The invention discloses a three-dimensional steel bridge 
tower vortex-induced vibration calculation method, which achieves the three-dimensional steel bridge 
tower fluid-
solid coupling numerical 
simulation through the dynamic mesh technology. The method comprises the steps of extracting the 
bending vibration mode coordinate values in the bridge direction and the transverse bridge direction througha 
Modal module of ANSYS 
workbench; performing function fitting by utilizing 
Matlab software to obtain a corresponding vibration mode function; inputting the vibration mode function into a user-defined 
program code UDF of the Fluent; analyzing the fluid to obtain a velocity field and a pressure field, obtaining generalized force by the user-defined 
program code UDF embedded into the Fluent, and substituting the generalized force into a 
structural vibration equation to solve to obtain generalized displacement; and obtaining an actual response of the structure through 
modal coordinate conversion, finally utilizing a dynamic mesh 
macro command to specify mesh movement so as to update the mesh position, and performing calculation of the next 
time step until convergence. According to the method, a computational fluid dynamics method is applied, and the 
business software Fluent is subjected to 
secondary development by compiling the user-defined 
program code UDF, so that the three-dimensionalsteel bridge 
tower fluid-
solid coupling numerical 
simulation is achieved, the UDF can achieve 
parallel computing of the Fluent, and efficiency is greatly improved.