Principles of Ship Performance Course Notes

477 Pages·2017·9.55 MB·English

EN400

Principles of Ship Performance

Course Notes

Version: May 2017
Table of Contents

I. Introduction

Course Policy
Equations and Conversion Factors
Symbols and Abbreviations

II. Course Notes

Chapter 1: Engineering Fundamentals
Chapter 2: Hull Form and Geometry
Chapter 3: Hydrostatics
Chapter 4: Stability
Chapter 5: Properties of Naval Materials
Chapter 6: Ship Structure
Chapter 7: Resistance and Powering of Ships
Chapter 8: Seakeeping
Chapter 9: Ship Maneuverability
Chapter 10: Submarines and Submersibles

III. Appendices

Appendix A: Table of Fresh and Salt Water Density
Appendix B: Table of Fresh and Salt Water Kinematic Viscosity
Appendix C: Properties of Common Geometric Shapes

IV. Ship Data Section (Curves of Form and Cross Curves of Intact Stability)

FFG 7 Class CVN 65 Class
DDG 51 Class AOE 6 Class
LCS 1 Class USNA Yard Patrol
27-B-1 Hydro Lab Model

V. Laboratory Handouts

Lab 1: Numerical Integration
Lab 2: Archimedes and Center of Flotation
Lab 3: Inclining Experiment
Lab 4: Righting Arm – Vertical & Transverse Shifts in Center of Gravity
Lab 5: Free Surface Effect and Damage Stability
Lab 6: Materials and Material Testing
Lab 7: Hull Resistance and Effective Horsepower
Lab 8: Propeller Demonstration
Lab 9: Seakeeping
Lab 10: YP Practical Exercise
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Course Wide Policies

Introduction

The world is becoming increasingly technologically advanced. The modern individual must rely
on a technical foundation to positively contribute to teams and problem solving. A Naval Officer
benefits from a solid foundation in engineering principles, whether their duties are to make policy
decisions, command skilled enlisted personnel, maintain and operate state-of-the-art equipment or
partner with civilian technicians and engineers.

USNA recognizes this fact and consequently maintains a requirement for students majoring in the
Division of Mathematics and Science, Division of Humanities and Social Sciences and General
Engineering to complete certain engineering courses. Principles of Ship Performance (EN400) is
just such a course. Affectionately known as ‘Boats,’ the course is relevant to all future Naval and
Marine Corp Officers, regardless of designator. Even if your future career path takes you into the
skies or the mud, you will interface with things that float. You have entered a seafaring service.

The Course

EN400 both develops a general technical foundation and applies these principles specifically to
how ships function. EN400 also approaches material to balance the training needs of a future ship
operator with the required level of mathematics and science understanding suitable for a Bachelor
of Science degree.

Students are introduced to a number of different engineering practices including mathematical
approximation, graphical interpolation and engineering modeling. These practices may appear
difficult to comprehend at first. Remember, they are being taught for a relevant purpose.

Course material is organized into chapters which can largely be viewed as ‘stand alone,’ however
the information and techniques used in early chapters will be called upon again. The first chapter
delivers a basic level of engineering knowledge that students should be familiar with before the
course begins. Students are advised to read Chapter 1 before the first day of class, as instructors
only provide a brief overview of its contents. If there are areas of Chapter 1 requiring further
assistance, raise concerns early and seek extra instruction. The understanding of this pre-requisite
information is vital for the Naval Engineering that follows.

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Laboratories

EN400 consists of 9 laboratory experiments ranging from computer labs to model boat towing in
the hydrodynamics laboratory (hydro lab). They are a vital element in understanding the course
material, totaling 40% of the time available per week. The theory and techniques first presented
in the classroom will come to life in the lab periods. Many labs have pre-lab sections to bridge
this gap between reading, lecture, and experimentation. The theory and techniques to be employed
in the lab are explained, and ensuring completion of the pre-lab before any lab leads to a smooth
experiment and more enjoyable experience.

Instructor Policy

Your section instructor will provide their own teaching, examination, and grading policy during
one of your first classes. Indeed, the everyday classroom environment is their responsibility. In
general, the course provides one homework and one lab per chapter. One quiz is administered
between each of the major exam periods. These are not merely an assessment tool for the
instructor, but also a means by which students can assess their own progress in the subject, before
an exam. Failure to submit work on time will hurt your grade directly, but it will also remove this
valuable self-assessment tool.

Conclusion

The facilities in Rickover Hall are some of the best available anywhere in the world, and
instructors and laboratory staff will add a great deal of technical and fleet experience to the
course material. Make the most of your time remaining before commissioning. Come prepared
to lessons and laboratories. You will only get out of this course the effort you put into it.

