高速风洞运转特性数值模拟

Numerical Investigations on Running Characteristics of High Speed Wind Tunnel

下吹-抽吸式高速风洞的起动和运转对模型测试有重要影响。为分析试验模型和扩压器对风洞起动和运转特性的影响,采用数值模拟方法,使用二维轴对称模型对Φ0.5m高速风洞的流场进行了研究,控制方程为粘性可压缩Navier-Stokes方程。对马赫数5和10两种状态下的流场行了对比,结果表明,试验段基本流态受试验舱静压控制,收集器对流动状态有很大影响。当带模型运转时,试验段内激波结构更为复杂,出现明显溢流,总压损失更大,所需起动压比越大;扩压器平直段直径决定了其静压恢复效率。扩压器平直段直径增大或安装模型时,临界运转压比都会明显增大;且马赫数越大,受到的影响越大。马赫数5带模型起动时,扩压器平直段直径<0.5m,气流壅塞,风洞无法启动。无模型时,当平直段直径>0.45m,扩压器不能发挥静压恢复作用,风洞运行时间明显缩短。

Starting and running characteristics plays an important role in the course of design and model tested in blowing-down and suction high speed wind tunnel.To analyze the effects of model tested and diffuser on the starting and running ofΦ0.5 m high speed wind tunnel,field structure and evolvement were simulated numerically.In the simulation,the flow field calculation simplified two-dimensional axisymmetric model was performed.The control equations were the conservational Navier-Stokes equations,which described two-dimensional viscous,compressible flows.The numerical simulation results of Mach number 5 and 10 showed that basic state of test section was under the control of static pressure in test cabin.Pickup collector had a great influence on the field structure.Running with model,shock system was more complex than that without model.There was evidently ovefall around pickup collector wall.There was more total pressure loss,which leaded to higher pressure-ratio when starting wind tunnel.The diameter of straight-pipe section in diffuser influenced the efficiency of static pressure recovery evidently.When enhancement of straight-pipe section diameter or in conjunction with model,critical running pressure-ratio became higher obviously.Bigger was Mach number,more distinctly was critical running pressure-ratio affected.The wind tunnel cannot start when the diameter of straight-pipe section is less than0.5 meter with model tested at Mach number 5.When the diameter of straight-pipe section is greater than 0.45 meter without model tested,the diffuser cannot play the role of static pressure recovery,and the operation time of the wind tunnel is significantly reduced.