller Efficiency H : Hull Efficiency : elative otative Efficiency t: hrust Deduction raction w: ake raction 0.5 n( N P V(1 w eware of Unit 1.64[ rps](55[ k ] ( M : 38, 570[ PS ] 10[ rpm] 8, 361[ k ] 1.7[ rps] N : 34, 710[ PS ] 98.5[ rpm] 5, 5[ k ] 1.64[ rps] 51 Power Prediction by Holtrop & Mennen Method EHP (Effective Horse Power EHP ( v V DHP (Delivered Horse Power EHP DHP HP N (Normal ontinuous ating ( : ransmission efficiency Sea Margin N HP(1 100 DM (Derated Maximum ontinuous ating N DM Engine Margin s (In calm water ( : Propulsive efficiency DHP D D OH D O : Open water efficiency H : Hull efficiency : elative rotative efficiency HP (rake Horse Power NM (Nominal Maximum ontinuous ating DM NM Derating rate EHP ( v Vs 1, , 54.7[ k ] 4, 484.5[ HP] EHP 4, DHP 39,613.5[ HP] 0.6 D DHP 39,613.5 HP 40, 41.9[ HP] 0.98 N 46, 485. DM 51,650.[ HP] Engine Margin 0.9 DM NM Derating rate 1PS = k 1HP = k Sea Margin N HP , ,485.[ HP]