Basic Study on Active-Feedback Control of Non-Linear Heat and Fluid Flow

为了寻求一种有效的热和流体流动的主动反馈控制方法，控制理论和控制装置得到了广泛的研究。得出以下结论：将次优控制理论应用于以跨向虚拟体力场为控制输入的数值模拟槽流。与简单反馈律相比，次优控制实现了显著的湍流减阻效果，但控制量较小。采用直接数值模拟的方法，在具有柔性壁面的湍流通道中测试了壁面变形的简单振荡模式。在平均流动特性和瞬时流动结构中观察到了实质性的影响。结果表明，湍流结构与壁面变形的大小有关，基于神经网络的最优控制算法能有效地控制热传导和Burgers方程。将该方法成功地应用于圆柱体下游速度脉动的控制，开发了12套襟翼执行器阵列，用于控制近壁准流向涡结构的运动学。研究发现，激励器的周期性运动对湍流统计特性的影响对展向速度分量有选择性的影响。模型预测的襟翼动态特性与实验结果吻合较好。安装在圆形喷嘴嘴唇上的一组襟翼可以显着地操纵轴对称射流的旋涡脱落现象。通过一系列的数值模拟和实验室实验，研究了壁面湍流中颗粒的动力学。研究了颗粒对换热现象的影响。

In pursuit of an effective active feedback control methodology for heat and fluid flow, control theories and control devices were studied extensively. The following conclusions can be derived :A suboptimal control theory is applied to the numarically-simulated channel flow with a spanwise virtual body force field as a control input. The suboptimal control achieves a significant turbulent drag reduction with fairly small control, when compared with simple feedback law.A simple oscillatory mode of wall deformation is tested in a turbulent channel with a flexible wall by using direct numerical simulation. The substantial influences are observed in the mean flow properties as well as instantaneous flow structures. The turbulent structures are found to be dependent on the scales of the wall deformation at both their enhanced and damped phases.The optimal control algorithm based on neural network (NN) was found to be effective for controlling the heat conduction and the Burgers equations. The present method is also applied to the management of velocity fluctuations downstream of a cylinder successfully.An array of twelve sets of flap actuators was developed so as to control the kinematics of the near-wall quasi-streamwise vortical structures. The effect of periodic motion of the actuators on the turbulent statistics was found to affect the spanwise velocity component selectively.A prototype electromagnetic flap actuator was developed with photo lithography. The dynamic characteristics of the flap predicted by models were in reasonable agreement with experimental results. A group of flap mounted on the circular nozzle lip can manipulate significantly the vortex shedding phenomena of an axisymmetric jet.Dynamics of particles in wall turbulence was examined by using a series of DNS and laboratory experiments. The effect of particle on heat transfer phenomena was also studied.