Chapter - 3. Natural Phenomena
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Transcript of Chapter - 3. Natural Phenomena
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Dock, Harbour & AirportEngineering
Chap – 3 “NATURALPHEN!ENA"
PREPARED BY :-
KARTIK ZALAAssi. Prof.,
Civil Engg. Departent,!ICT.
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CNTENT# "in#
"aves
Ti#es
C$rrents
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Wind is horizontal movement of air due to differences in air pressure
which are caused by differential heating and cooling.
In short wind means air in motion.
Wind Characteristics:-
Direction of wind usually specified by compass.
Frequency of wind is the percentage of the time in a year it
will blow from a particular direction.
Intensity gives the velocity of the wind.
Speed of wind is expressed in !nots" and wind stren#th is measured
in !mph.
(1 knot = 1.8! km"hr#
"I%D:-
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Waves are periodic undulations of the sea surface. Water
waves are #enerated by transfer of energy from air movin# overthe water.
Causes of Sea Waves:-Wind$
%evolution of the earth$
&ravitational force of the moon and sun$'arthuake$
)and slide and seashore$
"A!E&:-
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$ypes of Sea Waves:-
*eep sea waves
+hallow sea waves
,scillatory waves %un&ro!en waves' travellin# in deep water(
-ranslatory waves
apillary waves
+urfs %low hei#ht and lon# waves produced &y wind(
+urges %produced &y cyclone(-sunami %produced &y eruption of volcano or earthqua!e(
"A!E& '(onti)*:-
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"A!E& '(onti)*:-
D))* S)+ W+,) SCI+$/0 W+,)S
C+*I+/0 W+,)S
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Wave ,elocity:-
Where$ ) = )ength
- = Wave /eriod
Fetch:-
+traight line stretch of open water available for wave growth
without the interruption of land is called fetch.
Where$ 0 = Wave 0eight (m#
= etch (km#
"A!E& '(onti)*:-
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Wave en#th:-
Where$ ) = )ength of wave (m# =
- = Wave /eriod (sec#
"A!E& '(onti)*:-
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Wave 1rea!in#:-
Waves break when the forward velocity of the crest particlesexceeds the velocity of the wave propagation itself in deep water.
cean waves on &rea!in# a#ainst marine structure #ive rise to2.
ompression due to direct hori2ontal force$
+hearing action at the pro3ection on the face of the wall$
+uction effect due to return water$
+ea bed 4 oundation disturbance due to downward force.
"A!E& '(onti)*:-
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+&ove effects results in2..
Inertia orce
5ibration
Internal /ressure
'xpansion and contraction of cavities of the structure.
"A!E& '(onti)*:-
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Wave /eflection:-
6on breaking waves are acting on a vertical wall %&rea!
water(' do not loose their energy by the impact but are
reflected.
*ue to continuous interaction of the incidents and reflected
waves$ a wave of higher height %3 to 4 times( is formed which
is called Standin# Waves %Clapotis(.
"A!E& '(onti)*:-
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5ethods $o 5inimize Wave /eflection Inside $he
6ar&our:-
7reak water must in such a way that the reflected waves are not
diverted towards piers or any other structure.
-he interior slopes of breakwater can be designed for the wave
to break$ which spend the wave energy.
+pecial spending beaches can be planned at points of maximum
waves take place.
"A!E& '(onti)*:-
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*ue to gravitational force of sun and moon there is rise and
fall in ocean waters called $ID)S. -he rise in water level iscalled hi#h tide and fall in water level is called low tides.
In 5editerranean sea$ height is . to 1. m.
In the 7ulf of fundy$ height is 1 to !m.
TIDE&:-
Connecte$ to At%antic cean,Cop%ete%' enc%o(e$ b' %an$)
*t i( on the At%antic Coa(t)
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$ypes of $ides:-
Sprin# $ide:- -hese are highest tides which occur when sun$
moon and earth fall in line.
TIDE& '(onti).*:-
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$ypes of $ides:-
8eap $ide:- -hese are lowest tides which occur when the lines
connecting the earth with the sun and the moon form right angle.
TIDE& '(onti).*:-
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$ypes of $ides:-
Semi-diurnal $ide:- -hese are the tides which occurs twice
each lunar day.
unar Day means time ta!en &y moon to ma!e a complete
revolution around the earth.
Diurnal $ide:- -hese are high tides occur only one time a day.'.g. at lorida.
TIDE& '(onti).*:-
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$ypes of $ides:-
5i9ed $ide:- If one of the two daily high tides does not reach
the height of the previous tide$ it is called a mixed tide. '.g. 9. +.
:$ alifornia.
$idal 1ore:- -hese are high crested waves caused by the rush of
flood tide up a river. %egular occurrence in bay of fundy.
TIDE& '(onti).*:-
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ses of $ides:-
-ides can be used for harnessing the power.
-ides are used for entry and exit of ships in the harbour.
isherman takes an advantage of tides./orts remain clean due to tides.
0igh tide water can be used for harvesting salt.
TIDE& '(onti).*:-
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0ori2ontal movement of water is called current.
Causes of Currents:-
-ides$
Wind blowing over ocean$
*ifference in temperature$
-urbidity of water$Wave breaking at an angle of a beach.
C+RRE%T&:-
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)ffects of Currents:-
+couring and erosion$
*eposition(silting#$
Increase in corrosion rate$
*elay in construction operations$
+ignificant forces on marine structure$
)oads on moored vessels.
It is desira&le that to a lar#e e9tent 6ar&ours are free from
erosion and siltin#.
C+RRE%T& '(onti).*:-
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$ypes of Currents:-
/rimary urrent
-urbidity urrent
-idal and Wind drift urrent
Wind stress urrent
)ittoral urrent
C+RRE%T& '(onti).*:-
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