A Method for Approximate Prediction of Laminar–Turbulent Transition on Helicopter Rotors
A Method for Approximate Prediction of Laminar–Turbulent Transition on Helicopter Rotors
复制标题
直升机旋翼层流-湍流转变的近似预测方法
DOI：
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发表时间：
2018
影响因子：
1.5
通讯作者：
C. Heister
中科院分区：
文献类型：
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作者：
C. Heister
提出了一种预测直升机旋翼非定常雷诺平均Navier-Stokes(URANS)数值模拟中层流-湍流转变开始的近似方法。基于所提出的方法，研究了层流对所需转子功率和所产生的转子推力的影响，并与完全湍流结果进行了比较。对于层流边界层的计算，采用了基于Schlichting/Walz的积分方法和基于Baser和Velkoff的旋转速度剖面。根据Tollmien-Schlichting和横流不稳定性、绕流机制和附着线污染的经验准则，预测了层流-湍流转变的开始。该方法考虑了模拟旋翼尾迹的湍流度变化。不需要检测URANS溶液中的边界层边缘。利用典型转换测试用例的实验起始位置对该近似方法进行了验证。这包括层流翼型和后掠翼。为了覆盖前飞中的旋翼，计算了马赫尺度直升机模型旋翼上的起始位置，并与现有的热膜测量结果进行了比较。一般来说，预测的转子叶片层流长度会使所需的转子功率降低4-5%。转子推力几乎不受影响。
An approximate method is presented to predict the laminar-turbulent transition onset within the unsteady Reynolds-averaged Navier-Stokes (URANS) simulations of helicopter rotors. Based on the presented method, the influence of laminar flow on the required rotor power and generated rotor thrust is investigated and compared to fully turbulent results. To compute the laminar boundary layer, an integral method according to Schlichting/Walz and a set of rotating velocity profiles according to Blaser and Velkoff are used. The laminar-turbulent transition onset is predicted by empirical criteria with respect to Tollmien-Schlichting and crossflow instabilities, bypass mechanisms, and attachment line contamination. The method presented accounts for the turbulence-level variation of the simulated rotor wake. A detection of the boundary layer edge within the URANS solution is not required. The approximate method is validated using the experimental onset positions of representative transition test cases. This includes a laminar flow airfoil and a swept wing. To cover a rotor in forward flight, the onset positions on the model rotor of a Mach-scaled helicopter configuration are computed and compared to available hot-film measurements. In general, the predicted laminar flow lengths on the rotor blades reduce the required rotor power by 4-5%. The rotor thrust remains practically unaffected.