| The hydrodynamic drag device can utilize the water resistance to oppose or retard the motion of mechanism. The high-speed movement of the hydrodynamic drag device in free surface is a highly complex three-dimensional flow problem. The drag device has an irregular wall whose curvature and spatial distortion change greatly, when drag device rushes into the water with high velocity, its wall bears the strong impact of the flow, wall deformation will occur, it is a typical phenomenon of liquid-solid coupling problems. Hydrodynamic characteristics of this kind of device were analyzed with FLUENT software, and then fluid-solid interaction between fluid flow and drag device wall was investigated through ANSYS parametric design language software. The main points are as follows:(1)Taken the hydrodynamic drag device as studied object,according to its structural characteristics and operating conditions , established three-dimensional physical model and turbulence mathematical model under the Cartesian coordinate system. Meanwhile, numerical equation's discrete, control equation's solution, initial boundary conditions, free surface remodeling and other problems are deeply investigated, which lay a theoretical foundation for the movement analysis of drag device with free surface flow.(2)Based on the VOF method, the numerical simulation on the fluid flow dynamic process from inflow to outflow in device's flow channel can be carried out by using the Reynolds Averaged Navier-Stokes (RANS) Equations and the Renormalization Group (RNG)κ?εturbulence model. Its flow field distribution is in line with the classical fluid dynamics theory, the variety of the free surface is consistent to the actual physical phenomena.(3)Resistance and lift characteristics of hydrodynamic drag device in different submergence and different initial velocity with free-surface flow can be numerically simulated. The coefficient empirical formula has been put forward which can be used to predict the water greatest resistance and lift under different initial velocity and control the water resistance and lift by adjusting the actual submergence. The calculation results can shorten computing period and cut down experiment cost and supply an important reference for the structural design of the drag device and predictions of hydrodynamic characteristics which contribute to comprehensive study in the whole movement system.(4)Fluid and structure sequence coupling method is adapted in computation. The water pressure distribution on the wall of the drag device was calculated with FLUENT software and loaded on the ANSYS finite element model by the APDL language. Drag device's structural analysis is achieved in the ANSYS software platform, stress distribution and wall's deformation is discussed in different operating conditions. The analysis result proves the correctness of design of the drag device and also offers the theoretical basis and suggestions for the practical engineering application and safe operation of the drag device.The calculation results in this paper are helpful to drag device's hydrodynamic performance analysis and structure optimization and design and lay the foundation for hydrodynamic characteristics of drag device's variable motion with free-surface flow for the next step research.
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