Download File - SARAH ELEENA`s PORTFOLIO

FACULTY OF CHEMICAL AND NATURAL RESOURCES
ENGINEERING
FLUID MECHANICS (SKM1043)
SECTION 01
GENERIC SKILL ASSIGNMENT
SUBMISSION DATE: 15TH OCTOBER 2010
LECTURER: DR. ABDUL HALIM BIN MOHD YUSOF
GROUP 7:
1)
2)
3)
4)
5)
KHU SAY LI
MOHAMMAD HAFIZ BIN MAT AMIN
NUR SHAKIRA BT SAHAT
SARAH ELEENA BT MOHD USLI
SITI FARAH BT SHAMSUDDIN
AK090071
AK090121
AK090353
AK090255
AK090266
1
Table of Contents
Page
1.0 INTRODUCTION
1.1 Background of Tsunami
1.2 Background of Tropical Cyclone, Hurricane or Typhoon
1.3 Objectives
2.0 FINDINGS AND DISCUSSION
2.1 If the typhoon has winds of at least 120 km/hr, which category it belongs
to, and what extend of damage can occur as a result of this velocity?
2.2 Details of Formation of Tsunami
2.3 Details of Formation of Hurricane
2.4 Comparisons between Formation of Tsunami and Hurricane
2.5 Methods to Overcome or Reduce the Effects of Tsunami
2.6 Methods to Overcome or Reduce the Effects of Hurricane
3
3
4
5
7
7
10
15
3.0 CONCLUSION
23
4.0 REFERENCES
38
2
1.0 INTRODUCTION
Tsunami and tropical cyclone are two phenomena among many other disasters that cause
destructions to the human life.
a) On December 26, 2004, a massive underwater earthquake off the coast of Indonesia’s
Sumatra Island rattled the Earth in its orbit. The quake, measuring 9.0 on the Richter scale,
was the largest one since 1964. Dozens of aftershocks with magnitudes of 5.0 or higher
occurred in the following days. But the most powerful and destructive aftermath of this
devastating earthquake was the tsunami that it caused. The death toll reached higher than
220,000, and many communities suffered devastating property damage.
b) Tropical cyclones, commonly known as hurricanes in the North Atlantic Ocean and
typhoons in the western North Pacific Ocean, are one of the most devastating weather
phenomena in the world. The intense winds associated with the tropical cyclone often
generate ocean waves and heavy rains, which result in severe disasters.
1.1 Background of Tsunami
The term tsunami is Japanese and means "big wave in the port". The term was coined by
fishermen who returned to their ports in the evening after their villages and cities had been
devastated by a giant wave although they had not seen any waves on the open sea.
The phenomenon, tsunami, is a series of large waves of extremely long wavelength and
period usually generated by a violent, impulsive undersea disturbance or activity near the
coast or in the ocean. When a sudden displacement of a large volume of water occurs, or if the
sea floor is suddenly raised or dropped by an earthquake, big tsunami waves can be formed by
forces of gravity. The waves travel out of the area of origin and can be extremely dangerous
and damaging when they reach the shore. The word tsunami (pronounced tsoo-nah'-mee) is
composed of the Japanese words "tsu" (which means harbor) and "nami" (which means
"wave"). Often the term, "seismic or tidal sea wave" is used to describe the same
phenomenon; however, the terms are misleading, because tsunami waves can be generated by
other, non seismic disturbances such as volcanic eruptions or underwater landslides, and have
3
physical characteristics different of tidal waves. The tsunami waves are completely unrelated
to the astronomical tides – which are caused by the extraterrestrial, gravitational influences of
the moon, sun, and the planets. Thus, the Japanese word "tsunami", meaning "harbor wave" is
the correct, official and all-inclusive term. It has been internationally adopted because it
covers all forms of impulsive wave generation.
1.2 Background of Tropical Cyclone, Hurricane or Typhoon
The terms "hurricane" and "typhoon" are regionally specific names for a strong "tropical
cyclone". A tropical cyclone is the generic term for a non-frontal synoptic scale low-pressure
system over tropical or sub-tropical waters with organized convection (i.e. thunderstorm activity)
and definite cyclonic surface wind circulation.
Tropical cyclones with maximum sustained surface winds of less than 17 m/s (34 kt, 39 mph)
are called "tropical depressions”. Once the tropical cyclone reaches winds of at least 17 m/s (34
kt, 39 mph) they are typically called a "tropical storm" and assigned a name. If winds reach 33
m/s (64 kt, 74 mph), then they are called:

"hurricane" (the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline,
or the South Pacific Ocean east of 160E)

"typhoon" (the Northwest Pacific Ocean west of the dateline)

"severe tropical cyclone" (the Southwest Pacific Ocean west of 160E or Southeast Indian
Ocean east of 90E)

"severe cyclonic storm" (the North Indian Ocean)

