Study On The Characteristics Of Flow Noise Around Surface Columns Of Underwater Vehicles

The periscope,mast antenna and other columnar objects above the console will be partially in the water when the underwater vehicle is in the periscope state.When water flows through this area,there will be a flow phenomenon,resulting in Carmen vortex street and flow noise.These situations greatly affect the concealment of underwater vehicles.In practice,the periscope on the surface of most vehicles is cylindrical,and there are few other shapes.In this article,an elliptical cylinder with an axial ratio of 1:2 was set up,and its changes in flow and sound fields were studied in detail by changing its number and arrangement.It provides a theoretical basis for the optimization of periscope.In practical engineering,the flow around a cylinder often occurs at high subcritical Reynolds number.Therefore,the flow field condition in this paper is set as high subcritical Reynolds number,and the flow field and flow noise information around elliptical cylinders and cylinders are studied by two-dimensional simulation.It was found that the vortex shedding position of the elliptical cylinder has a significant backward shift compared to the cylinder,and both flow noise sound fields exhibit dipole directionality.Subsequently,multiple sets of different spacing ratios were set up,and two-dimensional simulations were used to analyze the flow field and flow noise information around two or three elliptical cylinders in series.The study found that under the flow field conditions of this article,each cylinder in the arrangement of double and triple elliptical cylinders bears less resistance compared to a single elliptical cylinder,and as the spacing ratio gradually increases,the resistance borne by the upstream elliptical cylinder gradually becomes the same as that borne by a single elliptical cylinder.At the same time,it is concluded that in the adjacent two elliptical columns,changes in arrangement will not affect the dominant factor of flow noise.Finally,this article set up multiple sets of different spacing ratios to explore the flow field and flow noise information around three-dimensional series double and triple elliptical cylinders,and compared and analyzed them with two-dimensional simulation results.Research has shown that the noise in the lift direction of double and triple elliptical cylinders is greatly affected by the spacing ratio,and shows a trend of first increasing,then decreasing,and then increasing with the increase of the spacing ratio.In the near field region,the flow noise sound field of double and triple elliptical cylinders exhibits quadrupole directionality.In the far field region,the flow noise sound field becomes dipole directionality,which provides a theoretical basis for the arrangement of multiple elliptical cylinders in practical engineering.When observing the flow state and estimating vortex shedding frequency,two-dimensional simulation can be used instead of three-dimensional simulation to reduce computational time.