The aim of this study is to further investigate the accuracy and the reliability of the actuator line model (ALM) predictions for turbulent separated wakes. Large eddy simulations (LES) of the flow around a NACA0009 airfoil are performed mimicking the geometry with the immersed boundary method. Results are validated against experiments and used to assess the accuracy of the ALM predictions for the same airfoil, with different values of the spreading parameter and of the reference velocity and for two values of the angle of attack. It is found that the ALM setup recently derived from linearized inviscid analysis leads to accurate results for the lower angle of attack, while at the higher one for which a significant separation of the boundary layer occurs, the ALM requires a different set of model parameters. This calls for a systematic investigation of the sensitivity to the ALM parameters for separated flows, which is carried out herein through a stochastic approach allowing continuous response surfaces to be obtained in the parameter space. The ALM parameters are calibrated against the results obtained with the immersed boundaries. With the calibrated model parameters, the ALM gives good predictions of the velocity and turbulent kinetic energy in the far wake. Finally, the proposed model parameters are used to predict the flow past a different geometry, a flat plate, at high angle of attack. The accuracy of the prediction of the far wake is again good, showing the robustness of the identified setup.

中文翻译：

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致动器线模型的评估和校准，用于预测湍流分离的尾流

本研究的目的是进一步研究湍流分离尾流的执行器线模型（ALM）预测的准确性和可靠性。使用沉浸边界方法模拟了NACA0009机翼周围的流动的大涡流模拟（LES）。通过实验验证了结果，并用于评估相同机翼，扩展参数和参考速度的不同值以及迎角的两个值时，ALM预测的准确性。结果发现，最近从线性无粘性分析得出的ALM设置可为较低的迎角提供准确的结果，而在较高的角度发生边界层明显分离的情况下，ALM需要一组不同的模型参数。这就要求对分离流对ALM参数的敏感性进行系统的研究，在此通过一种随机方法进行，该方法允许在参数空间中获得连续的响应面。针对通过浸入边界获得的结果来校准ALM参数。通过校准后的模型参数，ALM可以很好地预测空气流中的速度和湍动能。远远地唤醒。最后，建议的模型参数用于预测在大迎角情况下流经不同几何形状（平板）的流量。遥远苏醒的预测准确性再次良好，显示出所识别设置的鲁棒性。