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就高超声速再入体尾迹等离子体场而言,为进行其亚密湍流雷达散射截面的理论分析,提出了计算湍流尾迹脉动等离子体场强的理论模型及求解方法,即在研究高超声速尾迹流动特征的基础上,推导、使用包括化学组份浓度脉动强度的k-ε-g湍流模型,用以封闭高超声速粘性尾迹湍流运动时均控制方程组,并用全隐式有限差分法求解,算例小钝锥体的飞行条件为零攻角、M_∞=21.3,Re_(∞D)=1.33×10~6;M_∞=20.5;Re_(∞D)=3.22×10~5,计算结果得到了合理的参数分布;考虑电磁波在上述等离子体介质中的传播,以单电子多次散射模型─—畸变波Born近似方法,计算了湍流尾迹脉动等离子体雷达散射截面,给出散射能(RCS)在不同极化状态下的分布,分析了散射背景场脉动湍流对电磁波在其中传播的影响. 相似文献
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<正>A three-dimensional(3-D)approach based on the state space method is proposed to study size-dependent mechanical properties of ultra-thin plate-like elastic structures considering surface effects.The structure is modeled as a laminate composed of a bulk bounded with upper and bottom surface layers,which are allowed to have different material properties from the bulk layer.State equations,including the surface properties of the structure,can be established on the basis of 3-D fundamental elasticity to analyze the size-dependent static characteristics of the thin plate-like structure.Compared with two-dimensional plate theories based size-dependent models for thin film structures in literature,the present 3-D approach is exact,which can provide benchmark results to assess the accuracy of 2-D plate theories and various numerical approaches. To show the feasibility of the proposed approach,a 3-D analytical solution for a simply supported plate-like thin structure including surface layers is derived.An algorithm is proposed for the calculation of the state equations obtained to ensure that the numerical results can reveal the surface effects clearly even for extremely thin surface layers.Numerical examples are carried out to exhibit the surface effects and some discussions are provided based on the results obtained. 相似文献
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前体涡发生器对轴对称高超声速进气道激波振荡流动的影响实验 总被引:1,自引:0,他引:1
激波振荡是高超声速进气道不起动过程中常见的流动现象,会显著降低进气道气流捕获与压缩效率、产生剧烈的非定常气动力载荷而危害飞行器安全. 从激波振荡的控制出发,实验研究了前体转捩带位置的涡发生器对轴对称高超声速进气道激波振荡流动的影响. 分别在起动和激波振荡两种进气道流态下,选择无、0.5 mm与1 mm高度涡发生器工况进行对比研究. 并采用高速纹影与壁面动态测压同步记录非定常流动特征. 结果表明,1 mm高度内的涡发生器对起动状态的进气道主流流场结构、壁面压强分布影响不显著. 但对于激波振荡流动,涡发生器会明显缩小外压缩面分离区运动范围,缩短振荡周期,提升振荡周期内壁面压强的时均值. 涡发生器的影响程度随其高度的增大而增强,其中振荡周期从无涡发生器的4 ms缩短到1 mm高度涡发生器的3.13 ms. 此外,0.5 mm高度涡发生器会使得进气道内部测点的压强振荡幅值整体下降,相比无涡发生器工况的下降幅度可达23%. 流场结构与壁面压强信号的分析表明,涡流发生器主要通过其产生的流向涡影响激波振荡流动,包含流向涡对下游边界层的扰动以及流向涡与分离区的相互干扰. 相似文献