Numerical wave force model for A-Jacks armor units

A numerical model is developed to estimate wave forces on a single A-Jacks armor unit under hydrodynamic loading. The forces modeled include drag, inertia, buoyancy and slamming forces as the unit penetrates the free surface. Force calculations are based on a discretized form of the Morison's equation for submerged elements and Von Karman slamming at the free surface. The model integrates the equation of motion to determine rotation about the axis with the minimum stability. Wave flume tests for incipient rotational motion conditions are used to provide preliminary verification of the wave force model. Bulk forces on a matrix of units are also modeled using empirically determined sheltering coefficients to account for frontal area reduction. The bulk force model was in reasonable agreement with experimental measurements.