多孔介质对圆柱-翼型干涉噪声的影响

采用LES（large eddy simulation）+FW-H（Ffowcs Williams-Hawkings）方程，研究了圆柱表面使用不同PPI（pore number per inch）和厚度的多孔介质对圆柱尾迹及圆柱-翼型干涉噪声的影响，探索了多孔介质的降噪规律和机理。结果表明：多孔介质能稳定圆柱表面的剪切层，抑制旋涡脱落，从而削弱尾迹对下游翼型的影响，圆柱单音噪声最大可降79 dB，翼型单音峰值降低13.22 dB，宽频噪声降低20 dB；多孔材料PPI的变化对降噪效果影响较小，而厚度是影响流场模态、降噪效果及气动性能的一个关键参数；多孔材料厚度合适时，圆柱-翼型流场形态为“剪切层模态”，可有效降低湍流干涉噪声；多孔材料厚度较小时，发现了一种流场形态，即“剪切层-尾迹模态”，导致翼型噪声增大；合适的多孔介质厚度不仅降噪效果显著，对圆柱-翼型的气动性能也有改善作用。     

Modelling and analysis of initial icing roughness with fixed-grid enthalpy method based on DPM-VOF algorithm

Ice particles could form under the continuous impingement of incoming supercooled droplets in icing conditions, which will change the surface roughness to enhance the further heat and mass transfer during icing process. A fixed-grid porous enthalpy method based on the improved Discrete Phase Model(DPM) and Volume of Fluid(VOF) integrated algorithm is developed to solve the multiphase heat transfer problem to give more detailed demonstration of the formation of initial ice roughness. The algorith...     

碱金属工质在基于毛细泵回路的多孔芯蒸发器内的热质传输特性

以基于毛细泵回路(CPL)原理的多孔芯蒸发器为研究对象，耦合多孔芯、蒸汽槽道和蒸发器壳体等多个部件，通过数值模拟的方法对碱金属工质在蒸发器内部的流动和相变传热特性进行分析，得到蒸发器内部的气相体积分数、温度、压力以及速度等分布。结果表明:碱金属液体极高的导热系数使得多孔芯部分的平均过热度不足1K；以碱金属为工质的多孔芯蒸发器，其内部的蒸发属于表面蒸发，气液界面稳定在多孔芯和蒸汽槽道的界面处，且在相同参数条件下，其毛细抽吸力比使用传统工质的蒸发器高1~2个数量级，具有更大的传输能力。      

基于多孔介质的指尖密封各向异性传热模型

在指尖密封多孔介质流动模型的基础上，将指尖密封片之间的接触传热附加于固体导热之中，之后通过对密封固体结构与结构内流体的耦合各向异性传热进行理论分析，建立了指尖密封各向异性传热数学模型；基于商业软件Fluent中的用户自定义标量（UDS）方程功能，开发了多孔介质各向异性传热数值计算模块，并数值模拟了指尖密封结构内的流动与传热特性。结果表明:指梁与指尖靴区域的各向异性有效导热系数张量与孔隙率、径向和周向位置以及轴向接触热阻等因素相关；指尖密封最高温度出现在指尖靴与转子接触面的略下游处；与各向同性传热模型相比，采用各向异性传热模型时,指梁下部和指尖靴区域沿径向和轴向存在较大温度梯度，但温度沿周向的变化两者均很小；泄漏量随着压差的增加逐渐增大，随着转子转速的增加基本不变；指尖密封最高温度值随着压差的增加逐渐减小，随着转子转速的增加逐渐增大。      

Selective thermal emission and infrared camouflage based on layered media

Infrared camouflage based on artificial thermal metasurfaces has recently attracted significant attention. By eliminating thermal radiation differences between the object and the background, it is possible to hide a given object from infrared detection. Infrared camouflage is an important element that increases the survivability of aircraft and missiles, by reducing target susceptibility to infrared guided threats. Herein, a simple and practicable design is theoretically presented based on a multilayer film for infrared stealth, with distinctive advantages of scalability, flexible fabrication, and structural simplicity. The multilayer medium consists of silicon substrate, carbon layer and zinc sulfide film, the optical properties of which are determined by transfer matrix method. By locally changing the thickness of the coating film, the spatial tunability and continuity in thermal emission are demonstrated. A continuous change of emissive power is further obtained and consequently implemented to achieve thermal camouflage functionality. In addition, other functionalities, like thermal illusion and thermal coding, are demonstrated by thickness-engineered multilayer films.