Formation optimization of various spacing configurations for a fleet of unmanned surface vehicles based on a hydrodynamic energy-saving strategy

The purpose of this study is to optimize an energy-saving formation of a fleet of unmanned surface vehicles (USVs) for minimum energy consumption where the wave relies on its own hydrodynamic behavior. This work also provides new insights into the mechanisms of energy-saving formations based on the spacing configurations in terms of longitudinal offset and transverse separation. The numerical model is validated to meet precision demands with a prototype experimental test using a fleet of USVs. The echelon formation is constructed within the aft wedge wave pattern region considering the flow expansion of the Kelvin wave. A body force model is applied to replicate the impact of the propeller, and a mesh progressive refinement is executed to divide the functional zones of the computational domain. Energy consumption equations of formations are proposed to quantify the energy profit relationship between individual vehicles and fleets. The results highlight that the resistance component greatly contributes to the energy consumption, and that the hydrodynamic behavior mechanics impact the energy-saving capacity of the fleet. To achieve minimum energy consumption, the formation configurations are optimized based on the spacing partition to achieve energy-savings for individual vehicles and the whole fleet. These findings can be utilized for future energy-savings when using USV's for a variety of purposes, such as hydrographic surveying, data collection, reconnaissance, and general surveillance. •Optimize an energy-saving formation for a fleet of USVs.•Spacing configurations in terms of longitudinal offset and transverse separation.•Impact of hydrodynamic behavior mechanics on energy-saving capacity.•aft wedge wave pattern region considers flow expansion of the Kelvin wave.•Resistance component greatly contributes to the energy consumption.