EAE 05 Waves (9)

Question 1

Wave types

What is the period of Capillary waves?

Answer 1

<0.1 s

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Question 2

Wave types

What is the period of ‘chop’?

Answer 2

1-10 s

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Question 3

Wave types

What is the period of ‘swell’?

Answer 3

10-30 s

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Question 4

Wave types

What is the period of ‘seiche’?

Answer 4

10 min - 10 hour

The word originates in a Swiss French dialect word that means “to sway back and forth”, and (according to wikipedia) refers to a standing wave in an enclosed or partially enclosed body of water.

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Question 5

Wave types

What is the period of ‘Tsunami’?

Answer 5

10-60 min

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Question 6

Wave types

What is the period of ‘Tide’ waves?

Answer 6

12.4-24.8 hrs

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Question 7

What are surface ocean waves?

Answer 7

Surface ocean waves are along an air-water interface and affect only surface water

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Question 8

What are ‘internal waves’?

Answer 8

Waves along a water-water interface

• E.g between low density surface water and higher density deep water.
• They are much larger than surface waves

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Question 9

What is a transferse wave?

Answer 9

Particle motion is perpendicular to wave motion

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Question 10

What is a longitudinal wave?

Answer 10

Particle motion parallel to the direction of wave motion

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Question 11

What is the wave base?

Answer 11

Line below which water movement due to waves is negligible.

The wave base, in physical oceanography, is the maximum depth at which a water wave’s passage causes significant water motion. At water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.

(From wikipedia)

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Question 12

How does the wave base relate to the wavelength?

Answer 12

The wave base is approximately half the wavelength

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Question 13

What is wave steepness?

Answer 13

Wave height

────────────

Wavelength

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Question 14

What is a practical application of knowing the wave base?

Answer 14

Floating bridges, floating oil rigs & floating runways all have most of their submerged mass (pontoons) below the wave base.

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Question 15

Wht generates most waves?

Answer 15

Most waves are caused by the wind

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Question 16

How do strom waves behave?

Answer 16

Wind blowing over the ocean creates ‘stress’ deforming the ocean → capillary waves

This gives the wind something to ‘catch’ onto, increasing the interaction between wind and ocean surface energy

The wind increases wave height and speed, until wave speed = wind speed (fully developed sea)

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Question 17

What are the 5 factors that control wind waves?

Answer 17

• Wind waves
• Wind duration
• Fetch
• Original sea state (“old seas”)
• Water depth (in shallow water)

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Question 18

What is ‘Fetch’ for waves?

Answer 18

The horizontal distance over which wave-generating winds blow.

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Question 19

What is wave celerity?

Answer 19

The speed a particle moves along the wave vs. the speed the wavefor mores.

In deep water wave length increases with wave period.

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Question 20

What is shallow water transformation?

Answer 20

As deep water waves of swell move towards the continental margins, they eventually encounter water depths that are less than 1/2WL

• Height increases
• Wavelength decreases
• Wave period remains constant

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Question 21

When do waves break?

Answer 21

When H/L > ¹⁄₇ waves get steep and break.

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Question 22

What is the sequence of events with a Tsunami?

Answer 22

• Abrupt vertical movememtn along a fault on the sea floor
• Raises or drops the ocean water column above a fault
• Creates a tsunami
• Tsunami travels from deep to shallow water
• It is experience as alternating surges and withdrawls of water at the shore.

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Question 23

What are typical tsunamin parameters?

Answer 23

Wave length > 200 km

Wave Height ≈ 1 m (very low)

L is so large it is a shallow water wave everywher in the ocean!

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Question 24

What is the speed of a Tsunami?

Answer 24

It is a shallow water wave everywhere in the ocean → speed is dependent on depth.

c = √gd

∴ c = √9.8*4000 = 200 m/s = 712 km/h

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