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Chapter 1 Ship
Design
（船舶设计）
Lesson 2
Ships
Categorized
（船舶分类）
Introduction
（介绍）
The forms a ship can take are
innumerable.
一艘船能采用的外形是不可胜数的
A vessel might appear to be a sleek
seagoing hotel carrying passengers along
to
some
exotic
destination;
a
floating
fortress
bristling
with
missile
launchers;
。
or an elongated box
transporting tanks of crude oil and topped with
complex pipe
connections.
一艘
船可以看做是将乘客一直运送到外国目的地的优美的远航宾馆。
竖立有
< br>导弹发射架的水面堡垒及甲板上铺盖有复杂管系的加长罐装原油运输轮
None of these descriptions of external
appearance, however, does justice to
the ship system as a whole and
integrated unit
所有这些外部特点的描述都不能说明
< br>船舶系统是一个总的集合体
—
self-sufficient,seaworthy,
and
adequately
stable
in
its
function
as
a
secure
habitat for crew and
cargo.
——船员和货物的安全性功能：
自给自足，
适航，
足够稳定。
This is the concept that the naval
architect keeps in mind when designing the
ship
and
that
provides
the
basis
for
subsequent
discussions,
not
only
in
this
chapter
but
throughout the entire book.
这是一个造船工程师设计船
舶使必须记住的、
能为以后
讨论提供根据的观念，
不仅涉及本章也贯穿全书。
In
order
to
discuss
naval
architecture,it
is
helpful
to
place
ships
in
certain
categories.
For
purposes
of
this
text,
ships
are
classified
according
to
their
means
of
physical support and their designed purposes.
将船舶分成一些特定的种类来讨论
造船工程是有好处的。
< br>本文的目的就是根据船舶
物理支撑方式
和设计目的来将它
们分类。
Ships Typed According
to Means of Physical
Support
（根据物理支撑方式来分类）
The mode of physical support by which
vessels can be categorized assumes that
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the vessel
is operating under designed conditions- Ships are
designed to operate
above, on, or below
the surface of the sea, so the air-sea interface
will be used
as the reference datum.
船舶按物理支撑的分类方式假设，
船
舶是在设计工况的条件下航行。
船舶
预定
在海面上，
海面中或海面以下航行，因此使用空气与水的接触面作为基准面。
Because
the
nature
of
the
physical
environment
is
quite
different
for
the
three
regions
just
mentioned,
the
physical
characteristics
of
ships
designed
to
operate
in those regions can
be diverse.
由于上面提到的三个区域中物理环境的本质相差很大，
所以那些区域中的船的物
理特性也不同。
Aerostatic
Support
（空气静力支撑）
There are two categories of vessels
that are supported above the surface of
the sea on a self-induced cushion of
air. These relatively lightweight vehicles
are capable of high speeds,since air
resistance is considerably less than water
resistance,
and
the
absence
of
contact
with
small
waves
combined
with
flexible
seals
reduces the effects of wave impact at
high speed.
有两种靠自身诱导的气垫浮于海
面上
的船。
这些重量相对轻的船能够高速航行，
这是因为空气阻力比
水阻力小得多，
而且船舶
高速航行时，
弹性密封圈没有与小波浪接触，
因而降低了了波浪冲击的影响
。
Such vessels depend on lift
fans to create a cushion of low-pressure air in
an underbody chamber.
这种船依靠升力风扇在船体水下部分产生了低压气垫。
This cushion of air must be sufficient
to support the weight of the vehicle
above the water surface.
这种空气
气垫必须足够支撑水面上方船的重量。
The first
type of vessel flexible
“
skirts
”
that entirely surround the air
cushion and enable the ship to rise
completely above the sea surface.
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第一种船有完全围绕在
气垫周围并且能够使船完全漂浮在水面以上的弹性围裙
。
This is called an air cushion vehicle
(ACV) ,and in a limited sense it is
amphibious.
它
被
The other type
of air-cushion craft has rigid side walls or thin
hulls that
称
extend below the
surface of the water to reduce the amount of air
flow required
为
to maintain
the cushion pressure.
另一种气垫船带有刚性侧壁，且有延伸
到水下能够
气
减小空气流量的瘦船体，该气流用来维持气垫压力
。
垫
This type is
called a captured-air-bubble vehicle (CAB).
这种类型船称为束缚
船
气泡减阻船
（
A
It requires
less lift-fan power than an ACV, is more
directionally stable and
can be
propelled by water jets or supercavitating
propellers.
相对于
ACV
< br>来说，
，
某种有限的程度上适用于两栖
< br>。
它需要较低的升力风扇动
力
,
航向稳定性更好，并且能使用喷水推进器和超空泡螺旋桨。
It is not amphibious,
however, and has not yet achieved the popularity
of the
ACVs,
which
include
passenger
ferries,
cross-channel
automobile
ferries,
polar-exploration craft, landing craft,
and riverine warfare vessels.
但是，它不
是两栖用途的，也还没有
ACVs
那
么广的适用范围，
适用范围包括游客渡轮，
横越海峡车客
渡轮，极地考察
船，登陆舰及内河舰艇。
Hydrodynam ic
Support
（水动力支撑）
There are also two types of vessels
that depend on dynamic support generated
by
relatively
rapid
forward
motion
of
specially
designed
hydrodynamic
shapes
either
on or beneath the
surface of the water.
也有两种类型船，
它们依赖通过船的相对高速
前进运动来产生动力支持，
这<
/p>
种
船型的水上和水下部分的形状都经过特殊设计。
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A
principle of physics states that any moving object
that can produce an
unsymmetrical flow
pattern generates a lift force perpendicular to
the direction
of motion.
一个物
理定理这样陈述：
任何运动的物体都能造成不均匀的流态，
产生
一个垂直
于运动方向的升力。
Just as an airplane with (airfoil)
produces lift when moving through the air,
a
hydrofoil
located
beneath
the
surface
and
attached
by
means
of
a
surface
piercing
strut, can
dynamically support a
vessel
’s
hull above the
water.
正如装有空气翼的飞机在空气中移动时气翼上能
产生一个升力一样，
位于水面以下且其
上固定有穿透水面的柱体
的水翼，能够动态支撑水面以上的船体。
Planing
hulls are hull forms characterised by relatively
flat bottoms and
shallow
V-sections
(especially
forward
of
amidships)
that
produce
partial
to
nearly
full
dynamic support for light displacement vessels and
small craft at higher
speeds.
滑
行
Planing
craft
are
generally
restricted
in
size
and
displacement
because
of
the
船
required
power-
to-weight
ratio
and
the
structural
stresses
associated
with
体
traveling
at high speed in waves.
一般说来，
滑行船体的尺寸和排水量有限制。
这是因
的
< br>为需要满足动力和重量的比率要求，以及在波浪中高速航行时的结构应力要求。
特
征
Most
planing
craft
are
also
restricted
to
operations
in
reasonably
calm
water,
although some
“deep V”
hull forms are
capable of operation in rough water.
虽<
/p>
是
然有一些
?
深
V
型剖面船能够在恶劣的海况中航行，
但大多数滑行船体也都限制在相当平静
底
的水面上航行。
部
相
对
4 <
/p>
横
剖
面
Less
on 3 Principal
Dimensions
（主尺度）
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Principal
Dimensions
（主尺度）
Before
studying
in
detail
the
various
technical
branches
of
naval
architecture
it
is
important
to
define
various
terms
which
will
be
made
use
of
in
later
chapters.
The
purpose
of
this
chapter
is
to
explain
these
terms
and
to
familiarise
the
reader
with them.
