As an example, the armour of a breakwater is often scaled for stability to ensure that the armour will become unstable under the same conditions at scale as it would at prototype. Conversely, in a test for armour stability, the core material (material within the breakwater beneath the armour layer) is scaled based upon permeability, to ensure that the level of energy reflection generated by the internal parts of the breakwater is not excessively high, as it would be were the core material scaled for stability rather than permeability. If the reflection generated were too high, the armour material would become unstable under smaller wave conditions, resulting in over-engineering of the breakwater with excessively large material, and potentially significantly increasing the construction costs.
However, we often test a partially constructed breakwater phase during which core material may be exposed at the surface, as the armour material has not yet been placed. Under these circumstances, scaling the core material for permeability would make the material too big, causing it to be more stable than would otherwise be expected. The core material must therefore be scaled for stability in this instance.
Understanding this sort of complexity in scaling is crucial to ensure the most accurate results from our tests, so we draw on our many years of expertise in the area. Another essential element is our vast modelling hall, with its variety of basins, flumes and free-standing models, which allows us to build at an optimum scale for the task in hand.