CFD在高速飞行器热气弹问题中的应用

采用气动力/热/结构耦合的方法对高速细长体飞行器结构热静气动弹性问题进行了研究.为保证耦合计算精度，达到准确预测热气动弹性特性的能力，气动力和气动热计算采用CFD数值模拟方法，热应力和热变形计算采用有限元方法并通过热考核试验验证.以该简单细长体飞行器模型为研究对象，对其热静气动弹性特性进行了计算与分析，计算结果表明:CFD/CSD耦合可准确模拟热气弹问题，且气动加热造成结构温升不均衡是结构变形的主导因素，力热耦合静气弹变形与单纯受力分析变形形式不同，对飞行器气动特性影响规律不同.准确预测飞行器热气动弹性特性对飞行器结构设计十分必要.      

合成双射流控制机翼水滴撞击特性

在低速来流条件下,针对前缘位置嵌有合成射流/合成双射流激励器的机翼的水滴撞击特性开展了数值模拟研究,基于Fluent软件,采用Euler气液两相模型和欧拉壁面液膜（Eulerian wall film,EWF）模型,得到的计算结果表明:在合成射流或合成双射流的主动控制下,阻挡了机翼前缘等积冰重点防护区域内的水滴撞击,从而大幅降低了该区域的结冰强度.其机理是:在高频合成射流的作用下,机翼前缘上游附近形成了一对稳定的闭合回流区,形成了水滴的"真空区域".由于回流区内部水滴速度和质量分数较低,改变了机翼前缘水滴运动轨迹和水滴收集率分布,能够减少机翼前缘结冰程度并改变冰形,起到了虚拟气动外形的作用.      

低Reynolds数下合成双射流控制结冰翼型流动分离的数值模拟

通过FLUENT软件数值模拟的方法,分别对结明冰、混合冰、霜冰翼型的气动特性进行了研究,分析了合成双射流对改善结冰翼型流动分离的影响规律.结果表明:3种冰形均破坏了翼型的流线型,对翼型的气动力特性有不同程度的影响,其中霜冰对翼型气动力特性影响最小,明冰对翼型气动力特性影响最大,混合冰介于两者之间.开启合成双射流激励器,在小攻角情况下,结冰翼型的气动特性得到了有效的改善.而在大攻角情况下,合成双射流激励器不能完全消除分离涡,但可以推迟分离涡,分离涡厚度增加,分离涡最厚点推后.      

类前缘防热层流场与热响应耦合计算研究

本文在以往对类前缘防热层热响应计算分析基础上,进一步研究实现了外流场高超音速NS方程数值计算表面气动加热与防热层结构热响应的耦合计算,这对于常用的非耦合计算方法来说是一进步,也为进一步开展外流场/结构热响应/热应力全耦合一体化计算研究和防热层表面吹气强化传热问题的场协同研究打下了基础。     

带支撑装置的CRM-WBH模型流固耦合数值模拟

共同研究模型（common research model，CRM）机翼/机身/平尾组合体构型（CRM-WBH）是第4届AIAA阻力预测研讨会（Drag Prediction Workshop IV，DPW IV）选择的基准构型，DPW IV会议的统计分析结果显示计算结果与试验结果之间存在显著差异.采用CFD方法和流固耦合方法数值模拟了带支撑装置的CRM机翼/机身/平尾组合体模型（CRM-WBHS）的气动特性，主要目的是评估支撑装置和静气动弹性变形对CRM-WBH模型气动特性数值模拟结果的影响.通过与CRM-WBH模型CFD数值模拟结果和欧洲ETW风洞（European Transonic Wind Tunnel）测力、测压和模型变形测量结果的对比分析，表明模型支撑装置导致机翼上翼面激波位置前移，升力系数、阻力系数下降，俯仰力矩系数增加；静气动弹性变形主要影响机翼上表面激波位置和外翼处激波位置前负压，导致升力系数、阻力系数进一步下降，俯仰力矩系数进一步增加.CRM-WBHS模型的流固耦合数值模拟结果更加接近试验结果.      

