WATER WAVE DYNAMICS WATER WAVE DYNAMICS AND THE SECRET OF THE AND THE SECRET OF THE

TSUNAMISTSUNAMIS

Presenters:Presenters:-Isaac Katz-Isaac Katz-Zsuzsanna Kis-Zsuzsanna Kis-Kinneret Rozales-Kinneret Rozales

Mentor: Ronen AvniMentor: Ronen Avni

Location: Haifa, Technion city, Faculty Of Civil Engineering.Location: Haifa, Technion city, Faculty Of Civil Engineering.

THE PHYSICS OF WAVESTHE PHYSICS OF WAVES

The following mathematical equation, commonly referred toas the wave equation served as the scientific foundation for this work.Its derivatives are also here shown, although for shortness of spacenot explained.These basic equations have uncovered the firsts steps towardsan understanding of fluid dynamics in general and water-wavebehavior in particular and I think them crucial for any one to knowwho has an interest in this subjectespecially as they don’t require advanced education to understand.

WATER-WAVE EQUATION AND WATER-WAVE EQUATION AND ITS DERIVATIVESITS DERIVATIVES

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WAVE SPEED EQUATIONWAVE SPEED EQUATION

Long waves are non-dispersive: Their wave speed is independent of their period.It depends only on the water depth, in the form:

( c is wave speed, h water depth, g gravity).

where z is the time dependent surface elevation (wave amplitude)and u the horizontal particle velocity. It follows that u is independentof depth and the vertical particle velocity varies linearly with depth. Particles move on very flat elliptic paths in nearly horizontal motion.

The velocity structure in a long wave is described by

WAVES IN THE LABWAVES IN THE LABWe can see examples of waves all around us,Here we experiment with many objects to find out their propertiesAnd see how they relate to waves.

Using a pendulum, a moving boardand some sand we can see theinteresting results that show us howthe same underlying sinus wave shapeforms on different situations and materials.

And here we can see a wave forming from therhythmical up and down movement of a spring rope.The faster the rope is moved the more waves are formed,with nodes and anti-nodes developing harmoniously with the movement,we can thus see the rope evolving from a single waveform into multiple,complicated patterns which are not always symmetric.

A demonstration of waves with normalconditions approaching a ‘shore’if looked at closely one candistinguish de similarities of the basicwave form with the picture in the right.

WHAT DOES TSUNAMI WHAT DOES TSUNAMI MEAN?MEAN?

• Japanese word which in English means Japanese word which in English means Harbor WaveHarbor Wave

• Commonly known as ‘tidal waves’Commonly known as ‘tidal waves’

• Composed of a train of wavesComposed of a train of waves

CHARACHTERISTICS OF CHARACHTERISTICS OF TSUNAMISTSUNAMIS

• Long wave periodsLong wave periods

• Can achieve Can achieve extreme heights extreme heights

• Are rare eventsAre rare events

• At open sea, they At open sea, they travel extremely travel extremely fast, reaching fast, reaching velocities of 700 velocities of 700 Km/H (400 Mh/H)Km/H (400 Mh/H)

WHAT CAUSES TSUNAMISWHAT CAUSES TSUNAMIS

• Sub-marine earthquakeSub-marine earthquake• LandslidesLandslides• Volcanic eruptionsVolcanic eruptions• Cosmic – body impacts (asteroids, comets, etc.)Cosmic – body impacts (asteroids, comets, etc.)

WHAT HAPPENS TO A TSUNAMI WHAT HAPPENS TO A TSUNAMI AS IT APPROACHES LANDAS IT APPROACHES LAND

• Its height grows due to shoalingIts height grows due to shoaling

• They lose some energy as they rush onshoreThey lose some energy as they rush onshore

• Depending on the particular beach this Depending on the particular beach this makes surfing possiblemakes surfing possible

SPECULATION ON A MASSIVE SPECULATION ON A MASSIVE TSUNAMITSUNAMI• If an asteroid or comet 4 kilometers in diameter If an asteroid or comet 4 kilometers in diameter

were to strike the earth the resulting wave can were to strike the earth the resulting wave can make entire coastlines disappear and wreck havoc make entire coastlines disappear and wreck havoc on national infrastructures. If the body were large on national infrastructures. If the body were large enough, it would achieve the status of ELE enough, it would achieve the status of ELE (Extinction Level Event) and change our (Extinction Level Event) and change our fundamental way of lifefundamental way of life

THE IMPACT ON HUMANSTHE IMPACT ON HUMANS

• Tsunamis are considered catastrophic eventsTsunamis are considered catastrophic events

• They are rare, but very difficult to predictThey are rare, but very difficult to predict

• The death tolls of an attack can reach tens of The death tolls of an attack can reach tens of thousandsthousands

WAVE RESONANCEWAVE RESONANCEAn interesting wave phenomenon is the resonance effect that occurs whenAn interesting wave phenomenon is the resonance effect that occurs whena tsunami, or any other type of wave, comes into indirect contact with anothera tsunami, or any other type of wave, comes into indirect contact with anothermedium which has the same properties and part of its energy is transferred tomedium which has the same properties and part of its energy is transferred tothe other medium, thereby ‘resonating’ itself into places which otherwise itthe other medium, thereby ‘resonating’ itself into places which otherwise itwould have been impossible to enter.would have been impossible to enter.

WAVE SUPERPOSITIONSWAVE SUPERPOSITIONS

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The following mathematical equationsexpresses the processes of wave superpositions;when two waves come together and form a singleone with characteristics of both.In the picture we see an electronic wave simulatorwhich is showing this kind of phenomenon.

THANKS:THANKS:

• Ronen Avni for teaching us so very Ronen Avni for teaching us so very patiently the material and for his patiently the material and for his great examples.great examples.

• Technion for letting us use their Technion for letting us use their facilitiesfacilities

• Faculty of civil engineeringFaculty of civil engineering

• Ami and Guy for driving us around Ami and Guy for driving us around and helpand help