Wave Breaking

Question 1

motivation for investigation

Answer 1

-it dissipated E and controls wave height close to the shore, effects the forces felt by infrastructure
-breaking contributes to turbulence and mean current, therefore sediment and pollutant transfer
-used recreationally for surfing

Question 2

shoaling

Answer 2

energy conservation with dP/dx=0 as the wave feels the bed and undergoes transformation
-period remains unchanged

Ks = H/H0

Initiation of breaking
-as group velocity decreases and steepness increases the wave loses stability
-depth induced breaking

Question 3

breaking limits

Answer 3

-u_max > c
-(dw/dt)max > g

flat bed
-H_limit/L = 0.141
-H_limit/d = 0.8

slope requires Ni and gamma n dat

Question 4

breaker types

Answer 4

spilling: Ni < 0.45
plunging: 2.3 > Ni > 0.45, barrel looking
collapsing: 3.2 > Ni > 2.3, collapses @ shore
surging: Ni >3.2, dips down then comes up

-after breaking the wave stabilises and propogates as a broken wave with H decreasing as E dissipates

Question 5

Saturation

Answer 5

-H(d) with gamma.d being the max energy availaible at that depth
-saturation assumes E to be at its max according to the wave breaking criteria with excess E being dissipated
* reasonable first approximation
* hard to when saturation have been reached
* higher initial H/E means earlier breaking

Question 6

Energy dissipation

Answer 6

-saturation not applied to plunging breaker
-H now dependent on E flux balance assuming negligible friction loss and a gentle beach slope

dP/dx = -Db
- P [J/m]
- Db [J/m2s]