EN400 Course Coordinator

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EQUATIONS & CONVERSIONS

The following equations and conversions will be given as part of exams:

Densities of water at 59°F: ρ = 1.94 lb-s2/ft4 ρ = 1.99 lb-s2/ft4
FW SW

ρg = 62.4 lb/ft3 ρg = 64 lb/ft3
FW SW

Miscellaneous: 1 LT = 2240 lb g = 32.17 ft/s2

1 ft3 = 7.4805 gal 1 kt = 1.688 ft/s
L
2∫xy(x)dx
L T L
A = 2∫ y(x)dx A = 2∫ y(z)dz ∇ = ∫A (x)dx LCF = 0
WP Sect S Sect
A
0 0 0 WP

∆x

�y(x)dx = (1y0+4y1+2y2+4y3+2y4+4y5+...+4yn−1+1yn),n= even number
L 3 A (ft2) w wl
∆x = pp F =ρg∇ TPI = WP δT = δTrim =
# of stations−1 B in− ft2  PS TPI MT1"
420 
 
 LT 

T +T δTrim×d
P =ρgz Trim = T −T T = fwd aft δT = fwd/aft
hyd aft fwd mean 2 fwd/aft L
PP

TCG
KM = KB+BM = KG+GM tanφ= wt = ∆GM tanφ
GM
T

KG ∆ +∑±w Kg TCG ∆ +∑(±w )(±Tcg )
KGnew = old∆ old+∑±w i i TCGnew = old ∆old +∑±wi i
old i old i

ρi lb3
T =T ±δT ±δT FSC = t t i = , for rectangular shapes
final,fwd/aft initial,fwd/aft PS fwd/aft ρ∇ t 12
S S

G Z =G Z −G G sinφ−G G cosφ−FSCsinφ GM =GM −FSC Righting Moment =GZ∆
1 1 0 0 0 v v t eff

L −L My F σ
e = L −L ε= f o σ = σ= E =
f o L bending I A ε
o
L V V R EHP R V
λ= S M = S C = T η = PC = EHP = T S
L L L T 1ρSV2 p SHP 550 ft−lb
M M S 2 sec−HP

LV V 2 T
R = F = η = C =
n ν n gL prop 1+ 1+C t 1ρA V 2
t 2 O A

2π k ω 2V cosµ wl
ω= = ω =ω − w S tanθ=
T m e w g ∆BG
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SYMBOLS AND ABBREVIATIONS

Below is a list of symbols and abbreviations used in the course. Do not attempt to
memorize them now! Their meaning and uses will develop as the course progresses.

DWL Design water line
FP or F Forward perpendicular
P
O) ( Midships
AP or A Aft perpendicular
P
LBP or L Length between perpendiculars, ft
PP
LOA Overall length, ft
K Keel
D Depth, ft
T Draft, ft
T Draft at FP, ft
fwd
T Draft at AP, ft
aft
T Mean Draft, ft
m
Trim Trim = T - T , ft
aft fwd
δ Change in Trim
Trim
B Beam, ft
C Centerline
L
B Baseline
L
WL Waterline
A or WPA Waterplane area, ft2
wp
A Sectional Area, ft2
sect
∇ Submerged volume, ft3

∆ Displacement, LT (weight of the ship)
S
w weight of an object, LT (+ if weight added, - if weight removed)

(+ to starboard, - to port) or (+ fwd of midships, - aft of midships) or (+ aft of FP)
G Center of Gravity of ship
g Center of Gravity of an object
KG or kg Distance from keel to the center of gravity, ft
TCG or tcg Transverse Center of Gravity, ft (Distance from C to G)
L
LCG or lcg Longitudinal Center of Gravity, ft (Distance from FP or O)( to G)

F Center of Floatation
LCF Longitudinal Center of Floatation, ft
TCF Transverse Center of Floatation, ft
B Center of Buoyancy
LCB Longitudinal Center of Buoyancy, ft
TCB Transverse Center of Buoyancy, ft
KB or VCB Distance from keel to the center of buoyancy, ft

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M Transverse Metacenter
T
M Longitudinal Metacenter
L
TPI Tons per inch or Immersion, LT/in
MT1" Moment to trim one inch, ft-LT/in
KM Distance from keel to longitudinal metacenter, ft
L
KM Distance from keel to transverse metacenter, ft
T
GM Transverse Metacentric Height, ft (Distance from M to G)
T T
(+ M is above G, - M is below G)
BM Transverse Metacentric Radius, ft
T

φ angle of heel or list, degrees
θ angle of trim, degrees

P Pressure, psi
ρ Density, lb-s2/ft4
g Acceleration due to gravity (9.81 m/s2, 32.2 ft/s2 on Earth)
F Buoyant Force, LT
B

d Distance from FP to F, ft
fwd
d Distance from AP to F, ft
aft
δT Change in draft due to parallel sinkage, ft
PS
δT Change in draft forward, ft
fwd
δT Change in draft aft, ft
aft

RM Righting moment, LT-ft
GZ Righting arm, ft
FSC Free surface correction, ft
I Transverse second moment of area, ft4
t
I Longitudinal second moment of area, ft4
L
GM Effective Metacentric Height, ft,
eff

σ stress, psi (+ Tensile, - Compressive; or Bending)
σ yield strength, psi
y
UTS Ultimate Tensile Strength, psi
ε strain, in/in or unitless ratio
E Young’s Modulus or Modulus of Elasticity, psi
e elongation, in

