Question 3

A hurricane has a maximum sustained local wind speed of U₁0 = 45 ms¹¹.

a) What is the appropriate hurricane category?

b) What is the deep-water significant wave height (,) and peak frequency (fp) of waves produced

by the hurricane associated with U10?

c) If this wind speed occurs over water h= 15 m deep, determine the dimensionless shallow water

frequency hp and suggest whether we should use the JONSWAP or TMA spectrum to describe

the waves generated by this storm.

d) Plot the spectral energy density associated with this wind speed using the appropriate spectrum

you identified in part (c).

e) Using the spectrum from (d), determine the significant wave height H, at this depth of h = 15

m.

h

mg

The figure above shows the cross-sectional elevation of a deployable flood barrier used to protect

a community from coastal flooding. The barrier has length I and mass per unit width m (i.e., total

mass per unit distance into the page) and is connected to a frictionless hinge at ground level. As

flood waters rise, the barrier rotates about the hinge and adopts a position with angle such that

hydrostatic equilibrium is achieved for a given inundation height h.

a) Derive an expression for the water height has a function of m, 1, and 8. You may assume that

the mass of the barrier is uniformly distributed. Assume a density of sea water p= 1025 kg/m³.

b) Assuming m = 500 kg/m and I = 6 m, plot the water heighth as a function of 6 from 0 to 80°.

c) For the assumptions stated in (b), what is the maximum level of inundation that can be

accommodated by the barrier?