This paper presents the study of the losses generated in a Counter Rotating Open Rotor (CROR) configuration at three different operating conditions (approach, cutback and sideline). Unsteady Reynolds Averaged Navier-Stokes (URANS) and Large-Eddy Simulation (LES) approaches are used and compared to describe the flow field and the mechanisms of loss. Since no common circumferential periodicity occurs in the two blade rows of the configuration (11 blades for the front rotor and 9 for the rear rotor), a full 360${}^{\circ }$ simulation would be required. In order to reduce the related computational cost, a phase-lagged assumption approach is used. This method enables to perform unsteady simulations on multi-stage propulsive configurations including multiple frequency flows with a computational domain reduced to one single blade passage for each row. The phase-lagged approach requires a large data storage reduced in the study by a data compression method. The data compression method is based on a Proper Orthogonal Decomposition (POD) replacing the traditional Fourier Series Decomposition (FSD). The inherent limitation of the phase-shifted periodicity assumption remains with the POD data storage but this compression method alleviates some issues associated with the FSD, especially spectrum content issues. The analysis of the losses generated in the configuration is based on an entropy formulation. In particular, the losses are split between boundary layer contributions and the remaining domain where wakes and secondary flows occur. The study shows the influence of the leading edge vortex on the suction side boundary layer transition of the front and rear rotor blades at high rotational speed (cutback and sideline). The main source of losses is associated with the suction side boundary layer over the front and rear rotor blades with a main peak of loss production at around 75% of the blade chord.

本文介绍了在三种不同操作条件（接近、缩减和边线）下反向旋转开式转子 (CROR) 配置中产生的损耗的研究。使用非定常雷诺平均纳维-斯托克斯 (URANS) 和大涡模拟 (LES) 方法并进行比较来描述流场和损失机制。由于在该配置的两个叶片排（前转子有 11 个叶片，后转子有 9 个叶片）中没有出现共同的周向周期性，因此完整的 360${}^{\circ }$需要模拟。为了减少相关的计算成本，使用了相位滞后假设方法。这种方法能够对包括多个频率流的多级推进配置进行非稳态模拟，计算域减少到每行一个单个叶片通道。相位滞后方法需要在研究中通过数据压缩方法减少大量数据存储。数据压缩方法基于固有正交分解 (POD)，取代了传统的傅立叶级数分解 (FSD)。相移周期性假设的固有限制仍然存在于 POD 数据存储，但这种压缩方法减轻了与 FSD 相关的一些问题，尤其是频谱内容问题。配置中产生的损失分析基于熵公式。特别是，损失在边界层贡献和发生尾流和二次流的剩余域之间分配。研究显示了前缘涡对前、后转子叶片在高转速（切入和侧线）的吸力侧边界层过渡的影响。损失的主要来源与前后转子叶片上的吸力侧边界层有关，在大约 75% 的叶片弦长处产生损失的主要峰值。研究显示了前缘涡对前、后转子叶片在高转速（切入和侧线）的吸力侧边界层过渡的影响。损失的主要来源与前后转子叶片上的吸力侧边界层有关，在大约 75% 的叶片弦长处产生损失的主要峰值。研究显示了前缘涡对前、后转子叶片在高转速（切入和侧线）的吸力侧边界层过渡的影响。损失的主要来源与前后转子叶片上的吸力侧边界层有关，在大约 75% 的叶片弦长处产生损失的主要峰值。