在系统的学习船舶工程不同的技术分支之前，
应该定义一些术语以便于后面章节使用，
这很重要。本章旨在于解释这些术语，
并且让读者熟悉它们。
In the first
place the dimensions by which the size of a ship
is measured will
be considered; they
are referred to as
‘
principal
dimensions
’
. The ship, like
any
solid
body,
requires
three
dimensions
to
define
its
size,
and
these
are
a
length,
a
breadth and a depth.
首先，考虑用
来测量船舶尺寸的尺度；
它们即是“主尺度”
像任何其他固体一
样，船
舶需要三个尺度来定义其尺寸，
它们是长度，
宽度和高度。
Each of these
will be considered in turn.
我们将依次来讨论它们。
Length
（船长）
There are various ways of defining the
length of a ship, but first the length
between perpendiculars will be
considered.
有多种定义船舶长度的方法，
但是首先应该考虑艏艉两柱间长。
The
length
between
perpendiculars
is
the
distance
measured
parallel
to
the
base
at
the
level
of
the
summer
load
waterline
from
the
after
perpendicular
to
the
forward
perpendicular.
柱
间长指的是平行于基底夏季载重水线，
从艉柱到艏柱间的距离。
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The after
perpendicular is taken as the after side of the
rudder post where
there is such a post,
and the forward perpendicular is the vertical line
drawn
through
the
intersection
of
the
stem
with
the
summer
load
waterline
In
ships
where
there
is
no
rudder
post
the
after
perpendicular
is
taken
as
the
line
passing
through
the centre line of
the rudder pintles.
艉
柱
The length
between perpendiculars is used for calculation
purposes as will
指
be
seen
later,but
it
will
be
obvious
from
Figure that
this
does
not
represent
the
的
greatest length of the ship
.
两柱间长
（）
是用于后面的计算之用
的，
然而从图
中
< br>可以看
就
出两柱间长不是船舶的最大长度。
是
船
For
many
purposes,
such
as
the
docking
of
a
ship,
it
is
necessary
to
know
what
the greatest length of
the ship is.
舶
舵
明白船舶的最大长度是必要的，
很多地方都能用到最大船长，比如<
/p>
船舶入坞
。
柱
This length is known as
the
‘
length
overall
’
and is defined
simply as the
distance from
the extreme point at the after end to a similar
point at
the forward
的
end.
而
，是以从船艉端点到船艏端点间的距离来定义的。
艏
这个长度称为“总长”
柱
< br>This
can
be
clearly
seen
by
referring
again
to
Figure
.
In
most
ships
the
length
是
overall wilt exceed by a
considerable amount the length between
perpendiculars.
通
过
大多数船的总长都比两柱间长超出很多。
船
The
excess
will
include
the
overhang
of
the
stem
and
also
that
of
the
stem
where
艏
the stem is raked forward.
超出的长度包括船艉悬挂物和前倾型船艏悬挂物。
与
In modem ships having large
bulbous bows the length overall (L. O. A. ) may
夏
6
季
载
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have to be
measured to the extreme point of the
bulb.
现代大型球鼻艏船舶的总长（）应该以球鼻为端点测量。
A third length which is often used t
particularly when dealing with ship
resistance, is the length on the waterl
ine
第三种长度是水线长（）常用于计算船舶
阻力。
This is the distance measured
on the waterline at which the ship is floating
from the intersection of the stern with
the waterline to the intersection of the
stem with the waterline.
水线长指的就是在船舶所漂浮的水线上从船艏与水线的交点到船艉与水线的交点间的
距离
This length is not
a fixed quantity for a particular ship, as it will
depend
upon the waterline at which the
ship is floating and upon the trim of the ship.
一艘特定的船上的水线长不是一个固定值
,
它是取决于船舶所漂浮的水线的位置及船舶的纵
倾程度
Breadth
（型宽）
The
mid
point
of
the
length
between
perpendiculars
is
called
‘
amidships
’
and
the ship is usually
broadest at this point.
两柱间长的中点称为“船舯”且船
舶在
该处的宽度是最大的。
The
breadth is measured at this position and the
breadth most commonly used
is called
the
‘
breadth
moulded
’
.
我们所说的宽度
就是在船舯位置测得的，该宽度一
半称为“型宽”
。
It
may
be
defined
simply
as
the
distance
from
the
inside
of
plating
on
one
side
to a similar point on
the other side measured at the broadest part of
the ship.
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我们谨定义它为船舶最
宽处一侧船壳板的内侧到另一侧船壳板内侧的距离。
As
is the case in the length between perpendiculars,
the breadth moulded does
not represent
the greatest breadth of the ship, so that to
define this greatest
breadth the
breadth extreme is required.
就像两柱间长那种情况一样，
型宽不是船舶最大宽度，
以至于
有必要定义船舶的最大宽度
为计算宽度。
In many ships the breadth extreme is
the breadth moulded plus the thickness
of the shell plating on each side of
the ship.
对于很多船，计算宽度等于型宽交上船舶两侧船体外板的厚度。
In
the
days
of
riveted
ships,
where
the
strakes
of
shell
plating
were
overlapped
the
breadth
extreme
was
equal
to
the
breadth
moulded
plus
four
thicknesses
of
shell
plating, but in the
case of modem welded ships the extra breadth
consists of two
thicknesses of shell
plating only.
在铆接船的年代中，
由于
船舶外板列板
相重叠，
所以
计算宽度就等于型宽加上四倍的船壳板厚度，
然而现代焊接船仅加上两倍船壳板厚度
。
The breadth
extreme may be much greater than this in some
ships, since it is
the distance from
the extreme overhang on one side of the ship to a
similar point
on the other
side.
有
些
船
This
distance
would
include
the
overhang
of
decks,a
feature
which
is
sometimes
的
found
in passenger ships in order to provide additional
deck area.
这种距离可能
计
包括
甲板突出物
宽度，
我们能从客船
中发现这种特性，
这是为了扩大甲板面积。
算
宽
8
度
可
能
It
would be measured over fenders, which are
sometimes fitted to ships such
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as cross
channel vessels which have to operate in and out
of port under their own
power and have
fenders provided to protect the sides of the ships
when coming
alongside quays.
我们将这些突出物称为护舷材，
护舷材只用在某些船上，
例如海峡渡轮，
它们依靠
自身的动力来进出港
口，并且
停靠港口时
护舷能够保护船体舷侧免受损害。
Depth
（型深）
The third principal dimensions is
depth, which varies along the length of the
ship but is usually measured at
amidships.
第
三
This
depth
is
known
as
the
‘
depth
moulded
’
and
is
measured
from
the
underside
个
of the
plating of the deck at side amidships to the base
line.
主
尺
这种深度称为“型深”
。
指的就是
船舯舷侧甲板板下部
至基线间的距离。
度
It
Is
sometimes
quoted
as
a
‘
depth
moulded
to
upper
deck
’
or
‘
depth
moulded
是
to second deck
’,
etc.
有时引用为
“
顶
部
甲
板
型
深
”
或
“
次甲板型深”
等等。
它沿船长方向会发生变化但通常以船舯处的值为标准。
Where
no
deck
is
specified
it
can
be
taken
the
depth
is
measured
to
the
uppermost
c
o
n
t
In such cases the
depth moulded is measured from the intersection of
the
In some modem ships there is a
rounded
gunwale.
一些现代船舶有修圆的舷边。
deck line continued with the breadth
moulded line.
这种情况下，
型深就取自甲板
i
线与型宽线的交点
。
n
Other
Features
（其他特征参数）
u
o
The three
principal dimensions give a general idea of the
size of a ship but
u
there
are several ether features which have to be
considered and which could be
9
s
d
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different
in two ships having the same length,breadth and
depth.
