Influence Of Structuring Form For The Sea Opening In Seawater Pipeline System On Hydrodynamic Noise

The objective of the paper is to find an efficient numerical calculation method for hydrodynamic noise of the sea opening structure and finish the research on the influence of structuring form for the sea opening in seawater pipeline system on hydrodynamic noise.From the perspective of reducing hydrodynamic noise,an optimization idea is pointed out and the best sea opening structure with the least hydrodynamic noise within the scope of the discussion is obtained.The research method of the paper combines theoretical analysis,numerical simulation and experimental verification.At first,the sea opening structure in seawater pipeline system from a real submarine is set as the research objective.According to the theoretical analysis,the numerical solution technique for solving hydrodynamic noise is settled,which contains the choices of turbulence equations,the selection of acoustic model for FLUENT,and the determination of numerical solution method.At second,the geometric model is established,and the mesh is divided,then the numerical simulation is carried out.The computing method is to use standard k-ε model for the steady calculation firstly.When parameters meet the convergence index and the pressure curve of monitoring point tends to be stable,which refer to obtaining the reasonable convergence solution,it’s time to put the last step of the steady calculation as the initial value into the unsteady calculation.When the unsteady calculation tends to be stable,open the acoustic model to run the computation of the acoustic field.After a period of time for picking up information of sound field,the detailed analysis is implemented,and the analysis object includes the time-domain graph,the spectrogram,the spectrogram with logarithmic abscissa,and the OSPL(overall sound pressure level).At last,the test for the sea opening structure of an actual submarine is designed,and is run under the same cases with the numerical simulation,and then the test data is processed.The simulation results are compared with the experimental data,and the results show that the numerical calculation method can accurately simulate hydrodynamic noise of the sea opening structure.According to the calculation results on hydrodynamic noise under different operating modes of submarine,it figures out that the magnitude of velocity in the outlet pipe has little obvious effect on the trend of spectrum,but has influence on the magnitude of SPL(Sound Pressure Level)in the spectrum and the magnitude of OSPL,which refer to with the reduction of velocity in the water outlet,the SPL in the frequency range declines and the OSPL is also smaller.Based on the findings,the optimization scheme for the sea opening structure is put forward.Next,hydrodynamic noises of the sea opening’s original structure and optimized structures under two sets of flow conditions are contrasted.The results show that the partial optimized structures can achieve effective reduction of hydrodynamic noise,and points out that the 1.1 times optimized structure is the best sea opening structure with low noise within the scope of the discussion.The sea opening structure with low noise is applied under submarine’s eight working conditions,where good noise reduction effects are achieved under the eight cases,so optimization results caused by installing the best optimized sea opening structure are demonstrated.At last,two kinds of other optimized structures are discussed,which contain adding diversion device in the outlet chamber and changing the shape of outlet chamber,and the results show that the two kinds of models in the discussion don’t create obvious effects of reducing hydrodynamic noise,which require the further researches.