OCEN 671
Mid-Term Examination
Closed Book (50 min) Fall 2013
1. (6%) With the same on-shore wind, please determine which of the following order of the three continental shelves given below resulting in the surge elevation at the shore line from the largest to the smallest.
a. Parabolic, slope and flat b. Slope, parabolic and flat
c. Flat, slope and parabolic d. Slope, flat and parabolic
2. (3%) A wave train of wavelength 500m is propagating in water depth 50m. It can be considered as
a. Deep water wave b. Shallow water wave
c. Intermediate depth water wave d. None of them
3. (6%) The period of the wave described in Problem 2 is
a. 21.002 s b. 20.180 s
c. 24.026 s d. if none of them, given your solution
4. (6%) The group velocity of the wave described in Problem 2 is
a. 22.147 m/s b. 18.504 m/s
c. 10.405 m/s d. if none of them, given your solution
5. (5%) The bottom friction may reduce the amplitude of waves propagating in shallow water. The reduction increases with
a. The decrease in water depth b. A larger wave amplitude
A rougher seabed d. All of them
OCEN 671
Mid-Term Examination Page 2
6. (14%) A regular wave train of period T = 1.0 s is generated by a wavemaker (at x = 0). Suppose the wavemaker starts at t = 0 and a wave gage is deployed at x = 30 m (from the wavemaker). When will the (right-going) incident wave arrive at the gage? If the wave amplitude is 0.1 m, what is the energy density and the related energy flux? (The water depth in the tank is 2.0 m and density of water is 1,020 kg/m^3)
7. (12%) Regular incident waves of height 1 m and period 10s are propagating from the left to the right. It is partially reflected from and transmitted through the breakwater whose transmission and reflection coefficients are Kt = 0.2 and Kr = 0.8, respectively. What are the possible maximum and minimum wave heights at both sides of the breakwater?
.
OCEN 671
Mid-Term Examination Page 3
8. (34%) A pressure sensor is located in the deep water as shown in the sketch, where a = 10 m. Its pressure record of a progressive wave is shown in the figure,
Please find: 1) wave length L,
2) wave amplitude A,
3) the amplitude of the wave horizontal velocity at the pressure sensor.
4) the amplitude of the wave horizontal acceleration at the pressure sensor.
OCEN 671
Mid-Term Examination Page 4
9(14%) A deep water wave train of 18s period and 5 ft wave height propagates perpendicularly towards the shoreline.
a) What is its wave length and height at the water depth h = 15 ft?
b) According to the McCowan’s criterion, is this wave breaking there?
Assume that the slope of the beach is very gentle and the reflection wave is neglected. The bottom contours are straight and parallel to the shoreline.