Waves Pt 2 Flashcards
What happens when the wave “feels bottom”?
slows, and the accompanying** reduction** in the **wavelength results **in increased
height and steepness as the wave’s energy is condensed in a
smaller water volume.
How do we calculate the steepness of the wave?
height/wavelength
(h/L)
What happens to hight and wavelength when steepness increases?
Height Increases
Wavelength decreases
What are breakers?
**shallow **water waves that become too steep at surface so they collapse
How do breakers work?
particles at the wave’s crest move faster **toward **the shore resulting in the **curling **of the crest and the eventual breaking of the wave
What happens if the wave steepness exceeds 1:7?
wave becomes** too steep **and the wave breaks
What are the types of breaker waves?
Spilling
Plunging
Surging
What are spilling breakers?
-lasts long and** continually breaking** and slowly loosing energy across the surf zone
-Most common
-Flat bottom
What are plunging breakers?
-entire wave front steepens, curls and **collapses, relesing energy all at once.
-Occurs** in** steep bottoms**
What are surging?
-Don’t break because it never reaches a critical wave **steepness.
(H/L)=1:7
-diminishes** in size and** looses momentum** as water
rushes up beach face
-occurs in** steep bottoms**
What are stokes drift?
mass** transport** of water forward in
the direction of wave energy** movement.**
How do stoke drifts occur?
Negligible in open ocean
Slow movement against coast causes nearshore
currents
What is the general speed of a wave equation?
Celerity(Speed)=wavelength/time
What happens to wavelgth as celerity is reduced
Wavelength is shortened
What are shallow wave speed infuenced by?
influenced more by** depth**
than wavelength
What are deep water waves influecnced by?
influenced by wavelength than depth
What is dispersion?
Sorting of free waves as they move because** long period waves travel faster** than short period waves in deep water.
What is deep water group speed?
when a group
of waves travels if generated by the same source in
deep water
What is deepwater group speed equation?
Group wave speed=individual wave speed/2
What is the shallow water speed equation?
celerity=3.13 * Sqare root of depth
What is the deep water speed equation?
celerity=1.56*period
What is gravitational acceleration?
9.81
What happens to the old wave when a new wave is created?
Outer-most **wave’s energy **is **lost **in advancing the
wave form into undisturbed water
What are deep wave interactions?
when wave groups
meet they pass through **each other** and** continue**
What is constructive interference?
if crests coincide, they reinforce each other.
What is destructive interference?
if crests go against each other, they cancel each other
What is Wind Generated Wave Height?
controlled by speed,
duration and fetch.
What latitude is best for big waves?
40-50 degrees
When is there large fetch?
When there are no landmasses
What are the traits of westerlies in 40-50 degree latitude?
continuous and strong
What are episodic waves?
abnormally high
wave that is unrelated to local storm conditions
How can modeling rouge waves contribute to practical applications?
They can** help **in establishment of mooring systems that can stablilize offshore platforms
What is a tsunami?
long period sea wave that is **produced
by an earthquake, volcanic eruption, sediment
slide or faulting**
How long are tsunami wavelengths?
very long
100-200 km
60-120 miles
How long are tsunami periods?
long
(10-20 minutes)
What type of wave are tsunamis?
**shallow water **waves.
Because depth is less than one-twentieth the wavelength
What are the 3 stages of tsunamis?
Generation
Propogagnation
Inundation
What is generation?
The **point **of **source **of energy for tsunamis?
what is propagation?
movement of tsunami waves through space
What is Inundation?
**flooding **of coastal systems
What is the equation to calculate the celerity of a tsunami?
celerity=3.13* squareroot of depth
What is NOAA’S project DART?
Deep Ocean assesment and reporting of tsunamis
What are internal waves?
Waves created below the ocean’s surface at the** boundary between 2 destiny layers**
What are sources of internal waves?
Low pressure systems depress pycnocline and when
storm moves away will oscillate until reaching
equilibrium.
* **Speed **of currents above or **below pycnocline
changes quickly.
* Bathymetric changes.
Wat are standing waves?
surface water oscillates vertically
between fixed points called nodes but there is no
progression.
What happens to standing waves with 2 nodes?
A progressive wave directly reflected back on itself produces a
standing wave, because the two waves—original and reflected
—are moving at the same speed but in opposite directions.
What do standing properties depend on?
geometry
of the basin that the wave is in.
What are examples of closed basins?
-teacup
-lake
-ocean basin
What is the relationship between length of the basin and period?
when the length of the basin is
increased the period of the wave is increased
What is the relationship between depth of the basin and period?
when the depth of the water is
increased the period is decreased
Can standing waves occur in basins?
Yes, but the formula changes and the node is usually located at the opening of the basin to open water.
What are examples of energy from waves?
(1) using the changing level of the water to lift an object,
which can then do useful work because of its potential energy.
(2) using the orbital motion of
the water particles or the
changing tilt of the sea surface
to rock an object to and fro.
(3) using rising water to
compress air or water in a
chamber
