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Middle propeller cavitation noise numerical prediction characteristic extraction method based on inhomogeneous inflow

A technology of feature extraction and numerical prediction, applied in the fields of electrical digital data processing, special data processing applications, instruments, etc., can solve the problems of no optimal cavitation model and turbulence model, and no good

Active Publication Date: 2014-01-29
SOUTHEAST UNIV
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Problems solved by technology

[0002] The viscous numerical simulation of propeller cavitation is affected by the multiphase flow model, turbulence model, cavitation model and phase change critical pressure. There are few successful simulations of sheet cavitation at home and abroad, and there are no better cavitation models and The turbulence model, which successfully simulates the cavitation of the slice is aimed at the uniform inflow; the research on the cavitation radiation noise of the propeller is limited to the combination of the surface element method and the single pulse spherical cavitation radiation noise theory, or the use of the FW-H equation to combine the cavitation Therefore, it is a difficult research problem to predict propeller cavitation noise in non-uniform inflow. It is more difficult to extract propeller cavitation noise characteristics by numerically predicting propeller cavitation noise. is a research problem

Method used

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  • Middle propeller cavitation noise numerical prediction characteristic extraction method based on inhomogeneous inflow
  • Middle propeller cavitation noise numerical prediction characteristic extraction method based on inhomogeneous inflow
  • Middle propeller cavitation noise numerical prediction characteristic extraction method based on inhomogeneous inflow

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Embodiment 1

[0103] The E779A propeller is selected for verification by CFD calculation. The calculation domain is the whole channel area, and the hybrid grid division method is adopted. The rotation domain around the propeller is an unstructured grid, and the rest of the water domain is a structured grid. The distance from the upstream to the center of the propeller is 1D, and the distance from the downstream to the center of the propeller is 3.75D. The calculated cylindrical radius around the propeller is 1.471D, where D is the diameter of the propeller. Using slip grid technique and RNG turbulence model, ρ l =1000kg / m 3 , ρ v =0.02kg / m 3 , the surface tension coefficient γ=0.0717N / m, when the advancing speed coefficient J=0.71, calculate the cavitation index σ=1.763 and the thrust coefficient K when there is no cavitation T and moment coefficient 10K Q , see Table 1.

[0104] The non-uniform inflow axial velocity simulation uses the following formula:

[0105] u x =U 0 (f 1 f ...

Embodiment 2

[0114] To predict cavitation noise for DTMB4381 and DTMB4382 propellers, the mathematical formula in Embodiment 1 is used for non-uniform inflow. The side slope angles of DTMB4381 and DTMB4382 propellers are 0 degrees and 36 degrees respectively. When the advance speed coefficient J=0.9, the propeller speed n=30.5rps, the axial uniform inflow velocity is U 0 =6.22m / s, cavitation index σ=1.763, and p=44723pa, the circumferential distribution of cavitation of DTMB4381 propeller and DTMB4382 propeller blades is calculated, the radiation sound pressure is calculated, and the power spectral density is obtained, see Figure 8 , 9, 10.

Embodiment 3

[0116] The relevant experimental data and numerical results of a civil ship propeller are analyzed. The noise data is the sound pressure measured by the hydrophone at 2m directly below the propeller in the cavitation water tunnel. The sampling frequency is 195652Hz and the water velocity is 3.25m / s. The hydrostatic pressure in the cavitation water tunnel is 113000pa, and the noise and sound pressure data of the propeller speeds of 25rps and 28rps are measured respectively, and the measurement time is 5 seconds. The noise sound pressure power spectrum is as follows Figure 11 .

[0117] The uniform inflow velocity in the axial direction is U 0 =3.25m / s, p=113000pa, the propeller speeds are 25rps and 28rps respectively, and the iteration time of each step is 0.0005 seconds. The comparative verification of the slice cavitation area is as follows Figure 12 , calculate the circumferential distribution of blade cavitation, calculate the radiation sound pressure, and get the power ...

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Abstract

The invention discloses a middle propeller cavitation noise numerical prediction characteristic extraction method based on inhomogeneous inflow. The method includes the following steps: first conducting mesh generation on a propeller computational domain and checking mesh quality and defining boundary conditions; then setting a computational model in computational fluid dynamics (CFD) software, conducting stable iterative computation to obtain water dripping performance parameters and inflow opening speed to verify the model accuracy; conducting non-stable iterative computation by utilizing stable computation as the initial value of the non-stable computation in the CFD software and displaying the cavitation period state of a propeller piece and cavitation area change of a recording piece through post processing; finally computing the propeller cavitation radiation noise through the cavitation area of the propeller piece according to a single-vacuole radiation noise theory to conduct characteristic extraction.

Description

technical field [0001] The invention relates to a feature extraction method based on numerical prediction of propeller cavitation noise in non-uniform inflow, and belongs to the technical field of feature extraction of propeller cavitation radiation noise. Background technique [0002] The viscous numerical simulation of propeller cavitation is affected by the multiphase flow model, turbulence model, cavitation model and phase change critical pressure. There are few successful simulations of sheet cavitation at home and abroad, and there are no better cavitation models and The turbulence model, which successfully simulates the cavitation of the slice is aimed at the uniform inflow; the research on the cavitation radiation noise of the propeller is limited to the combination of the surface element method and the single pulse spherical cavitation radiation noise theory, or the use of the FW-H equation to combine the cavitation Therefore, it is a difficult research problem to p...

Claims

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Application Information

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IPC IPC(8): G06F19/00
Inventor 曹红丽方世良朱志峰
Owner SOUTHEAST UNIV
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