In this study, the nozzle flow influence on the forebody aerodynamics has been numerically investigated and validated with experiment. To understand the nozzle flow aerodynamics on the forebody, five different nozzle-exit profiles, which are often encountered in the experiments, are considered one at a time. One flow condition is considered at a nominal freestream Mach number of 4. The CFD simulations are performed using a two-dimensional axisymmetric four-equation transition shear stress transport (SST) turbulence model. The numerical results are compared with the Ludwieg tube Mach 4 experimental data and showed good agreement. The numerical results showed that despite the slight effect on the wall static pressure depending on the nozzle profiles considered, the physical flow phenomena such as shock shape are directly influenced. With the undeveloped nozzle flow profile case, however, significant pressure differences are observed. The distance between the model and the nozzle exit may significantly affect the forebody aerodynamic characteristics, and so, the consideration of the distance between the model and nozzle exit needs to be placed during the model setup to reduce the unwanted uncertainty in the measurement.

中文翻译：

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喷嘴流量对前体空气动力学的影响

在这项研究中，喷嘴流动对前体空气动力学的影响已经通过实验进行了数值研究和验证。为了了解前体上的喷嘴流动空气动力学，在实验中经常遇到的五种不同的喷嘴出口轮廓一次被视为一种。在名义自由流马赫数为 4 时考虑一种流动条件。 CFD 模拟是使用二维轴对称四方程过渡剪切应力传输 (SST) 湍流模型进行的。数值结果与 Ludwieg 管 Mach 4 实验数据进行了比较，显示出良好的一致性。数值结果表明，尽管考虑的喷嘴轮廓对壁面静压的影响很小，但直接影响物理流动现象，如冲击形状。然而，在未开发的喷嘴流动剖面情况下，观察到显着的压力差。模型与喷嘴出口之间的距离可能会显着影响前体空气动力学特性，因此，在模型设置过程中需要考虑模型与喷嘴出口之间的距离，以减少测量中不必要的不​​确定性。