Large Eddy Simulation Study On Wind Loads Of High-Rise Buildings With Top-Opening

Opening holes in the facade can not only improve the facade design of super high-rise buildings,but also weaken the structural wind effect.Opening a facade will change the flow field around the building and affect the distribution of wind pressure near the opening.However,the influence laws and mechanisms of factors such as opening size,number,opening method,and opening position still need to further research.This paper adopts the large eddy simulation method to study and analyze the influence of top opening form and opening size on the surface wind load of square section super high-rise buildings.The corresponding mechanism of the wind flow field was analyzed from the perspective of time-averaged and instantaneous flow fields.The main content is as follows:(1)A modified inflow turbulence generation method for large eddy simulation was proposed by combining the equilibrium boundary conditions with the Fluent inherent STG synthesis method were carried out to study its application in the prediction of unsteady wind loads on super high-rise buildings under the wind field of the atmospheric boundary layer.Taking a high-rise building with a top opening as the research object,and unsteady flow around the building was numerically calculated by adopting the LES method.The inflow turbulence for the LES is generated by adopting a modified generation method that combines the equilibrium boundary conditions with the Fluent inherent STG synthesis method to improve the simulation accuracy.The effectiveness of this numerical simulation method was verified by comparing the LES results of wind pressure coefficient of building surface to those of the corresponding wind tunnel test.The results show that combining the equilibrium boundary conditions with the Fluent inherent STG method combing to synthesize the large eddy simulation inflow pulsation can be capable of accurately reproducing the wind filed of the atmospheric boundary layer,as well as predicting the unsteady wind load on the structure surface.(2)Study on the influence of opening form on wind load around a super tall buildings by LES.Based on the verified simulation method and parameter settings,large eddy simulation of unsteady flow was conducted on the top non opening(standard square column),open and closed square openings(opening size 50 mm×50 mm)with the consistency between the incoming flow and the direction of the opening to research the influence on the wind load of super high buildings.The mean and fluctuating wind pressure distribution on the surface of square columns with and without top openings were analyzed,and corresponding influence mechanism of opening forms was analyzed from the perspective of time-averaged and instantaneous flow fields.The results show that the opening at the top affects the position of the flow separation point,the angle of shear flow diffusion,and the phenomenon of flow reattachment.Affected by the narrow tube effect,the wind speed at the entrance of the cave increases greatly,especially for the closed opening form of super-high buildings.The accelerated airflow inside the opening disrupts large-scale eddies,inhibiting the energy of eddies and weakening the surface wind pressure of the structure.At the edge of the top opening,large wind pressure values and wind pressure gradients appear due to flow separation,and there is a significant edge effect on the leeward side of the open opening.The effect of closed opening forms on reducing local wind pressure at the entrance is better than that of open opening forms.(3)Study on the influence of top opening size on wind load of super high-rise buildings by LES.Taking a super high-rise building with a top opening as the object,LES was carried out it to study the influence of opening size on the wind load of square columns considering top closed form and open openings form under four types of opening sizes(40mm)× 50 mm、40 mm × 80 mm、50 mm × 50 mm、50 mm × 80 mm).The variation law of wind load and the optimal opening plan were analyzed,and the mechanism of wind load influence were studied by the flow field.The results show that the influence of opening sizes on the wind pressure for the top top closed and open square columns is mainly concentrated in the opening area,while the influence on the wind pressure far from the opening area is relatively small.The flow field shape trend around square columns with different sizes of openings are basically consistent,with only slight differences in the area of the openings.For top enclosed square columns with openings,the larger the opening area,the better the wind load reduction effect on the windward and leeward surfaces.At the same time,the acceleration effect of the narrow tube effect on the airflow in the opening area is more obvious,leading to a significant increase in pulsating wind pressure at the corners of the windward opening.For square columns with open openings at the top,it is not that the larger the area of the facade opening,the better the wind load reduction effect in the windward opening area.The larger the opening area,the greater the wind pressure pulsation at the edge of the opening;In addition,a decrease in the area of the opening will cause the wind speed reflux position to move forward in the opening area,leading to an increase in the wind pressure pulsation on the inner wall of the opening.