共查询到20条相似文献,搜索用时 890 毫秒
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《International Journal of Non》2006,41(6-7):825-829
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A direct numerical simulation is combined with laboratory study to describe the turbulent flow in an annular high speed rotor–stator cavity. Comparisons are made for a turbulent flow characterized by a Reynolds number in a shrouded cavity of large aspect ratio , where and are the inner and outer radii of the rotating disk, and h is the inter-disk space. A close agreement is found between the computed results and the experimental data for the mean and turbulent fields.? To cite this article: S. Poncet, A. Randriamampianina, C. R. Mecanique 333 (2005). 相似文献
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Mohamed Maidi 《Comptes Rendus Mecanique》2006,334(5):285-291
An acoustic numerical code based on Ligthill's analogy is combined with large-eddy simulations techniques in order to evaluate the noise emitted by subsonic and supersonic round jets. We show first that, for centerline Mach number and Reynolds number , acoustic intensities compare satisfactorily with experimental data of the literature in terms of levels and directivity. Afterwards, high Reynolds number free and forced jets at Mach 0.7 and 1.4 are studied. Numerical results show that the jet noise intensity depends on the nature of the upstream mixing layer. Indeed, the subsonic jet is 4 dB quieter than the free jet when acting on this shear layer by superposing inlet varicose and flapping perturbations at preferred and first subharmonic frequency, respectively. The maximal acoustic level of the supersonic jet is, on the other hand, 3 dB lower than the free one with a flapping upstream perturbation at the second subharmonic. The results reported in this paper confirm previous works presented in the literature demonstrating that jet noise may be modified according to the inlet conditions. To cite this article: M. Maidi, C. R. Mecanique 334 (2006). 相似文献
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Walid Fakhfakh Slim Kaddeche Ali Abdennadher Daniel Henry Hamda Ben Hadid 《Comptes Rendus Mecanique》2006,334(5):332-339
A numerical study is conducted in order to determine the influence of a vertical magnetic field, the Reynolds number and a temperature stratification on the instabilities occurring in the Hartmann flow heated from below. For and , the results show that the vertical magnetic field has a stabilizing effect on both transverse oscillatory travelling waves and longitudinal stationary rolls . The temperature stratification is responsible of a destabilization of the transverse modes and the appearance of longitudinal modes non-existent for the isothermal Hartmann flow. Moreover, the extent of the domains of Re where the transverse modes prevail is found to narrow when Ha increases and to widen when Ra increases for a given value of Ha. On the other hand, for the modes, the extent of the domains of Re where they prevail increases when Ha grows. To cite this article: W. Fakhfakh et al., C. R. Mecanique 334 (2006). 相似文献
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Christophe Matignon Daniel Desbordes Henri Noël Presles 《Comptes Rendus Mecanique》2006,334(10):605-610
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《Journal of Fluids and Structures》2006,22(3):345-369
This paper presents the results of an investigation on the interference effects of a rigid square cylinder on the transverse vibrations of a spring-mounted square cylinder (test cylinder) exposed to a uniform flow. The interference effects were studied for the tandem, side-by-side and staggered arrangements. Experiments have been carried out for various relative dimensions of the test cylinder and the interfering cylinder; the tests for the staggered arrangements were conducted at several tandem distances between the two. The results indicate that there is a critical combination of relative dimensions and spacing that gives rise to maximum amplitude of vibration. Among the cases studied, tandem arrangement with and gives rise to maximum amplitude of vibration with . A tentative explanation is offered for the observed features based on flow-visualization studies conducted as a part of the experimental investigation. 相似文献
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Hot-wire velocity measurements are carried out in a turbulent boundary layer over a rough wall consisting of transverse circular rods, with a ratio of 8 between the spacing (w) of two consecutive rods and the rod height (k). The pressure distribution around the roughness element is used to accurately measure the mean friction velocity () and the error in the origin. It is found that remained practically constant in the streamwise direction suggesting that the boundary layer over this surface is evolving in a self-similar manner. This is further corroborated by the similarity observed at all scales of motion, in the region , as reflected in the constancy of Reynolds number () based on Taylor’s microscale and the collapse of Kolmogorov normalized velocity spectra at all wavenumbers.A scale-by-scale budget for the second-order structure function (, where u is the fluctuating streamwise velocity component and r is the longitudinal separation) is carried out to investigate the energy distribution amongst different scales in the boundary layer. It is found that while the small scales are controlled by the viscosity, intermediate scales over which the transfer of energy (or ) is important are affected by mechanisms induced by the large-scale inhomogeneities in the flow, such as production, advection and turbulent diffusion. For example, there are non-negligible contributions from the large-scale inhomogeneity to the budget at scales of the order of , the Taylor microscale, in the region of the boundary layer extending from to 0.6 ( is the boundary layer thickness). 相似文献
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Viatcheslav V. Kolmychkov Olga S. Mazhorova Yurii P. Popov Patrick Bontoux Mohammed El Ganaoui 《Comptes Rendus Mecanique》2005,333(10):739-745
Three-dimensional calculations have been done to simulate the onset of convective motion in ternary nondilute solution under phase transition conditions. The process is considered for Rayleigh number in the range , where subcritical convective motion with hexagonal flow pattern is identified. The results are in good agreement with the linear and finite amplitude theory of hydrodynamics instability. To cite this article: V.V. Kolmychkov et al., C. R. Mecanique 333 (2005). 相似文献