"tropical cyclone" (the Southwest Indian Ocean)
4
1.3 Objectives
1.3.1 To complete generic skill assignment for the subject Fluid Mechanics (SKM1043).
1.3.2 To identify the category and extend of damage of typhoon with at least 120 km/hr
winds.
1.3.3 To find out the details in formation of tsunami.
1.3.4 To determine the details in formation of tropical cyclone.
1.3.5 To compare the details in formations of tsunami and tropical cyclone.
1.3.6 To investigate methods to overcome or reduce the effects of tsunami.
1.3.7 To investigate methods to overcome or reduce the effects of hurricane.
2.0 FINDINGS AND DISCUSSIONS
2.1 If the typhoon has winds of at least 120 km/hr, which category it belong to, and
what extend of damage can occur as a result of this velocity?
2.1.1
Saffir-Simpson Hurricane Scale
The Saffir-Simpson Hurricane Scale (Simpson and Riehl, 1981) was
developed to provide a sliding scale of damage potential for hurricanes. It is used
for Western Hemisphere tropical cyclones that exceed the intensities of tropical
depressions and tropical storms (refer Table 2.1). The scale divides hurricanes
into five categories distinguished by the intensities of their sustained winds. To be
classified as a hurricane or typhoon, a tropical cyclone must have maximum
sustained winds of at least 119 km/h (33 m/s; 74 mph; 64 kn). The highest
classification in the scale, Category 5, is reserved for storms with winds
exceeding 249 km/h (69 m/s; 155 mph; 135 kn).
5
Table 2.1.1 Saffir-Simpson Hurricane Scale.
The scale separates hurricanes into five different categories based on wind speed. Most
weather agencies use the definition for sustained winds recommended by the World
Meteorological Organization (WMO), which specifies measuring winds at a height of 33 ft (10.1
m) for 10 minutes, and then taking the average. By contrast, the U.S. National Weather Service
defines sustained winds as average winds over a period of one minute, measured at the same 33
ft (10.1 m) height. Central pressure and storm surge values are approximate and often dependant
on other factors, such as the size of the storm and the location. Intensity of hurricanes is from
both the time of landfall and the maximum intensity.
6
2.1.2 Category of typhoon with winds of at least 120 km/hr
Typhoon or hurricane has winds of at least 120 km/hr is categorized as Category 1 based on
Saffir-Simpson Hurricane Scale.
Table 2.1.2 Intensity of Category 1 Hurricane
An example of Category 1 hurricane is Hurricane Humberto. Hurricane Humberto was a minimal
hurricane that formed and intensified faster than any other tropical cyclone on record before
landfall. Developing on September 12, 2007, in the northwestern Gulf of Mexico, the cyclone
rapidly strengthened and struck High Island, Texas, with winds of about 150 km/h (90 mph)
early on September 13. It steadily weakened after moving ashore, and on September 14 it began
dissipating over northwestern Georgia as it interacted with an approaching cold front.
The damage was fairly light, estimated at approximately $50 million (2007 USD). Precipitation
peaked at 14.13 inches (358.9 mm), while wind gusts to 137 km/h (85 mph) were reported. The
heavy rainfall caused widespread flooding, which damaged or destroyed dozens of homes, and
closed several highways. Trees and power lines were downed, knocking out power to hundreds
of thousands of customers. The hurricane caused one fatality in the State of Texas. Additionally,
as the storm progressed inland, rainfall was reported throughout the Southeast United States.
7
2.1.3 Extend of damage by typhoon with winds of at least 120 km/hr (category 1 hurricane)
The high winds of category 1 hurricanes of can blow down numerous trees and branches,
destroying homes and topple unanchored mobile homes. Poorly attached roof shingles or tiles
can blow off. Coastal flooding and pier damage are often associated with Category 1 storms.
Structures will sustain minor to significant damage, and trees fell on vehicles.
Tropical cyclones often knock out power to tens or hundreds of thousands of people,
preventing vital communication and hampering rescue efforts. Lamp posts, power lines,
mailboxes, signs and fences are also damage or destroy by fallen debris. Apart from that, the
debris might cause injuries or death to human being, live stocks and damage farmlands.
The thunderstorm activity in a tropical cyclone causes intense rainfall. Rivers and streams
flood, results in flash flooding, up to 5 ft (1.5 m) deep in some cases, which over wash and close
the roads and landslides can occur, forcing the evacuation of many homes and structures suffer
flooding damage.
Furthermore, upon moving ashore, category 1 hurricanes produce minor storm surge in
the region; the combination of surge and waves resulted in light beach erosion. The term "storm
surge" in casual (non-scientific) use is storm tide; that is, it refers to the rise of water associated
with the storm, plus tide, wave run-up, and freshwater flooding.
8
2.2 Details for Formation of Tsunami
2.2.1 Physical Characteristics of Tsunamis
All types of waves, including tsunamis, have a wavelength, a wave height, amplitude, a
frequency or period, and a velocity.
Diagram 2.2.1(a) Tsunami wave.

Wavelength is defined as the distance between two identical points on a wave (i.e.
between wave crests or wave troughs). Normal ocean waves have wavelengths of about
100 meters. Tsunamis have much longer wavelengths, usually measured in kilometers
and up to 200 kilometers.

Wave height refers to the distance between the trough of the wave and the crest or peak
of the wave.

Wave amplitude refers to the height of the wave above the still water line, usually equals
to 1/2 the wave height. Tsunamis can have variable wave height and amplitude that
depends on water depth.

Wave frequency or period is the amount of time it takes for one full wavelength to pass a
stationary point.

