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对迎风凹腔与逆向喷流组合热防护系统的冷却效果进行了分析, 研究了相同总压不同流速的逆向喷流对组合结构的流场、气动受力及壁面传热的影响. 通过与相关的实验结果对比, 验证了数值方法的可靠性. 研究发现:该结构能够有效地对飞行器鼻锥表面进行冷却, 引入很小总压的逆向喷流(逆喷总压比 PR=0.1), 组合结构的冷却效果就可以远远优于单一的迎风凹腔; 相同逆向喷流总压下, 逆喷速度越高, 逆喷流量越大, 外壁面的冷却效果越好; 随逆喷流速提高, 气动阻力也进一步减小. 本文研究的组合结构非常适用于 相似文献
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运用线性理论分析了粘性超薄液膜沿柱状纤维垂直下落的稳定性特征,研究了厚度低于100 nm的薄膜在外力驱动下的流动以及van der Waals力的影响.结果表明随着薄膜相对厚度的下降,纤维表面的曲率将使得线性扰动的发展得到抑制,而van der Waals力促进扰动的增长,这一竞争机制导致了增长率随薄膜相对厚度非单调的变化.还得到了流动的绝对和对流不稳定分区.结果表明van der Waals力扩大绝对不稳定流动区域,表面张力也会有利于绝对不稳定的发展,而外驱动力正好起到相反的作用. 相似文献
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The step-like contrast structure for a class of nonlinear singularly perturbed optimal control problems is considered. The existence of the step-like contrast structure for the singularly perturbed optimal control problem is proved by equivalence, which is based on the necessary conditions. The authors not only give the conditions under which there exists a step-like contrast structure, but also determine where the internal transition time is. Meanwhile, the uniformly valid asymptotic expansion of the step-like contrast structure solution is constructed by the direct scheme method. Finally, an example is presented to show the result. 相似文献
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Numerical investigation on properties of attack angle for opposing jet thermal protection system 下载免费PDF全文
The three-dimensional Navier-Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow condition. The numerical method is validated by the relevant experiment. The flow field parameters, aerodynamic forces, and surface heat flux distributions for attack angles of 0°, 2°, 5°, 7°, and 10° are obtained. The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters, aerodynamic force, and surface heat flux distribution of the supersonic vehicle nose-tip with opposing jet thermal protection system. When the attack angle reaches 10°, the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system, thus the thermal protection is failure. 相似文献
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The stability characteristics of an ultra-thin layer of a viscous liquid flowing down a cylindrical fibre are investigated
by a linear theory. The film with the thickness less than 100 nm is driven by an external force and under the influence of
the van der Waals forces. The results show that, when the relative film thickness decreases, the curvature of the fibre depresses
the development of the linear perturbations, whereas the van der Waals forces promote the instabilities. This competition
results in a non-monotonous dependence of the growth rate on the relative film thickness. The critical curves are also obtained
to describe the transition from the absolute instability to the convective instability, indicating that the van der Waals
forces can enlarge the absolutely unstable region. Furthermore, the surface tension can cause the development of the absolute
instability, whereas the external force has an opposite effect. 相似文献
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对迎风凹腔与逆向喷流组合热防护系统的冷却效果进行了分析, 研究了相同总压不同流速的逆向喷流对组合结构的流场、气动受力及壁面传热的影响. 通过与相关的实验结果对比, 验证了数值方法的可靠性. 研究发现:该结构能够有效地对飞行器鼻锥表面进行冷却, 引入很小总压的逆向喷流(逆喷总压比 PR=0.1), 组合结构的冷却效果就可以远远优于单一的迎风凹腔; 相同逆向喷流总压下, 逆喷速度越高, 逆喷流量越大, 外壁面的冷却效果越好; 随逆喷流速提高, 气动阻力也进一步减小. 本文研究的组合结构非常适用于远程、 需长时间飞行的高超声速飞行器的热防护. 相似文献
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Numerical investigation on properties of attack angle for an opposing jet thermal protection system 下载免费PDF全文
The three-dimensional Navier-Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow conditions.The numerical method is validated by the relevant experiment.The flow field parameters,aerodynamic forces,and surface heat flux distributions for attack angles of 0°,2°,5°,7°,and 10° are obtained.The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters,aerodynamic force,and surface heat flux distribution of the supersonic vehicle nose-tip with an opposing jet thermal protection system.When the attack angle reaches 10°,the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system,thus the thermal protection has failed. 相似文献
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