SHIP MOTIONS DURING REPLENISHMENT AT SEA OPERATIONS IN HEAD SEAS

During replenishment at sea operations the interaction between the two vessels travelling side by side can cause significant motions in the smaller vessel and affect the relative separation between their replenishment points. A study into these motions has been conducted including theoretical predictions and model experiments. The model tests investigated the influence of supply ship displacement and longitudinal separation on the ships’ motions. The data obtained from the experimental study has been used to validate a theoretical ship motion prediction method based on a 3-D zero-speed Green function with a forward speed correction in the frequency domain. The results were also used to estimate the expected extreme roll angle of the receiving vessel, and the relative motion between the vessels, during replenishment at sea operations in a typical irregular seaway. A significant increase in the frigate’s roll response was found to occur with an increase of the supply ship displacement, whilst a reduction in motion for the receiving vessel resulted from an increase in longitudinal separation between the vessels. It is proposed that to determine the optimal vessel separation it is vital that the motions of the vessels are not considered in isolation and all motions need to be considered for both vessels simultaneously.

AN EXPERIMENTAL STUDY OF SHIP MOTIONS DURING REPLENISHMENT AT SEA OPERATIONS BETWEEN A SUPPLY VESSEL AND A LANDING HELICOPTER DOCK

Hydrodynamic interactions during Replenishment at Sea (RAS) operations can lead to large ship motions and make it difficult for vessels to maintain station during the operation. A research program has been established which aims to validate numerical seakeeping tools to enable the development of enhanced operator guidance for RAS. This paper presents analysis of the first phase of scale model experiments and focuses on the influence that both the lateral and longitudinal separations between two vessels have on the interactions during RAS. The experiments are conducted in regular head seas on a Landing Helicopter Dock (LHD) and a Supply Vessel (SV) in intermediate water depth. The SV is shorter than the LHD by approximately 17%, but due to its larger block coefficient, it displaces almost 16% more than the LHD. Generally, the motions of the SV were larger than the LHD. It was found that hydrodynamic interactions can lead to large SV roll motions in head seas. Directions for future work are provided.

INTERNATIONAL DEVELOPMENT AND VALIDATION OF A DISTRIBUTED SIMULATION FOR NAVAL SHIP REPLENISHMENT AT SEA

Navies from Canada, France, Germany, Italy, and the United Kingdom collaborated to develop and validate a distributed simulation of ship replenishment at sea. The simulation models the seaway, ship motions including hydrodynamic interaction effects between ships, and the transfer of a solid payload between ships using replenishment gear. The simulation was developed using the High Level Architecture (HLA), which facilitates sharing of data and synchronization of simulation time among software components on networked computers. Simulation results were validated using experimental data. The project demonstrated successful application of distributed simulation to complex naval platform systems. Lessons learned are shared for several areas, including seaway modelling, ship hydrodynamic interaction, and planning of model tests and sea trials for simulation validation.

SCHEDULLING MODEL OF REPLENISHMENT AT SEA FOR STRICKING FORCE UNIT IN SEA OPERATION USING GENETIC ALGORITHM

Navy as a marine core in the defense force is responsible for providing security for realizing stability and security of the country. At any time there was an invasion of other countries past through sea, TNI AL must be able to break the enemy resistance line through a sea operation to obtain the sea superiority. But this time the endurance of Striking force Unit at only 7-10 days and required replenishment at sea to maximize the presence in the theater of operations to meet a demand of the logistics: HSD, Freshwater, Lubricating Oil, foodstuffs and amonisi. For the optimal replenishment at sea required scheduling model supporting unit to get the minimum time striking force unit was on node rendezvous. Replenishment at sea scheduling model for striking force unit refers to the problems Vehicle routing problem with time windows using Genetic Algorithms. These wheelbase used is roulette for reproduction, crossover, and mutation of genes. Genetic algorithms have obtained optimum results in the shortest route provisioning scenario uses one supporting unit with a total time of 6.89 days. In scenario two supporting unit with minimal time is 4.97 days. In the scenario, the changing of the node replenishment Genetic Algorithm also get optimal time is 4.97 days with two supporting units. Research continued by changing the parameters of the population, the probability of crossover and mutation that can affect the performance of the genetic algorithm to obtain the solution. Keywords: Genetic Algorithm, Model Scheduling, Striking Force unit

Modelling Fleet Performance over Complex Operating Scenarios

The Systems Availability Model (SAM) is a program designed to assess the Availability, Reliability and Maintainability (ARandM) characteristics of multiple systems used over operating scenarios that place varying demands upon those systems, such as that encountered in complex military, commercial shipping, industrial installations and deployed systems of systems. The unique ability of SAM to overlay system dependencies onto complex mission profiles makes it a uniquely powerful and flexible ARandM modelling tool. Mission profiles are built up from a variety of activities, each demanding use of different combinations of equipment, rather than a fixed time at risk approach adopted by many simpler modelling tools. This paper and associated presentation discusses: • The unique capabilities of SAM and, at a high level, how a SAM model is developed and its crossindustry applications; • The use of SAM to set system/equipment requirements, and understand the impact of equipment reliability on a fleet of ships undergoing complex operating scenarios; • Reflecting changes to mission requirements, and the knock-on effect of predicted performance; • How SAM can be used to understand the significance of individual systems during safety critical activities (e.g. replenishment at sea, close water navigation).

International Development and Validation of a Distributed Simulation for Naval Ship Replenishment at Sea

Navies from Canada, France, Germany, Italy, and the United Kingdom collaborated to develop and validate a distributed simulation of ship replenishment at sea. The simulation models the seaway, ship motions including hydrodynamic interaction effects between ships, and the transfer of a solid payload between ships using replenishment gear. The simulation was developed using the High Level Architecture (HLA), which facilitates sharing of data and synchronization of simulation time among software components on networked computers. Simulation results were validated using experimental data. The project demonstrated successful application of distributed simulation to complex naval platform systems. Lessons learned are shared for several areas, including seaway modelling, ship hydrodynamic interaction, and planning of model tests and sea trials for simulation validation.

An Experimental Study of Ship Motions During Replenishment at Sea Operations Between a Supply Vessel and a Landing Helicopter Dock

Hydrodynamic interactions during Replenishment at Sea (RAS) operations can lead to large ship motions and make it difficult for vessels to maintain station during the operation. A research program has been established which aims to validate numerical seakeeping tools to enable the development of enhanced operator guidance for RAS. This paper presents analysis of the first phase of scale model experiments and focuses on the influence that both the lateral and longitudinal separations between two vessels have on the interactions during RAS. The experiments are conducted in regular head seas on a Landing Helicopter Dock (LHD) and a Supply Vessel (SV) in intermediate water depth. The SV is shorter than the LHD by approximately 17%, but due to its larger block coefficient, it displaces almost 16% more than the LHD. Generally, the motions of the SV were larger than the LHD. It was found that hydrodynamic interactions can lead to large SV roll motions in head seas. Directions for future work are provided.