The Dynamic Behaviour of an ROV in Wave Affected Zones

Abstract

We present a method to directly predict the hydrodynamic response of a Remotely Operated Vehicle (ROV) as it transitions through the wave-affected splash zone during launch or recovery. ROVs are commonly used in offshore operations and for many different purposes. They are usually deployed from a purpose built Launch and Recovery System (LARS) located on the open deck of a surface ship. Current industry practice used for LARS design is to use a pre-defined dynamic amplification factor (DAF) together with high factors of safety. However, this does not properly account for the influence of different sea states and operational profiles. We therefore propose an improved method to directly predict the hydrodynamic response of an ROV as it transitions through the wave-affected splash zone. We apply the approach to a trencher ROV and validate using physical experiments completed in a wave tank. We demonstrate the need to for an accurate definition of the added mass and damping characteristics of the ROV. The method is incorporated into OrcaFlex for direct use within the design and analysis of a LARS system.