Study On Propulsion Performance And Optimization For Flapping-Hydrofoil Wave Powered Ocean Vehicles

Small ocean vehicles are playing an increasingly important role,and the energy problem is always an important bottleneck restricting their voyage.Flapping-hydrofoil wave powered ocean vehicles are transformed from ordinary ocean vehicles,the difference between them is that the former has two flapping-hydrofoils on both sides which are used to generate power.The addition of the flapping-hydrofoils changed its resistance,so the resistance value at different speeds need to be studied.The propulsion performance is closely related to the resistance value,and the applicable propulsion systems can save energy and increase the endurance.In addition,it is important to choose the propulsion mode,navigation with higher thrust and efficiency is also the development direction of small ocean vehicles under the same power.Based on the problems,the paper uses an entry point that matters the resistance research of flappinghydrofoil wave powered ocean vehicles,then choses counter-rotating propellers to propel and its propulsion performance is optimized.The main research work and results are as follows:(1)Based on the problem of the resistance value computation of flappinghydrofoil wave powered ocean vehicles,firstly the resistance theory and computation methods are presented,then the computational fluid dynamics(CFD)is choosed to calculate.According to the actual size parameters of the vehicles,the 3d model is built by SolidWorks,and commercial software “ANSYS ICEM” and “Fluent” are used to compute,to get the resistance value at different speeds.In order to determine the accuracy of simulation calculation,the theoretical value of friction resistance is calculated by using the 1957 ITTC empirical formula and compared with the simulation value.Based on this result the preliminary design of propulsion systems is carried out.(2)In the aspects of the choice of propulsion mode,counter-rotating propellers(CRP)are choosed to the small ocean vehicles propulsion.First,according to the calculation results of the resistance,the MAU propeller is selected for the preliminary design.Second,based on the parameters got from the preliminary design,the model are built and the simulated calculation is done.The calculation result is analyzed and compared with the design requirements.The parameters got from the preliminary design are modified.Then the simulated calculation is carried out to verify the rationality of the design.Three turbulent flow models are used in the process of simulated calculation,and the calculation result is compared with the experimental data of MAU propeller.In this paper,the thrust coefficients,torque coefficients and the propeller efficiency are showed in the open-water performance graph.Analysis shows that SST k-? has highest accuracy,so this model is used as the best model for subsequent calculations.(3)The design parameters of the counter-rotating propellers are optimized.First various models are built by different parameters,then the best model SSTk-? is used to calculate the thrust and efficiency,and finally get the optimal parameter.Second the equivalent single propeller model is built and its efficiency is compared with CRP in the same power coefficient,the result shows that CRP has a significant advantage in improving propeller efficiency.