Wave velocity is the speed of the wave. Velocities of normal ocean waves are about 90
km/hr while tsunamis have velocities up to 950 km/hr (about as fast as jet airplanes), and
9
thus move much more rapidly across ocean basins. The velocity of any wave is equal to
the wavelength divided by the wave period.
V = l/P
Tsunamis are characterized as shallow-water waves. These are different from the waves
observed on a beach, which are caused by the wind blowing across the ocean's surface. Windgenerated waves usually have period (time between two successive waves) of five to twenty
seconds and a wavelength of 100 to 200 meters. A tsunami can have a period in the range of ten
minutes to two hours and wavelengths greater than 500 km. A wave is characterized as a
shallow-water wave when the ratio of the water depth and wavelength is very small.
The rate at which a wave loses its energy is inversely related to its wavelength. Since a
tsunami has a very large wavelength, it will lose little energy as it propagates. Thus, in very deep
water, a tsunami will travel at high speeds with little loss of energy. For example, when the
ocean is 6100 m deep, a tsunami will travel about 890 km/hr, and thus can travel across the
Pacific Ocean in less than one day.
Diagram 2.2.1(b) Wave movements of tsunami.
As a tsunami leaves the deep water of the open sea and arrives at the shallow water near
the coast, it undergoes a transformation. Since the velocity of the tsunami is also related to the
water depth, as the depth of the water decreases, the velocity of the tsunami decreases. The
change of total energy of the tsunami remains constant.
Furthermore, the period of the wave remains the same, and thus more water is forced
between
the
wave
crests
causing
the
height
of
the
wave
to
increase.
Because of this effect, a tsunami that was imperceptible in deep water may grow to have wave
10
heights of several meters or more. Because the wavelengths and velocities of tsunamis are so
large, the period of such waves is also large, and larger than normal ocean waves. Thus it may
take several hours for successive crests to reach the shore. For a tsunami with a wavelength of
200 km traveling at 750 km/hr, the wave period is about 16 minutes. Thus people are not safe
after the passage of the first large wave, but must wait several hours for all waves to pass. The
first wave may not be the largest in the series of waves. For example, in several different recent
tsunamis the first, third, and fifth waves were the largest.
In contrast, if the trough of the tsunami wave reaches the coast first, this causes a
phenomenon called drawdown, where it appears that sea level has dropped considerably.
Drawdown is followed immediately by the crest of the wave which can catch people observing
the drawdown off guard. When the crest of the wave hits, sea level rises (called run-up).
Run-up is usually expressed in meters above normal high tide and
may reach a
maximum vertical height onshore above sea level of 30 meters. A notable exception is the
landslide generated tsunami in Lituya Bay, Alaska in 1958 which produced a 60 meter high
wave. Run-ups from the same tsunami can be variable because of the influence of the shapes of
coastlines. One coastal area may see no damaging wave activity while in another area
destructive waves can be large and violent. The flooding of an area can extend inland by 300 m
or more, covering large areas of land with water and debris. Flooding tsunami waves tend to
carry loose objects and people out to sea when they retreat.
2.2.2 Formation of Tsunami
2.2.2.1 Earthquake
By far, the most destructive tsunamis are generated from large, shallow earthquakes
with an epicenter or fault line near or on the ocean floor. These usually occur in regions of
the earth characterized by tectonic subduction along tectonic plate boundaries. The high
seismicity of such regions is caused by the collision of tectonic plates. When these plates
move past each other, they cause large earthquakes, which tilt, offset, or displace large
areas of the ocean floor from a few kilometers to as much as a 1,000 km or more. The
11
sudden vertical displacements over such large areas, disturb the ocean's surface, displace
water, and generate destructive tsunami waves. The waves can travel great distances from
the source region, spreading destruction along their path. For example, the Great 1960
Chilean tsunami was generated by a magnitude 8.3 earthquake that had a rupture zone of
over 1,000 km. Its waves were destructive not only in Chile, but also as far away as
Hawaii, Japan and elsewhere in the Pacific. It should be noted that not all earthquakes
generate tsunamis. Usually, it takes an earthquake with a Richter magnitude exceeding 7.5
to produce a destructive tsunami.
(i)
(ii)
Drawing of tectonic plate boundary before earthquake.
Overriding plate bulges under strain, causing tectonic uplift.
(iii)
Plate slips, causing subsidence and releasing energy into water.
12
(iv)
The energy released produces tsunami waves.
Diagram 2.2.2.1 (i), (ii), (iii) Tsunami Formation by Earthquakes.
2.2.2.2 Volcanic Eruption
Although relatively infrequent, violent volcanic eruptions also represent impulsive
disturbances, which can displace a great volume of water and generate extremely destructive
tsunami waves in the immediate source area. According to this mechanism, waves may be
generated by the sudden displacement of water caused by a volcanic explosion, by a volcano's
slope failure, or more likely by a phreatomagmatic explosion and collapse or engulfment of
the volcanic magmatic chambers. One of the largest and most destructive tsunamis ever
recorded was generated in August 26, 1883 after the explosion and collapse of the volcano of
Krakatoa (Krakatau), in Indonesia. This explosion generated waves that reached 135 feet,
destroyed coastal towns and villages along the Sunda Strait in both the islands of Java and
Sumatra, killing 36, 417 people. It is also believed that the destruction of the Minoan
civilization in Greece was caused in 1490 B.C. by the explosion/collapse of the volcano of
Santorin in the Aegean Sea.
2.2.2.3 Submarine Landslides, Rock Falls and Underwater Slumps
Less frequently, tsunami waves can be generated from displacements of water resulting
from rock falls, icefalls and sudden submarine landslides or slumps. Such events may be
caused impulsively from the instability and sudden failure of submarine slopes, which are
13
sometimes triggered by the ground motions of a strong earthquake. For example in the 1980's,
earth moving and construction work of an airport runway along the coast of Southern France,
triggered an underwater landslide, which generated destructive tsunami waves in the harbor of
Thebes. Major earthquakes are suspected to cause many underwater landslides, which may
contribute significantly to tsunami generation. For example, many scientists believe that the
1998 tsunami, which killed thousands of people and destroyed coastal villages along the
northern coast of Papua-New Guinea, was generated by a large underwater slump of
sediments, triggered by an earthquake.
