微涡旋控制多元强化水处理集成技术及其应用

基于微涡旋控制混合理论、后台阶流理论及接触絮凝理论,分别设计开发了列管混合器、星形翼片隔板絮凝反应器及V型斜板沉淀设备,并通过工艺集成形成微涡旋控制多元强化水处理技术。该技术在钢厂废水处理改造项目的中试运行结果表明,出水浊度≤2NTU,处理水量在超设计负荷15%时,出水浊度仍保持在2NTU左右;可节省药剂费用22%,节省占地30%以上。

媒介、环境与受众的涡旋互动——论广告传播在数字互动媒介中的涡旋控制模式

本文借助于现象学、传播学、流体力学及其他与广告学相关的学科理论，研究数字媒介广告的信息源、媒介、受众与数字环境之间的互动关系，试图消除广告传播在数字媒介中的障碍，优化广告传播在数字媒介中的传播方式，在广告受众与数字媒介形成互动的基础上重点探讨广告传播中的广度与深度的控制及数字互动媒介中“突发事件”漩涡规避问题。

基于超表面的涡旋波束控制技术研究综述

轨道角动量(Orbital Angular Momentum,OAM)复用技术因OAM模式间的正交性和模式的无限性,能极大程度地提升信道容量与频谱效率,对解决当前无线通信频谱拥挤问题具有重大潜力。然而,OAM波束的衍射特性和发散角问题严重限制了通信质量。对OAM通信的技术的难点进行了介绍,并对比分析了现有OAM波束控制天线的优势与不足,其中超表面天线因其结构简单、成本低和优异的电磁调控能力,在OAM波束控制中具有独特优势。其次重点梳理了基于超表面实现OAM波束控制的不同实现方式以及发展现状,最后综述了未来发展方向,为OAM波束控制相关技术的发展和未来大容量通信的实现提供了一定指导。

轨道角动量天线波束控制技术的研究进展

轨道角动量(Orbital Angular Momentum,OAM)因其模数的无限性与正交性在提升通信容量方面有着巨大的潜力,对解决频谱资源不堪重负的现状有很强的现实意义,而OAM波束自身的发散角限制了其远距离通信的能力。OAM波束控制技术作为OAM波束固有的发散角问题的解决方案,极具研究价值和发展前景。介绍了近年来OAM波束控制技术的研究进展,包括抛物面天线法、透镜天线法、谐振腔法、超表面法以及其他波束控制技术。OAM波束控制技术尚不成熟,针对不同类型以及不同应用领域还需进行不同侧重的研究。

Experimental investigation on control of vortex shedding mode of a circular cylinder using synthetic jets placed at stagnation points

Control of flow around a circular cylinder by synthetic jets has been experimentally investigated in a water tunnel with particle image velocimetry(PIV) technique.The synthetic jets are positioned at both the front and rear stagnation points.With power spectrum analysis,proper orthogonal decomposition(POD) method and other techniques for data processing,particular attention is paid to the control of vortical structures around the circular cylinder,in which the excitation frequency f e is one to three times of the natural frequency f0 and the cylinder Reynolds number and the excitation amplitude are fixed.The influenced-scope of the synthetic jet enlarges as the excitation frequency increases,and thus the synthetic jet dominates the global flow field gradually.For the natural case and the control case at fe/f0=1,the distributions of the first two POD modes and the power spectra for their POD coefficients all exhibit the characteristics of the natural shedding with antisymmetric mode.For fe/f0=2 and fe/f0=3,the variations in the third and fourth POD modes and the corresponding power spectra indicate that the wake vortex shedding mode changes and the dominant frequency becomes the excitation frequency.For fe/f0=2,the wake vortex sheds downstream with either the antisymmetric or the symmetric mode;for fe/f0=3,the synthetic jet vortex pair interacts with the near wake shear layers from both sides to induce a pair of the symmetric wake vortices,which is gradually converted into an antisymmetric mode when shedding downstream.