这三个主尺度能
够总体的描述船舶的尺寸，
然而，
也得考虑其他的几个特征参数且同样长、
宽、
高的两艘船的
这些特征参数可能是不同的。
The more important of these will
now be defined.
现在来定义
这些重要的
特征参数。
Sheer
（舷弧）
Sheer
is
the
height
of
the
deck
at
side
above
a
line
drawn
parallel
to
the
base
and
tangent to the deck line at amidships.
舷弧是甲板边板离平行于基线且相切于船舯甲板线的直线的突出高度
The sheer can vary along the length
of the ship and is usually greatest at the
ends.
舷
弧
In modern
ships the deck line at side often has a variety of
shapes: it may
沿
be flat with
zero sheer over some distance on either side of
amidships and then
船
rise as
a straight line towards the ends; an the other
hand there may be no sheer
长
at
all
on
the
deck,
which
will
then
be
parallel
to
the
base
over
the
entire
length
.
方
现代船舶甲板边线的形状多种多样：一方面，
船舯两侧的某些长度方向可能是平的，
没有舷
向
弧，
但接着以向上的斜直线的形式向首尾两端延伸；
另一方面，
甲板上面可能完全没有舷弧，
会
整个船长方向上甲板都平行于基底。
发
生
In older ships
the deck at side line was parabolic in profile and
the sheer
was
quoted
as
its
value
on
the
forward
and
alter
perpendiculars
as
shown
in
Figure
.
而且首尾端最明显
So called
‘
standa
rd
’
sheer was given by the f
ormulae
：
老式船舶纵剖面上的甲板
边线呈抛物线状，
舷弧取自首尾两柱方向上的值，如图
所
示。
所谓的舷弧
“标准值”
用公
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式给出：
首舷弧
（
in
）
=
+
20
尾舷弧
< br>（
in
）
=
+10
这些公式用英制单位表示为：
首舷弧
（
cm
）<
/p>
=
+
尾舷弧
（
cm
）
=
+
It
will be seen that the sheer forward is twice as
much as the sheer aft in
these standard
formulae.
通过上面的标准公式可以看出，
首舷弧值
是尾舷弧值的两倍。
It
was
often
the
case,however,
that
considerable
variation
was
made
from
these
standard values.
然而，
这种情况时常发生。
这些标
准值也会发生相当大的变化
，
Sometimes the sheer forward was increased while
the sheer after was reduced.
有时首舷弧会变大而尾舷弧会减小。
Occasionally the lowest point of the
upper deck was some distance aft of
amidships
and
sometimes
departures
were
made
from
the
parabolic
sheer
profile.
顶
部
甲
The
value
of
sheer
and
particularly
the
sheer
forward
was
to
increase
the
height
板
of the deck above water(the
‘
height of
platform
’
as it was called)
尤其是首舷
的
弧增加了甲板离水面的高
度（称为“平台高度”
）
最
and
this
helped
to
prevent
water
being
shipped
when
the
vessel
was
moving
through
低
rough
sea. The reason for the abolition of sheer in some
modem ships is that their
点
depths are so great that
additional height of the deck above water at the
fore end
离
is unnecessary
from a sea keeping point of view.
这有助于防止
船舶在汹涌的海况中
航行时甲板上浪。
某些现代船舶废除舷弧的
原因是它们的型深如此之大，
以至于首部额外的甲
船
板高度就耐波性观点而言是不必要的。
舯
Deletion of sheer also
tends to make the ship easier to construct, but on
the
尾
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偶
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other
hand
it
could
be
said
that
the
appearance
of
the
ship
suffers
in
consequence.
<
/p>
舷弧的取消也使得船舶的建造容易得多，
但是就另一方面而言结果
是船的外
表变得难
看了。
Draught and
Trim
（吃水和纵倾）
The
draught at which a ship floats is simply the
distance from the bottom of
the ship to
the waterline.
船舶漂浮时的吃水指的就是船底离吃水线的距离。
If the waterline is parallel to the
keel the ship is said to be floating on
an
even
keel,
but
if
the
waterline
is
not
parallel
then
the
ship
is
said
to
be
trimmed.
如果水线平行于龙骨，
那么就说船舶平浮；
但是若不平行，
那么就说船舶发生了纵倾。
If the draught at the after end is
greater than that at the fore end the ship
is trimmed by the stem and if the
converse is the case it is trimmed by the bow
or by the head.
如果船尾吃水比船艏大，
那么就发生了艉倾；
若船艏吃水比船尾
大，
那么就发生了艏倾。
The
draught can be measured in two ways, either as a
moulded draught which is
the distance
from the base line to the waterline, or as an
extreme draught which
is the distance
from the bottom of the ship to the waterline.
吃水可以分为两种：型吃水，即基线离水线的距离；计算吃水
，即船底与水线间的距离。
In
the
modem
welded
merchant
ship
these
two
draughts
differ
only
by
one
thickness
of
plating
，
but
in
certain
types
of
ships
where,
say,
a
bar
keel
is
fitted
the
extreme
draught would be measured to the
underside of the keel and may exceed the moulded
draught by 15~23cm (6~9in).
对于现代焊接形式的商船，
这两种吃水仅是相差一块壳板厚
度的
区别，
但是对于
有些装有棒龙骨的船
，
计算吃水的测量至龙骨下表面，
因此计算吃水可
能比型吃水大
15-23cm(6-9in)
。
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It is
important to know the draught of a ship, or how
much water the ship is
‘
draw
ing
’,
and
so
that
the
draught
may
be
readily
obtained,draught
marks
are
cut
in the stem and the stem.
了解船
舶的吃水或者说船舶“吃”水量，这很重要，因
此一
艘船的吃水
能够直接获取，
船艏和船艉都刻有吃水标志。
These are figures giving the distance
from the bottom of the ship.
吃水标志也就是一些离船底有一定距离的一些数字。
In imperial units the figures are 6in
high with a space of 6in between the top
of one figure and the bottom of the
next one.
这是数字用英制单位表示，
6in
高
，
而且上下相邻的两个数字的间距也是
6in
。
When the water level is up to the
bottom of a particular figure the draught
in feet has the value of that figure.
当水位到达船底的某一个数字时，
吃水就是那个
数字的英尺值了。
If metric units
are used then the figures would probably be 10cm
high with a
10cm spacing.
若用十
进制单位表示，那么这些数字就可能是
10cm
高
，间隔
10cm
。
In many large vessels the structure
bends in the longitudinal vertical plane
even
in
still
water
t
with
the
result
that
the
base
line
or
the
keel
does
not
remain
a straight line.
就许多大型船舶而言，
即使是在平静的海况下，
它们的纵向垂
直面都发生了弯曲，
结果是
基线或龙骨都不能保持为一条直线。
The mean draught at which
the vessel is floating is not then simply obtained
by taking half the sum of the forward
and after draughts.
这就意味着船舶
漂浮时吃水不能仅仅用艏艉吃水和的一半来表示。
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To ascertain how much the vessel is
hogging or sagging a set of draught marks
is
placed
amidships
so
that
if
da
，
dx
and
df
are
the
draughts
at
the
after
end,amidships and the forward end
respectively then
为了确定船舶中拱或中垂程度，
< br>在船舯做了一套吃水标志，因此如果船尾、船舯和船艏吃水分别为
da
、
dx
和
df
那么
中拱或中垂
=-d
x+
（
da+df
）
< br>/2
When use is made of
amidship draughts, it is necessary to measure the
draught on
both
sides
of
the
ship
and
take
the
mean
of
the
two
readings
in
case
the
ship
should
测量船舶两侧吃水，
使用两个数
be
heeled to one side or the other.