In general, the energy of tsunami waves generated from landslides or rock falls is rapidly
dissipated as they travel away from the source and across the ocean, or within an enclosed or
semi-enclosed body of water such as a lake or a fjord. However, it should be noted that the
largest tsunami wave ever observed anywhere in the world was caused by a rock fall in Lituya
Bay, Alaska on July 9, 1958. Triggered by an earthquake along the Fairweather fault, an
approximately 40 million cubic meter rock fall at the head of the bay generated a wave, which
reached the incredible height of 520-meter wave (1,720 feet) on the opposite side of the inlet.
An initial huge solitary wave of about 180 meters (600 feet) raced at about 160 kilometers per
hour (100 mph) within the bay debarking trees along its path. However, the tsunami's energy
and height diminished rapidly away from the source area and, once in the open ocean, it was
hardly recorded by tide gauge stations.
2.2.2.4 Asteroids, Meteorites and Man-made Explosions
Fortunately, for mankind, it is indeed very rare for a meteorite or an asteroid to reach the
earth. No asteroid has fallen on the earth within recorded history. Most meteorites burn as
they reach the earth's atmosphere. However, large meteorites have hit the earth's surface in the
distant past. This is indicated by large craters, which have been found in different parts of the
earth. Also, it is possible that an asteroid may have fallen on the earth in prehistoric times –
the last one some 65 million years ago during the Cretaceous period. Since evidence of the
fall of meteorites and asteroids on earth exists, it can be concluded that they have fallen also
in the oceans and seas of the earth, particularly since four fifths of our planet is covered by
water.
14
The fall of meteorites or asteroids in the earth's oceans has the potential of generating
tsunamis of cataclysmic proportions. Scientists studying this possibility have concluded that
the impact of moderately large asteroid, 5-6 km in diameter, in the middle of the large ocean
basin such as the Atlantic Ocean, would produce a tsunami that would travel all the way to the
Appalachian Mountains in the upper two-thirds of the United States. On both sides of the
Atlantic, coastal cities would be washed out by such a tsunami. An asteroid 5-6 kilometers in
diameter impacting between the Hawaiian Islands and the West Coast of North America,
would produce a tsunami which would wash out the coastal cities on the West coasts of
Canada, U.S. and Mexico and would cover most of the inhabited coastal areas of the
Hawaiian islands. Conceivably tsunami waves can also be generated from very large nuclear
explosions. However, no tsunami of any significance has ever resulted from the testing of
nuclear weapons in the past. Furthermore, such testing is presently prohibited by international
treaty.
2.3 Details for Formation of Hurricane
2.3.1 Introduction
A tropical cyclone is referred to by names such as hurricane, typhoon, tropical storm,
cyclonic storm, tropical depression, and simply cyclone. Hurricanes are massive tropical
cyclonic storm systems with winds exceeding 119 km/hr (74 miles/hour). The same phenomenon
is given different names in different parts of the world. In the western Pacific they are called
typhoons, and in the southern hemisphere they are called cyclones. But no matter where they
occur they represent the same process. Hurricanes are dangerous because of their high winds, the
storm surge produced as they approach a coast, and the severe thunderstorms associated with
them. Although death due to hurricanes has decreased in recent years due to better methods of
forecasting and establishment of early warning systems, the economic damage from hurricanes
has increased as more and more development takes place along coastlines. It should be noted that
15
coastal areas are not the only areas subject to hurricane damage. Although hurricanes loose
strength as they move over land, they still carry vast amounts of moisture onto the land causing
thunderstorms with associated flash floods and mass-wasting hazards.
2.3.2 Formation of Tropical Cyclone
Few things in nature can be compared to the destructive force of a hurricane. Called the
greatest storm on Earth, a hurricane is capable of annihilating coastal areas with sustained winds
of 249448.32 kilometer per hour or higher, intense areas of rainfall, and a storm surge. In fact,
during its life cycle a hurricane can expend as much energy as 10,000 nuclear bombs.
The scientific term for a hurricane, regardless of its location, is tropical cyclone. In
general, a cyclone is a large system of spinning air that rotates around a point of low pressure.
Only tropical cyclones, which have warm air at their center, become the powerful storms that are
called hurricanes.
Tropical cyclones, commonly known as hurricanes in the North Atlantic Ocean and
typhoon in the western North Pacific Ocean, are one of the most devastating weather phenomena
in the world. The intense winds associated with the tropical cyclone often generate ocean waves
and heavy rains which usually results in severe disasters. However, whatever they are called,
tropical cyclones all form in the same way.
Hurricanes form over tropical waters (between 8 and 20 degrees latitude) in areas of high
humidity, light winds, and warm sea surface temperatures [typically 26.5 degrees Celsius (80
Fahrenheit) or greater]. Tropical cyclones are like giant engines that use warm, moist air as fuel.
That is why they form only over warm ocean waters near the equator. The warm, moist air over
the ocean rises upward from near the surface. Because this air moves up and away from the
surface, there is less air left near the surface. Another way to say the same thing is that the warm
air rises, causing an area of lower air pressure below.
16
Diagram 2.3.2 (a) Activities of Tropical Cyclones
As a result of the extremely low central pressure (often around 28.35 in. /960 millibars
but sometimes considerably lower, with a record 25.69 in. /870 millibars registered in a 1979
NW Pacific typhoon), surface air spirals inward cyclonically (counterclockwise in the Northern
Hemisphere and clockwise in the Southern Hemisphere), converging on a circle of about 30 km
diameter that surrounds the hurricane's “eye.” The circumference of this circle defines the socalled eye wall, where the inward-spiraling, moisture-laden air is forced aloft, causing
condensation and the concomitant release of latent heat; after reaching altitudes of tens of
thousands of feet above the surface, this air is finally expelled toward the storm's periphery and
eventually creates the spiral bands of clouds easily identifiable in satellite photographs.
The heat boosts the air will increases the buoyancy, so it continues rising. To compensate
for the rising air, surrounding air sinks. As this air sinks towards the surface, it is compressed by
the weight of the air above it and warms. The pressure rises at the top of the layer of warming
air, pushing air at the top of the layer outward. Because there is now less air in the layer, the
