Waves Flashcards
(29 cards)
what do waves transport across oceans?
energy, not water mass - via orbital motion in water column. (gravity brings water straight back down after going up)
at what depth does orbital wave motion stop?
at 0.5 x wavelength (L)
what is wave shoaling
the process where waves slow down, get taller, and compress as they enter shallow water
when does shoaling start?
when water depth = 0.5 x wavelength (Lo)
what is wave height (Hsig)
the average height of the highest 1/3 of waves - used in irregular wave analysis
what causes wave breaking?
when the base of the wave is slowed by friction at the sea bed and the crest of the wave keeps rushing forward till it crashes over. (combination of wave height to depth ratio, beach slope, and wave energy.)
what changes in wave properties occur during shoaling?
Wavelength (L) ↓
Height (H) ↑
Wave period (T) constant
Velocity (C) ↓
Energy Density (E) ↑
Energy Flux (P) constant
what is wave energy flux?
the rate at which wave energy is carried forward (P=E xCxN)
what is the difference between sea and swell waves?
sea = young, choppy, close to generation force, swell = mature, consistent , travels away from generation force.
H (s) vs h
H (s) - sig wave height
h - water depth (height of water column)
most dominant wave type
ordinary gravity waves (and infra gravity waves next?)
what is wave period?
the time it takes for two crests or troughs to pass a certain point. T = L/C
wave terms - L, H, C, T, h or d
L = length
H = height (sig)
C = velocity or celerity
T = period
h / d = water depth
do wave orbits increase or decrease in size with depth?
decrease until nothing (stays within water column)
currents vs waves with the movement of things
currents transport objects in the ocean through water, but waves are only energy transfers.
Do ocean waves move water across the ocean?
No—they move energy through orbital motion. Water particles move in loops and return to their position.
airy/ linear wave
(simplest wave theory) symmetrical, small, deep ocean waves, (ignores water column beneath the wave and depth isn’t important?)
C, L, T relo equation
C=L/T, T=L/C, L=CxT
wave life cycle
generation to propagation to shoaling (coastal zone) to breaking (surf zone)
what are the two wave generation mechanisms and how does it work
miles, phillips. wind-wave interaction.
what are the two stages of growth described by Miles-Phillips mechanisms?
Linear growth (capillary waves) and exponential growth (wind-wave interaction)
phillips
wind cause random pressure (atmospheric) fluctuations generating capillary waves lead to miles
miles
existing waves grow as wind blows over them. crest - low pressure, trough - high pressure, leads to exponential growth.
sweeping mechanism
explains energy transfer from short period waves to long period waves after generation
