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111.
不可压缩二维流动Navier—Stokes方程的有限元解 总被引:1,自引:0,他引:1
对不可压缩流体沿二维后台阶流动的N-S方程的流函数-涡量式用有限元方法加以求解,固壁上的涡量用时间迭代法加以确定。分别计算Re=200,400,800和1000时流动区域的流函数和涡量值,并在Re=800时与有关文献的结果相比较,基本吻合。且在此基础上讨论了出口条件对计算结果的影响。本文的方法对分析流经液压阀口等流动问题具有借鉴意义。 相似文献
112.
本文通过数值方法求解均匀动脉中的非平稳脉动流,给出了通过测量非平稳脉动血流量确定壁面切应力的方法.作为算例,采用实测的大鼠颈总动脉流量信号,求出了均匀动脉壁面切应力波形.进一步对求得的切应力波形进行经验模态分解(EMD),得到了切应力波形的各内在模态(IMF),以及Hilbert幅值谱.从切应力波形经Hilbert-Huang变换得到的IMF和Hilbert谱图可以明显地看出切应力各频率成分的物理意义.所得结果为进一步深入研究非平稳脉动切应力与血管重建的关系提供了一种方法学基础. 相似文献
113.
润滑剂边界滑移及其对弹流润滑特性的影响 总被引:4,自引:7,他引:4
基于润滑剂在弹性流体动力润滑状态下表现出类似塑件固体的非牛顿特性,根据塑性屈服和流体动力润滑理论,建立了考虑润滑剂在固液界面滑移的线接触弹流润滑失效预测模型。计算结果显示:载荷和滑滚比对润滑油膜厚度影响显著;在一定载荷和滑滚比下,润滑油膜将丧失承载能力而破裂。与现有理论及实验数据对比,线接触弹流润滑失效预测模型的计算结果与实验结果具有较好的一致性。 相似文献
114.
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116.
A.O. Borisyuk 《Flow, Turbulence and Combustion》1998,61(1-4):269-284
An acoustic model of a larger human blood vessel is developed. This model takes into account the main features of the acoustic
generation and propagation of noise in the human chest from the source (turbulent pressure fluctuations in blood flow) to
a receiver resting on the skin, and allows the consideration of a simple stenotic narrowing in the vessel. The low Mach number
turbulent wall pressure models of Corcos, Chase, Ffowcs Williams, and Smol'yakov and Tkachenko are used to describe random
sources in the vessel. The relationships obtained permit one to analyse the dependence of the resultant acoustic field in
the thorax on the parameters of the blood flow and the vessel, and show the possibility of finding characteristic signs of
the presence of a stenosis by comparison of noise fields from intact and diseased arteries.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
117.
Near-wall data for the strongly perturbed flow in a neutrally stable boundary layer encountering a steep, smooth, two-dimensional
hill are presented. Observations were made on the centerplane of a water channel at thirteen stations relative to the hill
by laser Doppler anemometry. The large reverse flow region that is formed on the lee of the hill was particularly scrutinized
through seven measuring stations. Results are presented for the mean and turbulent properties of the flow. Wall shear stress
was evaluated through fitting procedures that resorted to the near wall behavior of the velocity profile. Logarithmic fits
as well as predictions through the Reynolds stress profiles are also presented. 相似文献
118.
The elliptic blending approach is used in order to modify an Explicit Algebraic Reynolds Stress Model so as to reproduce the correct near wall behaviour of the turbulent stresses. The anisotropy stress tensor is expressed as a linear combination of tensor bases whose coefficients are sensitised to the non-local wall-blocking effect through the elliptic blending parameter γ. This parameter is obtained from a separate elliptic equation. The model does not use the distance from the wall thus it can be easily applied to complex geometries. It is validated against detailed DNS data for mean and turbulence quantities for the case of flow and heat transfer between parallel flat plates at three Reynolds numbers as well as against experimental data for the flow in a backward facing step at Re
H = 28,000. The comparison with DNS results or experiments is quite satisfactory and shows the validity of the approach. 相似文献
119.
This paper focuses on a resonance mechanism that can lead to significant disturbance amplification at conditions which are sub-critical to nonlinear instabilities. Particularly, direct spatial resonance instability is investigated, which is present in the basic three-dimensional viscous compressible boundary-layer flow due to a rotating-disk. Within this purpose, the linearized system of stability equations is treated numerically making use of a spectral Chebyshev collocation method. The analysis provides critical resonant Reynolds numbers above which growth occurs. Amplitudes of the response of the degeneracies decaying rapidly due to their high damping rates are shown to exist for small enough Reynolds numbers while the flow is still in the laminar state. If the flow is restricted to the incompressible case, the results of Turkyilmazoglu and Gajjar (in Sadhana Acad P Engs 25:601–617, 2000) are completely reproduced. The influences of compressibility are then explored by means of varying the Mach and Prandtl numbers in the cases of heating/cooling the wall as well as the isothermal wall. In general, compressibility effects are found strongly in favor of stabilizing as the Mach number increases, while a strong destabilization is observed by lowering the critical values of Reynolds numbers in the cases of wall heating and insulation. The modal interaction and coalescence of the eigenmodes calculated here create local algebraic growth by rapid development of relatively large amplitudes which might then provide the onset of nonlinear effects followed by transition. 相似文献
120.
An experimental study of natural convection in a parallelepipedal enclosure induced by a single vertical wall is described. The upper half of this wall was warm and the lower half cold. The other enclosure walls were insulated. The temperature and flow measurements were performed in the high Rayleigh number regime (1010<Ra<5×1010) by using water as the working fluid. The Rayleigh number was based on the enclosure height and the temperature difference between the warm and the cold part of the driving wall. The flow field featured two flat cells, one filled with warm fluid along the top horizontal wall, and the other filled with cold fluid along the bottom horizontal wall. Each of these cells was surrounded by an additional cell as tall as half the enclosure height. The above flow structure prohibited extensive thermal contact between warm and cold fluid, thus limiting the role of convection on the heat transfer process in the cavity. The findings of this study differ significantly from the findings of previous studies based on the ‘classical’ enclosure model possessing two isothermal vertical walls, the one warm and the other cold, and support the view that the use of ‘more realistic‘ temperature boundary conditions in enclosure natural convection needs careful examination. 相似文献