| Once airborne pollutants are discharged into the environment during the normal operation and accident of nuclear power plants,it will have a great impact on public health,environment and ecosystem.The transport and diffusion of airborne pollutants in the atmosphere is extremely complex.The flow characteristics of atmospheric wind field such as wind vector change and atmospheric turbulence are the most important factors affecting the diffusion of airborne pollutants.Atmospheric boundary layer wind tunnel is an important means to study the flow characteristics of atmospheric wind field.It can intuitively restore the atmospheric wind environment during field test,and it is of great significance to study the diffusion law of airborne pollutants.In this paper,a nuclear power plant is taken as the research object,and the meteorological data at different heights are observed by the meteorological tower of the nuclear power plant.The atmospheric boundary layer height,wind speed profile and turbulence intensity profile in the meteorological tower area are studied.The field test results were used to adjust the wind tunnel flow field,and the influence of passive simulation devices such as wedge rough element on the flow characteristic parameters of the atmospheric boundary layer wind field was discussed.The wind profile index under the condition of neutral stratification in the field was restored to the wind tunnel experiment,and the relative error was 3.89 %.The main work and achievements of this paper are as follows :(1)The meteorological data at different heights of the tracer source were observed by the meteorological tower,and the tracer diffusion test was carried out.The concentration of SF6 tracer at the sampling point was detected by gas chromatograph,and the characteristics of the atmospheric wind field of the release source and its influence on the diffusion of airborne pollutants were revealed.The analysis shows that the atmospheric wind field in the field test is neutral stratification,and the wind profile index is 0.334.The turbulence intensity profile is obtained by using the corresponding relationship between the turbulence intensity profile and the wind profile index.(2)The simulation test of the flow characteristics of the atmospheric wind field was carried out in the atmospheric boundary layer wind tunnel.The influence of the number,size and arrangement of the wedge and rough elements on the key parameters of the flow field characteristics of the wind tunnel was analyzed in detail.The wind profile index observed in the field test was reduced to 3.89 % of the relative error in the wind tunnel.The wind tunnel test results show that the wedge size and transverse distance are the most important factors affecting the flow field characteristics of the wind tunnel.The influence of the roughness element on the key parameters of the large airflow field such as the boundary layer height,the average wind speed of the inflow and the turbulence intensity in the wind tunnel is 4 – 8 times that of its own height.(3)According to the wind tunnel test results,the numerical simulation method is used to study the influence of wedge and rough element on the flow characteristic parameters of the atmospheric boundary layer wind field,revealing the blocking effect of wedge turbulence generator and the influence of rough element on the near-surface of wind tunnel.The numerical simulation results are consistent with the overall law of wind tunnel test,but the numerical simulation of turbulence intensity near the ground is slightly insufficient. |
PDF Full Text Request