An Investigation into the Effects of the Experimentation Scale Upon Unsteady Non-Darcy Flows Through Rubble Mound Breakwaters

As the pore pressure within core materials in rubble mound breakwaters affect the armours stability, it
is often necessary to consider scale effects when related designs call for a hydraulic model study based
on the Froude criterion. This paper describes findings of an analytical evaluation of unsteady
transitional flow regimes through coarse porous media in an attempt to develop a modelling law based
on similarities between hydraulic behaviours of the model and the prototype. A non-linear analysis
approach based on the so-called modified Forschhiemer equation has been employed in developing
necessary equations needed for scale effects assessments. It has been made clear that the grains scale
ratio is not a constant and its power varies with variations of the flow regime. The extent of the
validity of findings in enabling correct interpretation of experimental results have been examined
using available field data published by previous researchers for rubble mound structures.