基于迁移深度强化学习的串列翼射流流动控制
JET FLOW CONTROL OF TANDEM WINGS BASED ON TRANSFER DEEP REINFORCEMENT LEARNING
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摘要: 串列翼有前后翼共同分担升力、减小诱导阻力等优点, 但复杂的尾迹干扰造成流场不稳定, 影响气动性能的进一步提高. 为了克服这些问题, 本文提出了一个基于迁移深度强化学习的射流主动控制方案, 用近端策略优化算法(Proximal Policy Optimization, PPO)来训练智能体, 通过调节翼面射流强度, 达成稳定升力并减小阻力的目的, 训练是在雷诺数为1000, 上下翼间距h = 0.5c(翼型弦长)、前后翼间距d = 2c的典型工况下开展的, 之后把策略迁移到四种不同的布局上, (a) h = 0.5c, d = 3c; (b) h = 0.5c, d = 4c; (c) h = −0.5c, d = 2c; (d) h = 0c, d = 2c, 以此来考察其在不同空间结构下的泛化能力和鲁棒性. 结果表明: 在训练工况下, 前翼和后翼的升阻比分别上升了22.89%, 5.37%; 在迁移工况下, 前翼的升阻比分别增长了17.27%, 18.03%, 19.35%, 31.64%, 后翼分别增长了4.86%, 3.97%, 23.68%, 18.07%. 而且对升力系数的功率谱做了剖析表明, 此控制策略可以很好地遏制周期性涡脱落, 气动效应的振荡. 本研究证实了基于强化学习的迁移控制策略能够在复杂非定常流场中有应用价值以及高效率, 为串列翼飞行器的高速高效主动流动控制供应了新的思路与理论支撑.Abstract: Tandem wings share lift and reduce induced drag with the front and back wings, which is a benefit. However, the complex wake interference makes the flow field unstable, which stops the improvement of aerodynamic performance even further. An active jet control method based on transfer deep reinforcement learning is suggested in this paper to get around these issues. To teach the smart agent, the Proximal Policy Optimisation (PPO) method is used. The goal is to stabilise lift and lower drag. This is done by changing the jet strength on the wing surface. For the training, the Reynolds number is set to 1000, the distance between the upper and lower wings is h = 0.5c (aerofoil chord length), and the distance between the front and back wings is d = 2c. The approach was then moved to four different layouts: (a) h = 0.5c, d = 3c; (b) h = 0.5c, d = 4c; (c) h = −0.5c, d = 2c; (d) h = 0c, d = 2c. This was done to see how well it could be used in other situations and how stable it was. The findings show that the lift-to-drag ratio of the front wing increased by 22.89% and that of the rear wing increased by 5.37%. During migration, the lift-to-drag ratio of the front wing increased by 17.27%, 18.03%, 19.35%, and 31.64%, and that of the rear wing increased by 4.86%, 3.97%, 23.68%, and 18.07%. Also, looking at the power spectrum of the lift coefficient shows that this control approach can stop the vortex shedding and oscillations of the aerodynamic effect quite well. This study shows that the reinforcement learning-based migration control approach can work well in complex unsteady flow fields. It also gives us new ideas and theoretical support for making active flow control of tandem-wing aircraft fast and effective.
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