Numerical Visualization of Air Intake Induced by Free Surface Vortex

Free surface vortex control is vital in a pump sump system because the air absorbed by free surface vortex induc- es noise, vibration, and cavitation corrosion on the pumping system. In this study, the change of free surface vor- tex and air absorption in a pump intake has been investigated by the Volume of Fraction （VOF） method with steady multiphase flow model in order to represent the behavior of the free surface vortex exactly. The homoge- neous free surface model is used to apply interactions of air and water. The results show that air intake by the free surface vortex motion can be visualized using the iso-surface of air volume fraction. The vortices make an air column from the free surface to the pump intake. Also, it was found that the flee surface vortex can be controlled by installing curtain walls.

Numerical Study of Controlling Jet Flow and Noise using Pores on Nozzle Inner Wall

In this paper, the feasibility of controlling the subsonic jet flow and its noise using pores of blind holes added on the nozzle inner wall is explored numerically. These pores are intended to introduce disturbances to the shear layer so as to change the flow mixing. This passive strategy has not been attempted so far. A convergent nozzle with a cylindrical extension is selected as the baseline case. Three nozzles with pores on the inner wall are set up. Validations of the numerical settings are carried out, then the compressible turbulent jets at the exit Math number Mj = 0.6 in the four nozzles are calculated by large eddy simulations （LES）, while the ra-diated sounds are predicted by the FW-H acoustic analogy. The results show that the blind holes have produced some effects on weakening the turbulence intensity in the shear layer. Comparison reveals that both temporal and spatial correlations of the turbulent fluctuations in the modified cases are suppressed to some extent. Meanwhile, the porous nozzles are shown to suppress the pairing of vortices and enhance the flow mixing, and therefore, the development of shear layer and the fragmentation of large scale vortices are accelerated.

Shock Wave Induced Separation Control By Streamwise Vortices

Control of shock wave and boundary layer interaction finds still a lot of attention. Methods of this interaction control have been especially investigated in recent decade. This research was mostly concerned with flows without separation. However, in many applications shock waves induce separation often leads to strong unsteady effects. In this context it is proposed to use streamwise vortices for the interaction control. The results of experimental investigations are presented here. The very promising results were obtained, meaning that the incipient separation was postponed and the separation size was reduced for the higher Mach numbers. The decrease of the RMS of average shock wave oscillation was also achieved.

Active control of vortex-induced vibration of a circular cylinder by using the oscillatory plate immersed in the cylinder wake at low Reynolds number

As a typical fluid-solid interaction problem,vortex-induced vibration(VIV)is common in engineering,so it is vital to study its control mechanism.Numerical simulations of the active control of VIV of a cylinder are carried out in this study.The splitter plate with harmonic oscillation is used as the control device for the dynamic response of the cylinder.The displacement response,lift and drag coefficient,vibration frequency of the cylinder,energy efficiency of control strategy,and characteristics of the flow field are widely analyzed to reveal the physical mechanism of the control system.The results show that the displacement response of the cylinder can be limited in a small range by the control without feedback in most cases except for high reduced velocity.In addition,the control strategy can be changed through feedback control to keep much superior control effects at the high reduced velocity.The oscillatory splitter plate delays the vortex shedding of shear layers generated on the cylinder,the wake vortices with opposite sense of rotation are paralleled with the streamwise direction,and crosswise distances of them are reduced.Thus,the lift on the cylinder is greatly decreased due to the modification of the flow pattern induced by the oscillatory splitter plate.

Numerical Study of Combining Steady Vortex Generator Jets and Deflected Trailing Edge to Reduce the Blade Numbers of Low Pressure Turbine Stage

A flow control system that combined steady Vortex Generator Jets and Deflected Trailing-edge(VGJs-DT) to decrease the low pressure turbine(LPT) blade numbers was presented.The effects of VGJs-DT on energy loss and flow of low solidity low pressure turbine(LSLPT) cascades were studied.VGJs-DT was found to decrease the energy loss of LSLPT cascade and increase the flow turning angle.VGJs-DT decreased the solidity by 12.5%without a significant increase in energy loss.VGJs-DT was more effective than steady VGJs.VGJs-DT decreased the energy loss and increased the flow angle of the LSLPT cascade with steady VGJs.VGJs-DT can use 50%less mass flow than steady VGJs to inhibit the flow separation in the LSLPT cascade.The deflected trailing edge enhanced the ability of steady VGJs to resist flow separation.Overall,VGJs-DT can be used to control flow separation in LPT cascade and reduce the blade numbers of low pressure turbine stage.