IMS 13 - Waves

Waves

Source

·         Wind (radiated all directions)

·         Coastal landslides, calving icebergs (splash waves)

·         Seafloor motion, turbidity current, volcano eruption, fault slippage (seismic waves / tsunami)

·         Moon sun gravity pull (tide)

·         Tidal motion, turbidity, ships

·         Diff density (internal waves)

ü  Water–water interface

ü  Height > 100 m

Property

·         Ripples / capillary waves (L < 1.74 cm)

·         More energy, becomes gravity waves > 1.74 cm

·         Wave period, T, interval between successive crests

·         Still water lvl = 0 energy lvl (halfway between crest & trough)

·         Wave steepness = H /L

·         Steepness > 1/7; unsupportable & breaks

·         Water x travel, waveform travels; energy passed circularly (Circular Orbital Motion)

·         Diameter = height

·         Wave base = depth of negligible circular orbits; ½ of L

·         High L, high speed

·         Shallow-water waves depth < 1/20 L

Transitional waves

·         Between shallow & deep

·         L = 2x – 10x depth

Energy depend on

·         Speed, period & distance of wind

·         Speed reduce, wave steepness reduce, become long crested waves (swells)

Speed depend on

·         Depth & wavelength

Swells

·         Uniform, symmetrical waves radiate from origin

·         Little energy loss; transport energy

·         Possible @ distant shoreline with x wind

Interference Pattern

·         Diff storm swells join

·         Constructive

·         Destructive

·         Mixed Interference

ü  2 swells of various heights & lengths

ü  Form diff sequence of high & low waves

ü  Irregular wave pattern when swell approach shore

ü  Large hazardous waves @ open ocean

·         Deep waves toward shallow water; Depths < L/2 à transitional wave

Speed reduce, wavelength reduce, energy contribute height, steepness rise, wave break
Surging breaker – abrupt beach slopeUnnoticed @ deep water till shore

Breaker Types

·         Spilling breaker – gradual beach slope

·         Plunging breaker – steep beach slope

Tsunami

·        Sudden sea topography change

·        Fault slippage / avalanche / eruptions

·        Displace crust, earthquakes, seafloor rupture

·        Ocean basin volume change

·        L > 200 km (shallow-water wave everywhere)

·        700 km/hr @ open ocean; height 0.5 m