Prediction With Numerical Calculation And Model Test For Drag Performance And Form Optimization For Drag Reduction Of A Manned Submersible

Manned submersibles are very important vehicles for exploring and making use of ocean resource. The use of manned submersibles is wide spread, and the designs of them have various kinds of forms for different purpose. The form of manned submersibles is even different for the same purpose. It needs calculation for hydrodynamic performances and prediction of effective power of manned submersibles in preliminary design. Accordingly, it offers the base of fixing power equipments of manned submersibles. It needs form optimization for drag reduction in order to save power for manned submersibles of preliminary design in precondition of satifying use demand.In this dissertation, in order to predict the effective power of a manned submersible, the submersible model is predigested into a like type of computational model, which major appendages are predigested to somewhat simpler forms, and some small appendages are ignored. The flow field of the computational model is numerically simulated using CFD method, and the drag coefficient of the computational submersible model is obtained. The computational and tested results of drag coefficient are compared. A form factor is introduced by comparing the computational and tested results. The simplified form for the manned submersible is calculated with CFD method, and the form factor is applied in the predictions of the drag and required power of the manned submersible.To optimize the form of the manned submersible for drag reduction, it is necessary to study for finding an effective numerical simulation method, and analyze thereby the drag performance of the manned submersible. A workable computational method is obtained, and it is used as a basis for form optimization of the manned submersible. In searching that method, the drag calculations of the main body and major appendages of the manned submersible are investigated. The flow field around the bodies is discretized into structured grids, and the influence of different turbulence models and turbulence intensity of inlet on drag results is discussed. The numerical simulation method is obtained for conducting form optimization of the manned submersible.The form of the manned submersible is complex, with many appendages, and it will move with various attitudes. It is necessary to do tested research for hydrodamic performances of the manned submersible moving in different attitudes. To conduct model tests in a towing tank, a scaled model of the manned submersible is made, and a test program is worked out to cover the moving attitudes as required by the project. To obtain the drags for driving the manned submersible model at different yaw angles and in the cases of both ascending and descending, a towing device is dedicatedly made for the tests, making possible to easily adjust both the yaw angle and submergence of the tested model. From measured total drags of both the submersible model with the towing swords and the towing swords without the model at different speeds and yaw angles, drag data reduction is made following the dynamic similitude with equivalent Reynolds Number. The total drag coefficients, and thus the effective power of the corresponding full hull in each case are obtained.The main body and battery pods of the manned submersible are considered for optimization. Form optimizations of 2-D bodies are conduceted instead of considering 3-D forms. 2-D forms are optimized with multi-island genetic algorithm for drag reduction, and the optimum results are applied to the 3-D form. After comparing different optimized forms, an optimum form of the manned submersible is obtained, which is shown, by calculation, about 13% drag reduction for the manned submersible, and more than 20% drag reduction for per unit volume.