weight of the entire layer is less, and the pressure at the ocean surface drops. The drop in
pressure draws in more air at the surface, and this air converges near the center of the storm to
form more clouds.
The upward velocity of the air and subsequent condensation make the eye wall as the
region of heaviest precipitation and highest clouds. Because the outward increase in pressure is
greatest there, the eye wall is also the region of maximum wind speed. In contrast, the hurricane
eye is almost calm, experiences little or no precipitation, and is often exposed to a clear sky.
17
Temperatures in the eye are 5°C–8°C (10°F to 15°F) warmer than those of the surrounding air as
a result of sinking currents at the hurricane's core.
Air from surrounding areas with higher air pressure pushes in to the low pressure area.
Then that new air becomes warm and moist and rises, too. As the warm air continues to rise, the
surrounding air swirls in to take its place. As the warmed, moist air rises and cools off, the water
in the air forms clouds. The whole system of clouds and wind spins and grows, fed by the
ocean’s heat and water evaporating from the surface.
Much of the released energy drives updrafts that increase the height of the storm clouds,
speeding up condensation. This positive feedback loop, called the Wind-induced surface heat
exchange, continues for as long as conditions are favorable for tropical cyclone development.
Factors such as a continued lack of equilibrium in air mass distribution would also give
supporting energy to the cyclone. The rotation of the Earth causes the system to spin, an effect
known as the Coriolis effect, giving it a cyclonic characteristic and affecting the trajectory of the
storm.
The Earth's rotation imparts an acceleration known as the Coriolis effect, Coriolis
acceleration, or colloquially, Coriolis force, is acceleration which causes cyclonic systems to turn
towards the poles in the absence of strong steering currents. The poleward portion of a tropical
cyclone contains easterly winds, and the Coriolis effect pulls them slightly more poleward.
The westerly winds on the equatorward portion of the cyclone pull slightly towards the
equator, but, because the Coriolis effect weakens toward the equator, the net drag on the cyclone
is poleward. Thus, tropical cyclones in the Northern Hemisphere usually turn north (before being
blown east), and tropical cyclones in the Southern Hemisphere usually turn south (before being
blown east) when no other effects counteract the Coriolis effect.
The Coriolis effect also initiates cyclonic rotation, but it is not the driving force that
brings this rotation to high speeds – that force is the heat of condensation. Storms that form north
of the equator spin counterclockwise. Storms south of the equator spin clockwise. This
difference is because of Earth's rotation on its axis.
18
Infrared image of a powerful
southern hemisphere
cyclone, Monica, near peak
intensity,
showing clockwise rotation due to
the Coriolis effect
As the storm system rotates faster and faster, an eye forms in the center. It is very calm
and clear in the eye, with very low air pressure. Higher pressure air from above flows down into
the eye. When the winds in the rotating storm reach 39 mph, the storm is called a “tropical
storm.” And when the wind speeds reach 74 mph, the storm is officially a “tropical cyclone,” or
hurricane.
Tropical cyclones usually weaken when they hit land because they are no longer being
“fed” by the energy from the warm ocean waters. However, they often move far inland, dumping
many inches of rain and causing lots of wind damage before they die out completely.
Diagram 2.3.2(b) A cumulonimbus cloud. A tropical cyclone has so many of these; they form
huge, circular bands.
19
Diagram 2.3.2(c) The small red arrows show warm, moist air rising from the ocean's surface, and
forming clouds in bands around the eye. The blue arrows show how cool, dry air sinks in the eye
and between the bands of clouds. The large red arrows show the rotation of the rising bands of
clouds.
2.4 Comparisons between Formations of Tsunami and Hurricane
Tsunami and hurricane are both violent disaster on earth. Besides, both formations occur
from the sea which means the starting place for both of the phenomena to occur and take place is
at the sea. However, their formation is differing by their factors that lead to their formation.
Tsunamis are caused by sudden changes in the seafloor, generally earthquakes and more
rarely large landslides. To generate a tsunami, the earthquake must occur under or near the
ocean, be large, and create vertical movements of the seafloor.
20
Underwater landslides, which occur when large masses of sediment shift along the
seafloor, are another common cause of tsunamis. The tsunamis generated by landslides tend to be
relatively localized and typically do less damage than the earthquake formed tsunamis.
When these events occur under the water, huge amounts of energy are released as a result
of quick upward bottom movement.
A tsunami carries an enormous amount of energy that is spread over a large volume of
water in the deep sea. However, when a tsunami reaches shallow water, such as a coastline, the
energy is concentrated into a smaller volume and the wave's power overwhelms whatever is in its
path. In shallow water, its speed decreases and its amplitude increases to dangerous heights,
sometimes 50 feet or higher, and it spreads inland many hundreds of feet (in some cases a mile
or more). A tsunami is not a single wave, but a set that may last for several hours, and the first
wave is not always the largest.
While the formation of hurricanes does not involve the changes of landslide under the sea
but, it is caused by the warm ocean waters near the equator. Many tropical
cyclones develop when the atmospheric conditions around a weak disturbance in the atmosphere
are favorable. The formation of hurricanes is more to the changes of temperature at different
places and the changing of pressure formed when the warm water is rises upward from near the
surface. As the warm air continues to rise, the surrounding air swirls in to take its place. As the
warmed, moist air rises and cools off, the water in the air forms clouds. The whole system of
clouds and wind spins and grows, fed by the ocean’s heat and water evaporating from the
surface.
In addition, both phenomena produce energy during their formation. In the formation of
tsunamis, the sudden lurching earthquakes release energy while in the hurricanes, the
condensation occurs from the warm ocean produce latent heat. However, that energy is
transformed to form other energy. Much of the earthquake's energy, which can be equivalent to
many atomic bombs, is transferred to the water column above it, producing a tsunami.
While, the latent heat produced in condensation process will increase buoyancy caused
the air continues rising and formed clouds. The Coriolis effect will make the clouds spinning
which then formed a hurricane.
21
COMPARISONS OF FORMATION OF TSUNAMI AND HURRICANE
Tsunami
Form from displacement of water:

