基于卷积神经网络的合成双射流控制机翼分离流场识别与参数优化

Recognition and parameter optimization of separated flow field in airfoil controlled by dual synthetic jet based on convolutional neural network

  • 摘要: 为进一步拓宽合成双射流(DSJ)技术在翼型分离流动控制领域的工程应用,采用数值模拟的方法,研究了DSJ对分离流的控制机理与控制规律,构建控制参数向量与气动参数之间的RBF神经网络代理模型,通过改进的粒子群算法(PSO)搜索一定约束下所能达到的最佳气动参数,并搭建Inception-V3卷积神经网络模型对平均速度场所对应的控制参数进行识别,以实现根据目标流场调整激励器参数,使其气动性能达到最优的目的。结果表明:DSJ对分离流的控制机理包括:动量注入效应、涡掺混效应、抽吸效应;射流控制参数对控制效果有较大影响,迎角为16°~21°时,无量纲控制频率F+在0.5~4.0范围内都具有较好的控制效果,迎角为22°~24°时,最佳无量纲控制频率为3~4,同时动量系数越大,增升减阻效果越明显;RBF神经网络具有良好的泛化能力,测试误差不超过17%;PSO优化结果显示,在16°≤α≤24°、0 < F+ < 4、0 < Cμ < 0.0954约束内,翼型所能达到的最大升力系数为1.793,最小阻力系数为0.013;Inception-V3模型在测试算例中的均方误差最大为0.1023,模型预测得出的控制向量所对应的速度场与原始速度场在小失速迎角下一致性较好,在大失速迎角下一致性较差。

     

    Abstract: For broadening the engineering application of dual synthetic jet (DSJ) in the field of separation flow control, the control mechanism and law of the DSJ were studied numerically, and the RBF neural network model was constructed to describe the relationships between the control parameters and the aerodynamic parameters. Moreover, the optimal aerodynamic parameters that could be achieved under certain constraints and control parameters were searched based on improved particle swarm optimization (PSO) algorithm. In addition, Inception-V3 model was established to identify the control parameters based on the average velocity field with the purpose of adjusting the control parameters of the actuators according to the target flow field, then achieving the optimal control effects that can realize the optimal aerodynamic performance of the airfoil. Results show that, the following issues are contained in the control mechanism of the DSJ on separation flow:momentum injection effect, vortex mixing effect and suction effect. The control parameters have a significant impact on the control effects. When the attack angle is in the range of 16°~21° and 22°~24°, the non-dimensional optimal frequency F+ is in the range of 0.5~4.0 and 3~4, respectively. Meanwhile, the larger the separation zone is, the bigger the non-dimensional optimal frequency F+ is. A larger momentum coefficient lead to a more significant effects of lift promotion and drag reduction. A great generalization ability is realized by the RBF neural network model, whose maximum test error is less than 17%. The PSO optimization results show that the maximum lift coefficient and the minimum drag coefficient could be realized under different conditions, with the values being 1.793 and 0.013 respectively, with 16° ≤ a ≤ 24°, 0 < F+ < 4, and 0 < Cμ < 0.0954. The Inception-V3 model, whose maximum mean square error of test cases is less than 0.1023, has the outstanding ability to predict the control parameters. Apart from that, the average velocity field corresponding to the control parameters predicted by the model is greatly consistent with the original velocity field at small attack angles, but the consistency is bad at large attack angles owing to the great sensitivities to the control parameters.

     

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