Research On Wind Load And Response Characteristics Of High Chimney With Regular Octagonal Section

With the rapid development of electric power industry in China,and chimney is the landmark building of the thermal power plant,its height and gradually increase to200 m.In order to test wind-resistant performance of high chimney,especially chimney with specially-shaped section,as well as guarantee its safety and provide reference for the relevant code of China,the wind load and wind-induced response characteristics of the regular octagon section chimney with a height of 210 m are studied by means of rigid model and aeroelastic model in wind tunnel test and finite element response analysis.The main contents and conclusions are summarized as follows:(1)Through different proportion to align the octagon section of rigid segment model test to study the effect of Reynolds number,compared the change rule of wind pressure distribution and drag coefficient of the normal octagon section model under different Reynolds number.It is found that the wind pressure coefficient of the leeward surface of the small scale segment model is affected by the wind speed under a particular wind direction,and wind pressure distribution is not sensitive to wind speed conditions in other cases.Comparing wind pressure distribution and drag coefficient change under the same Reynolds number,it is found that there is a certain difference in the Reynolds number effect among different proportional models.(2)The Reynolds number effect of regular octagon section model is compared under different flow conditions,it is found that regular octagon section is sensitive to flow conditions within the range of Reynolds number under test,the increase of turbulence resulted in the decrease of the drag coefficient of the model.The lift coefficient of the model was calculated by using wind tunnel test,and the shedding frequency of regular octagon section is analyzed.It is found that the vortex shedding frequency is influenced by the wind direction,which means Strouhal number of regular octagon section under different wind direction is different,and Strouhal number varies little with Reynolds number under the same wind direction.(3)The surface wind pressure characteristics of three-dimensional chimney model are analyzed,it is shown that the circumferential distribution of wind pressure on the external surface of single chimney is similar to that of a small section.The average wind pressure coefficient is slightly different along the height,and thepulsating wind pressure coefficient appears at each corner of regular octagon section.Comparing the distribution of wind pressure on exterior surface between section model and chimney model,it is found that the value of wind load the chimney based on the smaller scale model is conservative.(4)The wind pressure distribution of the chimney model within surrounding buildings under each wind direction is obtained through test,and the influence of peripheral buildings on wind pressure distribution and drag coefficient of chimney surface is analyzed.The results show that the influence of peripheral buildings on the average wind pressure outside the chimney is mainly the shelter effect.The dense and low building group which is close to the windward side of chimney caused the wind pressure coefficient at the lower part of the chimney is negative,and caused the increase of local resistance coefficient of the chimney.(5)The wind-induced vibration of chimneys was studied by means of rigid model test and finite element response analysis,and the most unfavorable condition has been determined.The response characteristics show that resonance components appear in both the downwind and cross wind responses,and the peripheral buildings have an influence on the percentage of total response.Comparing wind induced response of chimneys under different damping ratio,the results show that the decrease of damping ratio caused the significant increase of wind vibration coefficient of chimney.(6)The influence of different aerodynamic shapes on wind vibration response was studied by aeroelastic model,it is found that the wind induced vibration of the regular octagon section is influenced by the wind direction.Vortex-induced vibration is found in both models of wind direction with large drag coefficient,but circular section model has a smaller wind speed range of vortex-induced vibration than the regular octagon section,the aerodynamic shape of regular octagon section under other wind direction is better than that of circular section.