共查询到19条相似文献,搜索用时 125 毫秒
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在激波区使用自适应壁对跨音速翼型的激波/边界层的相互作用(干扰)进行控制,可改变机翼的气动性能,这种被动控制可通过在翼型的激波区开一凹腔,其上覆盖一弹性橡胶膜柔壁来,本文给出用Navier-Stoker方程数值模拟这一自适应控制翼型的跨音速粘性绕流,提出了一个适应于本特殊情况(物面边界局部地区在求解过程中有变化)的处理办法。并探讨了自适应柔壁对当代跨音速翼绕流的影响。 相似文献
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大型低速二元风洞侧壁边界层控制及对单段翼型实验结果的影响 总被引:1,自引:0,他引:1
本文简述了NF-3风洞二元实验段侧壁边界层吹除控制系统及具有吹气的模型实验方法,给出了不同吹气系数对风洞边界层的控制效果以及对相对厚度为7%的单段翼型实验结果的影响。初步实验研究结果表明,该控制系统能有效地改善风洞侧壁边界层的流动状态,减小侧壁干扰,改善翼型实验中的二元流动特性 相似文献
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流体力振动翼型和襟翼的绕流特性研究…李锋超薄膜磁头滑块气动力特性............……饱和非饱和土壤中溶质运移的数值模拟……半浮区液桥热毛细对流速度场特征.....……浮体直棱角附近流场的奇异性.........……后向台阶湍流拟序结构的实验研究.....……Y型柱体绕流特性及风荷载.........……,…崔尔杰征宁孙秦学王保育汪翼云.....……傅仙罗邱克俭戚隆溪解京昌唐泽眉....……朱林生胡文瑞戴遗山连淇祥顾志福低超声速圆球绕流后体流场的数值模拟……昊应湘扰动本构方程及粘弹流体拉伸流动不稳定性...……高速二元柔壁自适应风洞消除三元… 相似文献
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在二元翼型风洞实验段中的侧壁边界层将引起模型展向流动的不均匀性,使预想的二元流动受到三元扭曲,引起实验数据的误差,目前消除或减少侧壁干扰的有效方法之一是采用侧壁抽吸技术。本文就抽吸的有效性,抽吸区域和阻尼材料等问题进行了讨论和分析,并对抽吸技术中的问题提出了一些看法。 相似文献
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本文利用渐近展开匹配法分析钝头翼型的跨音速绕流,导出了描述前缘附近流动的一级近似、二级近似下的速位方程、边界条件及相应的近似解析解,并构成关于翼表面速度的一致有效合成解,消除了跨音速小扰动近似的前缘奇性,对于大展弦比后掠翼绕流,可利用翼型绕流分析结果,消除机翼前缘奇性。 相似文献
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由仿生学原理构建的可渗透翼型对湍流气动噪声抑制作用已展现良好的应用前景。对NACA 0012可渗透翼型和实体翼型进行了数值计算,得到了声涡相互作用下气动噪声声场和流场,分析了可渗透壁对翼型流场和声场的影响。研究表明,相对实体翼型,可渗透壁通过减小声源强度降低了主纯音噪声声压级幅值和远场总声压级,消除了高阶离散纯音,但对噪声的指向性没有较大改变。进一步的流场分析表明,可渗透壁对翼型气动性能影响不大的情况下能够降低边界层扰动和翼型后缘大尺度涡旋强度,并推迟分离泡转捩和再附位置。 相似文献
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Flow blockages are used to promote the transition of a flame to a detonation. The structure of shock waves formed with different configurations of blockages was experimentally determined for subsonic incoming flow. High speed subsonic flows could develop ahead of a turbulent flame and the interaction of such flows with blockages could lead to the formation of interacting shock waves, slipstreams, and expansion waves. A blow-down test setup was designed to study the interacting shock pattern formed with different configurations of blockages. The flow was found to accelerate to low supersonic velocities during its passage over the blockages. The shock structure downstream of the blockages was found to depend on the shape, size, and number of blockages as well as the spacing between them. While a parabolic-shaped blockage provided shocks of maximum strength, large blockage ratio values did not permit the formation of shocks. The shear layer, formed in the flow downstream of the blockages, reflected the expansion fan as shock waves and was found to be a major feature influencing the formation of the interacting structure of oblique shocks. The structure and strength of the shock waves are analyzed using hodograms. The formation of the interacting family of shock waves using different configurations of blockages and the spacings between them are discussed. 相似文献
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Chao Chen Lili Du Chunjing Xie Zhouping Xin 《Archive for Rational Mechanics and Analysis》2016,221(2):559-602
The existence and uniqueness of two dimensional steady compressible Euler flows past a wall or a symmetric body are established. More precisely, given positive convex horizontal velocity in the upstream, there exists a critical value \({\rho_{\rm cr}}\) such that if the incoming density in the upstream is larger than \({\rho_{\rm cr}}\), then there exists a subsonic flow past a wall. Furthermore, \({\rho_{\rm cr}}\) is critical in the sense that there is no such subsonic flow if the density of the incoming flow is less than \({\rho_{\rm cr}}\). The subsonic flows possess large vorticity and positive horizontal velocity above the wall except at the corner points on the boundary. Moreover, the existence and uniqueness of a two dimensional subsonic Euler flow past a symmetric body are also obtained when the incoming velocity field is a general small perturbation of a constant velocity field and the density of the incoming flow is larger than a critical value. The asymptotic behavior of the flows is obtained with the aid of some integral estimates for the difference between the velocity field and its far field states. 相似文献
