Abstract
For the high-precision simulation of engine jet effects, an improved delayed detached eddy simulation (IDDES) method based on the two-equation shear stress transport (SST) model is developed, and the fifth-order finite-volume weighted essentially non-oscillatory (WENO) scheme is employed to enhance accuracy of spatial discretization, and then numerical investigation of powered jet effects by RANS/LES hybrid methods is carried out. The effects of the grid distributions and the accuracy of the spatial schemes are discussed during the RANS/LES validation analysis on the fully expanded jet flow and Acoustic Reference Nozzle (ARN) jet flow. The results show that, by enlarging the grid density and improving the accuracy of the spatial schemes, the velocity distributions in the jet flow can be better predicted, the non-physical steady flow after the jet nozzle can be shortened, the instantaneous flow structures are clearer and the turbulent intensities are more accurate. Then IDDES simulation of turbofan engine jet flow is carried out. The mixing characteristics of the external fan jet flow and internal core jet flow as well as the ambient flow are obtained, and the three-dimensional turbulent structures are also given.
Highlights
Large⁃Eddy Simulations of Chevron Jet Flows with Noise Predictions[ J]
For the high⁃precision simulation of engine jet effects, an improved delayed detached eddy simulation ( IDDES) method based on the two⁃equation shear stress transport ( SST) model is developed, and the fifth⁃order finite⁃volume weighted essentially non⁃oscillatory ( WENO) scheme is employed to enhance accuracy of spatial dis⁃ cretization, and numerical investigation of powered jet effects by RANS / LES hybrid methods is carried out
The effects of the grid distributions and the accuracy of the spatial schemes are discussed during the RANS / LES validation analysis on the fully expanded jet flow and Acoustic Reference Nozzle ( ARN) jet flow
Summary
摘 要:从动力喷流效应精细化模拟需求出发,在 k⁃ω SST 湍流模型基础上建立了 IDDES 混合方法, 采用了有限体积五阶 WENO 格式提高空间离散格式精度,开展了动力喷流效应混合方法数值模拟分 析及应用研究。 基于自由发展喷管流动和 ARN2 喷管算例,开展了动力喷流效应混合方法数值模拟 验证分析,结果表明增加网格密度和提高空间离散格式可有效改善喷流速度分布预测结果,缩短喷管 出口下游非物理流动稳定状态,瞬态流场结构更加清晰合理,湍流强度预测更加准确。 在此基础上, 针对较为实际的涡扇发动机模型,完成了动力喷流效应混合方法数值模拟分析,得到了内、外涵喷流 和外界气流的相互干扰及掺混特征,得到了三维湍流结构特征。 高雷诺数喷流流动的可行方法。 Shur 和 Spalart 等 人[4] 针对复杂喷管喷流流动开展了 RANS / LES 混 合方法数值模拟研究,Cai 等[5] 基于该方法结合高 阶格式讨论了网格分布、边界条件处理等对喷流流 动数值模拟的影响。 Brunet 等[6] 基于 Zonal⁃DES 方 法,针对较为实际的机翼 / 挂架 / 短舱构型,开展了跨 声速情况下的动力喷流数值模拟研究,基于简单的 SA、SST 湍流模型和复杂的 DRSM 湍流模型的混合 方法都取得了与试验较为吻合的结果。 国外还有一 些其他研究人员,如 Grinstein 和 Fureby 等[7] 认为不 使用亚格子模式的隐式 LES 方法( ILES 方法,又称 NLES 方法) 能够较好地捕捉复杂喷流湍流结构, Eastwood 等[8⁃9] 采用 RANS / NLES 方法对简单轴对 称喷管和发动机复杂喷流进行模拟并得到良好效 果。 从公开的文献资料来看,国内采用 RANS / LES 混合方法对动力喷流流场数值模拟研究成果仍相对 较少。 在非定常 RANS 方法计算结果的基础上采用结 合了三阶 MUSCL 插值格式的 SST⁃IDDES 方法进行 续算,无量纲时间步长 Δt 取为 0.000 5。
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