Earthquake

Volcanic eruption

Submarine Landslides, Rock Falls and
Hurricane
Form from circulation of warm air and water
on the surface of water.
Underwater Slumps
Originate under water or on the sea bed.
Form on the surface of the ground.
Wavelength is very small but height is big near Clouds in bands around the eye with diameter
shallow coastline.
of 400 to 500 miles.
Normally occur at Pacific Ocean (about 80%).
Occurs at the eight hurricane basins.
2.5 Methods to Overcome or Reduce the Effects of Tsunami
2.5.1 Tsunami Warning System
Geophysical Research Letters, researcher Y. Tony Song of NASA's Jet Propulsion
Laboratory, Pasadena, Calif., demonstrated that real-time data from NASA's network of global
positioning system (GPS) stations can detect ground motions preceding tsunamis and reliably
estimate a tsunami's destructive potential within minutes, well before it reaches coastal areas.
The method could lead to development of more reliable global tsunami warning systems, saving
lives and reducing false alarms
22
Diagram 2.5.1(a) NOAA Tsunami Warning System
Diagram 2.5.1(b) Deep Water Buoy
23
According to the diagram, the sensor will rest on the bottom of the ocean .It will
continuously measure the pressure. A spike in the pressure on the ocean floor most likely
means that a tsunami has just passed over the sensor. Once the measured pressure spikes, the
sensor will send a signal acoustically to a buoy with a hydrophone and transmitter.
The
buoy would be resting on the surface of the water. Once the buoy has received the signal
from the pressure sensor, it will transmit via satellite to an Early-warning station the
information it has. The Early-warning station will be able to inform the endangered areas of
incoming danger.
A pressure sensor can measure the pressure of a liquid or gas. An underwater pressure
sensor works by measuring a mechanical deflection of a membrane to measure the change in
pressure. To detect a tsunami, a pressure sensor would be placed at the bottom of the ocean
floor.
Once a certain pressure threshold is exceeded, the system will know that there is a
strong likelihood of a presence of a tsunami. The sensors constantly monitor the pressure
through the calculation:
where
P = the overlying pressure in newtons per metre square,
ρ = the density of the seawater= 1.1 x 103 kg/m3,
g = the acceleration due to gravity= 9.8 m/s2 and
h = the height of the water column in metres.
The pressure sensor must be watertight. If it is not, the water could short circuit the
sensor, putting it out of commission. The system used three Keller America Inc. pressure
sensors. They can sense the range of pressures from 0 to 1.5 PSI. The pressure sensors can
output between 0 and 10 volts.
One experiment was done in Hydro-Lab and started by running the logging measurement
program for each sensor. The data was recorded every 0.02 seconds. Immediately after the
data started to be logged, the wave generator was started. The waves were placed around the
24
middle of the tank. This meant that the waves would take some amount of time to reach the
sensors. This data is shown below:
Tsunami Amplitude:1 inch
Tsunami Period: 2.50 seconds
Wind Amplitude: 5 inches
Wind Period: 0.714 seconds
Plot of sensor 1 voltage output of tsunami and wind waves
This experiment was run with the amplitude of the tsunami wave at 1 inch, and the wind
wave amplitude was 5 inches. The period of the tsunami wave was 2.50 seconds, and the
wind wave period was 0.714 seconds. This plot shows that the tsunami waves and wind
waves oscillated around 7.8V.
There is a significantly higher pressure increase as a longer wave passes over an area.
The peak voltage of the wind-generated wave depends on which sensor is being used. Sensor
1 displayed a peak voltage of 7.94V. To use this data to detect a “tsunami”, a cut-off voltage
could be set at a voltage that is above the peak voltage of the wind-generated wave. A
program could be written to send a warning out once this cut-off voltage is met or exceeded.
2.5.2 Natural Barrier
Besides warning systems, natural factor (vegetation) such as shoreline tree cover also can
mitigate tsunami effects. Some locations in the path of the 2004 Indian Ocean tsunami
escaped almost unscathed because trees such as coconut palms and mangroves absorbed the
25
tsunami's energy. In one striking example, the village of Naluvedapathy in India's Tamil
Nadu region suffered only minimal damage and few deaths because the wave broke against a
forest of 80,244 trees planted along the shoreline in 2002. Environmentalists have suggested
tree planting along tsunami-prone seacoasts. Trees require years to grow to a useful size, but
such plantations could offer a much cheaper and longer-lasting means of tsunami mitigation
than artificial barriers.
Diagram 2.5.2 (a) Mangrove forest sites
Researchers and engineers consider that vegetation may strengthen coasts against tsunami
attack by increasing the resistance force. Harada and Imamura (2005) quantitatively
evaluated the hydrodynamic effects and damage-prevention functions of coastal forests
against tsunamis with a view to using them as tsunami counter measures. They also
performed numerical simulations, including an evaluation of the quantitative effects of
coastal forests in controlling tsunami reduction and damage. They found that an increase in
forest width can reduce not only inundation depth, but also the currents and hydraulic forces
behind the coastal forest. Coastal vegetation is an economically viable countermeasure,
especially for developing countries, like Sri Lanka, and also has additional advantages such
as enhancing the environment, minimizing local erosion by wave attack, and enhancing
26
biodiversity. Moreover, coastal vegetation helps to develop sand dunes in front of the forest
by trapping sand carried by the wind, which plays a significant role in reducing tsunami
energy.
The capacity of forests to mitigate the impacts of a tsunami can be estimated by fluid
dynamics models. These models, that examine the hydrodynamic relationship of a fluid
moving through vegetation, require various parameters and associated coefficients to
estimate forest resistance to tsunamis of different heights and pressures. The most important
numbers to obtain are volumetric occupancy, drag coefficient, inertia coefficient and
Manning’s coefficient of roughness. These are estimated from measurements of the diameter
and height of tree trunks, height and density of the canopy, and tree density. If the effective
projection area is known, one can convert this to volumetric occupancy, and then the
Manning coefficient, drag coefficient and inertia coefficient can be determined.
Diagram 2.5.2 (b) Vegetation model: Volume of submerged obstacles, volume of water and
volumetric occupancy
Figure above illustrates some of the key concepts related to the hydraulic model. It
shows that volumetric occupancy is a function of the volume of water relative to the volume
of submerged trees. A stream of water striking a tree trunk and imparting impact and
27
frictional forces, along with the associated coefficients of inertia and drag is also portrayed in
the figure. A full description of the technical aspects of modeling as applied to the Pancer
Bay, East Java.
2.6 Methods to Overcome or Reduce the Effects of Hurricane
2.6.1 Introduction
Hurricane attacks in summer would bring about a great destruction to economy and
lives. If we can destroy hurricane while it is forming or displace it from the original track to
let it land at a less populated region, we can reduce the loss in economy and lives.
However, there is no way to use the two ways mentioned above to reduce the damage
caused by typhoon at the moment with the existing science and technology. Moreover, these
methods are not economically applicable as the cost would be extremely high even though
we have got the most advanced technology to do so.
Typhoon cannot be destroy or prevent. But early prevention can be made to make sure the
effect caused by typhoon is less. Some of the prevention steps are to give early warning to
the residents at the affected area so that evacuation can be made immediately.
2.6.2 Techniques of typhoon prediction
-Use artificial satellites to take satellite images
-Application of climatology, statistics and dynamics
-Predict the position and the track of the typhoon
Constraints of predicting typhoon:
-Applying satellite images and other data for prediction still cannot reach 100% certainty
about the initial position of the typhoon, its track and wind speed at present.
28
