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Ocean Modelling for Resource Characterization Chapter | 8 221

generally greater than the vertical velocities, and CFD will neglect effects of
stratification and Earth’s rotation (e.g. Coriolis).
CFD is routinely used to deal with fluid/structure interaction and scenarios
where there are strong shocks. The temporal and spatial scales are considerably
different between CFD and ocean model simulations. In the latter, timescales
of lunar, seasonal, and decadal are not uncommon, whereas CFD models may
be dealing with simulation timescales of several seconds to few hours. CFD
models will resolve fairly limited spatial scales (albeit at high resolution), such
as the diameter of a tidal stream turbine, whereas ocean models are applied
to regional (e.g. 10 km) and ocean basin (1000 km) length scales. CFD models
usually require a special treatment of the free surface as their moving boundary
condition. However, ocean models are usually based on a 2D approximation
(depth-averaged) and compute water elevation or free surface as a state variable,
more conveniently.

8.9 MODELLING CASE STUDIES
To demonstrate some of the principals introduced in this chapter, we examine
two modelling case studies—a wave resource model of Galway Bay (Ireland)
and a tidal resource model of Orkney (Scotland). We focus on model setup and
validation for the Galway Bay case study, and model setup and interpretation of
3D results for the Orkney case study.

8.9.1 Wave Model of Galway Bay (Ireland)
5
SmartBay is Ireland’s national marine test and demonstration facility, suitable
for the testing of scaled devices. It is located in Galway Bay, on the west coast
of Ireland (Fig. 8.17). The presence of an island chain, the Aran islands, at the
entrance to the bay, leads to relatively quiescent wave conditions within the bay,
yet a wave climate that is characterized by ‘scaled’ Atlantic conditions [26].
The purpose of this exercise is to describe the setup of a SWAN wave model
of Galway Bay, including sources of data, validation, and some results on wave
resource assessment.

Model Setup
The model bathymetry was derived from the EMODnet dataset—available at
a grid resolution of 1/480 × 1/480 degrees (approximately 200 m) throughout
Europe. This bathymetry data was bilinearly interpolated onto a spherical model
grid, which covered the inner nested region shown in Fig. 8.17 (which has
dimensions approximately 1.0×0.5 degrees). The same bathymetry dataset was
used to define the coastline, and was corrected from LAT to MSL.

5. See http://www.smartbay.ie/.