Download - Ocean Waves – Chp 10 Newest Extreme Wave (2006) Shark Park – off Channel Islands (San Miguel), CA
Ocean Waves – Chp 10
Newest Extreme Wave (2006) Shark Park – off Channel Islands (San Miguel), CA
• Announcements
– MIDTERM – Monday 4pm• Covers: Chapters 1-9 (excluding Chp 7), (not Todays)
• 40 Multi Choice Qs
• 5 Short answer Qs
• All based on Lecture Notes/Qs
• Bring GREEN Scantron (Bookstore)– #2 Pencil
• HW-3 due Wed
• HW-4, HW-5 (Nat. Bridges) due w/ Final
• See Syllabus (website) for details
• Announcements
– Your Homework – Do it!
• If you don’t you loose 30-45% of your grade!!!
• Turn it in!
• DON”T WAIT TILL THE LAST MINUTE
• HELP me to HELP YOU
– FYI HW-3, Skip Question d) on Page 6
• In Search of The Perfect Wave
• Development of Wave Theory
• What is a Wave?
• Wave Theory
• Analyzing Natural Waves
• Wave Generation by Winds
• Wave Interactions with Seafloor
• Applications of Wave Theory
OUTLINE
• In Search of The Perfect Wave (1966)
• In Search of The Perfect Wave
• Development of Wave Theory
• What is Wave?
• Wave Theory
• Analyzing Natural Waves
• Wave Generation by Winds
• Wave Interactions with Seafloor
• Applications of Wave Theory
OUTLINE
• Development of Wave Theory
– Sir Isaac Newton (1642-1727)• First mathematical descriptions of waves, 1687 Principia.
• Proposed motion of water particles in a wave was circular
– Franz Gerstner (1756-1832)• Develops 1st primitive wave theory
– Particles traveling at the crest of wave move up/forward
– Particles traveling at the trough of wave move down/backward
– Motions traced a circle
» Height @ surface = Height of Wave
• Development of Wave Theory– Ernst Weber (1795-1878) - Anatomy Professor– Wilhelm Weber (1804-1891) - Physicist
• Built first WAVE Tank– Confirmed Gerstener’s circular Motions.
• Development of Wave Theory
• WWII – Securing a Beach Head– Commanders wanted to Known type of Sea Conditions– Walter Munk
• (Army Corp. Engineers)
– With Harald Sverdrup (SIO)• Undertake Surf forecasting
– Prediction of waves @» Given location/time
– 1960s_Munk’s lifes work• Deploys buoy devices etc.
– Alaska New Zealand
• Munk Concludes– “Predictions of surfing conditions @ Honolulu possible, but from what I know of the Surfing profession I don’t suggest this as a lucrative enterprise” ???
. . .Before his time. . . But TODAY >>>>
• High Tech Surf Forecasts Now Exist– Web Cams, Reports, Forecasts/ Conditions etc.
SurfersHow Many?
1,736,000. -Rode a waveOnce/year
Estimates5 -17 million. . .Overall
1960s ≤10,000
Matt Warshaw-Encyclopedia of Surfing
• Development of Wave Theory– Technology Drives the Study of Waves
• Wave Heights, Wind speeds, mea. using Satellites & Buoys
– Major Application behind Study of Waves• Application to Coastal Engineering Problems
• Vessel Safety @ Sea
• In Search of The Perfect Wave
• Development of Wave Theory
• What is a Wave?
• Wave Theory
• Analyzing Natural Waves
• Wave Generation by Winds
• Wave Interactions with Seafloor
• Applications of Wave Theory
OUTLINE
• What is a Wave?– Waves result from the movement of E through a medium
• = progressive waves – e.g. oceanic, seismic, sound waves
Challenge Qs
– What do Progressive Ocean waves arise from?• A disturbing Force
– Force that Transmits E to the water column or surface via Wind or Earthquake
– What are Waves from Episodic Events (e.g. Winds, Earthquakes) called?
Free Waves - travel without any further influ. of Disturbing force
–What are Waves from Continual Events (e.g. tides) called?
Forced Waves - under continual influence of disturbing force
(e.g. gravity from Moon or Sun)
NOTE: Restoring Forces - Drain the Wave of it’s E
• What is a Wave?– Anatomy of a Wave
• As E is transferred thru fluid the wave particles move in circular motion – aka orbital
Where is the Crest (Peak)?
