Research On Vortex-Vibration Of Rectangular Bar In Port Crane

Port crane, characterized with large face area, small damping and high flexibility, is usually utilized in coastal area with frequently occurred gale, which makes the wind load control become the main controlled load for structure design of port crane. Tension bar, however, as one of the main parts of port crane, are characterized with big slender ratio and low rigidity, which can easily cause Vortex-vibration. More importantly, fierce vibration will cause cracking of tension bar by metal fatigue, which makes operation safety impossible.As for the rectangular bar, the common anti-vibration measure is drilling holes on the rectangular bar, which prevents the occurrence of vortex shedding, decreases the lift coefficient, and makes vortex shedding frequency far away from natural frequency. As a result, the vibration condition of tension rod will be improved. The researches, however, on how to drill hole on rectangular bar are so limited that the design of rectangular bar contains defects and can case vibration with great amplitude, so the present study about opening on rectangular bar is of great significance.Several researches proved that the direction, size and form of holes drilled on tension bar all could influence the occurrence of vortex shedding, so this paper, based on the port crane in SHANHAIGUAN ship building factory, applied computational fluid dynamics software-ANSYS CFX 11.0 intending to dig out the best measure against vortex shedding and find the optimal hole drilling method. The following is the main content of my work:(1) For different R values(width/height) of rectangular bar, the numerical simulation was carried out to get fluctuation curve that St(Strouhal number), C_L(lift coefficient),C_D(drag coefficient) changing under different R, out of which the influence of R was figure out. The research findings can instruct the section design of the rectangular bar.(2) The influence of vortex shedding caused by size and form of holes with two different drilling types of crosswind drilling and downwind drilling was researched, which could present the best dimension and location of holes on rectangular bar. The research findings can instruct opening design of rectangular bar.(3) Take port crane in SHANHAIGUAN ship building factory, the numerical simulation for tension bar model was carried out, based on what findings the modification for improving the vortex vibration condition of tension bar was listed.