航空检测

采用LaVision的时间分辨PIV系统测量了固体火箭发动机在风洞中的热气流喷射过程，并研究了喷射火焰热的内核与环绕热核的外部气体流动之间的相互作用。

无损检测，是用非破坏方法检查材料、毛坯和零件的内部或表面缺陷并评价其整体质量的技术，又称无损探伤。能发现材料或工件内部和表面所存在的缺欠，能测量工件的几何特征和尺寸，能测定材料或工件的内部组成、结构、物理性能和状态等。

本文详细介绍了NASA在高温隔热材料热流计法测试技术方面的研究工作，介绍了用于模拟典型空间飞行器再入气动加热过程中高温隔热材料在大温度梯度下的有效导热系数热流计法测试装置的设计和一些典型材料的测试。在测试中，被测试样的冷面保持在室温左右，试样热面则最高被加热到将近1000℃，试样所处环境气压变化范围为1E-04托～760托，所有测试都是在干燥氮气环境下进行。研制完成后的测试设备分别对三种不同密度的高温隔热材料进行了不同热面温度和不同气压下的测试。

理化公司无源、负刚度隔振技术解决航空低频隔振难题 日前，理化公司采用无源、负刚度隔振技术解决了北京航天航空大学真空、旋转的环境下的低频隔振需求。 北京航天航空大学某课题组的研究，目标是解决太空领域的相关技术难题，根据太空环境的特点，课题研究不仅需要避免高频振动的影响，难点在于如何消除低频的振动带来的干扰因素，同时隔振设备要能在旋转的环境中使用。因此，如何在真空、旋转的环境下实现低频减振成为了课题研究能否进行的先决条件。 据此，理化公司分析了其真空、旋转的环境，结合产品特点，为其定制了一套无源隔振方案，这套解决方案不仅可以消除高频振动的影响，而且可以实现0.5-1 Hz或更低频率振动的影响，不受其旋转环境的影响，同时负载也可以高达几吨。 之所以提供无源隔振是因为航空领域对隔振效果要求极高，需要实现低频隔振，同时要适应其旋转的环境。而目前其他的隔振技术最优的隔振效果也只能达到1.5-2.5 Hz，而理化公司提供的无源隔振方案不需要电源和气源，采用负刚度组件实现隔振，不仅可以实现高频隔振，而且能解决低频隔振的难题，实现0.5-1 Hz或更低的谐振频率，同时负载也可以高达几吨。 从此案例可以看出，理化公司很好的应用了无源负刚度技术为客户提供了定制隔振解决方案。在隔振领域理化公司拥有专业的服务人员，会在客户提出需求后，根据现场情况，量身定做解决方案，尤其适合精密仪器和特殊环境的要求，比如真空等环境。 理化公司无源、负刚度隔振技术在航空航天领域得到了广泛的应用，其使用效果如下图所示，不仅解决了高频的振动，同时解决了难度更大的低频振动带来的影响，可实现0.5-1 Hz或更低。 理化公司是MinusK隔振平台在国内的代理商，其产品在显微镜微观领域、光学领域、生物学领域、航天航空等领域应用广泛，为科研提供了更精密的实验环境。MinusK产品的特点即是无源，无需提供电源和气源，采用负刚度技术，不仅可以实现高频隔振，而且能解决难度更大的低频隔振，可实现0.5-1 Hz或更低频率的隔振，负载从几十公斤到几吨，均可在真空和洁净室使用。

Themotionofionsatatmosphericpressureisgovernedbyelectricalfield-andviscousdrag-forcestoacomparableextent. Thusacomprehensivedescriptionoftheconditionsinanatmosphericpressureionsourcehastoincorporatethe-inmanycasesverycomplex-bulkgasflowsinthesourcegeometry. Numericalmethods,inparticularmoderncomputationalfluiddynamics(CFD)solversystems,arethetoolsofchoicetosimulatethegasflowinAPionsources.Rigorousapplicationofthesemethodscouldresultinanimportantstepforwardonthewayfromtrial-and-errortowardsmodeldrivendesignapproachesfornewAPionsourcegeo-metries. Fromourlatestresearchefforts(seeposter070insessionTP04fordetails)weproposethatsuchamodeldrivendesignprocessispossibleandfeasible. Toanalyzethecurrentstateofthetech-nologyandtoproofthatCFDisausefultoolevenforcomplexfluiddynamicalproblems,wesimulatedthegasflowinacommerciallyavailableAPionsource(BrukerMPIS)andvalidatedtheflowsimulationswithappro-priateexperimentalmethods. Inthiscontributionwepresenttheactualflowsimulation,anexperimentalverification,andadetaileddiscussionoftheresults.

Controlling the flow over aerodynamic bodies has been a challenging problem for many years. Different open loop control techniques have been used in several flow configurations with some degree of success. However, in most cases the effectiveness of the controller is limited to the design conditions. In the present work, Proper Orthogonal Decomposition (POD) is used to derive low dimensional models of the subsonic flow over a cavity, in an effort to develop a feedback control system that can control the characteristic of the flow field. The Galerkin method is used as an additional tool to capture the time evolution of the flow field, reducing the problem into a system of ordinary differential. The stochastic estimation method is then used to link the variables that can be physically measured with those involved in the model. Particle Image Velocimetry (PIV) data and surface pressure measurement for the unforced flow (baseline) and for several open loop forcing conditions are used to derive the models.

We discuss a new phenomenon of turbulent thermal diffusion associated with turbulent transport of aerosols in the atmosphere and in laboratory experiments. The essence of this phenomenon is the appearance of a nondiffusive mean flux of particles in the direction of the mean heat flux, which results in the formation of large-scale inhomogeneities in the spatial distribution of aerosols that accumulate in regions of minimum mean temperature of the surrounding fluid. This effect of turbulent thermal diffusion was detected experimentally. In experiments turbulence was generated by two oscillating grids in two directions of the imposed vertical mean temperature gradient. We used Particle Image Velocimetry（PIV） to determine the turbulent velocity field, and an Image Processing Technique based on an analysis of the intensity of Mie scattering to determine the spatial distribution of aerosols. Analysis of the intensity of laser light Mie scattering by aerosols showed that aerosols accumulate in the vicinity of the minimum mean temperature due to the effect of turbulent thermal diffusion.