7/29/2019 Naval Architecture PPT
1/79
OCEN 201Introduction to Ocean &
Coastal EngineeringBasics of Naval Architecture
7/29/2019 Naval Architecture PPT
2/79
Ships by Configurations
Surface displacement: Conventional ships(single hull); Catamaran (double hull, large deck
area, small displacement, excellent stability).
Near (above) Surface: Air cushion vehicles;
Hydrofoils and planning hull craft (smalldisplacement, high speed)
Submerged: Submersibles; submarines;Underwater habitats; Submerged buoys.
Semi submersibles: Very deep, small waterplane
Bottom supported: Temporary & Permanent
jack-up;
7/29/2019 Naval Architecture PPT
3/79
Tanker (with a bulbous bow)
7/29/2019 Naval Architecture PPT
4/79
Small Water-plane Area Twin-Hull (SWATH)
7/29/2019 Naval Architecture PPT
5/79
Ferry (Catamaran, or SWATH)
7/29/2019 Naval Architecture PPT
6/79
Container Ship
7/29/2019 Naval Architecture PPT
7/79
Container Ship
7/29/2019 Naval Architecture PPT
8/79
7/29/2019 Naval Architecture PPT
9/79
7/29/2019 Naval Architecture PPT
10/79
7/29/2019 Naval Architecture PPT
11/79Cruise ship with a bulbous bow
7/29/2019 Naval Architecture PPT
12/79
7/29/2019 Naval Architecture PPT
13/79
7/29/2019 Naval Architecture PPT
14/79
Trimaran
7/29/2019 Naval Architecture PPT
15/79Tri-maran Sailboat
7/29/2019 Naval Architecture PPT
16/79
View from the below
7/29/2019 Naval Architecture PPT
17/79
Hydrofoil Craft
7/29/2019 Naval Architecture PPT
18/79
7/29/2019 Naval Architecture PPT
19/79
Rules and Regulations
The rules and regulations are issued by organizations
which may be divided into three categories:
-Classification societies: have established standards
of construction by the production of rules whichhave done much to ensure the safety of ships. (ABS,DNV, BV)
-Governmental Authorities: concern for the safety
of ships and the well being of all who sail the ships(behavior of the people). (Coast Guard)
-International Authorities, IMO (InternationalMaritime Organization)
7/29/2019 Naval Architecture PPT
20/79
Basic Topics of Naval Architecture
Hull: Hydrostatic, hydrodynamicperformance (Resistance)*
Structure: Strength of hull**
Machinery and Propulsion: Main engine**& propellers*
Ship Control: (maneuvering, sea keeping)**
7/29/2019 Naval Architecture PPT
21/79
Deck Machinery**
Navigation: Sensors & Radar**
Communications**
Damage Control:**
Rigging and Mooring:*
Economic feasibility:**
** Not covered in detail
7/29/2019 Naval Architecture PPT
22/79
Definition (Terminology):
Principal Dimensions (length, breadth, depth etc)
-Length.Lbp ( or Lpp) Length between two perpendiculars
FPForward perpendicular (vertical line through intersection
of stem and waterline (w.l).)
APBackward perpendicular (vertical line through the center
of rudder pintle)
LoaOverall Length
LwlWaterline Length (calculation length)
also see Table 6-2 at p175 (old edition at p142)
7/29/2019 Naval Architecture PPT
23/79
W.L.
A.P
Loa
Lwl
Amid Ship
Lbp
F.P.
Forward Sheer
After Sheer
Sheer is the height measured between deck at side and base line.
7/29/2019 Naval Architecture PPT
24/79
Definition (Terminology):
Principal Dimensions
-Breadth, depth & draft. Breadth (moulded) (inside of plate on one side to another side)
Breadth maximum Depth (measured at midship)
Camberthe rise of the deck at the centerline. 2% of breadth
Bilge radius
Rise of Floor
Flat of keel (thicker plate)
Tumber home
Rake of stem
Draught and trim
7/29/2019 Naval Architecture PPT
25/79
Flat of KeelRise of Floor
Depth
Moulded
Breadth
moulded
Bilge radius
Centerline
Deck
Base Line (Top of
Flate keel)
CamberBreadth Extreme
Fonder
w.l.
