Concept Design And Navigation Performance Optimization Of Transformable Multi-navigation State Marine Craft

For the specific backgrounds and demands,the concept of Transformable Multi-Navigation State Marine Craft(TMSMC)is put forward.By combining traditional ship design method and Multidisciplinary Design Optimization(MDO)method,passing through concept design and multi-objective optimization,the final plan with high navigation performance is given efficiently.Based on the decomposition and analysis of application patterns' characteristics,using the design principles and rules of ship and underwater vehicle,TMSMC is designed with surface/underwater navigation states and trimaran/monohull shapes.Design process and analysis method of such conceptual ship are summarized.Buoyancy and stability are checked to ensure the rationality.Some design redundancies are retained,primary plan which is feasible but not optimal is provided only by considering function realization and criterion limitation.According to the properties of TMSMC,design parameters related to deformation mechanism are determined.Design variables include longitudinal cutting length of side hull,longitudinal spacing between the center of main hull and side hull in folded state,transverse spacing between the centers and longitudinal spacing between the stern transom plates in unfolded state.Navigation performance is divided into five disciplines,which are stability,buoyancy,rapidity,seakeeping and general arrangement(GA),corresponding state variables are area from 0°to 30°under GZ(surface stability),underwater initial metacentric height(underwater stability),underwater trim moment,total resistance at cruising speed,maximal amplitude of pitch motion response to unit wave amplitude when cruising in head waves(resonance)and the constraint function of design variables.Considering the coupling of disciplines,stability,buoyancy and GA are regarded as system-level constraints.Surface rapidity,seakeeping and additional underwater stability are as optimization objectives.System hierarchy and data transfer form of optimization model are cleared.The multi-objective optimization framework is constructed based on Multi-Disciplinary Feasible(MDF).Based on the characteristics of hulls and disciplines,the correlation between variables,the range of design parameters and constraint conditions,the trend of optimization objectives are all defined.With targeted methods,each discipline is analyzed and expressed reasonably.On the basis of primary plan,surface stability is calculated directly by modeling,underwater stability and buoyancy are analyzed on the principle of handling loads,rapidity and seakeeping are discussed with CFD method.The first three are expressed as Response Surface Methodology(RSM)model through Full Factorial Design(FFD),and the other two are as Radial Basis Functions(RBF)model through Optimal Latin Hypercube Design(Opt LHD).GA is expressed with explicit function which shows the geometric relation among design variables.Optimization framework and disciplinary models are integrated in Isight,after which the multi-objective optimization is carried out by means of Elitist Non-Dominated Sorting Genetic Algorithm(NSGA-II).Additionally,the single-objective optimization is used as contrast and verification.At last,the final optimized plan of TMSMC is selected from the Pareto front by taking rapidity as prior consideration.Compared with the primary plan,navigation performance is improved in every respect.