Studying On Hydrodynamic Characteristics Of AUV With Numerical Model And Experiments

Small AUV (Autonomous Underwater Vehicle) is one kind of unmanned anduntethered underwater vehicles which can fulfill many kinds of oceanicenvironmental survey. To fulfill some certain measurement, one kind of smallAUV is developed by Tianjin University and the National Oceanic TechnologyCenter. This paper describes a dynamics model of the AUV. External forces acting onthe vehicle are analyzed, such as gravity, buoyancy, hull and control planehydrodynamic forces etc. This model allows the analysis of the stability,maneuverability and controllability. Applying Computational Fluid Dynamics (CFD) method, one kind of typicalhull form is chosen to study the drag characteristic of small AUV with low speed.The results emphasize that the drag coefficient of the AUV is varied with its speed.This is very different from torpedo etc. with high speed, so the drag coefficient oftorpedo is not suitable for the AUV even if the two have the same hull form. Based on the usual assumption that the drag of the streamlined vehicle can bebroken down into individual drag components, CFD method is employed to studythe hydrodynamics of all components of the AUV. Through computational resultsanalysis, the hull form of the AUV is modified to reduce drag and thehydrodynamic characteristics are achieved.Two hydrodynamic tank tests are carried out to study the hydrodynamiccharacteristics of the AUV. Based on the first test, the measurement andconnection method and the underwater depth are adjusted. The first experimentaldata are compared with the numerical results and the computational model isrectified according to the test results. The modified CFD model is applied to carryout new computations to study the hydrodynamic characteristics of the AUV. Thesecond test results are also compared with the numerical results and it proves thatthe numerical model is computationally efficient and has reasonable accuracy.