Page 180 - Fundamentals of Ocean Renewable Energy Generating Electricity From The Sea

In Situ and Remote Methods for Resource Characterization Chapter | 7 169

FIG. 7.8 Low profile (trawl-resistant) ADCP mooring. The acoustic release above the instrument
is used during the deployment stage; a similar acoustic release, in the base of the instrument frame,
is used during recovery. The top part of the mooring, which is buoyant, separates from the heavy
base when the (recovery) acoustic release is triggered. The top and bottom parts of the mooring are
connected by a cable, which is coiled inside the base prior to deployment.

period from their neighbouring constituents over the length of the record should
be included. For example, to analyse a signal for M2 and S2 requires a time
series of length
−1 −1
1 1 1 1

T r = − = − = 14.77 days (7.5)
T S2 T M2 0.500 0.517525
where T r is the required length of a signal to resolve M2 and S2 constituents.
Table 7.4 lists the record length that would be required to resolve semidiurnal
and diurnal constituents. Note that 30 days would be sufficient to resolve at least
M2, S2, N2, K1, and O1 constituents, which tend to dominate in most shelf sea
regions. However, despite theoretical estimates of the record length required to
resolve tidal constituents, deployment length often depends on external factors
such as cost, logistics, battery life, internal memory, and weather windows
suitable for deployment and recovery.
ADCPs have various modes of operation, one of which is high-resolution
pulse-pulse coherent mode; for example, the bin depth of the instrument can be