-There are many factors influencing the typhoon track. There are some patterns still failed
to be fully handled, which could only roughly be applied in the various predicting
methods.
-The capricious characteristic of tropical cyclone and their fluctuation characteristics of
movement and wind intensity make the predicting work very difficult.
2.6.3
Ways to reduce effects of hurricane
2.6.3.1 Reduce the temperature of the sea using ammonium nitrate, NH4NO3
2.6.3.2 Using barges
2.6.3.3 Use a fleet of about 20 submarines
2.6.3.4 Use of supersonic jets
2.6.3.5 Hurricane-proof building
2.6.3.6 Coastal barriers
2.6.3.1 Reduce the temperature of the sea using ammonium nitrate, NH4NO3.
The warm water acts as the fuel to power up the hurricanes. Hurricanes typically need an
ocean temperature of about 80º F, 26º C, to form. What can be done is by cooling the water
temperature at the ocean. Once a disturbance forms and sustained convection develops, it can
become more organized under certain conditions. Hurricanes grow stronger over warm
waters and correspondingly lose strength over cool waters. If the disturbance moves or stays
over warm water at least 80°F, and upper level winds remain weak, the disturbance can
become more organized, forming a depression. Therefore, once the eye of the storm moves
over land will begin to weaken rapidly, not because of friction, but because the storm lacks
the moisture and heat sources that the ocean provided. This depletion of moisture and heat
hurts the tropical cyclones ability to produce thunderstorms near the storm center. Without
this convection, the storm rapidly diminishes the formation of hurricanes.
To cool the ocean temperature, ammonium nitrate, NH4NO3 can be used. It can reduce
the water temperature at the ocean. This temperature reduction property also allows its use in
instant cold packs. 14 kg of ammonium nitrate could be used to freeze 14 liters, 14 kg, of
29
water. The amount of ammonium nitrate required to reduce the temperature from 25º C to the
freezing point to reduce the temperature of the sea from 25º C to 0º C, then only about 1/4 the
amount of NH4NO3 are needed and to make a temperature reduction by about 3º C, the
amount can be reduced further by a factor of 1/8th. So the amount would be less than 1/30th
that needed to induce freezing for this low amount of temperature reduction.
There is a reason though why induce freezing method are being used. We would want to
keep the temperature reduced over the covered area for some time so that the hurricane has
time to dissipate. If the water were frozen at the surface, then it would require some time for
this to melt. For the freezing, about the same amount in weight as the water we wanted to
freeze.
2.6.3.2 Using barges
Another way to reduce the hurricanes is by using barges which would be towed ahead of
the hurricane. Each barge would sink a 500 foot long tube into the ocean water. Pumps
aboard the barge would pull cool water from depth and spray it across the warm surface in
the path ahead of the hurricane. The cooling of the surface water would disrupt the
convection currents.
2.6.3.3 Use a fleet of about 20 submarines
Applying the concept of fluid mechanics, the third solution is by using a fleet of about 20
submarines, each equipped with eight pumps designed to shoot 480 metric tons of cold water
per minute to the ocean's surface. These require a very efficient pump that can spray cool
water at very high velocity as the hurricanes are moving very fast. These would be stationed
out in front of the storm. In just one hour, the fleet could lower the water's surface
temperature by three degrees, disrupting the air circulation and weakened it when
approaching the coastal area.
30
2.6.3.4 Use of supersonic jets
Besides that, supersonic jets also can slow down the heart of a hurricane. The jets
level off at about 10,000 ft and race toward the eye of the hurricane, accelerating in
unison. Very quickly they approach the outer edge of the storm. Here, they fan out in an
even lateral formation, from 1000 ft to 6000 ft, each jet trailing the other by 5 miles.
Blasting through the storm, they simultaneously push the throttles to maximum,
breaking the sound barrier, and continuing their acceleration about 1500 mph. The sonic
boom of each jet sends out a shock wave into the surrounding air. Within the shock wave,
the furious winds stop momentarily. But almost as quickly as they stop, the winds behind
push them up to speed again. Only, in so doing, the storm loses some momentum; not all,
but enough to measure. By using this method, the speed of the hurricanes can be reduced
from 160 mph to 125 mph, making it drop from category 5 to category 3.The raging beast
of storm has not been stopped, but it's certainly been humbled.
2.6.3.5 Hurricane-proof building
A hurricane-proof building has a proper design and construction which helps it withstand
hurricanes. With the advent of advanced technology over the years, a variety of methods have
been studied and tested, that can help a building survive strong winds and storm surge (flooding
31
due to storms). There are a few things which are considered while designing a hurricane-proof
building. They are storm surge and wind loading considerations. Then, there are building
components which need to be chosen correctly.
2.6.3.5.1 Storm Surge
Storm surge mainly occurs in the coastal areas. The waves generated due to strong
winds are very powerful and can seriously batter a building. So, these beach-front
buildings should be powerful enough to bear the waves of the ocean rising to 20 feet or
more. If there is a chance that the waves can reach the building, it is ideal to elevate the
building on wooden, steel or concrete pilings. The building can also be anchored to solid
rock, along with the elevation. The walls on the first floor are constructed using
Sheetrock or drywall by default. Sheetrock is a building material made of a layer of
gypsum plaster pressed between two thick sheets of paper, then kiln dried. As a result,
these walls can completely deteriorate when wet or exposed to lateral forces, allowing
high winds accompanied by water to pass through it. This situation, termed as gutting, is
a frequent occurrence in storm surge areas. Constructing the walls on the first floor using
sheetrock is not an ideal solution for storm surge gutting. However, it can save the rest of
the building from destruction.
2.6.3.5.2 Concrete
Concrete can be used for the construction of a building to make it resistant to
strong winds, pounding waves and in a few instances, flying debris. Reinforced concrete,
a strong dense material which is used in home construction must ideally be reinforced
with steel. This is also called 'rebar'. Rebar is liable to rust and wet in humid conditions,
but counter measures can be taken to nullify its corrosion due to moisture.
2.6.3.5.3 Wind Loading Conditions
Wind loading conditions are associated with the construction of the roof of a
building. Strong winds affecting the roof surface results in negative forces and creates a
lifting force. There is high possibility that a building can be destroyed in this way during
32
a hurricane. This lifting of the roof or 'peeling' weakens the building substantially. To
avoid this, the upper structure should be securely fixed through the walls to the
foundation. On the more conventional side of securing a roof, roof trusses (triangular
brackets of brick or stone) are 'toe nailed' into the top of the walls. Although these nails
provide zero structural advantage, they are helpful in holding the trusses in place while
the roof is being built. The rest is then left to the forces of gravity and friction to protect
the roof. Nowadays, advanced technology methods have developed in such a way that the
roof can be anchored to the walls. Trusses wrapped by metal straps nailed to the wall are
another method for strengthening a roof.
2.6.3.5.4 Earth Sheltering
Earth Sheltering is another component in the construction of a building, strong
enough to hold against hurricanes and tornadoes. Earth sheltering means building walls
using earth against external thermal mass. Earth sheltering reduces heat loss and helps
maintain a steady indoor air temperature. That is precisely the reason why cellars and
basements of buildings can be a safe refuge in case of a natural disaster.
2.6.3.5.5 Building Components
Weak points like garages, doors, windows and other openings are easy targets for
blowing debris and wind pressure. Once these give up, the whole building is at a risk.
Moreover, the roof may also be lifted off a building. Here, hurricane shutters can prove
effective.