使用船舯吃水时
，
据是必要的，
以防船舶向一
侧或另一
侧倾斜。
The difference between
the forward and after draughts of a ship is called
the
‘
trim
’
, so that trim T = da - df, and as previously
stated the ship will be said
to be
trimming by the stern or the bow according as the
draught aft or the draught
forward is
in excess.
船舶首尾吃水的不同称为“纵倾”因
而
纵倾
T=
d
a-
d
f
，
正如前面所说的那样，
船舶艉吃
水或艏吃水过多时，
将发生艏倾或艉倾。
For a given
total load on the ship the draught will have its
least value when
the ship is on an even
keel.
对于稳定航行的船，
在已知的总载荷作用下，
船舶吃水将有
一个最小值。
This is an important point when a ship
is navigating in restricted depth of
water or when entering a dry dock.
这一点对于在限制水深的区域航
行的船或船舶进
入干船坞时很重要
Usually a ship should be designed to
float on an even keel in the fully loaded
condition, and if this is not
attainable a small trim by the stem is aimed at. <
/p>
船
舶的设计通常应满足在满载荷作用下船能够平浮的要求，
如果船达不到这种状况，
那么就设
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计成小角度艉倾。
Trim
by
the
bow
is
not
considered
desirable
and
should
be
avoided
as
it
reduces
the
’
height of
platform
’
forward and
increases the liability to take water on
board in rough seas.
艏倾这种情况是不
期望发生的，
应该避免
,
这是因为艏倾
会降低艏部
“平台高度”
，增加在恶劣海况中甲板上浪的可能性
。
Freeboard
（干舷）
Freeboard may be defined as the
distance which the ship projects above the
surface of the water or the distance
measured downwards from the deck to the
waterline.
干舷被定义
为船舶离水面的距离，
或甲板与下部水线的间距。
The freeboard to the weather deck, for
example, will vary along the length of
the ship because of the sheer of the
deck and will also be affected by the trim,
if any. Usually the freeboard will be a
minimum at amidships and will increase
towards the ends.
例
如
，
由
干
舷对船舶的适航性有重要的影响。
Freeboard
has an important influence on the seaworthiness of
a ship.
于
The
greater
the
freeboard
the
greater
is
the
above
water
volume,
and
this
volume
受
provides
reserve buoyancy, assisting the ship to rise when
it goes through waves.
到
干舷值越大，
船舶水上部分的体积也就越大，而且这部分体积用来提供储
备浮力，促使
甲
船舶在波浪中航行时能够
上浮
。
板
舷
The above
water volume can also help the ship to remain
afloat in the event
弧
15
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of damage.
水上部分的体积也能帮助船舶破损时保持漂浮状态。
It will be seen later that freeboard
has an important influence on the range
of stability.
干舷对船舶稳定性的变化有重要影响，这种情况后面将会介绍到
Minimum
freeboards
are
laid
down
for
ships
under
International
Law
in
the
form
of Load Line Regulations.
国际法
载重公约
中设定了船舶干舷最小值。
Lesson 4 Basic Geometric
Concepts
（基本几何概念）
The
main
parts
of
a
typical
ship
together
with
the
terms
applied
to
the
principal
parts are
illustrated in
示例船舶的主要部分以及相关的名字都在图
中
画出来了。
Because,at
first,they
are
of
little
interest
or
influence,superstructures
and
deckhouses
are
ignored
and
the
hull
of
the
ship
is
considered
as
a
hollow
body
curved
in all
directions,surmounted by a watertight deck.
首先，
由于没有利害关系或影响，
船舶上层建筑和甲
板室都被忽略了，
船体看成所有方向上都是曲线、
上部用水密甲
板覆盖的
中空壳体。
Most
ships
have
only
one
plane
of
symmetry,
called
the
middle
line
plane
which
becomes the principal plane of referenc
e.
大多数船舶只有一个对称面，
称为中线面，
这是主要谈论的面。
The shape of
the ship cut by this plane is known as the sheer
plan or profile.
被该面截得的船型称为舷弧面或纵剖面。
The
design
waterplane
is
a
plane
perpendicular
to
the
middle
line
plane,
chosen
as a plane of
reference at or near the horizontal; it may or may
not be parallel
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to the
keel.
设计水线面垂直于中线面，
取作水平或接近水平的面；
它可能不与龙骨平行。
Planes perpendicular to both the middle
line plane and the design waterplane
are called transverse planes and a
transverse section of the ship does, normally,
exhibit symmetry about the middle
line.
与中线面和设计水线面都垂直的面称为横剖面，<
/p>
船舶横剖面通常关于船体中线面对称。
Planes at right angles to the middle
line plane, and parallel to the design
waterplane are called
waterplanes,whether they are in the water or
not,and they
are usually symmetrical
about the middle line.
与中线面成一定交角且平行于设计水<
/p>
线面的平面称为水线面，
无论在水中与否，
它们都成立，
而且它们通常关于中线面对称。
Waterplanes are not necessarily
parallel to the keel. Thus, the curved shape
of a ship is best conveyed to our minds
by its sections cut by orthogonal planes.
水线面不一定平行于龙骨。
因此，
通过被正交面截得的面，
能够向我们最清楚地表达船舶的
曲线形状。
Lesson 5 Ship Form and Form
Coefficients
（船型系数）
Requirements of Ship
Form
（船型需求）
The
hull form of a ship must be designed to fulfil
certain requirements, and
the first to
be considered is the provision of sufficient
buoyancy to carry the
v
a
r
In
other words the ship form must provide a certain
displacement up to the load
i
waterline. Calling this
displacement
△
it follows th
at
换句话说，
船舶必须提
o
供一定的排水量，直至载重水线处。
称这个排水量为△，表示如下
u
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△
=g
Vρ
were
ρ
is the density of the water in which
the ship is floating, g is the
acceleration due to gravity,and V is
the underwater volume.
其中
ρ
是船舶所在水域的密度，
g
是重力加速度，
V
是水下部分的体积。
It may be said, therefore, that
the designer must so design the form that some
underwater volume V is
obtained.
因此可以说设计师应该有目的地设计船型
，以便能够获得一些水下部分体积
V
。
Another important requirement of the
underwater form is that the centroid of
the volume must be in a particular
position in the fore and aft direction.
水下部分的船型的另一个重要的要求就是，
< br>体积中心必须在首尾方向的特定位置处
Form
coefficients
（船型系数）
If the ship form consisted simply of
rectangular block of length equal to the
length
between
perpendiculars,
breadth
equal
to
the
breadth
moulded,and
depth
equal
to
the draught,then the underwater volume would be
given simply by
如果船型仅由长、
宽、
深分别等于两柱间长、
型宽、
吃水的长方体组成，
那么水下部分体
积将仅由如下给
出
V=L
×
B
×
d
It
will, however, be clear that the actual volume is
less than the volume of this
block,
or
in
other
words
the
ship
form
can
be
imagined
to
have
been
cut
out
of
this
block.
而
，
真实的体积很明显小于这个长方体体积，
或者换句话说，
船型假想为是从这
个长
方
体中切出来的。
What is called the ‘block coefficient’
is the ratio of the actual volume of the
underwater form to the volume LBd. In
other words
所谓的“方形系数”就是真实船
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型水下部分体积与
L
Bd
体积的比值。用另一种方式表示为
Block coefficient
CB=V/(L×B×d)
方形系数
CB
=V/
（
L
×
B
×
d
）
When
the
ship
designer
has
decided
what
volume
is
required
he
then
has
four
factors
to
consider:
the
length,
breadth
and
draught
of
the
ship,and
also
the
block
c
o
There is an
infinite number of combinations of these factors
which will give the
e
required result and the
problem is to decide what are the best values of
the four
f
parameters.
