chapter 9 waves

8/7/2019 Chapter 9 Waves

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Wave Types

Surface Waves

Wind Generated Waves

Storm SurgeTides

Seismic Sea Waves (Tsunamis)

Standing Waves

Internal Waves

Same varieties as surface waves


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Anatomy of a Wave

Wave Crest: High point of the wave form.

Wave Trough: Low point of the wave form.

Wave Length: Distance from a point on one wave to the same point on the next

wave.


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Categories of Surface Waves

Deep Water Waves

Transition Waves

Shallow Water Waves

where,

h = Water depth

L = Wavelength

2

Lh "

220

Lh

L

20

Lh


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Wave Speed, Wave Length, and Wave

Period

Relationships for Surface Waves

T

LC!

where,

C = Wave Celerity

L = Wave Length

T = Wave PeriodC

LT !

TCL v!


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Calculating Wave Speed (Celerity)From Latin Celermeaning Swift

sec)/(5.1222

cmLLggL

CDeep !!! TT

Notice deep water wave speed is a function of wavelength and longer waves move faster.

Notice shallow water wave speed is a function of water

depth. Shallow water waves travel faster in deeper water.

where,

g = Gravity = 980cm/sec2

L = Wave length in centimeters

h = Water depth in centimeters

sec)/(3.31980 cmhhhgghCShallow !!!!


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Orbital Motion of Deep Water Waves

Notice water motion follows a circular path


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Orbital Motion of Shallow Water Waves

Notice water motion follows an elliptical path


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A Stationary or Standing Wave

Water flows back and forth about a node, a point with no vertical watermotion. The endpoints are antinodes, points with maximum vertical

water motion.


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Uninodal Standing Wave

Yellow dashed line indicates undisturbed sea level. Dots indicate water

motion.


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Binodal Standing Wave

Yellow dashed line indicates undisturbed sea level. Dots indicate watermotion.


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Standing Wave in an Open Basin

Yellow dashed line indicates undisturbed sea level. Dots indicate watermotion.


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Equations for Standing Waves

ghC!

gh

LT B

2!

where,

C = Wave Celerity

LB = Basin Length

T = Wave Period

g = Gravity

h = Water Depth

Notice wave speed is calculated with the shallow water

wave equation. This is also called the gravity wave speed.


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Internal Wave Propagation


motion.


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Internal Uninodal Standing Wave

Yellow dashed line indicates undisturbed sea level. Dots indicate water motion.


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Internal Binodal Standing Wave

Yellow dashed line indicates undisturbed sea level. Dots indicate water motion.


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Generating Internal Waves

The above images show how internal waves can be generated by passage of

a denser fluid or even a submarine.


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Atmospheric Internal Waves

Rising air cools, water condenses clouds form. Sinking air warms and

clouds evaporate.


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Internal Wave Propagation


motion.


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Breaking Atmospheric Internal

Waves

Internal waves break just like surface waves as shown by the above

photograph of an atmospheric internal wave traveling along the interface

between warmer air below and cooler air above. Black Forest, Germany.


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Wave Refraction

The image at right is a

photo of refracted

converging internalwaves taken from the

space shuttle. The

waves occurred off the

coast of Somalia and

were possibly caused by

variations in bottomtopography.


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Wave DispersionThe image at right

is a photo of

refracted dispersing

internal waves

taken from the

space shuttle. The

waves are formed

as water enters the

Mediterranean Sea

through the Strait of

Gibraltar. Shallow

water near the

edges slows that

part of the waveallowing the center

to move faster as it

flows through.


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chapter 9 waves

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