Research On Wind-Induced Effect Characteristics Of Crane Main Beam Based On Numerical Simulation

Due to the "slimming" characteristics of the main beam of the crane,the flexibility of the main beam is enhanced which makes it increasingly sensitive to wind loads,and gradually becomes a wind-sensitive structure.Especially in the coastal operation process,the crane may encounter a harsh wind environment such as a typhoon,wind load of the main beam is enhanced makes it cannot be ignored.Therefore,the study of the wind load of the main beam of the crane helps to understand the mechanism of the wind load and improve the wind resistance of the whole machine.It is difficult to achieve a series of wind field flow simulations in wind tunnel experiments.Therefore,computer numerical simulation has become the first choice.How to ensure the rationality of numerical simulation is the key to the study of wind load of main beam,which has great research significance and engineering application value.Firstly,this paper uses the computational fluid dynamics software Fluent to verify the applicability of the turbulence model around single square cylinder and the rationality of the discrete method of calculating the regional grid.The drag coefficients and the wake vortex shapes are compared with the related literatures to find Realizable k-? turbulence model has the best simulation results.In order to verify the accuracy of the Realizable k-? turbulence model for the wind load simulation of the crane mian beam,the wind load coefficients and wind load reduction coefficients are obtained by simulating the flow around rectangular beams and compared with the related literatures.The results show that the wind load coefficients and the wind load reduction coefficients of the rectangular beams are mostly consistent with literatures.Therefore,it is feasible to use the Realizable k-? turbulence model to study the wind load of the trapezoidal beam.Secondly,numerical simulation of wind flow around single trapezoidal beam with different aspect ratios and tandem beams with different aspect ratios and spacing ratios are researched.The results show that the aspect ratio has a great influence on the flow field characteristics.The drag coefficients,wind load coefficients and wake vorticities of trapezoidal beams increase with the increase of the aspect ratio,which is significantly different from rectangular beams.The wind load reduction coefficients of the tandem trapezoidal beams are negative at low spacing ratios,but which are positive in crane Standard,indicating that the Standard has an underestimation of wind load reduction.At high spacing ratios,the wind load reduction that exists in numerical simulation is ignored by the crane Standard,indicating that underestimation is present.With the increasement of spacing ratio,there is a critical ratio Scr*that divides the flow field into suppression region,reattachment region,and impinging region.In the suppression region,the wake vortex of up-flow beam is restrained,but happened in the down-flow beam.In the reattachment region,the wake of up-flow beam attaches to the up-flow face of the down-flow beam,wake vortex happenes behind both of them.In the impinging region,votex behind the up-flow beam directly impinges to up-flow face of rear beam.Finally,combined with the 2000t-62m gantry crane of Zhongshan Base,the influence of wind load loading method on the strength of the crane is studied.The results show that the strength of crane under "Standard loading" and "CFD loading" meets the using requirement under full-load condition.However,the stress under "CFD loading" is 9.46%larger than the"Standard loading",indicating that the Standard has an underestimation of the wind load effect,mainly because the "Standard loading" does not take into account the viscous force of wind and the lift force caused by the asymmetric beams.Under the wind-load condition,the stress of"CFD loading" is larger than "Standard loading" with 8.62%.The reason is the same as the full-load condition.The wind load mainly affects the displacement of the gantry crane in the direction of the cart track running," CFD Loading "larger than the "Standard loading" with 18.42%.In summary,the wind load coefficients,wind load reduction coefficients and flow field characteristics of the crane beams are greatly affected by the shape,aspect ratio and spacing ratio of the beams.Therefore,it is necessary to study the wind load.