A CFD-Based Analysis Method for Free Motion in Low-Speed ​​Inclined Entry into Water

Abstract

The invention provides a CFD-based analysis method for low-speed inclined water free movement, comprising the following steps: determining the model data size according to the test, and establishing a three-dimensional model; selecting a physical model, and adopting large eddy simulation method and local eddy viscosity wall self-adaptation Model and VOF model to solve unsteady and two-phase flow problems; carry out grid division, verify grid independence and numerical method stability; set boundary conditions and initial conditions; set solver related parameters, determine the discrete method; The results are visualized and the solution is run. The invention uses CFD software to solve the cavitation development and ballistic characteristics of the six-degree-of-freedom body inclined into the water at low speed, accurately simulates the water entry process, has better consistency with the test results, and improves the calculation accuracy.

Description

technical field [0001] The invention relates to the field of computational fluid dynamics, in particular to a CFD (Computational FluidDynamics)-based analysis method for low-speed inclined water-entry free motion. Background technique [0002] The problem of water entry involves a wide range of fields, including the first entry and exit of the ship during navigation, airdrop UUV, cross-media vehicle entry and even diving. However, the impact load generated at the moment of entering the water may cause damage to the structure; the cavitation generated during the underwater navigation affects its navigation attitude and ballistic stability in the water, and may even cause problems such as sinking and bouncing; currently, for three-dimensional, inclined There are still relatively few studies on water entry problems, and most calculations are based on two-dimensional, vertical water entry, etc. [0003] The water entry process is very short, involving gas, liquid, and solid pha...

AI Technical Summary

Problems solved by technology

However, the impact load generated at the moment of entering the water may cause damage to the structure; the cavitation generated during the underwater navigation affects its navigation attitude and ballistic stability in the water, and may even cause problems such as sinking and bouncing; currently, for three-dimensional, inclined There are still relatively few studies on the problem of water entry, and most calculations are based on two-dimensional, vertical water entry, etc.

[0003] The water entry process is very short, involving gas, liquid, and solid phases at the same time, which is an unsteady, nonlinear, and strongly turbulent motion. In addition, because the density of water is more than 800 times that of air, and the viscosity coefficient is 59 times that of air, the structure When crossing the gas-liquid interface, it brings complex and strong reactions, which makes it difficult to solve

At present, the solution to the water entry problem is mostly based on the CFD method. Among them, the RANS (Reynolds time-averaged, a turbulence numerical simulation method) method has become the main method, but it smooths out all the behavioral details of the pulsation motion through the average operation, and loses the information contained in the pulsation motion. There is a large amount of meaningful information in the item, and the eddies of different scales are treated equally without distinction, which is not realistic

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