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Yinxin ZHU Wenqiang PENG Zhenbing LUO Qiang LIU Wei XIE Pan CHENG Yan ZHOU 《中国航空学报》2023,36(7):366-377
To effectively reduce the loss of strong shock wave at the trailing edge of the supersonic cascade under high backpressure, a shock wave control method based on self-sustaining synthetic jet was proposed. The self-sustaining synthetic jet was applied on the pressure side of the blade with the blow slot and the bleed slot arranged upstream and downstream of the trailing-edge shock,respectively. The flow control mechanism and effects of parameters were investigated by numerical simulation. The res... 相似文献
395.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(4):1866-1892
Studies on small-scale jets’ formation, propagation, evolution, and role, such as type I and II spicules, mottles, and fibrils in the lower solar atmosphere’s energetic balance, have progressed tremendously thanks to the combination of detailed observations and sophisticated mathematical modelling. This review provides a survey of the current understanding of jets, their formation in the solar lower atmosphere, and their evolution from observational, numerical, and theoretical perspectives. First, we review some results to describe the jet properties, acquired numerically, analytically and through high-spatial and temporal resolution observations. Further on, we discuss the role of hydrodynamic and magnetohydrodynamic instabilities, namely Rayleigh–Taylor and Kelvin–Helmholtz instabilities, in jet evolution and their role in the energy transport through the solar atmosphere in fully and partially ionised plasmas. Finally, we discuss several mechanisms of magnetohydrodynamic wave generation, propagation, and energy transport in the context of small-scale solar jets in detail. This review identifies several gaps in the understanding of small-scale solar jets and some misalignments between the observational studies and knowledge acquired through theoretical studies and numerical modelling. It is to be expected that these gaps will be closed with the advent of high-resolution observational instruments, such as Daniel K. Inouye Solar Telescope, Solar Orbiter, Parker Solar Probe, and Solar CubeSats for Linked Imaging Spectropolarimetry, combined with further theoretical and computational developments. 相似文献
396.
Guided wave propagation analysis in stiffened panel using time-domain spectral finite element method
《中国航空学报》2022,35(10):208-221
Stiffened panels have been widely utilized in fuselages and wings as critical load-bearing components. These structures are prone to be damaged under long-term and extreme loads, and their health monitoring has been a common concern. The guided wave-based monitoring method is regarded as an efficient approach to detect the damage in stiffened plates because of its wide monitoring range and high sensitivity to micro-damage. Efficient simulation of wave propagation can theoretically demonstrate the detection mechanism of the method. In this study, a Time-Domain Spectral Finite Element Method (TD-SFEM) is adopted to study the wavefield in stiffened plates, where continuous Absorbing Layers with Increasing Damping (ALID) strategy is proposed to circumvent the disturbance of reflected waves on boundaries. After the convergence analysis, the developed TD-SFEM with ALID is validated by the finite element method first. Then, wave scattering and the influence of the stiffener are investigated in detail by comparing the results with the non-stiffened structure. Finally, the effects of the parameters of the stiffener, such as the height and width, on wave propagation are studied, respectively. The results illustrate that the proposed TD-SFEM with ALID is an efficient approach to study the wave propagation in the stiffened plate and can reveal the mechanism of influence of the stiffener. It is found that the height of the stiffener changes the interference of wavefield in the plate, while the effects of the width are mainly in wave scattering and mode conversion. 相似文献
397.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(1):199-215
This study presents the analysis of planetary waves (PWs) using daily mean wind velocities for four years (August 2013 to July 2017) of continuous measurements using MF radar over the low latitude Indian region Kolhapur (16.8° N; 74.2° E). The MF radar at Kolhapur was upgraded in 2013. These are the first results of PWs after the upgradation of MF radar. The seasonal and intra-seasonal variabilities of East-West (EW) traveling PWs in the MLT region have been studied. In the present work, the data was analyzed to study the waves with various periodicities (e.g. 3–4, 5–8, 15–17, and 30–60 days). The 3.5 day [Ultra-Fast Kelvin (UFK)] wave shows semiannual variability with burst like wave activity observed during the summer months and December solstice. In addition, it is observed to be stronger in the spring equinoctial period. A strong semiannual oscillation (SAO) has been observed in a 6.5-day wave with peaks near the equinoxes. Similar to SAO over the low latitude MLT region, the wave activity is stronger in April/May than in September/October. The 6.5-day waves are observed to be stronger when the background mean wind is westward. From the analysis, it has been seen that the period before and after the equinoctial period is favorable for the 6.5-day wave propagation. The 16-day wave has no significant seasonal dependence; instead, the waves spread to almost all seasons. The Madden-Julian Oscillations (MJOs) have been observed to be propagating with an average wind speed of ~ 5 m/s when the background mean wind is eastward. The occurrence of MJO is observed during the summer and winter months. These results are the first of their kind in two aspects: first, they show the PWs with enhanced altitude coverage covering up to 110 km, and second, they show the PWs not contaminated due to equatorial electro jet influence. 相似文献
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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(5):2384-2393
In this paper, we show the potential of satellite altimetry to study the interaction of Rossby waves with the shear flow. The Miles-Ribner approach, which was developed in gas dynamics in the 1960 s, is used to describe Rossby waves interacting with the Gulf Stream and Kuroshio areas. The region of interaction is approximated by a nonzonal vortex layer. We apply the main formulations of the problem of a nonzonal vortex layer on the β-plane in the formulation of Miles-Ribner to observations in the real ocean. Earlier, we showed that the interaction of waves with a nonzonal flow gives rise to a new class of solutions, which is absent in the case of a zonal flow. This new class of solutions can be interpreted as the pure emission of Rossby waves by the nonzonal flow. We apply this theoretical approach to the areas of the Gulf Stream and Kuroshio as well. We use for analysis altimetry data available at Copernicus Marine Environment Monitoring Service. The analysis of Hovmöller diagrams in the areas under consideration confirms the previously obtained theoretical conclusions of the problem of the interaction of planetary waves with a nonzonal flow on the β-plane in the formulation of Miles-Ribner. The incident waves, as well as refracted and reflected waves are distinguished. The speed of refracted and reflected waves exceeds the speed of incident waves, which confirms the conclusions about the existence of mechanisms for the amplification of planetary waves when they interact with a nonzonal flow. 相似文献