Draft (d)
Mid Cross Section of a ship
7/29/2019 Naval Architecture PPT
26/79
If W.L. is parallel to the baseline (keel line),
the ship is floating evenly.
If not parallel, the ship has a trim.
Trim = dadf
Trim (in radians) = (dadf )/ L
Average draft = (da + df )/ 2
Free board (f.b) is the distance measured
downwards from the deck to the W.L.Usually f.b. is minimum at midship
Minimum f.b is required by International
Law.
7/29/2019 Naval Architecture PPT
27/79
Line Drawing:
Using the methods of descriptive geometry, the form of
a hull is drawn on a scale (1:50 or 1:200) drawing,
which is called Lines Drawing, or simply the lines
or lines plan. (See p34 Figure 3.4 Lines plan).
Lines drawing mainly consists ofthree plan views
Sheer plane (Buttock plane, Buttock lines) : parallel
to the longitudinal central plane (2m, 4m, etc are the
distances from the center plane)
7/29/2019 Naval Architecture PPT
28/79
Half-Breadth plane (Water plane, Waterline planes):
parallel to the base plane (2m, 4m, .are the distance
form the base plane)
Body Plan (Ordinate station, Transverse section,
0-10 bow stern (US), 10-0 (UK)): parallel to the mid-
section (# of stations indicated the distance from the
mid-section or bow).
Diagonals (Bilge Diagonal) Fair form and fairness of line, checking the
consistency of point, smoothness of lines
Table of Offsets
7/29/2019 Naval Architecture PPT
29/79
Line Drawing
7/29/2019 Naval Architecture PPT
30/79
7/29/2019 Naval Architecture PPT
31/79
Hull characteristics (coefficients
(non-dimensional)
- Coefficient of Form ( Fatness of a hull)
Block Coefficient CB
whereL= Lpp or Lbp and T= Draft
CB 0.38~0.90 even bigger
- Midship Section Coefficient
CM = immersed area of mishap section (A) / (BT)
0.67~0.98
BC
LBT
7/29/2019 Naval Architecture PPT
32/79
-Prismatic or Longitudinal Coefficient: 0.55~0.80
-Waterplane Coefficient
-Displacement /Length Ratio
BP
M M
CCL A L B T C C
area of water plane0.67 - 0.87
where --Length of Load water plane
= Beam of W.P.
WPCLB
L
B
3 3
BB
C LBT B TC
L L L L
7/29/2019 Naval Architecture PPT
33/79
-Breadth /Length Ratio :
-Draft/Length Ratio
-Draft/Breadth Ratio
-These coefficients are related to the resistance and
stabilityof the ship and can be used to estimate
them empirically.
B
L
T
L
T
B
7/29/2019 Naval Architecture PPT
34/79
Important Hydro-Static Curves or Relations(see Fig. 6-3, pp148)
Displacement Curves (displacement [molded, total]
vs. draft, weight [SW, FW] vs. draft (T))
Coefficients Curves (CB , CM , CP , CWL, vs. T)
VCB (KB,ZB
): Vertical distance of Center of
Buoyancy (C.B) to the baseline vs. T
LCB (LCF,XB
): Longitudinal Distance of C.B or
floatation center (C.F) to the midship vs. T
7/29/2019 Naval Architecture PPT
35/79
7/29/2019 Naval Architecture PPT
36/79
StabilityA floating body reaches to an equilibrium state, if
1) its weight = the buoyancy2) the line of action of these two forces become collinear.
The equilibrium: stable, or unstable or neutrally stable.
Stable equilibrium: if it is slightly displaced from its
equilibrium position and will return to that position.
Unstable equilibrium: if it is slightly displaced form its
equilibrium position and tends to move farther away from
this position.
Neutral equilibrium: if it is displaced slightly from this
position and will remain in the new position.
