The Numerical Simulation Study On Tornado Load Of Nuclear Power Conventional Island Based On Fluid-solid Coupling Method

Tornado is a strong cyclone produced by air convection,which has great destructive power.As the occurrence of tornado probability is low,the load code of design of building has not included the relevant anti-tornado design yet in China.However for the structures of nuclear power plants and thermal power plants,once destroyed,it will have a huge impact on the national economy.Therefore,the tornado load must be considered in its design life In order to reproduce the interaction between the structure and the tornado field,this paper uses the software of ANSYS-CFX to simulate the fluid-solid coupling effect of the steel frame structure of the main nuclear power plant in the conventional nuclear power plant and the three-dimensional tornado field.The tornado load and displacement response under the action of the tornado are studied.Then,the variation of the tornado load under different azimuth angles is studied in order to provide advices to the design of structure in a tornado.Firstly,based on the computational fluid dynamics theory,the numerical model of the tornado is established by the computational fluid dynamics software of ANSYS CFX.The numerical simulation results are analyzed.The results show that the tangential wind speed and the radial change of the numerical wind field has a good agreement with radar measured data and Rankine vortex model.Thus,the numerical simulation of the simulated tornado wind field is reliable.Then,the influence of vortex ratio on the characteristic parameters and vortex core structure of the tornado wind field is discussed.It is found that the maximum tangential velocity of the tornado wind field decreases with the vortex ratio increases,and the corresponding core radius increases.The pressure drop at the center of the tornado field decreases.The vortex core shape of the tornado field also changes from funnel to drum-shaped.Secondly,based on the weak coupling strategy,the CFD numerical simulation of the fluid-solid coupling effect of the steel frame structure and the three-dimensional tornado field is carried out by using the software of ANSYS-CFX,and the tornado load under the action of the tornado wind field is analyzed.Displacement response was studied.The results show that when the tornado strikes the structure,the values of structural load of two-way fluid-solid coupling are larger than those of one-way fluid-solid coupling,and the maximum value is 20KN in the long direction of frame structure.The displacement of two-way and one-way fluid-solid coupling has a great difference.The relative error can be reached to 36%.Therefore,it is necessary to consider the coupling effect between the structure and the tornado field in the design of the anti-tornado.Finally,the influence of the azimuth angle and the radial position of the tornado field on the structural tornado load are discussed.The structure is placed at different azimuth angles of the wind field,and it is found that the structural forces at 30°and 60 ° are more dangerous than other azimuths.Then,the tornado load under different radial positions in the wind field is analyzed.It is found that the tornado load at the core radius of the wind field is larger.At the same time,in the design of important civil structure,the location of the structural roof,near vortex surface and the edge of the windward surface,the location of the maximum wind pressure and so on should be taken seriously when designing these important civil structures.