OWC

use flapper valves so you need only a unidirectional turbine

I remember doing a complicated calculus calculation for the oscillation of a water column in the instrument leg lines for an orifice plate (3rd yr university, fluid dynamics course, 35 years ago). The math is complicated, but can be done. It depends on the ratio of the diameter to length of tubing, density of fluid, viscosity, temperature, etc.

You have probably already encountered these articles:

http://adsabs.harvard.edu/abs/1982JEner...6..157R

http://www.mech.ed.ac.uk/research/wavepower/turbine/index.htm

Evidently Wells turbines need to be spun up to speed, like the early electric clocks. They won't start rotating with just a pressure differential. You might find it useful to construct a working model to discover some of the other quirks of this beast.

Can you use 4 flapper valves and make the mechanical equivalent of a full-wave rectifier bridge? And a flywheel (capacitor) to keep it moving at a steady pace. Always wondered if that would work.