Open Water Performance Study With Tandem Propellers In Nozzle Based On CFD Method

With the development of science and technology, the emergence of special propulsion for various new water ships or underwater navigation is needed. There appear a lot of different thruster, and the tandem propellers in nozzle is put forward because they can meet the requirement of propulsion of some marine transport ship with limited air structure for thrusters. It has certain theoretical meaning and engineering value for further research on the open water performance of tandem propellers in nozzle. In this paper, main works are as follow:In this paper, the formula of turn local propeller plade value to global coordinate value are established, and use mathematical programming software and 3D modeling software to establish the 3D geometric model of propeller. the 3D geometric model of DTMB4119 propeller and tandem propellers in nozzle of DCA-A3 is established.In order to study the open water performance of DTMB4119 propeller, respectively study the number of unstructured grid and three kinds of turbulence model(standard k ?? model, RNG k ?? model and SST k ?? model) to calculate the influence of accuracy of the results. In the study, thrust coefficient, torque coefficient and open water efficiency as the main indexes of propeller open water performance, with the experiment results as a reference, The calculation results of CFD(Computational Fluid Dynamics) show that: The selection of the turbulence model has a great influence on the result of the calculation, in the same amount of grid, The accuracy of the results of the standard k ?? turbulence model and the RNG k ?? turbulence model are higher in the low advance coefficient. But when the advance coefficient near or exceed the best open water efficiency of advance coefficient,the calculation accuracy is very poor. Although when the SST k ?? turbulence model under the condition of small advance coefficient, the precision of the thrust coefficient of slightly less than that of standard k ?? turbulence model and the RNG k ?? turbulent model, But when the advance coefficient is close to or exceed the best propeller open water efficiency of advance coefficient, its main indexes of open water performance results are in good agreement with the experimental results, and the accuracy is higher than the standard k ?? model and RNG k ?? model, the average error remains within 6%.On the basis of previous verification, the SST k ?? model is chose to calculate the hydrodynamic performance of DCA-A3 tandem propellers in nozzle with CFD method. And compare the results with the experimental results to verify the accuracy of the models, the result shows: the thrust coefficient and torque coefficient of average error is controlled within 6%. It is proved that the computational model is accurate. Meanwhile, The control variable method is adopted to calculate the open water performance of tandem propellers in nozzle under different angular spacing and different pitches by CFD to find the best parameters of angular different spacing and different pitch ratios. The results prove that 200 is the best angular spacing, the hydrodynamic performance is poor if any angular spacing is higher or lower than 200. As the pitch ratio decrease the thrust coefficient and torque coefficient are bigger, the hydrodynamic performance is better.