In
the
meantime,however,
the
block
coefficient
only
will
be
considered.
f
这些因数有无数种组合，
能够给出最理想的结果，
并且问题就是如何决定这四个系数的最佳
i
值。
同时，
但唯独将只考虑方形系数。
c
i
Generally it is
governed by resistance
considerations.
这一般是由阻力因素决定的。
e
At
this
stage
it
may
be
said
that
fast
ships
require
low
values
of
block
coefficient
n
while in slow ships high
values of the block coefficient are
permissible.
t
在此阶
段，
可以说高速船舶要求方形系数值低，
而低速船只允许方形系
数值高。
.
In
slow
speed
ships,
say
of
the
bulk
carrier
type,
a
high
value
of
block
coefficient
当
means a large displacement
on given principal dimensions, which means that
there
船
is a large amount of
displacement available for the carriage of cargo.<
/p>
对于低速
舶
船，
例如散货船，
高的方形系数值意味着在主尺度一定的情况下排水量大，
< br>这就意味着有很大
设
排水量来维持货物运输。
计
In fast ships it is
essential to keep down the value of the block
coefficient,
师
so they
normally have lower block coefficients than slow s
hips.
对于高速船，降低
已
方形系
数值是必要的，因此相比于低速船它们有更低的方形系数值。
经
19
决
定
需
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The
influence of block coefficient on the shape of the
hull form is that in ships
with high
values of this coefficient considerable parallel
middle is likely to be
found
and
the
slopes
of
the
waterlines
at
the
ends
are
steep,
whereas
with
low
block
coefficients parallel
middle is often quite short or may not exist at
all and the
slopes of the waterlines at
the ends will be small also.
方形系数对船型的影响表
现为，
对于方形系数值高的船，
会发现
平行中体程度相
当大而且船舶两端水线范围陡，
而对
于方形系数值低的船，
平行中体通常很小或可能
完全不存在，
而且船舶两端水线范围也很陡。
Another
coefficient
which
is
useful
is
what
is
known
as
the
‘prismatic
coefficien
t’.
另外一个有用的系数就是所谓的“棱形系数”
。
The ship form could be
imagined to have been cut from a prism of length
equal
to
the
length
of
the
ship
and
of
constant
cross
section
of
area
equal
to
The
immersed
midship area. Thus<
/p>
船型可以想象为是从棱柱体中切割出来的，
棱柱体长度等于船长且
截面
积等于船舯浸没部分的面积的。
因此
Prismatic coefficient
Cp=V/(Midship area×L)
棱形系数
Cp=V/
（舯面积×
L
< br>）
This particular
coefficient has its use in dealing with
resistance.
处理船舶阻力时能用到这个特殊的系数。
A coefficient which is used to express
the fullness of the midship section
is
the
midship
area
coefficient.
If
the
midship
section
is
imagined
to
be
out
out
of a
rtx:tangle of dimensions breadth ×draught then
一个用来表示船舯剖面丰满
度的系数是中站面系数。
若将船舯剖面想象为是从尺度等于船宽吃水的矩形中切割出来的，
那么
Midship area coefficient
Cm=Midship area/(B×d)
中站面系数<
/p>
Cm=
舯面积
/
（
B
×
d
）<
/p>
The three coefficients so
far discussed are related to one another
since
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CB=V/(L×B×d)=[V/(Midship area×L)
]×[Midship area/(B×d)]
CB=Cp×Cm
目前为止讨论的这三种系数是相互关联的，因为
CB=V/
（
L
×
B
×
d
）
=[V/
（舯面积
×
L
）
]
×
[
舯面积
/
（
B
×
d
）
]
CB=Cp
×
Cm
Generally
speaking,
as
the
block
coefficient
becomes
finer
the
midship
area
coefficient becomes
finei, as does the prismatic
coefficient.
一般认为
,
方形系数越小，中站面系数也越小，棱形系数也一样。
The
waterplane
area
of
a
ship,
.
the
area
enclosed
by
any
particular
waterline,
can also be
expressed in terms of a coefficient and the area
of the circumsecting
rectangle. Hence
waterplane area coefficient
Cw=Waterplane area/(L×B)
船舶水线面面积，
即被特殊水线包围的面积，
也能够用一个系数和该面的外切矩形来表
示。因此，水线面系数
Cw=
水线面面积
/
< br>（
L
×
B
）
Chapter 2 Ship
Rudiments
（船舶基本原理）
Lesson 7 Equilibrium and
Stability
（平衡性和稳定性）
Introduction
（引言）
In chapter 2 the condition for static
equilibrium was defined in terms of the
balance of forces and moments.
第二章中的静力平衡状态是以力和力矩的平衡来定义的
From Newton’s laws of motion, it is
seen that a body can be at rest or moving
at constant speed only if the sum of
all forces and moments acting on the body is
equal to zero.
从牛
顿运动定律中可以知道，
若作用于物体上的合外力和和外力矩等于零，
< br>那么物体将
21
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处于静止或以恒定不变速度运动。
The concept of stability is somewhat
more complex.
稳定性的概念某种程度上更
复杂些。
Here,one
is
concerned
with
whether
or
not
a
body
will
return
to
an
initial
state
of
static equilibrium when disturbed by an unbalanced
force or moment.
其中一种
情况与物体受到
不平衡的力或力矩的干扰时是否能够回复到初始静力平衡状态有关。
While
in
the
broader
sense
equilibrium
refers
to
an
overall
balance
of
forces,
which involves no
acceleration or deceleration, static equilibrium
is defined as
follows:A body at rest is
said to be in static equilibrium.
静力平衡如下
定义：处
于静止状态的物体就出于静力平衡。
但广义上的平衡指
的是合力的平衡，
与加速和减速无关。
If this body is disturbed by an outside
force and returns to its original
position
when
the
force
is
removed,
it
is
said
to
be
in
stable
equilibrium.
An
example
of
this condition is a round ball lying in an upward
facing bowl,as in Figure (a).
若
此
物
The
ball will always return to its rest position when
disturbed by an outside
体
force.
受
外
当受到外力作用时，圆球将总能回到静止位置。
力
Figure (b)
illustrates the condition of neutral
equilibrium.
作
图
（
b
）用
图说明了中性平衡状态。
用
而
The ball lying
on a flat horizontal plane will come to rest at
any point on
the plane if motion is
started and then stopped by an outside force
(including
当
friction).
若球在水平面上运动，
然后受到外力
（包括摩擦力
）
作
用而静止，那么球将停
外
22
力
移
除
v1.0
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在水平面上的任意位置。
Unstable equilibrium is illustrated
in Figure (c) ,where a round ball
is
balanced
on
top
of
an
inverted
bowl.
Any
slight
disturbance
of
the
balanced
position
will result in the
ball rolling off the bowl.
图
（
c
）用图说明了非稳定平衡，
图中
圆球在倒置的碗的顶部处于平衡状态。
平
衡位置的任意细微的扰动将导致圆球从碗上滚落下
来。
The Basis for Ship
Equilibrium
（船舶平衡原理）
Consider a ship floating upright on the
surface of motionless water.
假如一艘船平浮于静止的水面上。
In order to be at rest or tn
equilibrium, there must be no unbalanced forces
or moments acting on it.
为了使
船静止或出于平衡状态，
那么就一定没有不平衡的力和
力矩作用
于船上。
There are two forces
that maintain this
equilibrium
：
the force of
gravity and
the force of buoyancy.
