Study On The Flow Characteristics Around Structures Attached With Porous Media

For marine structures,such as marine risers,underwater vehicles,etc.,the generation and changes of vortices in the wake area have an important impact on resistance,vortex-induced vibration or flow noise.Porous structure is an effective structure for eddy current control and has played an important role in the application of hydraulic engineering and chemical catalysis.This paper studies the mechanism of the problem of flow around the structure by attached with porous media on the surface of the marine structure,and in-depth study of the performance of porous media on the rectification and noise reduction performance of the structure.This paper reviews the research progress of turbulent pulsation and the use of porous media for flow control,and analyzes the feasibility of using porous media to reduce the drag and noise of structures.Taking marine structures with additional porous media as the research object,based on STAR-CCM+ software,combined with the RANS equation and FW-H acoustic model(The Ffowcs Williams and Hawkings Acoustic Model)numerical simulation method,the feasibility and accuracy of the current calculation method are verified.The hydrodynamic characteristics of typical marine structures attached with porous media are studied,and the performance of porous media for drag reduction and noise reduction is analyzed.Apply the established numerical simulation method to calculate the connection part of the two-dimensional cylinder,hydrofoil and underwater vehicle podium with porous media on the surface,and analyze the velocity field,pressure field,vorticity field,far-field noise and lift drag in the wake area coefficient,discuss the influence law of porosity,pore density and material thickness of porous media on flow field and flow noise.Test the light cylinder and porous cylinder in the circulating water tank to observe the rectification effect of the porous medium.Numerical analysis shows that the formation of large-scale vortex shedding structures can be suppressed by laying porous media on the cylinder and hydrofoil,the vortex vortex frequency is reduced,the velocity near the wake area is reduced,the width of the wake is widened,and turbulent pulsation and flow noise are effectively controlled;Numerical calculation of the additional porous media at the connection of the podium enclosure shows that the porous medium can greatly reduce the wall shear stress,the viscous friction resistance is correspondingly reduced,and the noise at the monitoring point is reduced.In this paper,numerical simulation is used to study the influence of porous media’s parameters on the flow field characteristics,lift-drag coefficient and noise of the structure,and analyze the characteristics of porous media’s parameters on the flow field around the structure and its resistance and noise reduction mechanism.It provides a theoretical reference for the drag reduction and noise reduction applications of marine structures and underwater vehicles.