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CHAPTER 5. COASTAL STRUCTURE MODELS
Ramkema (1978) presented an isothermal compression model law (in
graphical form) that can be used to scale pressures measured in a Froudescaled model up to prototype values. Also, Ramkema stated that the spatial
pressure distribution over the protruding structure will be geometrically
similar to the prototype distribution, but he warned that the model law may
not be applicable to the case of compression impacts caused by breaking
waves.
Hammer Shock. The third type of shock pressure that breaking waves
can produce on vertical structures is hammer shock, which is shown as
the bottom illustration on Figure 5.7. Kamel (1968) related the theoretical
maximum pressure that occurs to the elasticity of the vertical-wall structure
material and the compressibility of the water. He ignored the effects of
trapped air. Kamel’s relationship is
P, =
/’'fi „ Pw
Vw
(5.53)
Pw
"T Pv t>tl
where
pt
- theoretical maximum pressure
pv
- mass density of the vertical wall
pw
- mass density of the water
Cv
- speed of sound in vertical wall
Cw
- speed of sound in water
Vw - velocity of the wave front impacting the wall
Kamel’s experimental plate-drop tests never produced any pressure values greater than 50% of the theoretical estimates because an air cushion
prevented the plates from instantaneously impacting the water. Hudson,
et al. (1979) cited additional reasons why actual maximum pressures are
unlikely to exceed 0.5
Hudson, et al. concluded that model tests of
wave-induced hammer shock on vertical-wall structures are considered unnecessary, but they also pointed out that model tests scaled to the Froude
criterion are useful for examining the relative magnitudes of hammer shock
for different geometric shapes, such as concave breakwaters.
5.4.2 Vertical-Wall Structure Scale Effects
Physical models of vertical-wall structures have many of the same laboratory effects as discussed in Chapter 4 in connection with short-wave, fixedbed hydrodynamic models. These include effects related to model boundary
CHAPTER 5. COASTAL STRUCTURE MODELS
Ramkema (1978) presented an isothermal compression model law (in
graphical form) that can be used to scale pressures measured in a Froudescaled model up to prototype values. Also, Ramkema stated that the spatial
pressure distribution over the protruding structure will be geometrically
similar to the prototype distribution, but he warned that the model law may
not be applicable to the case of compression impacts caused by breaking
waves.
Hammer Shock. The third type of shock pressure that breaking waves
can produce on vertical structures is hammer shock, which is shown as
the bottom illustration on Figure 5.7. Kamel (1968) related the theoretical
maximum pressure that occurs to the elasticity of the vertical-wall structure
material and the compressibility of the water. He ignored the effects of
trapped air. Kamel’s relationship is
P, =
/’'fi „ Pw
Vw
(5.53)
Pw
"T Pv t>tl
where
pt
- theoretical maximum pressure
pv
- mass density of the vertical wall
pw
- mass density of the water
Cv
- speed of sound in vertical wall
Cw
- speed of sound in water
Vw - velocity of the wave front impacting the wall
Kamel’s experimental plate-drop tests never produced any pressure values greater than 50% of the theoretical estimates because an air cushion
prevented the plates from instantaneously impacting the water. Hudson,
et al. (1979) cited additional reasons why actual maximum pressures are
unlikely to exceed 0.5
Hudson, et al. concluded that model tests of
wave-induced hammer shock on vertical-wall structures are considered unnecessary, but they also pointed out that model tests scaled to the Froude
criterion are useful for examining the relative magnitudes of hammer shock
for different geometric shapes, such as concave breakwaters.
5.4.2 Vertical-Wall Structure Scale Effects
Physical models of vertical-wall structures have many of the same laboratory effects as discussed in Chapter 4 in connection with short-wave, fixedbed hydrodynamic models. These include effects related to model boundary