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Title: Physical testing of RHIB and mother ship interactions for Launch and Recovery simulation validation

Author(s): N. Carette et al

Abstract: The LAURA JIP (Launch and Recovery system of any small naval craft), is developing a Naval Launch and Recovery (L&R) standard which will allow ships from various Navies to exchange small craft with each other. It is vital that the safe operating limits of these L&R operations are fully understood. To support this understanding a numerical modelling capability is being developed. This capability will also provide operator guidance to Navies as well as assist L&R system designers to optimize and validate their systems. The scenario is very complex due to the role various aspects play in the interactions between the smaller craft and the mother ship. It is vital that these are fully understood and modelled accurately. The LAURA JIP will develop this numerical simulation capability by: (1) a hybrid simulation environment whereby the various aspects of the L&R process will be modelled using various numerical tools and (2) a time domain seakeeping program that appropriately accounts for the hydrodynamic interaction effects that occur during L&R evolutions, including the effect of the boat rope. The aspects of the L&R operation considered include viscous forces acting on a RHIB operating at low speed, wave interaction between the mother ship and the RHIB, towing and lifting line forces, course control of the RHIB, as well as slamming and impact loads on the RHIB. To assist in the validation of these numerical modelling tools a series of scaled physical model tests have been undertaken. These tests include: (1) captive planar motion manoeuvring tests with two different RHIBs to derive manoeuvring forces in calm water, (2) towing tests of a RHIB in calm water, with and without a lifting line, (3) captive and free sailing tests of a patrol boat to measure the diffracted and radiated waves in the close vicinity of the ship as function of wave and sailing conditions and (5) an extensive set of tests with a RHIB towed from the patrol boat to record the motions of both vessels as well as tow line forces. This paper will present an overview of the numerical modelling approach and an outline of the experiments conducted to validate these numerical tools.