Where is the Trough (Valley)
What is the Wavelength (λ)?
Dist. b/w peaks (crests) What is the Wave height (h)?
Dist. b/w Crest - Trough
λ
h
• What is a Wave?– Anatomy of a Wave
• What is the Period of a Wave?– Amount of Time passing b/w wave peaks
» (how far are the peaks apart in time)
• What is the Wave frequency?– How often peaks are passing same point in time
• What is a Wave?– Classification of Waves
• According to their?– Period
– Wavelength
– Frequency
– Distributing force
• What is a Wave?– Summary
int
• In Search of The Perfect Wave
• Development of Wave Theory
• What is a Wave?
• Wave Theory
• Analyzing Natural Waves
• Wave Generation by Winds
• Wave Interactions with Seafloor
• Applications of Wave Theory
OUTLINE
• Wave Theory• Mathematical description of waves allows us to?
– Predict behavior under diff. circumstances– Forecast their arrival on beaches
• Surf forecasters make use of Wave theory to predict:– When & Where ocean waves have their greatest impact on shore.
• Wave Theory– Wave Speed (Velocity ~ V)
• V = Wavelength / Period (Time) or V = λ / T– Waves with different wavelengths and periods travel @ diff speeds
– Since λ /T are proportional increases in Wind speed (C) lead to?
» Increases in either Wavelength or Period or both
» Note: the PERIOD does NOT change once Wave is formed
• Wave Theorycalculating wavelength (λ)
λ = T2g/2π
– T = period time – g = Acceleration of gravity 9.8 m/s-2 or (32 feet/sec)– π = Pi ~ 3.1415
λ
• Wave Theory– What are Shallow water waves?
• Waves traveling in H2O whose depth is less than one-twentieth (1/20) of the wavelength of the wave
– What are deep water waves?• Waves whose propagation is NOT affected by the seafloor
– What are intermediate water waves?• Surface waves in b/w the deep and shallow water approximations
1/20 > h/ λh/λ > 1/2
or Velocity (V)
• Wave Particle Motions– For Deep-water waves
• Diameter of wave orbital – Based on Height
• Challenge Question?– What happens to the diameter of
» wave orbitals with depth?
– They shrink (diminish)
» disappear
• Wave Particle Motions– For Shallow-water waves
• Diameter of wave orbital hits bottom– Becomes ovular b/c of:
» friction/ drag effects etc.
» e.g. notice Kelp moving
Back/ fourth
• Wave Energy (E)
E = 1/8 p g H2
• P = water Density
• g = accel. of gravity
• H = height of Wave
– WHAT TO KNOW– Equation states that:
• E increases as the Square of the waves Height– i.e. if you 2X the wave height 4X Wave E!!!
– e.g. 6 m (20 foot) wave has 4 Xs as much E as 3 m (10 foot) wave
~ 10 feet
~> 20 feet
• In Search of The Perfect Wave
• Development of Wave Theory
• What is a Wave?
• Wave Theory
• Analyzing Natural Waves
• Wave Generation by Winds
• Wave Interactions with Seafloor
• Applications of Wave Theory
OUTLINE
• Analyzing Natural Waves
• Wave Interference– Challenge Questions
• What is produced when Crests/ troughs of Waves are offset?– Destructive interference
» Cancel each other out
• What is produced when two wave Crests overlap exactly?– Constructive interference
» Doubling of wave height!
• Wave Interference– Summary
• Wave E Spectrum– Knowing H and frequency of Waves wave E spectrum
• @ given location / set of conditions exist?
Wave E spectrums
• In Search of The Perfect Wave
• Development of Wave Theory
• What is a Wave?
• Wave Theory
• Analyzing Natural Waves
• Wave Generation by Winds
• Wave Interactions with Seafloor
• Applications of Wave Theory
OUTLINE
WIND WIND WIND WIND
• Wave Generation by Winds– From Atm. Winds to sea surface. . . .– Some wind E causes surface currents
• Most Wind E waves
• Wave Generation by Winds– Challenge Qs
• What factors of wind determine the severity of the waves?– Speed of Wind
– Length of Time in Blows (duration)
– Distance over which it travels aka?
» Fetch
»Fetch
• From Calm to Fully Developed Sea– IT all starts with the Wind swells
– What are Swells?• Long wavelength - surface waves (group)
– traveled long distances
– (more stable then wind waves)
Coming to a Shore Near YOU!!!!