有两个维持这种平衡的力：重力和浮力。
When the ship is at rest, these two
forces are acting in the same vertical
line,and
in
order
for
the
ship
to
float
m
equilibrium,
they
must
be
exactly
equal
numberically as well
as opposite in direction.
船舶静止时，这两个力作用在同
一条
竖直线上，而且，为了使船平浮于水面上，那么力就一定是大小相等方向相反。
The force of gravity acts at
a point or center of gravity where all of the
weights
of the ship may be said to be
concentrated.
重力作用于一点，
或者这样说，
重心是船
舶全部重量集中的点。
Gravity always acts vertically
downward.
重力作用方向总是竖直向下。
The force of buoyancy acts through the
center of forces is considered to be
23
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acting.
通过力的中心的浮力被认为作用于力的中心
This forces always acts vertically
upward.
这个力的作用方向总是竖直向上。
When
the
ship
is
heeled,
the
shape
of
the
underwater
body
is
changed,
thus
moving
the position of the
center of buoyancy.
船舶横倾时
,
水下部分的形状发生变化，因此浮力中心的位置发生变化。
Now, when the ship is heeled by
an external inclining force and the center of
buoyancy has been moved from the
centerline plane of the ship, there will usually
be a separation between the lines of
action of the force of gravity and the force
of buoyancy.
如果，
船
舶受到外界倾斜力作用发生横倾，
浮心偏离了船舶中线面时，
重
力与
浮力作用线将发生了分离。
This
separation
of
lines
of
action
of
the
two
equal
forces,
which
act
in
opposite
directions,
forms
a
couple
whose
magnitude
is
equal to
the
product
of
one
of these
forces(that
is,displacement) and the distance separating them.
两个作用于相反方向上的力的作用线的分离，
形成
了一个力偶，
其大小等
于其中任意一
个力
（即，
排水量）
和两个力作用线的间距的乘积。
In
Figure (a) , where this moment tends to restore
the ship to the upright
position, the
moment is called a positive righting
moment
，
and the perpendicular
distance between the two lines of
action is the righting arm
(GZ).
图
（
a
）中，
这个力矩试图去使船回复至平浮位置，
这种力矩称为正扶正力矩，
而且，
两个力的作用线
间
的距离称为正扶力臂（
GZ
上横线）
。
Suppose
now
that
the
center
or
gravity
is
moved
upward
to
such
a
position
that
when
the
ship
is
heeled
slightly,the
buoyant
force
acts
in
a
line
through
the
center
o
24
f
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浮力作用线通过重心。
In the
new position, there are no unbalanced forces, or
in other words, the
ship has a zero
moment arm and a zero moment.
在这个新位置，没有不平衡力，或者说，船舶力臂和力矩都为零。
the
ship is in neutral
equilibrium,with both the righting
moment and the
righting
arm
equal
to
zero.
船舶处于中性平衡状态，其中正扶力矩和正扶力臂都等于零。
If
one
moves
the
center
of
gravity
still
higher,as
in
Figure
(c),
the
separation
between the lines
of action of the two forces as the ship is
inclined slightly is
i
n
In this
case,the moment does not act in the direction that
will restore the
ship
to
the
upright
，
but
rather
will
cause
it
to
incline
further
In
such
a
situation,
t
the
ship
has
a
negative
righting
moment,
or
capsizing
moment,
and
a
negative
righting
h
arm(GZ).
e
这种情况下，力矩不是作用于使船
回复平浮的方向，
而是使船倾斜程度更大。
这种状态
下，
船舶产生反向正力矩或者说是倾覆力矩，和反向正力臂（
GZ
上横线）
o
p
These three
cases illustrate the forces and relative position
of their lines
p
of action in
the three fundamental states of
equilibrium.
o
绘图说
明了这三种情况下的力和在三种基本平衡状态下它们作用线建的相对位置。
s
The Position of the
Metacenter and
Equilibrium
（稳心和平衡位置）
i
t
The metacenter
M,discussed in chapter 3,is defined as the
intersection of the
vertical
through
the
center
of
buoyancy
of
an
inclined
body
or
ship
with
the
upright
e
vertical
when the angle of inclination approaches zero as a
limit.
稳心
M
，已经
在第三章谈论过了，
定义为通过倾斜物体或船舶的浮心的竖直线
与船舶的横倾角度限制为零
d
25
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r
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时通过浮心的垂直线的交点。
This
intersection
then
lies
on
both
the
line
of
action
of
the
center
of
gravity
when the ship is
upright and the line of action of the buoyant
force.
而，
这个交点的位置取
决于船舶平浮时重心作用线和浮力作用线。
Consequently, it can be readily seen
from the previous section that when the
metacenter is above the center of
gravity,as in Figure (a) ,there is a positivie
righting
moment
formed
when
the
ship
is
inclined,
and
the
ship
is
tn
stable
equilibrium.
因
此
When the
metacenter and the center of gravity coincide, as
in Figure 7.
2(b)
，
，
no moment
is produced and the ship is in neutral
equilibrium.
很
容
若
稳
易
When
the
metacenter
is
below
the
center
of
gravity,as
in
Figure
(c),a
negative
心
从
or capsizing
moment is formed,and the ship is in unstable
equilibrium.
与
前
若
中
面
稳
心
In considering this relation
between the metacenter and the ship's state of
的
心
重
equili
brium,it is necessary to remember that the
definition of the metacenter is
剖
位
合
actually
valid
only
for
angles
of
inclination
from
0°up
to
the
range
of
7°to
10°.
面
置
，
当讨论稳心与船舶平衡状态的关系时，
有必要记住，
稳心的定义仅适用于船舶倾斜角为
0
°
至
中
比
如
7
°
或
1
0
°
。
<
/p>
看
重
图
出
Beyond
this,
the
intersection
of
the
lines
of
action
of
the
center
of
buoyancy
心
，
and the vertical
centerplane of the ship has no significance.
低
，将没有力矩产生，
船舶处于中性平衡状态。
稳
，
26
心
如
位
图
置
v1.0
可编辑可修改
除此以外，
浮心作用线与船舶垂直中心面的交点没有意义了。
< br>
Therefore, the use of the relative
positions of the metacenter and the center
of gravity as a criterion of stability
is limited to small angles of inclination.
因此，
使用稳心和重心的相对位置作
为评定稳定性的标准这种方法，
仅限于小角度倾斜。
Obviously stability itself cannot be
limited to such a restricted range.
稳定性明显不能仅限于如此限制范围。
Consequently,one must differentiate
between overall stability at any angle
of inclination and initial stability at
small angles of inclination.(θ<10°)
因此，<
/p>
我们应该区分任意倾斜角度的整体稳性和小角度（θ
<10
°）倾斜的初稳性。
Metacentric Height:A Measure of Initial
Stability
（稳性高：衡量初稳性）
The metacentric height,both transverse
and longitudinal, is defined as the
distance
between
the
center
of
gravity
and
the
transverse
or
longitudinal
metacenter,
measured vertically tn the upright
equilibrium position.
稳性高度，<
/p>
包括横向和纵向，
定义为船舶平浮时重心与横稳心或纵稳心间的竖
直距离。
In
Figure
7,
3,
the
metacentric
height
is
GM,
with
the
ship’s
center
of
gr
avity
at either G or other wise
specified,the metacenter and metacentric height
refer
to the transverse metacentric
height. If the longitudinal metacenter is being
discussed, the associated metacentric
height is designated GML and spoken of as
the longitudinal metacentric
height.
