Vortex-induced Vibration Of Cylinder Structure At Low Reynolds Number

The global are appearing easily connected with the advancement of science,leading to economy prosperity.However,the requirement of great amount of energy is continuously rising.Hence how to extract the abundant energy in the ocean has become the hottest research problem at present among all.But there still exists numerous problems in mining procedure,one of them named as vortex-induced vibration.The VIV phenomenon results from the placement of the column structure in the flow zone,thus the column emerges brittle failure damaged by the VIV.What’s more the stability and safety of the column structure get more hard to be guaranteed.Thereby,it’s vital to suppress the negative influence of vortex-induced vibration to the column structure.Based on the favourable function by solving the problem from VIV in engineering,this essays discusses and analyzes the suppression methods in regard to vortex-induced vibration of column structure at low Reynolds numbers.The main research is as follows:(1)By concluding and analyzing the consequences about researches of vortex-induced vibration suppression methods for column structure home and abroad,a fluid-solid coupling systems model with regard to cylindrical structures’vortex-induced vibration has been established.Through the ANSYS software,the numerical investigation of the VIV’s suppression methods in the single cylinder structure has been carried out,which was in the two-dimensional laminar flow model.The surface roughness of the column influences the position of the flow separated point on the surface and the plates placed in the wake area of the column structure prevent the interaction of the upper and lower shear layers to suppresses the vortex-induced vibration,two methods above has been researched respectively.(2)The vortex-induced vibration response of single-rounded cylindrical structure has been studied in low-Reynolds number.The investigation emphasizes the effects of parameters like the Re,fillet radius and reduction velocity on the cross-flow amplitude value,fluid force characteristics,phase change,spectral characteristics and wake mode.The results show that the single-rounded column can suppress the VIV phenomenon.With a low reduction velocity in lower Reynolds number,smaller fillet radius has the more obvious suppression effect on the VIV of a single-rounded cylindrical structure.When the reduction velocity and the Re number become higher,the bigger fillet radius can obtain the great consequence too.In all cases,the mode of the column structure’s wake presents as 2S mode.(3)The vortex-induced vibration response of cylinder with flat-plate in low Reynolds number has been studied.It focused on the effects of length and spacing ratio of the flat plate on the transverse stream’s amplitude value of the vortex-induced vibration of a single fillet cylindrical structure,fluid force characteristics,phase change,frequency spectrum characteristics and wake modal,etc.The results show that placing the plate in the wake zone can suppress the VIV phenomenon.In the case of U_r=4.0,the length of the plate in the wake zone L=1D has the best suppression effect on the vortex-induced vibration response of the cylindrical structure.When U_r=5.0,the length of the plate in the wake zone L=2D has the best suppression effect too.The number of the frequency in the lift coefficient PSD curve of the column structure with a flat plate placed in the wake zone will raise firstly and then drop down with the increase of the spacing ratio,and the energy corresponding to the main frequency shows the same law of change.