霜冰条件对翼型气动性能影响数值研究

利用商用软件Fluent并采用四方程Transition SST模型针对NRELS809翼型在不同温度.液态水含量(LWC)、攻角等条件下所得到结冰翼型,在Re=1.0E+06时进行流场计算并得到各项气动参数。同时对结冰软件Lewice相同条件得到结冰后翼型进行对比计算,并对各实验环境因素对于翼型周围流场影响进行了对比分析,最终得出结论:实验结冰翼型与软件模拟结冰翼型气动性能差异较大,同时在霜冰生成的条件范围内,环境温度相对越高、LWC越低、攻角相对越大,其翼型的气动性能表现更好,但均低于无结冰发生翼型的气动性能。     

风向对侧向进气装置外流场影响的数值研究

采用三维数值模拟方法及Polyhedra多面体网格重组技术研究了船舶侧向进气装置在不同风向下的气动性能,计算结果表明多面体网格在保证计算精度情况下可有效提高计算效率3倍左右,同时给出两侧百叶窗关键气动参数的分布规律,并对比分析了不同风向下外流场结构的变化情况.得出侧向进气两侧气动参数差异较大,在保证两侧百叶窗进气流量相仿时易会导致燃气轮机进气畸变的产生的结论,为船用进气装置布置形式的设计提供一定的参考数据.     

结冰环境热合成双射流激励器工作特性数值研究

为研究结冰环境中热合成双射流激励器工作特性,采用离散相模型(discrete phase model,DPM),结合动网格方法,数值研究了结冰环境中来流速度、液滴含量、液滴直径对激励器工作特性的影响.结果表明,来流速度较小时,双射流激励器出口形成热合成射流融合区,由于热射流的加热作用,温度较高,环境中的过冷液滴难以进入...     

结冰对风力机叶片影响的数值研究

本文利用商用CFD软件Numeca针对NREL Phase VI风轮结冰前后进行数值计算,计算包含风速由5 m/s至17 m/s区间各典型工况,并对计算结果进行了气动参数和载荷等相关分析。由此得出结论:结冰可以带来最高达51%的功率损失,同时会使风力机提前失速以及提高了启动风速等;结冰会导致在较高风速下叶根挥舞弯矩急剧增大从而增大叶片叶根强度要求;另一方面由叶片沿展向载荷分布得出结冰对整机影响主要集中在大于90%叶展的外侧区域,该区域是除冰防冰系统主要作用区域。     

先进双发民用飞机跨音速绕流数值模拟

采用求解椭圆型和抛物型偏微分方程的方法及多块风格技术，生成机翼／机身／短舱／挂架复杂组合体外形的贴体及与边界正交的计算网格。应用有限体积法高效求解欧拉方程，模拟先进双发民用飞机的跨音速绕流，并计入机翼边界的粘性效应，获得存在短舱、挂架干扰的翼身组合体气动特性，计算表明，短舱，挂架对超临界机翼的气动特性有显著的影响，计算与实验模型的机翼表面压力分布（测量值）符合良好。     

Multi-Zone Ice Accretion and Roughness Models for Aircraft Icing Numerical Simulation

A mathematical multi-zone ice accretion model used in the numerical simulation of icing on airfoil surface based on three water states, namely, continuous film, rivulets and beads is studied in this paper. An improved multi-zone roughness model is proposed. According to the flow state of liquid water and film flow, rivulets flow governing equations are established to calculate film mass distribution, film velocity, rivulet wetness factor and rivulet mass distribution. Force equilibrium equations of droplet are used to establish the critical conditions of water film broken into rivulets and rivulets broken into beads. The temperature conduction inside the water layer and ice layer is considered. Using the proposed model ice accretion on a NACA0012 airfoil profile with a $4^◦$ angle of attack under different icing conditions is simulated. Different ice shapes like glaze ice, mixed ice and rime ice are obtained, and the results agree well with icing wind tunnel experiment data. It can be seen that, water films are formed on the surface, and heights of the films vary with icing time and locations. This results in spatially-temporally varying surface roughness and heat transfer process, ultimately affects the ice prediction. Model simulations indicate that the process of water film formation and evolution cannot be ignored, especially under glaze ice condition.     