7/29/2019 Naval Architecture PPT
37/79
Motion of a Ship:
6 degrees of freedom
- Surge
- Sway
- Heave
- Roll
- Pitch
- Yaw
Axis Translation Rotationx Longitudinal Surge Neutral S. Roll S. NS. USy Transverse Sway Neutral S. Pitch S.z Vertical Heave S. (for sub, N.S.) Yaw NS
7/29/2019 Naval Architecture PPT
38/79
Righting & Heeling Moments
A ship or a submarine is designed to float in the
upright position.
Righting Moment: exists at any angle ofinclination where the forces of weight and buoyancy
act to move the ship toward the upright position.
Heeling Moment: exists at any angle of inclination
where the forces of weight and buoyancy act to
move the ship away from the upright position.
F di l t hi
7/29/2019 Naval Architecture PPT
39/79
G---Center of Gravity, B---Center of Buoyancy
M--- Transverse Metacenter,
If M is above G, we will have a righting moment, and
if M is below G, then we have a heeling moment.
W.L
For a displacement ship,
7/29/2019 Naval Architecture PPT
40/79
For submarines (immersed in water)
G
B
G
If B is above G, we have righting momentIf B is below G, we have heeling moment
7/29/2019 Naval Architecture PPT
41/79
7/29/2019 Naval Architecture PPT
42/79
Static Stability & Dynamical Stability
Static Stability: Studying the magnitude of the
righting moment given the inclination (angle) of the
ship*.
(That is, the rolling velocity and energy are notconsidered.)
Dynamic Stability**: Calculating the amount of work
done by the righting moment given the inclination ofthe ship.
7/29/2019 Naval Architecture PPT
43/79
Static Stability1. The initial stability (aka stability at small
inclination) &,2. the stability at large inclinations.
The initial stability: studies the right moments or right
arm at small inclination angles (< 5 degree).
The stability at large inclination (angle): computes theright moments (or right arms) as function of the inclination
angle, up to a limit angle at which the ship may lose its
stability (capsizes). (Cross curves of stability (see Fig.
6-7 at pp 156) & Curves of Static Stability (see Fig. 6-8
at pp157) )
The initial stability is a special case of the latter.
7/29/2019 Naval Architecture PPT
44/79
Initial stability Righting Arm: A symmetric ship is inclined at a small angle
d. C.B has moved off the ships centerline as the result of the
inclination. The distance between the action of buoyancy andweight, GZ, is called righting arm.
Transverse Metacenter: A vertical line through the C.B
intersects the original vertical centerline at point,M
.
sin
if 1
Small angle inclination
5 0.087266
GZ GM d
GMd d
d
7/29/2019 Naval Architecture PPT
45/79
Location of the Transverse Metacenter
Transverse metacentric height : the vertical distance
between the C.G. andM(GM). It is important as anindex of transverse stability at small angles of inclination.
GZ is positive, if the moment is righting moment. M
should be above C.G, ifGZ >0.
If we know the location ofM, we may find GM, and thus the
righting arm GZ or righting moment can be determined
given a small angle d.
Righting Moment = GZ
7/29/2019 Naval Architecture PPT
46/79
; the distance from C.B. to
( ) the distance from the baseline to .
,
where is the vertical coordinates of the C.B.
The vertical distance between the metacenter
x
M
xM B
B
IBM BM M
H KM M
IKM = H = + Z
Z
.
& C.G,
xM G B G
IGM H Z + Z Z
E l f
7/29/2019 Naval Architecture PPT
47/79
Examples of
computing KM
d
B
3
2
2
3
2
2
) Rectangular cross section
1, ,
2 12
12
12 2
) Triangular cross section
2 1 1, ,
3 12 2
6
2
6 3
B x
x
B
B x
x
B
a
dZ I LB LBd
I BBM
d
B dKM BM Z
d
b
dZ I LB LBd
I BBM
d
B dKM BM Z
d
d
B
7/29/2019 Naval Architecture PPT
48/79
Ship Resistance (Drag )
A ship actually moves at the same time through twofluids, water and air, with widely different density.
While the lower part of the hull is moving through
water, the upper part is moving through air. Because
, the air resistance is usually much smaller
than the water resistance, except for those aerostatic
support of hydrodynamic support crafts.