• From Calm to Fully Developed SeaWhat is Wave Steepness ~ S ?
• S = H/ λ Challenge Q
• What happens when steepness exceeds 1/7 or (0.142) ?– e.g. wavelength = 7m, wave height ≥ 1m
the formation of White caps
0.16
Discovered aboard FLIP
• In Search of The Perfect Wave
• Development of Wave Theory
• What is a Wave?
• Wave Theory
• Analyzing Natural Waves
• Wave Generation by Winds
• Wave Interactions with Seafloor
• Applications of Wave Theory
OUTLINE
• Wave Interactions with Seafloor– When deep water waves hit seafloor what happens?
• 1) Friction slows down wave, decreases wavelength
• 2) Orbitals become ovular
• 3a) Height/steepness of Wave increases
• 3b) Wave overly steep: S > 1/7 Breaks!
• Wave Interactions with Seafloor– Bathymetry Matters
• RECALL
http://www.youtube.com/watch?v=7BOhDaJH0m4&feature=related
TUBE – a product of an ocean floor
• WAVES– Now the Whole Package Comes together
– A SUMMARY of Some Concepts & Big Waves– http://www.kqed.org
/quest/television/science-of-big-waves
• In Search of The Perfect Wave
• Development of Wave Theory
• What is a Wave?
• Wave Theory
• Analyzing Natural Waves
• Wave Generation by Winds
• Wave Interactions with Seafloor
• Applications of Wave Theory
OUTLINE
• SURF Forecasting– Confirming your knowledge
• What are the major factors u need to form Considerable Waves?
• Fetch (long distance for wind to blow)
• Sustained High winds
• Bathymetry effects– Most intense waves occur where?
» It gets Very shallow Very fast
» And or the wave bends around an obstruction
Pipeline, HI
• Challenge Question– Could Anyone really surf Lake Tahoe?
• ?
– What conditions would be needed? • Sustained High Winds
• Lots of Fetch– What direction?
• Bathymetric
Obstruction
where?
So Locate the best Possible Surf break?
1600’
• 11/29/2009- Powerful Winter Storm Hits Tahoe Basin– 60-100 mph Winds from South!– It Can been done! and Was!!!
Munk would be proud
• Applications of Wave Theory– Tsunamis
• A real Serious Threat!
• Warning System (when earthquake registers – Send the Alert)• Few minutes all you need – get to Higher Ground (2nd story)
• Applications of Wave Theory– Tsunamis
• Generated by vertical displacement of seafloor – (earthquakes)
– Landslides
– Eruptions
• Do they Have Large or Small Wavelengths?– Very Large: When reach shore, What Happens?
– a Big WAVE!
• Challenge Question?– If out to see in row boat earthquake/ Tsunami Hits
» Could you notice a change in sea level change?
» NO – b/c the very longggggg wavelength –
» Small sea surface height change/time
• Applications of Wave Theory– Tsunamis
• Generated by vertical displacement of seafloor – Creates upsurge of Water
Propagates outward
» Very Tall waves
Exceed sea levelhttp://www.youtube.com/watch?v=4Xebwzb3dDE&feature=related
ANIMATION / Summary
http://www.youtube.com/watch?v=g15sZ_d2WUY&feature=related
• Applications of Wave Theory – Final Thoughts
– Knowing what we Know about Waves• What can we do?
• Early detection of Earthquakes etc. Tsunami Warning System
• Erosion – Next Time (Beaches/ Tides etc.)
• Can we make our own surf?
• Applications of Wave Theory– Human Made Surf Breaks?– A potential Reality
Will Bournemouth Surf Reef Ever Produce Waves? Australia
JUST NEED THE RIGHT conditions -Pending . . .
http://www.kqed.org/quest/television/science-of-big-waves
• Remember Midterm Monday – – Green Scantron– Study your notes
• Have a Peaceful Weekend
http://www.youtube.com/watch?v=ElpzfM5knYA&feature=related
Tsunami CBS
http://www.youtube.com/watch?v=g15sZ_d2WUY&feature=related
http://www.youtube.com/watch?v=4Xebwzb3dDE&feature=related
Tsunami Graphic
http://www.youtube.com/watch?v=deX7R9RbmX0&NR=1
ROGUE waves