Anti-icing performance of superhydrophobic surfaces

This article studies the anti-ice performance of several micro/nano-rough hydrophobic coatings with different surface chemistry and topography. The coatings were prepared by spin-coating or dip coating and used organosilane, fluoropolymer or silicone rubber as a top layer. Artificially created glaze ice, similar to the naturally accreted one, was deposited on the nanostructured surfaces by spraying supercooled water microdroplets (average size ∼80 μm) in a wind tunnel at subzero temperature (−10 °C). The ice adhesion strength was evaluated by spinning the samples in a centrifuge at constantly increasing speed until ice delamination occurred. The results show that the anti-icing properties of the tested materials deteriorate, as their surface asperities seem to be gradually broken during icing/de-icing cycles. Therefore, the durability of anti-icing properties appears to be an important point for further research. It is also shown that the anti-icing efficiency of the tested superhydrophobic surfaces is significantly lower in a humid atmosphere, as water condensation both on top and between surface asperities takes place, leading to high values of ice adhesion strength. This implies that superhydrophobic surfaces may not always be ice-phobic in the presence of humidity, which can limit their wide use as anti-icing materials.     

超疏水铝导线的制备及其防覆冰性能研究

Aluminum is widely used in transmission lines,and the accumulation of ice on aluminum conductor may inflict serious damage such as tower collapse and power failure.In this study,super-hydrophobic surface (SHS) on aluminum conductor with micro-nanostructure was fabricated using the preferential etching principle of crystal defects.The surface microstructure and wettability were investigated by scanning electron microscope and contact angle measurement,respectively.The icing progress was observed with a self-made icing experiment platform at different environment temperature.The results showed that,due to jumping and rolling down of coalesced droplets from SHS of aluminum conductor at low temperature,the formation of icing on SHS could be delayed.Dynamic icing experiment indicated that SHS on aluminum conductor could restrain the formation of icing in certain temperature range,but could not exert influence on the accumulation of icing.This study offers new insight into understanding the anti-icing performance of actual aluminum conductor.     

Remote monitoring of ice loading on wind turbine blades based on total internal reflection

The paper presents an optical method for monitoring of transparent icing, which is applicable for remote monitoring of wind turbine blade icing. The method is based on the effect of total internal reflection of light. A point light source is formed on a wind turbine blade. When icing appears on the blade, a light circle is formed around the light source at the ice–air interface as a result of refraction and reflection of light beams; the observed size of the beam depends on the icing thickness. Using several light sources, the method enables field monitoring of icing on the wind turbine blades.     

离心泵流量突增过程瞬态流动研究

为研究离心泵流量突增过程所表现的外部瞬态水力特性及其内部流动机理,对离心泵在管路阀门突然开启条件下的特性进行数值模拟和实验研究。测试了不同稳定流量下的离心泵外特性和内流场,验证了稳态工况下的仿真结果。在稳态实验与仿真的基础上,利用分离涡模型(DES)对离心泵流量突增过程的流场进行了数值模拟研究。结果表明,流量突增的瞬态过程的流量-扬程曲线明显偏离稳态值,其主要原因是流量变化引起的流体加速效应及泵内的旋涡结构的不断演化。     

膜蒸馏装置热容腔流场数值模拟的可行性分析

本文运用CFD软件,采用水作为工质,在第Ⅲ代膜组件基础上,对旋转切向入流空气隙膜蒸馏热容腔内的流场进行了模拟计算,通过数值模拟结果与实验数据的比较分析,验证了针对膜组件热容腔进行理论模拟所设置的物理模型和边界条件是符合实际的,理论模拟值和实验值的误差在20%范围内,其结果较为理想.     

Convective heat transfer in axisymmetric enclosures of different configurations under the conditions of their axial rotation and external heating

The phenomenon of the intensification of convective heat transfer through air cavities under the conditions of their axial rotation and external heating based on the rise of centrifugal body forces in differently heated air medium has been substantiated theoretically and confirmed experimentally. The criterion dependencies for convection coefficients of axisymmetric cylindrical and conical closed air cavities subjected to external heating and axial rotation have been obtained using the results of the physical and numerical experiments. Both single-layer cylindrical cavities and two-layer ones with perforating internal orifices have been considered.