Summary: Water resistance (submerged part of a hull)
Air resistance (upper part of hull &
superstructure)
a w
7/29/2019 Naval Architecture PPT
49/79
Types of Water Resistances1. Wave-Making Resistance: Waves are generated on
the surface of water and spread away from a ship.Waves possess energy. Thus a ship making waves
means a loss of its energy. Wave-making
resistance is important to surface ships, especially
those of high speeds.2. Frictional Resistance: arising due to the viscosity
of water, i.e. tangential stresses. Because of
viscosity & velocity gradient in the direction normal
to the ship hull, there is a mass of fluid beingdragged along with a ship. Energy necessary to drag
the mass of fluid is the work done by the ship
against the frictional resistance.
7/29/2019 Naval Architecture PPT
50/79
3. Eddy-making Resistance: Due to the viscosity of the
fluid, the flow separates from the surface of a hull and
eddies (vortices) are formed. These eddies induce the
changes in the velocity field and thus change the
normal pressures on a hull. The changes in the
pressure field around a ship result in the eddy-making
resistance.
Air resistance (mainly resulting from wind resistance).
Appendage resistances: are caused by the appendages
of a ship, such as propellers, rudders and bilge keels.
R N F R
T F R air app
R R R
R R R R R
Naked Ship esistance
Total
7/29/2019 Naval Architecture PPT
51/79
Computation of Frictional Resistance
810
72
10
Re /
(1947 ATTC line)
0.242log Re , for Re 4.5 10 .
0.075 , for Re 10log Re 2
F
F
F
LV
CC
C
Reynolds Number (non - dimensional)
Schoenherr formula
1957 ITTC line formula
2
.
1
2
F FF V SC Frictional Resistance
7/29/2019 Naval Architecture PPT
52/79
7/29/2019 Naval Architecture PPT
53/79
Influence of Roughness of a plate on CF
The formulas for computing CF
are applied to the flat plates with
smooth surface. The rough surface (of a ship) will result in theincrease ofC
F. Roughness (on the surface of a hull) may be
classified into 3 types.
1. Structural roughness: caused by welded joints, warviness ofshell plating on the hull. A newly-built ship will have
(for Schoenherr formula).
2. Corrosion
3. Fouling: caused by the attachment of marine organisms such as
seaweeds, shells and barnacles.
Corrosion & fouling occur for ships having sailed for a certain
period of time. They will decrease the velocity of the ship. Ship
owner will decide when the ship should go to the dock for cleaning.
0.0004fC
7/29/2019 Naval Architecture PPT
54/79
Wave-Making ResistanceWave-making resistance is important to
1. a surface ship (negligible for submarine); &2. its speed is high. Accurately speaking, its Froude # ,
or in U.S. the speed/length ratio, is high.
It is noticed that the speed to length ratio is a dimensional
coefficient, where Vis in knots,L in feet.
A nautical mile/hr (knot) = 0.5144 m/s.
R
VF
gL
V
L
6
2
R
1 is equivalent to 0.3
When 0.1, & is negligible.
When 0.45, , is dominant in .
1R ( determined via model tests)
2
R
R W W
R W W T
W W
VF
L
F C R
F C V R R
V SC C
7/29/2019 Naval Architecture PPT
55/79
Ship Wave Pattern
Lord Kelvin (1887) considered a single pressure point traveling
in a straight line over the surface of the water, sending outwaves which combine to form a characteristic pattern.
Transverse Waves
Divergence Waves
7/29/2019 Naval Architecture PPT
56/79
Ship Wave Pattern
Kelvin wave pattern illustrates and explains many of the
features ofship waves. Ship wave pattern is similar to the
combination of two Kelvin wave systems generated by two
pressure points, with one near the bow and the other near the
stern.
7/29/2019 Naval Architecture PPT
57/79
Wave pattern of a ship
7/29/2019 Naval Architecture PPT
58/79
Wave pattern behind a moving duck
7/29/2019 Naval Architecture PPT
59/79
Wave Pattern of a small boat (divergence wave pattern)
7/29/2019 Naval Architecture PPT
60/79
Wave Pattern of a small boat (divergence wave pattern)
7/29/2019 Naval Architecture PPT
61/79
A Towing Carriage and A Ship Model
7/29/2019 Naval Architecture PPT
62/79
A Towing Carriage
7/29/2019 Naval Architecture PPT
63/79
Overview of MarinTeks Shop Model Tank (Norway)
7/29/2019 Naval Architecture PPT
64/79
Propulsive Devices
Paddle-Wheels: While the draft varying with ship displacement,
the immersion of wheels also varies. The wheels may come out
of water when the ship is rolling, causing erratic course-keeping,
& they are likely to damage from rough seas.
