Numerical Simulations Of A Large Closed-transonic-speed Wind Tunnel

With the rapid development of aerospace technology,more and more wind tunnel equipment are needed for aerodynamic study.In fact,the number of wind tunnels and its test capability has become a measure of countries'aerospace technology development level.In order to satisfy the increasing requirement of aerodynamic tests,it is very necessary to build more wind tunnels with larger scale,stronger test capabilities,and more functions.Due to the complex structure and a long design and construction period,it is extremely important to ensure the safe operation of wind tunnels within service life.In this paper,the numerical simulations of a large closed-transonic-speed wind tunnel under the varied working conditions were carried out.The main work and conclusions are as follows.(1)Finite element models for the large closed-transonic-speed wind tunnel were established with ANSYS WOEKBENCH,The whole structure of the wind tunnel was divided into several sections to reduce the difficulty of model processing and calculation time under the premise of ensuring rationality.(2)Stress analysis was performed on the wind tunnel under the internal pressure and stress distributions were obtained.Strength assessment of the wind tunnel was completed conforming to JB4732-1995 Steel Pressure Vessels-----Analysis Design Code based on stress category approach.Results show that the requirements for the strength of the wind tunnel structure are satified with a large safety margin.(3)Both stress analysis and limit load analysis were carried out to investigate the load-bearing capacity of different structures of the small end of the reducer in the stable section.Results show that the flanged reducer can reduce the local stress level and increase the load-carrying capacity based on the stress category approach.However,limit load analysis show that the three different structions give almost the same load-carrying capacity,implying that a local structure has little effects on the overwhole load-carrying capacity.(4)As the wind tunnel would undertake four different alternating load conditions during the life service,fatigue analysis for the wind tunnel was conducted.With the calculated peak stress strength Sv and based on fatigue design curve provided by JB4732-1995 Steel Pressure Vessels-----Analysis Design Code.The cumulative fatigue damage factor of the equipment was calculated.The value is 0.51 which is less than 1,meaning that fatigue failure will not happen for the structure in service with the life of 30 years.(5)Buckling analysis was carried out to consider the possibility of structure buckling when the wind tunnel is in vacuum.The linear eigenvalue method was employed to calculate the critical buckling load for each section of the equipment.It turns out that plenum chamber has a maximun critical buckling load of 1.01 MPa while the square cylinder in sub diffusion section has a minimun critical buckling load of 0.36MPa.So it is reached that buckling will not occur when the wind tunnel is under the vacuum condition.(6)The whole model of the wind tunnel equipment was established to conduct the seismic analysis.Actual constraints were imposed to calculate the natural vibration period of the equipment by the modal analysis.Seismic analysis the wind tunnel was carried out under the action of seismic load and internal pressure.Strength assesment was also performed conforming to JB4732-1995 Steel Pressure Vessels-----Analysis Design Code..Results show that the overall strength of the wind tunnel meets the requirements specified by the code.