基于Ludwieg管的高超声速边界层转捩实验

高超声速边界层层/湍流转捩是高超声速飞行器气动力和气动热设计中的难点和热点问题.为了降低开展高超声速边界层不稳定性与转捩实验研究的门槛，研究基于Ludwieg管原理设计并建造了一座Mach 6高超声速管风洞，重点对Ludwieg管风洞的启动和运行过程开展了数值模拟，分析了储气段弯管布局对试验段流场的影响；之后，对该高超声速风洞的自由来流品质进行了静态和动态的标定，验证了风洞的设计Mach数，并给出了流场的动态扰动特征；最后，基于7°半张角尖锥标模开展了高超声速边界层转捩实验，通过表面齐平式安装的高频PCB传感器获得边界层不稳定波，分析了高超声速边界层不稳定波的演化特征.以上工作表明，Ludwieg管相对常规高超声速风洞具有建设和运行成本低、运行效率高、流场品质好等优点，适合开展高超声速边界层转捩等基础实验研究. 

Hypersonic Boundary-Layer Transition Experiments in Ludwieg Tube

Hypersonic boundary layer laminar/turbulent transition is one of the most difficult and prevalent problems in hypersonic vehicle design. To lower the requirement of experiment research on hypersonic boundary layer instability and transition, a Mach 6 hypersonic wind tunnel was designed and constructed based on the Ludwieg tube principle. This research focused on the starting and operating processes of Ludwieg wind tunnel using the numerical method. The influence of the bending storage section on flow quality in test section was analyzed. Thereafter, the static and dynamic characterizations of the hypersonic flow in the test section of hypersonic wind tunnel were carried out. The design Mach number of the wind tunnel was verified, and the dynamic disturbance characteristics were given. Finally, the experimental investigation on hypersonic boundary layer transition was carried out based on the 7° half-angle sharp cone model. The instability waves were obtained by the high frequency PCB pressure sensors which were flush mounted on the cone surface, and the evolution characteristics of unsteady waves in hypersonic boundary layer were analyzed. This study indicates that Ludwieg tube wind tunnel has advantages such as low construction and operation cost, high operation efficiency and good flow field quality compared with conventional hypersonic wind tunnel, and it is extremely suitable for fundamental experimental research such as hypersonic boundary layer transition.