Numerical Study Of Fluid Flow Past A Circular Cylinder Surrounded By Six Small Rods

Cylindrical structure is commonly used in engineering structures,the ocean platform pillar,drilling pipe and marine risers can all be simplified to cylinders.There usually are a number of attached pipelines around the main pipe while oil mining or drilling,which could be increase or decrease the flow force on the main pipe.To study the influence on flow characteristics of the main pipe with attached pipelines,and to be better applied in engineering,uniform flow past a circular cylinder surrounded by 6 identical small rods is simulated in this work using a commercial code of FLUENT.The variations of lift and drag coefficients and Strouhal number with the diameters of small rods,distance between attached rods and main cylinder,relative angleαand the Reynolds number(Re≤600) are investigated.The simulations show that:at low Reynolds number conditions,the diameter of small rods has little influence on the fluid forces,but can lead to larger Strouhal number as it increases.The variation of G/D can lead to larger changes in fluid forces as well as Strouhal number of the main cylinder,And pronounced reduction of drag and lift forces and Strouhal number are observed in the rang of 0.2＜G/D＜0.4.The average drag coefficient,the amplitude of lift coefficient,the average lift coefficient and Strouhal numher will change to some degree as the relative angleαincreases,the average drag coefficient at G/D=1,the amplitude of lift coefficient at G/D=0.125 and the average lift coefficient at G/D=0.185 and 1 will get relatively large change,while Strouhal number will have obvious change at G/D=0.375,0.5 and 1.However,the changes of the force coefficients on the large cylinder are all controlled in 15%of the single cylinder level,and this is small for engineering problems.The drag and lift coefficients of the big cylinder with 6 small rods won't increase compared with that of single cylinder as the Reynolds number increases,and in addition the small rods can reduce the amplitude of lift coefficient of the big cylinder a lot. So flow could be well controlled with the 6 small rods,and the drag and lift force on the big cylinder could be effectively reduced,that will be good reference for practical engineering.