| The compositive test station of the propulsive water-jet pump usually carried out independent waterjet tests. During the test process, water-flow into the intake duct is uniform flow for waterjet propulsion. However, when the waterjets were installed on the ship hull,velocity distribution in the intake duct will produce a lot of nonuniformity because of the hull's effect. The nonuniformity has a great influence on the calculation for system efficiency of waterjet & hull system. In order to quantitatively reflect the effect of the hull on waterjets,we special define momentum influence coefficient a and kinetic energy influence coefficient ? to respectively the influence degree of the boundary layer on momentum and kinetic energy. In the past, most of the researchers relied on experience formula in handling these two parameters, and in this paper, the PIV method was applied to the measurement of velocity distribution in intake duct for a waterjet-propelled ship model according to ITTC procedures. Two parameters were calculated basing on the measured results.This article adopts three-dimensional PIV underwater equipment in the measurement of velocity distribution in intake duct research for a waterjet propulsion ship. The experimental research is basing on ship model towing tank, a trimaran model installed two waterjets is chosen as the research object. We have set reasonable connection scheme design before the test; During the test , we have discussed the mechanism of the ship motion changes in the process impact on the measurement results according to the PIV principle combined with load balance monitoring data; Finally, we are coming to the reasonably testing results, analysising the cross-section velocity distribution, flow distribution, observing fine flow field in detail such as flow separation, determining the appropriate calculation shape in intake duct cross section, calculating the momentum influence coefficient and kinetic energy influence coefficient. In the end, this paper analyzes the rationality of these two parameters.Later then, computational fluid dynamics (CFD) tools have been applied in the assist validation. Based on RANS method, the numerical researches on open water performance of propeller and self-propulsion test for waterjet-propelled trimaran have been carried out. In the research of open water performance of propeller, moving reference frame (MRF) model has been used to simulate the rotation of real propeller, and the calculated open water performance will be applied to later calculations. In the research of self-propulsion test,virtual disk model is dedicated to simplifying the rotation of impeller, which will significantly reduce the number of grid, and improve the computational efficiency. Finally,non-dimensionalized velocity distribution profile has been reached under the same working condition. A comparison between CFD results and PIV results could provide better understand for the distribution law. What's more, CFD researches could offer explanations for the conclusions which are lack of evidence from the phenomenon view, and detailed observation of experimental phenomena. It is expected to give full play to the advantages of the CFD calculation.To sum up, the core content of the paper is the first application of PIV equipment in the inlet duct velocity distribution measurement of a waterjet propulsion model. The combination of numerical calculation and experimental study could reach a more comprehensive cognition on measured results in self-propulsion test. It is of great significance of the test scheme,experience in the process of experimental study and experiment conclusion for same type followed-up. |
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