图
中
，
G
M
< br>表示稳心高度，
而船舶重心用
G
或
G1
表示。
除非特别说明，
要不然稳心和稳心
高指代的是横稳心高度。<
/p>
若讨论纵稳心，
那么相对应的稳心高就定义为
GM1
，
并称为纵稳心高。
If M is above G, the metacentric height
is positive. If M is below
G
，
GM is
negative.
27
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若
M
在
G
上面，
那么稳心高度值就为正。
若
M
低于
G
，那么
< br>GM
（上横线）的值就为负。
GM
is
the
measure
of
the
initial
stability
or
the
ability
of
the
ship
to
resist
initial
heel
from
the
upright
position.
A
ship
with
a
positive
GM
will
tend
to
float
upright and will
resist initial inclining ship with a negative GM
will not float
upright and may be said
to be initially unstable. Some ships develop a
negative
GM
because
of
a
condition
of
off-center
loading
and
become
unstable
in
the
upright
position.
Because
of
the
change
in
the
underwater
hull
form
with
angle
of
inclination,
such
a
ship
will
list
to
either
port
or
starboard
until
it
reaches
a
point
of
stable
equilibrium.
用来衡量
初稳性，
或者说是衡量
船舶抵抗从平衡位置开始横倾的能力
。
船
GM
（上横线）
舶
GM(
上横线
)
值为正时，
船将处于正浮状态
，
且能初步抵抗倾斜力作用
。
船舶
GM(
上横线
)
值
为负时，
船不能正浮，
而且可能开始变
得不稳定
。
由于偏心载荷的作用，
使得
一些处于平浮
位置的船的
GM(
上横线
)
变为负值，
船变得不稳定了。
由于船体水下部分的体积因倾斜角而发
生变化，
这样的船将向左倾或向右倾直至到达平衡点
。
Since the longitudinal metacenter ML is
always located quite high above the
ship ( Figure ,it is possible to state
that a negative longitudinal metacentric
height GML will not occur under noirmal
conditions. Longitudinal stability is
discussed in the next
chapter.
由
于
纵
（引言）
稳
心
A
ship
when
at
rest
in
still
water
experiences
hydrostatic
pressures
which
act
Lesson
8 Resistance
（阻力）
normally to the immersed surface. It
has already been stated when dealing with
M
buoyancy and stability
problems that the forces generated by these
pressures have
L
28
总
是
位
v1.0
可编辑可修改
a vertical
resultant which is exactly equal to the
gravitational force acting on
the mass
of the ship, . is equal to the weight of the ship.
If the forces due to
the
hydrostatic
pressures
are
resolved
in
the
fore
and
aft
and
transverse
directions
it
will
be
found
that
their
resultants
in
both
of
these
directions
are
zero.
Consider
what happens when the ship moves
forward through the water with some velocity V.
The
effect
of
this
forward
motion
is
to
generate
dynamic
pressures
on
the
hull
which
modify
the original normal static pressure and if the
forces arising from this
modified
pressure
system
are
resolved
in
the
fore
and
aft
direction
it
will
be
found
that
there
is
now
a
resultant
which
opposes
the
motion
of
the
ship
through
the
water.
If
the
forces
are
resolved
in
the
transverse
direction
the
resultant
is
zero
because
of
the symmetry of the ship form.
< br>停
在
静
水
中
的
船
受
A
nother
set
of
forces
has
to be
considered
when the
ship
has
ahead
motion.
All
到
fluids possess to a greater
or less extent the property known as viscosity and
一
therefore
when
a
surface
such
as
the
immersed
surface
of
a
ship
moves
through
water,
般
tangential forces are
generated which when summed up produce a resultant
opposing
作
the motion of the
ship. The two sets of forces both normal and
tangential produce
用
resultants which act in a
direction opposite to the direction in which the
ship
于
is moving. This total
force is the resistance of the ship or what' is
sometimes
没
called the
’drag‘.It is sometimes convenient to split up the
total resistance
入
29
水
中
v1.0
可编辑可修改
into a
number of components and assign various names to
them. However, whatever
names they are
given the resistance components concerned must
arise from one of
the
two
types
of
force
discussed
t
i.
forces
normal
to
the
hull
surface
or forces
tangential to that
surface.
船前移时，
还得考
虑另一组力。
所有流体多多少少都有所谓的粘性，
因此当
像没入水中
船体表面那样的表面在水中移动
时，
就会产生一些
次要的力
，
将这些
次要的力
相加
就会产生
一个阻止船前移的合力。
这两组力，
< br>包括
主要的和次要的
力
，
产生作用于与船舶移动方向相
反的方向上的
合力。
这种合力是船舶阻力，
或
者有时称为
?
拖曳力
?
。有时将总阻力
分解成一些分力是很方便的，
并且赋予它
们不同的名字。
但是，
无论它们被赋予了何种名字，
这些相关的阻力分力必须
源
于上述讨论的两种类型力中任意一个，即
< br>作用于船体的主要力
和次要力
。
The
ship
actually
moves
at
the
same
time
through
two
fluids
of
widely
different
densities.
While
the
lower
part
of
the
hull
is
moving
through
water
the
upper
part
is
moving
through
air.
Air
，
like
water,
also
possesses
viscosity
so
that
the
above
water portion of a
ships hull is subjected to the same two types of
forces as the
underwater portion.
Because, however, the density of air very much
smaller than
water the resistance
arising from this cause is also very much less in
still air
conditions. However, should
the ship be moving head on into a
wind
，
for example,
then
the
air
resistance
could
be
very
much
greater
than
for
the
still
air
condition.
This type of
resistance is, therefore, only to a limited extent
dependent on the
ship speed and will be
very much dependent on the wind speed.
实
际
上
船
在
30
两
种
v1.0
可编辑可修改
上由风速决定。
Types
of Resistance
（阻力类型
）
It was stated
above that it is sometimes convenient to split up
the total
resistance into a number of
components; these will now be
considered.
上面已经陈述过，
< br>有时将总阻力分解成一些分力是很方便的；
现在将讨论这些分力。
The redistribution of normal
pressure around the hull of the ship caused by
the
ahead
motion
gives
rise
to
elevations
and
depressions
of
the
free
surface
since
this
must
be
a
surface
of
constant
pressure.
The
result
is
that
waves
are
generated
on the surface of
the water and spread away from the ship. Waves
possess energy
so
that
the
waves
made
by
the
ship
represent
a
loss
of
energy
from
the
system.
Looked
at in another way the
ship must do work upon the water to maintain the
waves. For
this reason the resistance
opposing the motion of the ship due to this cause
is
called
‘wave
-
making
resistance’.With
deeply
submerged
bodies
the
changes
in
the
normal pressure around
the hull due to ahead motion have only a small
effect on
the free surface so that the
wave resistance tends to be small or negligible in
such cases.
由
于
前
行
运
动
The
resistance
arising
due
to
the
viscosity
of
the
water
is
appropriately
called
引
‘viscous
resistance’
or
often
‘frictional
resistance’.
The
thin
layer
of
fluid
起
actually
in
contact
with
the
immersed
surface
is
carried
along
with
it
but
because
的
of
viscosity a shear force is generated which
communicates some velocity to the
31
船
体
周
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可编辑可修改
adjacent
layer.
This
layer
tn
turn
communicates
velocity
to
the
next
layer
further
out
from the hull and so on. It is clear then that
there is a mass of fluid which
is being
dragged along with the ship due to viscosity and
as this mass requires
a force to set it
in motion there is a drug on the ship which is the
frictional
resistance. The velocity of
the forward moving water declines in going
outwards
from
the
hull
and
although
theoretically
there
would
still
be
velocity
at
infinite
distance the
velocity gradient is greatest near the hull and at
a short distance
outwards
the
forward
velocity
is
practically
negligible.
