Study On Vortex Induced Vibration Of Circular Cylinder With Variable Diameter

Flowing around a circular cylinder is widely used in engineering,but also has a large number of theoretical and experimental researches.Due to the existence of the vortex shedding and Carmen vortex in the wake flow,so the cylinder will be influenced by the fluctuating lift and drag force.The vibration caused by the fluctuating lift is called the vortex induced vibration,and the vortex induced vibration in engineering should be avoided.So in this paper,in an attempt to find out optimal solutions to reduce the vortex induced vibration,wavy circular cylinder,the fold line circular cylinder and rotating cylinder of different variable cross-section shape were compared and analyzed in supercritical Reynolds number conditions,by using large eddy simulation method.Firstly,the research status and research methods of the flow around the circular cylinder at home and abroad are studied,and the basic theory of the flow around the circular cylinder and the numerical simulation are introduced.Then,based on the existing research methods,three dimensional modeling of wavy circular cylinder,the fold line circular cylinder and rotating cylinder is carried out.Then,different models are imported into FLUENT,and the non-steady state solution of different cylinders is carried out.Finally,the Fourier method of the lift and drag coefficient is carried out,and then the time-average drag coefficient,RMS lift coefficient and Castro number are obtained.The different type cylinder are compared and analyzed.The flow mechanism of the water flowing from saddle plane to node plane is obtained.It is also found that the rotation direction of the alternating vortex is opposite in the cylinder node.By comparing the RMS lift coefficient of the three forms,the conclusion is that the efficiency of the fold line cylinder is better than that of the wavy type,and the wavy cylinder is better than that of the rotating cylinder.Through a comparative study on the wavy cylinder,fold line cylinder,rotating cylinder,the flow mechanism of flow around a variable cross section cylinder is revealed,which provides a reference for the flow characteristics study of flow around the variable cross section cylinder,and an exploration of vibration inhibition.