Three-dimensional compressible flow simulations were conducted to develop a Hyperloop pod. The novelty is the usage of Gamma transition model, in which the transition from laminar to turbulent flow can be predicted. First, a mesh dependency study was undertaken, showing second-order convergence with respect to the mesh refinement. Second, an aerodynamic analysis for two designs, short and optimized, was conducted with the traveling speed 125 m/s at the system pressure 0.15 bar. The concept of the short model was to delay the transition to decrease the frictional drag; meanwhile that of the optimized design was to minimize the pressure drag by decreasing the frontal area and introduce the transition more toward the front of the pod. The computed results show that the transition of the short model occurred more on the rear side due to the pod shape, which resulted in 8% smaller frictional drag coefficient than that for the optimized model. The pressure drag for the optimized design was 24% smaller than that for the short design, half of which is due to the decrease in the frontal area, and the other half is due to the smoothed rear-end shape. The total drag for the optimized model was 14% smaller than that for the short model. Finally, the influence of the system pressure was investigated. As the system pressure and the Reynolds number increase, the frictional drag coefficient increases, and the transition point moves toward the front, which are the typical phenomena observed in the transition regime.

中文翻译：

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Hyperloop吊舱的计算流体动力学模拟，预测层流-湍流过渡

进行了三维可压缩流模拟以开发Hyperloop吊舱。新颖之处在于使用了Gamma过渡模型，可以预测从层流到湍流的过渡。首先，进行了网格依赖研究，显示了关于网格细化的二阶收敛。其次，在系统压力为0.15 bar的情况下，以125 m / s的行进速度对两种设计进行了简短和优化的空气动力学分析。短模型的概念是延迟过渡以减小摩擦阻力。同时，优化设计的方法是通过减小正面面积来最大程度地减小压力阻力，并向吊舱的正面引入过渡部分。计算结果表明，由于豆荚形状，短模型的转变更多地发生在背面，与优化模型相比，摩擦阻力系数减小了8％。优化设计的压力阻力比短设计的压力阻力小24％，其中一半是由于额叶面积的减少，另一半是由于后端形状平滑。优化模型的总阻力比短模型小14％。最后，研究了系统压力的影响。随着系统压力和雷诺数的增加，摩擦阻力系数增加，并且过渡点向前方移动，这是在过渡状态下观察到的典型现象。其中一半归因于额叶面积的减少，另一半归因于平滑的后端形状。优化模型的总阻力比短模型小14％。最后，研究了系统压力的影响。随着系统压力和雷诺数的增加，摩擦阻力系数增加，并且过渡点向前方移动，这是在过渡状态下观察到的典型现象。其中一半归因于额叶面积的减少，另一半归因于平滑的后端形状。优化模型的总阻力比短模型小14％。最后，研究了系统压力的影响。随着系统压力和雷诺数的增加，摩擦阻力系数增加，并且过渡点向前方移动，这是在过渡状态下观察到的典型现象。