The Research On Performance Of Propeller' Hydrodynamics, Cavitation And Noise

With the development of the large-scale and high speed ship, the load of ship propeller is heavier and heavier. The phenomenon of cavitation inevitably occurs on the surfaces of propeller and rudder, which will reduce the performance of the propeller, result in cavitation and erosion, bring on dramatic increasing in the hull pressure fluctuations and cavitation noise, so that the ship propeller noise becomes a major noise source of the ship. Presently, ship acoustic stealthy technique becomes a popular problem within shipbuilding research. As one of the three major noise sources, the cavitation noise of the ship propeller has become more and more attentive.In this paper, the hydrodynamic performance, cavitation performance and noise performance of propeller were studied systematically by using the method of integrating the theory of panel method with CFD numerical simulation technology. The numerical method research on steady and the unsteady hydrodynamic performance of the propeller was carried out, and the performance of the propeller and propeller - rudder in the viscous flow field was simulated and analyzed. The cavitation performance of propeller was analyzed and the non-cavitation noise and cavitation noise of propeller were discussed based on the panel method and CFD technology.In this paper, the development process of ship propellers was expounded systematically at first, which summed up the theory, experimental research status and development trends of the propeller hydrodynamic performance, cavitation performance and noise performance at home and abroad. Meanwhile, the applications and future prospects of computational fluid dynamics software in the prediction of ship propellers performance were analyzed.The prediction problem of propeller hydrodynamic performance in the uniform flow field and non-uniform flow field was studied by theory systematically, and the corresponding numerical procedures was composed, which including the steady hydrodynamic performance prediction and unsteady hydrodynamic performance prediction of propeller. The steady hydrodynamic performance of propeller was solved using low-level panel method based on velocity potential, and the unsteady one was solved using time-domain method. Meanwhile, in order to reduce computing time and reduce the computer's storage capacity, the mathematical model of propeller will be calculated using the method of key propeller blade, the unknown parameter on the other blades can be calculated according to a certain phase angle, and the calculation methods of unsteady performance for each time step are basically the same as the calculation methods of steady performance.In the paper, the method of overall iterative combined with the uniform pressure Kutta condition was used to predict the cavity performance of propellers in uniform flow field and non-uniform flow field. The integral equation of the problem was induced by using Green's formula, while the kinematics boundary conditions, dynamic boundary conditions, infinite conditions, uniform pressure Kutta condition were used as the determinate solution conditions. The influence of mesh partition method,mesh number and the wake model were took into account to the forecast results of the cavitation distribution in propeller's blades. Though the comparison of the calculation results and the experimental results, the reliability of the program was validated. By the basis of comparison, cavitation performance of the propeller in non-uniform flow was calculated and the change of distribution scope on the blades was calculated during a period.The open water performance of the propeller in viscous flow field was studied by adopting solve technique of Reynolds average Navier-Stokes(RNS) equations while periodicity boundary conditions were introduced to build the model and set the parameters. Directly Cutting Method, Rake Cutting Method and Spline Curve Method were used respectively in light of different skew angles of the blades. By making numerical simulation on the open water propeller in single blade channel flow field and all blades channel flow field, propulsive performance coefficient curves of different blades and skew angles and the distribution of pressure coefficient in different sections were concluded. The advantages and disadvantages of the periodicity boundary conditions were found out by contrasting the results of single blade channel method and all blades channel method, and the feasibility of applying periodicity boundary conditions to calculate open water performance of the propeller was analyzed. In the paper, validation to the CFD uncertainty was presented and different kinds of error and uncertainty were also analyzed during CFD simulation. General propeller P4381 was chosen to develop grid convergence research and analyze the grid error and numerical error of uncertainty accounting for the bases. At last, some numerical results were compared with experimental results for studying the validity confirmation. Results indicated that the study on validation of CFD simulation could make some errors and uncertainty quantitatively described and show the way clearly for the CFD workers to improve the simulation results. On the other hand, the study of validity confirmation could be used to improve the reliability of the simulation results by comparing them with normal data.By slipping grid model combined many blocks of mixing mesh method, some numerical simulation was made on the unsteady performance of propeller and the interaction performance of propeller-rudder. In the course of unsteady calculation, Boundary Profiles were used to input the experimental data. The pressure distribution nephogram of the propeller blades at different time, the pressure coefficient distribution curve at a cross-section, the pressure coefficient change of the test point in one period as well as the thrust and torque coefficients of one blade were obtained by numerical calculation. It shows that simulation results and experimental results and Hoshino calculated results have good consistency from the results analysis. Through the hydrodynamic performance calculation and analysis of the propeller and rudder combination in the viscous flow, it can be seen that the presence of the rudder will come to a corresponding increase in both the propeller thrust coefficient and torque coefficient and the increasing of distance between the propeller and rudder will decrease the interaction and the presence of the rudder will make the radial and tangential velocity distributions take on extending up and down while the axial velocity distribution has the opposite conclusion and so on.The numerical simulation of the Two-dimensional hydrofoil in steady cavitation flow was made. The impact of cavitation model, turbulence model and wall function selection on the calculation results was analyzed. The comparison between the calculative results in different cavitation number and experimental data was also analyzed. Various factors and parameters selection during cavitation calculation could be obtained though analyzing the results. At the same time, unsteady characteristics of cavitation flow around the three-dimensional hydrofoils were analyzed。The inception, development, burst, shedding process of the cavitation around the three-dimensional hydrofoils was simulated, and the change of wing lift and resistance with time in the course of cavitation development and evolvement was numerical calculated. DES (Detached Eddy Simulation) was introduced into the cavitation performance calculation of the propeller, which is the mixing method based on RANS/LES. The appropriate parameters to made numerical simulation calculation of the propeller cavitation phenomenon was selected in light of the results of aerofoil cavitation calculation. Lastly, the cavitation performance of propeller in uniform and non-uniform flow was analyzed. Based on the acoustics module of CFD software, numerical prediction and analyses were made on the noise performance of the propeller. The noise of propeller with and without cavitaion was calculated respectively. The sound pressure level and sound power spectral density in different positions, the noise attenuation characteristics with distance changing, the impact of the different calculation steps on the calculation results, the impact of velocity changes in flow on frequency spectrum as well as the impact of change of the cavitation number on the acoustic spectral characteristics related to the propeller and so on were solved in the paper.