Door Specifications: Doors leading out of the house should open outward in
hurricane-prone areas. In case of a hurricane, an inward opening door will be
blown inside the house. Doors opening inward have potential to cause a major
structural failure to the building.

Windows: Usually in hurricane-prone areas, windows tested to withstand 150mile per hour wind are installed. These windows should have glass with
protective membranes and plastic panes. And these panes should be fixed more
firmly than the normal window panes. In hurricane-prone areas, aluminum
shutters can prevent a major damage.
33
2.6.3.6 Coastal barriers
The effect of hurricane can be reduced by making some barrier at the coastal area. By doing so,
the impact of the hurricane that crashed on land can be minimized. Some of the devices that can
be used to create as a barrier to the hurricane are:
2.6.3.6.1 Sea walls
The sea walls act as barrier to the wave. When the wave strikes the shore, the
wave will bounce back to the sea. The seawalls also act like the breakwater. It will
distract the movement of the waves by altering the pattern of the waves during the
collision of the waves and the wall. During the hurricane season, having seawall as
protective mechanism is one of the best idea as it will reduce the velocity of the waves
that try to pass by.
2.6.3.6.2 Breakwater
34
Breakwaters aim to protect a coast or activities along the coast line from wave
action. Breakwaters that are used to reduce the wave caused by hurricane must be
extremely big to make sure the effect is severe. The breakwater will act as a barrier to the
wave by slowing down the wave. The waves that are coming will be split up and the
waves that pass through the breakwater will be calmer. As for hurricane, the effect of the
gigantic wave will be reduced and less destruction will occur to the coastal area.
2.6.3.6.3 Natural barrier
The mangroves tree acts as natural barrier against the hurricane. When hurricanes
strike a place, they will bring along strong wind. By planting mangroves tree along the
shore, the speed of the hurricane can be reduced as they pass through the mangroves
because it is hard to uproot the mangrove tree because of their strong roots. Besides that,
hurricanes also bring together huge wave that when passing through the mangrove tree,
the root will acts as wave breaker and make the energy brought by the waves to spread
away. By this action, less destruction will be caused by the wave as well as by the
hurricanes.
35
3.0 CONCLUSION
Tsunami and tropical cyclones both cause catastrophes to the Earth. Through the study of
formations of these two natural phenomena, the effects and extend of damage of tsunami and
tropical cyclones can be reduced to the minimum. Fluid mechanics plays a vital role in
further research on the topic. Therefore, as an engineer, we should have full understanding of
the subject in order to solve the problem.
4.0 REFERENCES
http://www.aoml.noaa.gov/hrd/tcfaq/E2.html
http://cawcr.gov.au/bmrc/pubs/tcguide/globa_guide_intro.htm
http://www.aoml.noaa.gov/phod/index.php
http://www.aoml.noaa.gov/hrd/tcfaq/A1.html
http://www.cramster.com/reference/wiki.aspx?wiki_id=66368
http://www.cramster.com/reference/wiki.aspx?wiki_name=List_of_notable_tropical_cyclone
s
http://www.sciencedirect.com/science
http://wapedia.mobi/en/Saffir-Simpson_Hurricane_Scale
http://wikipedia.com
36