CMS-Wave:Transmission

Wave Transmission over structures

(Summarized from from JCR SI 59 pp7-14)

Impermeable Structures

Low-crested or submerged impermeable structures

Wave transmission is exhibited by fall of the overtopping water mass. The ratio of structure crest elevation to incident wave height is a key parameter governing the wave transmission. CMS-Wave calculates the transmission coefficient $K_{t}$, defined as the transmitted wave height divided by the incident wave height, based on the simple expression (Goda, 2000):

$K_{t}=0.3\left(1.5-{\frac {h_{c}}{H_{i}}}\right){\text{, for }}0\leq {\frac {h_{c}}{H_{i}}}\leq 1.25$

(Eq. 10)

Composite breakwater protected by a mound of armor units at its front

$K_{t}$ is calculated as

$K_{t}=0.3\left(1.1-{\frac {h_{c}}{H_{i}}}\right){\text{, for }}0\leq {\frac {h_{c}}{H_{i}}}\leq 0.75$

(Eq. 11)

where:
$h_{c}$ is the crest elevation of the breakwater above the still water level
$H_{i}$ is the incident wave height.

Permeable Structures

For permeable structures, wave transmission is calculated using modifications to d'Angremond et al (1996) formula.

Permeable rubble-mound breakwaters

$K_{t}$ is calculated using as:

$K_{t}=0.64\left[1-\exp \ \left(-{\frac {\xi }{2}}\right)\right]\left({\frac {B}{H_{i}}}\right)^{-0.31}-0.4{\frac {h_{c}}{H_{i}}}{\text{, for }}\mathrm {B} <10H_{i}$

(Eq. 12)

The remaining permeable structures effectively use a factor to increase transmission.

Highly permeable

Approximately $K_{t}$ from Eq. 12 increased by 25% (factor of 1.25)

Floating breakwater

Approximately $K_{t}$ from Eq. 12 increased by 50% (factor of 1.50)