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Yves Burtschell Ghislain Tchuen David E. Zeitoun 《European Journal of Mechanics - B/Fluids》2010,29(5):351-356
Hydrogen injection has been investigated numerically in a flow configuration caused by strong shock–boundary layer interaction named Viscous Mach Interaction (VMI). The geometry that leads to this configuration is used as a hypersonic inlet. The subsonic zone, because of boundary layer detachment, allows hydrogen to be injected along the wall of the central body where combustion processes occur along a slip line when hydrogen is mixed with the incoming air flow far from the wall of the central body. 相似文献
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The formation and development of hydrodynamic disturbances generated by low-frequency vibrations of a local region on a flat plate behind a rectangular step in separated flow is investigated in a wind tunnel. The results are obtained at a small subsonic flow velocity using the hot-wire anemometry. It is established that the wall vibrations induce separation zone disturbances representing streaky structures accompanied by wave oscillation packets. Laminar boundary layer separation favors the wave packet growth followed by wall flow turbulization. 相似文献
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N. V. Smelova 《Fluid Dynamics》1997,32(1):79-85
A solution of the problem of supersonic flow past a wavy wall with an adjacent subsonic layer is obtained. The solution is
a generalization of the well-known solutions [1] of the linear problem of purely subsonic and purely supersonic flow past
a wavy wall and goes over into these solutions in the limiting cases of infinite and zero wall-layer thickness, respectively.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 97–103, January–February,
1997. 相似文献
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Numerical entropy generation is studied in the case of steady, subsonic Euler flow along a kinked solid wall. For a standard upwind finite volume discretization the numerical entropy error, a component of the global discretization error, appears to be zeroth-order in mesh size. Two possible causes of the zeroth-order entropy error are studied. First an investigation is made of the local truncation error on a kinked grid. Although this error also appears to be zeroth-order in the neighbourhood of the kink, it probably does not cause the zeroth-order entropy error. Next a study is made of the existence of a singularity in the exact solution. Probably, the Euler flow solution is singular at the kink in the wall. The form of this likely singularity is unknown. Therefore the construction of a computational method which uses a priori knowledge about the singularity is not possible. Finally it is shown by numerical experiments that the subsonic Euler flow along a kinked wall still can be computed with vanishing entropy errors by using an appropriate sequence of continuously curved walls which converge to the kinked wall in the limit of zero mesh width. 相似文献
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In this paper, we study the global subsonic irrotational flows in a multi-dimensional (n ≥ 2) infinitely long nozzle with variable cross sections. The flow is described by the inviscid potential equation, which
is a second order quasilinear elliptic equation when the flow is subsonic. First, we prove the existence of the global uniformly
subsonic flow in a general infinitely long nozzle for arbitrary dimension with sufficiently small incoming mass flux and obtain
the uniqueness of the global uniformly subsonic flow. Then we show that there exists a critical value of the incoming mass
flux such that a global uniformly subsonic flow exists uniquely, provided that the incoming mass flux is less than the critical
value. This gives a positive answer to the problem of Bers on global subsonic irrotational flows in infinitely long nozzles
for arbitrary dimension (Bers in Surveys in applied mathematics, vol 3, Wiley, New York, 1958). Finally, under suitable asymptotic assumptions of the nozzle, we obtain the asymptotic behavior of the subsonic flow in
far fields by means of a blow-up argument. The main ingredients of our analysis are methods of calculus of variations, the
Moser iteration techniques for the potential equation and a blow-up argument for infinitely long nozzles. 相似文献