Forward
velocity
is
therefore confined to a
relatively narrow layer adjacent to the layer is
called
the ‘boundary layer’. The width
of the layer is comparatively small at the bow
of the ship but thickens in going
aft,as will be seen from Figure ,which shows the
fall off in velocity at various
positions in the length.
由于水
粘性产生的阻力适宜称为“粘性力”或常称为“摩擦阻力”
。
与
船体没入水
中部分的表面相接触的一层很薄的流体，
随船一起移
动，
由于水的粘性作用产生了一个剪切
力，
该剪切力将向相邻的流体层传递一些速度。
这层流体又依次向离船体更远的下一层流
体
传递速度，
等等。
这样就很清楚了，
有大量的流体由于粘性作用将被拖着与船一起运动，
而
且由于这些液体一个力来运动，
所以船体上将产生一个拉力，
即摩擦阻力。
从船侧向外，
水
前行的速度逐渐衰减。
虽然理论上无限远处的水仍然有速度，
但是船体附近的水的速度梯度
最大，
离船很近
的一段距离处水的前行速度事实上可以忽略不计。
因
此水的前行速度仅限于
临近船体相对较窄的流体层。
这流体层称为“边界层”
。
流体层的宽度在船首处
较窄，但是
向船尾逐渐变厚，
就像图
所
示的那样，
沿着船长方向的不同位置处速度逐渐减小。
The
actual
thickness
of
the
boundary
layer
is
indeterminate
but
the
point
where
the forward velocity has fallen to
about 1% of what it would be if the water were
frictionless is considered to be the
outer extremity of the boundary layer. Thus,
in Figure 8. 1 where the velocity V1 of
the water relative to the body is of what
it
would
be
at
the
same
point
if
the
water
was
frictionless
would
be
the
outer
edge
32
v1.0
可编辑可修改
of the
boundary layer.
边界层的真实厚度是不确定
的，
但如果水没有摩擦力，
那么前行速度减小至
原来的
1%
的
点被认为是边
界层的最外层。所以，若水无摩擦，那么图
中
水
相对于
船体的速度
V1
是
原
< br>来速度
的
倍
的地方就是边界层的外缘。
Theoretical investigations on flow
around immersed bodies show that the flow
follows the type of streamline pattern
shown in Figure where there are sharp
changes of curvature on the surface of
the body, and party due to the viscosity
of the fluid, the flow separates from,
the surface and eddies are formed. This
separation
means
that
the
normal
pressure
of
the
fluid
is
not
recovered
as
it
would
be
according
to
theory
and
in
consequence
a
resistance
is
generated
which
is
often
referred
to
as
’eddy
-
making
resistance’.This
type
of
resistance,
like
wave
-making
resistance, arises from a
redistribution of the normal pressures around the
hull
in
contrast
to
the
frictional
resistance
which
arises
because
of
tangential
viscous
forces.
对浸没船体周围流体
的研究表明，
流体遵循流线型
，如图
所示。然而，船体表面曲率
变化非常的大的地方，
部分是由于流体粘性的作用，
流体与船体表面发生分离，
形成漩涡。
这
种分离意味着流体主压力没有恢复到原来的状
态，
由理论结果产生了一个称之为
“
漩
涡阻力”
的阻力。
对比与由粘性力产生的摩擦阻力，
这种阻力像兴波阻力一样是有船体周围
主压力
的<
/p>
重新分布造成的。
The
fourth type of resistance! is that due to the
motion of the above-water
form
through
the
air,
as
has
already
been
mentioned,
and
could
consist
of
a
combination
of frictional and eddy resistance.
这
四
种
33
已
经
提
The
shape of a ship hull is determined by many
competing influences. For ease
v1.0
可编辑可修改
of
construction,
it
should
be
a
rectangular
box;
for
adequate
transverse
stability,
it
must
be
wide;
for
adequate
strength
as
a
beam
being
bent
in
a
longitudinal
plane,
it must be deep. All
these factors influence the shape of a hull, but
often the
primary
factor
is
the
dynamic
interaction
of
the
hull
with
the
water.
The
interactions that govern the resistance
of the hull to steady forward
motion
—
a
resistance that determines the choice
of propulsive power
—
usually
demand the
greatest attention from the
naval architect.
船体形状是由
很多相互矛盾的影响因素
造成的。
为了便于建造，
船体应当为矩形盒型；
为
了保持一定的
横向稳定性，
船必须宽；
为了维持纵向平面上梁的弯曲强度，<
/p>
船必须深。
所有这
些因素都影响船体形状
，
但是通常最主要的因素就是
船体与
水间的动态交互作用。
这种交互
作用决定船体稳定前行阻力——
这阻力决定推进功率的选择，通常要求造船师的极大关注。
Resistance to steady forward motion has
four components:(1)friction between
the
water
and
the
hull
surfaces,(2)energy
expended
m
creating
the
wave
system
caused
by
the hull, (3)energy put into eddies shed by the
hull and its appendages.,the
ruddier),
and(4)resistance by the air to above-water, parts
of the ship.
影
响
Frictional
resistance is proportional to the product of water
density, area
稳
contact
with
the
water,square
of
water
speed
relative
to
the
ship,
and
a
friction
of
定
coefficient. This
resistance can be minimized by reducing the area
of a hull’s
前
wetted
surface,but
usually
very
little
can
be
accomplished
in
the
face
of
many
other
行
demands on hull size and
shape. A smooth surface is an obvious factor in
reducing
的
fricition,but
a
surface
that
is
smoother
than
ordinary
painted
steel
has
a
benefit
阻
is
that
trivial
compared
to
its
cost.
The
friction
coefficient
is
largely
a
function
力
of the
Reynolds number(the product of water density times
ship speed times ship
由
length,divided
by
water
viscosity);it
is
not
controllable
by
a
designer
since
water
四
34
个
部
v1.0
可编辑可修改
density
and viscosity are beyond control and ship length
and speed are almost
inevitably
dictated by other considerations. The friction
coefficient was the
subject
of
intense
research,
especially
during
the
first
half
of
the
20th
century,
but
since that time most ship designers have employed
values standardized by the
International Towing Tank
Conference.
摩擦阻力与，
水的密度、
船体与水的接触面积、
水相对于船的速度的平方和
摩擦系数，
的
乘积成正比。
能够通过减
小船体湿表面积来使摩擦阻力最小化，
但是通常在为了维持船体尺
寸和形状的要求下，
这种情况是不可能实现的。
使接触面光滑
是减小摩擦力的最明显的因素，
但
是
相
对
于
Wave
making
and
eddy-
making
resistance
components
are
often
lumped
into
a
single
造
“residuary
resistance,”
especially
when
resistance
measurements
are
extrapolated
价
from
model
testing.
Wave
making
is
usually
by
far
the
larger
component
of
residuary
而
resistance;it is therefore
given more attention in research and in the
designing
言
of a hull.
Indeed,wave making increases so rapidly as ship
speed increases that
，
it
eventually requires more power to overcome than is
practicable to build into
将
a
ship. For a ship of conventional type,it is
virtually impossible to operate at
原
a speed-to length ratio
(speed in nautical miles per hour, divided by the
square
始
root of the
waterline length in feet) higher than
approximately that realm even
油
a
trivial
increase
in
speed
requires
a
virtually
infinite
increase
in
power
in
order
漆
to fulfill the energy
demand of the wave system. Small craft can escape
this
钢
limitation by planing,
but the amount of power required for the
transition to a
表
planing
mode is beyond practicality for conventional
ships.
面
处
35
理
的
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