Numerical investigations on drag reduction of a civil light helicopter fuselage
Numerical investigations on drag reduction of a civil light helicopter fuselage
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DOI：
10.1016/j.ast.2020.106104
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发表时间：
2020-07
影响因子：
5.6
通讯作者：
W. Shi;Jie Li;Haoxue Gao;Heng Zhang;Zhao Yang;Youxu Jiang
中科院分区：
文献类型：
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作者：
W. Shi;Jie Li;Haoxue Gao;Heng Zhang;Zhao Yang;Youxu Jiang
本文以减小直升机阻力为目的，对轻型民用直升机机身进行了数值研究。采用reynolds - average Navier-Stokes （RANS）和一种混合的RANS- les方法：改进的延迟分离涡模拟（IDDES）方法对某原型直升机机身进行了数值模拟。RANS方法通过模块化直升机机身的实验数据进行了验证，IDDES方法已经在其他研究中得到了应用，并取得了良好的效果。两种方法计算的民用直升机气动系数数值结果基本一致。与RANS方法相比，IDDES方法能够预测机身/部件的大分离流和流场中的小尺度涡旋。结果表明，混合方法捕获了滑杆后周期性分离的分离涡，而RANS方法模拟的同一位置的流动仍然是附着的。此外，混合方法捕获了机身/尾臂连接处沿对角线向上发展的分离涡，而RANS模拟无法预测。随后，在数值模拟的基础上，通过外形优化，在α= 0迎角和0.2马赫数条件下进行了直升机减阻设计，并通过力试验验证了数值结果。结果表明，起落架的优化旨在减小起落架引起的强卡门涡脱落效应，从而大大降低总阻力。结合对机身/尾臂过渡段的优化，该方法抑制了机身分离流，减小了压力阻力，过渡段坡度的调整可使阻力减小1.18%，过渡段的延长可使阻力减小2.64%。尾桁布置优化结果表明，与原尾桁布置相比，较低尾桁布置可分别减少4.37%（RANS）和3.89%（试验）阻力。
The paper presents the numerical investigations for a light civil helicopter fuselage with the purpose of reducing the helicopter drag. Two numerical methods: Reynolds-Averaged Navier-Stokes (RANS) and a hybrid RANS-LES method: improved delayed detached-eddy simulation (IDDES) method are performed for the simulation of a prototype helicopter fuselage. The RANS method is validated by a modular helicopter fuselage with experimental data, while the IDDES method has already been used in other studies and good results have been achieved. The numerical results of the civil helicopter in terms of the aerodynamic coefficients obtained by the two methods are consistent with each other. Compared to the RANS method, the IDDES approach is capable of predicting the large separation flow of the fuselage/components and the small-scale vortices in the flow field. It is found that the hybrid method captures the periodically detached separating vortices behind the skid struts, while the flow at the same position simulated by the RANS method is still attached. Moreover, separating vortices, which develop diagonally upwards, are captured at fuselage/tail-boom junction by the hybrid method, whereas RANS simulation doesn't predict. Subsequently, the design of the helicopter drag reduction is carried out at α= 0 deg angle of attack and 0.2 Mach number through shape optimization based on the numerical simulations, and the numerical results are verified by the force tests. It shows that the optimization of the landing skids aims at reducing the strong Karman vortex shedding effect induced by the skids, which greatly decreases the total drag. Combined with the optimization of the fuselage/tail-boom transition, this approach suppresses the separation flow of the fuselage and reduces the pressure drag, and the adjustment of transition slope benefits of up to 1.18% drag reduction, while the extension of transition reduces the drag by 2.64%. The optimization of tail-boom layout demonstrates that lower tail-boom layout can contribute to a drag reduction by 4.37%(RANS) and 3.89%(test), respectively, when compared to the original tail-boom layout.