VT Visual testing
PT Dye penetrant testing
MT Magnetic particle testing
RT Radiographic testing
UT Ultrasonic testing

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BHP Brake Horsepower, HP
SHP Shaft Horsepower, HP
DHP Delivered Horsepower, HP
THP Thrust Horsepower, HP
EHP Effective Horsepower, HP
η Hull Efficiency
H
η or PC Propulsive Efficiency or Propulsive Coefficient
P

R Total Hull Resistance, lb
T
V Ship Speed, ft/s
S
S Wetted surface area of the submerged hull, ft2

C Coefficient of Total Hull Resistance
T
C Coefficient of Viscous Resistance
V
C Coefficient of Skin Friction
F
C Coefficient of Wave Making Resistance
W
C Correlation Allowance
A
R Reynolds Number
n
F Froude Number
n
ν Kinematic Viscosity, ft2/s
K Form Factor
λ Scale Factor

V Speed of Advance, ft/s
A
V Speed of the Wake, ft/s
W
η Propeller Efficiency
propeller
A Blade Area, ft2
0
C Coefficient of Thrust Loading
t

ω Frequency (rad/s)
ω Natural frequency (rad/s)
n
ω Wave frequency (rad/s)
w
ω Encounter frequency (rad/s)
e
ω Natural Heave frequency (rad/s)
heave
ω Natural Roll frequency (rad/s)
roll
ω Natural Pitch frequency (rad/s)
pitch
T Period of Roll (s)
roll

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COURSE OBJECTIVES
CHAPTER 1

1. ENGINEERING FUNDAMENTALS

1. Be familiar with engineering graphing, drawing, and sketching techniques

2. Explain what dependent and independent variables are, notation used, and how
relationships are developed between them

3. Be familiar with the unit systems used in engineering and specifically this course

4. Understand unit analysis and be able to use units effectively in calculations and in
checking your final answer for correctness

5. Use exact numbers and significant figures correctly in calculations

6. Conduct linear interpolation on data tables and graphs

7. Obtain a working knowledge of scalars, vectors, and the symbols used in
representing them, as related to this course

8. Obtain a working knowledge of forces, moments, and couples

9. Obtain a working knowledge of and be able to solve basic problems related to the
concept of static equilibrium

10. Understand the difference between a distributed force and a resultant force

11. Calculate the geometric centroid of an object

12. Calculate the first moment of area of a region about an axis

13. Calculate second moment of area of a region about an axis, including application
of the parallel axis theorem

14. Name and describe the six degrees of freedom of a floating ship, and know which
directions on a ship are associated with the X, Y, and Z axes.

15. Know and discuss the following terms as they relate to naval engineering:
longitudinal direction, transverse direction, athwartships, midships, amidships,
draft, mean draft, displacement, resultant weight, buoyant force, centerline,
baseline, and keel.

16. Be familiar with the concepts involved in Bernoulli’s Theorem
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1.1 Graphing, Drawing, and Sketching

Graphing, sketching, and drawing; are they different? Bananas, oranges, and coconuts are all
edible fruits, yet they all have a sharp contrast in taste and texture. But they all must be peeled to
be eaten. Clearly there are similarities and differences in bananas, oranges, and coconuts just as
there are in graphing, sketching, and drawing.

The common thread in graphing, drawing, and sketching is that they are all forms of visual
communication. Each says something important about the relationship of two or more
parameters. Engineering is all about communicating ideas to others, and these are three principle
methods by which ideas are communicated. A graph, drawing, or sketch must effectively
communicate information to a different party unrelated to the work. See Table 1.1 for a
summary of similarities and differences in these three visual communication methods.

Graph Drawing Sketch
• Form of visual communication
Similarities: • Effectively communicate information to a party unrelated to the work
• Says something about the relationship between two parameters
• Relationship between • Relationship • Quick “free-hand”
variables or data between objects picture of drawing or
• Exact coordinates, • Exact shape graph
Differences:
axes and scales • To scale • General relationship
• Title, legend, and between (not exact)
units • Some labels

Table 1.1 Comparison between Graph, Sketch and Drawing

1.1.1 Graphs are used to represent the relationships between variables, such as data taken
during an experiment. Graphs are also used to represent analytical functions like y = mx + b.
Graphs require that you use exact coordinates and visually represent relationships between
variables in perfect proportions on the paper. A proper graph can be time consuming and require
skill to prepare. Computers and spreadsheet programs can be used as tools in effectively
preparing a graph.

Graphs are to be done on graph paper (or with a computer) that has major and minor axes in both
the vertical and horizontal directions. Major axes are to be subdivided such that they are easy to
read and construct. Axis subdivisions should be consistent with the line spacing on the graph
paper. Axis subdivisions that require a lot of interpolation and guessing when obtaining data are
to be avoided.

Graphs must have a title that describes what is being plotted, and each axis must have a title that
thoroughly describes the variable being plotted. Additionally, each axis title must include the
symbol for the variable being plotted, and appropriate units for that variable.

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