Propellers: Its first use was in a steam-driven boat at N.Y. in1804. Advantages over paddle-wheels are,
1) not substantially affected by normal changes in draft;
2) not easily damaged;
3) decreasing the width of the ship, &4) good efficiency driven by lighter engine.
Since then, propellers have dominated in use of marine
propulsion.
7/29/2019 Naval Architecture PPT
65/79
Paddle Wheels Propulsion (Stern)
7/29/2019 Naval Architecture PPT
66/79
Paddle Wheels Propulsion (Midship)
7/29/2019 Naval Architecture PPT
67/79
Propeller (5-blade)
7/29/2019 Naval Architecture PPT
68/79
Propeller (5-blade)& Rudder
7/29/2019 Naval Architecture PPT
69/79
Jet type: Water is drawn by a pump & delivered sternwards as a
jet at a high velocity. The reaction providing the thrust. Its use
has been restricted to special types of ships.
Other propulsion Devices:
1. Nozzles (Duct) Propellers: main purpose is to increase the
thrust at low ship speed (tug, large oil tanker)2. Vertical-Axis Propellers: Advantage is to control the direction
of thrust. Therefore, the ship has good maneuverability.
3. Controllable-Pitch Propellers (CCP): The pitch of screw can
be changed so that it will satisfy all working conditions.4. Tandem and Contra-rotating Propellers: It is used because
the diameter of a propeller is restricted due to limit of the draft
or other reasons (torpedo). The efficiency of the propeller
usually decreases.
7/29/2019 Naval Architecture PPT
70/79
Jet Propulsion
7/29/2019 Naval Architecture PPT
71/79
Nozzle Propellers
7/29/2019 Naval Architecture PPT
72/79
Vertical-Axis Propellers
7/29/2019 Naval Architecture PPT
73/79
Vertical-Axis Propellers
7/29/2019 Naval Architecture PPT
74/79
Controllable Pitch Propellers (CPP)
7/29/2019 Naval Architecture PPT
75/79
Contra-rotating Propellers
7/29/2019 Naval Architecture PPT
76/79
Type of Ship Machinery (Engine)
1.Steam Engine
2.Steam Turbine
3.Internal combustion engines (Diesel engine)
4. Gas Turbines
5. Nuclear reactorsturbine
Engine (Brake) Power: Measured at right behind the
7/29/2019 Naval Architecture PPT
77/79
Engine (Brake) Power: Measured at right behind the
enginePB
Delivered horsepower (PD
): the power delivered to the
propeller.
Thrust horsepower (PT):
=
- Efficiency of the Propeller in open water
- Thrust delivered by the propeller
- Advancing velocity of the propeller
T D O A
O
A
P P T V
T
V
Efficiency of the shaft
transfer energy from the engine to the propeller
D B S SP P
Effective horsepower (P or EHP):
7/29/2019 Naval Architecture PPT
78/79
Effective horsepower (PE
, or EHP):
RTtotal resistance
Vsadvance velocity of ship
/ = =
- quasi-propulsive coefficient (efficiency)
- Hull coefficient (efficiency)
E T S
S TE T H
A
E E TD H R O H O
D T D
D
H
P R V
V RP P
V TP P P
P P P
Propulsion Efficiency
7/29/2019 Naval Architecture PPT
79/79
Propulsion Efficiency
Total propulsion efficiency
can also be replaced by or
A more meaningful measure of hydrodynamic performance
of a propeller is: a quasi-propulsive coefficient,
,
, where is the shaft
ET S B I
S
D
ED
D
DS S
S
P P P PP
P
P
P
P
transmission efficiency
and thus, .
- 98% for ships with main engine aft
- 97% for ships with main engine amidship
T D S
S