Abstract This paper investigates the secondary vortex flows over an oscillating low-pressure turbine blade using a direct numerical simulation (DNS) method. The unsteady flow governing equations over the oscillating blade are discretized and solved using a spectral/hp element method. The method employs high-degree piecewise polynomial basis functions which results in a very high-order finite element approach. The results show that the blade oscillation can significantly influence the transitional flow structure and the wake profile. It was observed that the separation point over vibrating T106A blades was delayed 4.71% compared to the stationary one at Re = 51,800. Moreover, in the oscillating case, the separated shear layers roll up, break down and shed from the trailing edge. However, the blade vibration imposes additional flow disturbances on the suction surface of the blade before leaving from the trailing edge. Momentum thickness calculations revealed that after flow separation point, the momentum thickness grows rapidly which is due to the inverse flow gradients which generate vortex flows in this area. It was concluded that the additional vortex generations due to the blade vibrations cause higher momentum thickness increment compared to the conventional stationary LPT blade.

中文翻译：

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使用谱/马力元法的振荡低压涡轮二次流DNS

摘要 本文使用直接数值模拟 (DNS) 方法研究了振荡低压涡轮叶片上的二次涡流。振动叶片上的非定常流动控制方程使用谱/hp 元素方法进行离散和求解。该方法采用高阶分段多项式基函数，从而产生非常高阶的有限元方法。结果表明，叶片振荡对过渡流结构和尾流剖面有显着影响。据观察，与 Re = 51,800 时的静止叶片相比，振动 T106A 叶片上的分离点延迟了 4.71%。此外，在振荡情况下，分离的剪切层会卷起、破裂并从后缘脱落。然而，在离开后缘之前，叶片振动会对叶片的吸力表面施加额外的流动扰动。动量厚度计算表明，在流动分离点之后，动量厚度迅速增加，这是由于在该区域产生涡流的反向流动梯度。得出的结论是，与传统的固定 LPT 叶片相比，由于叶片振动而产生的额外涡流会导致更高的动量厚度增量。