Understanding Wave Dynamics

• Waves involve the interface of fluids with varying densities

Types of Progressive Waves

• Progressive waves include Longitudinal, Transverse, and Orbital
• Longitudinal waves, like sound, involve particle movement parallel to energy transfer
• Transverse waves, exemplified by a rope, feature particle motion perpendicular to energy transfer
• Orbital waves, such as ocean waves, have particles moving in a circular path

Wave Characteristics

• Crest is the highest point of a wave
• Trough is the lowest point of a wave
• Wavelength (L) is the horizontal distance between successive crests or troughs
• Wave Height (H) is the vertical distance between crest and trough
• Steepness is the ratio of wave height to wavelength (H/L)
• Period (T) is the time it takes for one wavelength to pass a fixed point
• Frequency (f) is the number of wavelengths passing a fixed point per unit of time.

Perturbing and Restoring Forces

• Perturbing force causes waves
• Restoring force returns the water to a still state
• Capillary Waves have wavelengths less than 1.74cm, with wind as the perturbing force and surface tension as the restoring force
• Gravity Waves begin when crests become pointed, wavelengths are greater than 1.74cm. Wind is the disturbing force, and gravity is the restoring force
• Tides have the moon and sun as the perturbing force
• Tsunami's can be triggered by earthquakes, volcanoes, landslides or storms

Deep-Water Waves

• Water depth is greater than ½ the wavelength
• There's negligible water movement due to waves below wave base

Shallow-Water Waves

• Water depth (d) measures less than 1/20 of the wavelength (L)
• Water "is aware" of the seafloor
• Speed in meters/second equals 3.13 times the square root of the depth (d½); depth must be in meters

Transitional Waves

• Transitional Waves possess characteristics mirroring both deep- and shallow-water dynamics
• Speed depends on both water depth and wavelength
• Wavelengths exist at >2x but <20x the water depth

Wave Height

• Wave height is directly related to wave energy
• Wave heights usually span less than 2m (which is 6.6 ft)
• Waves collapse, known as breaking, when steepness (H/L) exceeds 1/7

Factors Affecting Wave Energy

• Wind speed, wind duration, and fetch influence wave energy
• Fetch refers to the distance over which wind blows

Fully Developed Sea

• Characterized by an equilibrium condition, where waves cease to grow
• Highest documented wave height: 34 meters, 112 feet

Swell

• Features uniform, symmetrical patterns
• Travel outward from storm areas
• Move across significant distances while sustaining energy
• Exhibit decreasing steepness
• Have long crests

Wave Dispersion

• Longer wavelength waves travel faster and outdistance other waves
• Wave train describes a group of waves with similar characteristics
• Decay distance signifies the area over which waves shift from choppy conditions to uniform swell

Wave Interference

• Swell from different sources may interact leading to:
  • Constructive Interference: Waves in phase producing larger waves
  • Destructive Interference: Waves out of phase canceling each other out
  • Mixed Interference: Waves in and out of phase creating a complex pattern

Approaching Shore

• Constant wavelength waves touch the bottom, the wavelength shortens
• Velocity decreases, and wave height increases
• Swell becomes surf
• Waves slow, steepen, and break

Types of Breakers

• Spilling Breakers occur on gently sloping sea floors, expending wave energy over longer distances
• Plunging Breakers form on moderately steep sea floors, releasing wave energy over shorter distances
• Surging Breakers arise on the steepest sea floors, spreading energy over the shortest distance

Wave Refraction

• Wave refraction happens when waves approach the shore at an angle, causing them to bend
• As waves reach shallower water, they slow down

Focusing

• Irregular topography focus wave energy
• Headlands experience high erosion
• Sediment gathers in bays

Wave Reflection

• Reflection occurs when waves and wave energy bounce back from barriers
• Reflected waves can interfere with incoming waves
• Constructive interference can lead to the creation of dangerous plunging breakers

Internal Waves

• Internal waves are linked with pycnocline
• They are larger than surface waves
• Tides, turbidity currents, winds, and ships cause them
• Internal waves pose potential hazards for submarines