共查询到20条相似文献,搜索用时 203 毫秒
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以二次等参元离散的表面Helmholtz积分方程作为计算方程,采用一系列数值处理技术,克服了表面Helmhaltz积分方程求解声学问题时出现的解的不唯一性和积分函数奇异性。应用方程对模型球进行计算,数值解与解析解的比较结果表明,该方法可满意地计算球的辐射声场。 相似文献
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基于半系统法的统一Reynolds方程,对点接触混合润滑进行数值模拟。在流体润滑区,采用Reynolds方程求解流体压力,在固体接触区采用简化Reynolds方程求解压力。弹性变形使用离散卷积-快速傅里叶变换(DC-FFT)计算。为了加快迭代收敛速度,在数值求解过程中使用渐进网格加密(Progressive Mesh Densification,PMD)算法。数值模拟结果表明,该模型可以快速地求解光滑和粗糙表面条件下的各种润滑情况,包括全膜、混合和边界润滑;随着卷吸速度的增加,润滑状态从边界到混合再到全膜润滑是个光滑过渡的过程。 相似文献
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建立了连续波脉冲信号传输的几何模型、运动方程和连续性方程.给出了计算流体约束随时间变化时,管道中的压力和流体速度,给出适当的边界条件和初始条件,利用特征方法求解运动方程和连续性方程联立的偏微分方程,对连续波泥浆脉冲信号动态传输特性进行数值分析. 相似文献
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车辆动力学平衡点是汽车非线性动力学分析中的关键参数。但车辆系统的非线性特征使传统的解析方法无法求解平衡点,而基于梯度的数值方法和遗传算法在求解精度和求解效率都存在局限性。为准确有效地求解车辆动力学平衡点,提出一种基于实数编码遗传算法和拟牛顿法的混合求解方法。利用达芬方程验证所提出的方法的有效性。给出基于轮胎魔术公式的3自由度车辆动力学系统模型,利用提出的混合求解方法得到不同转角输入下车辆平衡点,并与单独的遗传算法求解的结果进行对比。研究结果表明,该混合求解方法得到的结果更加准确,该方法能够快速、有效地求解3自由度车辆动力学平衡点。 相似文献
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离心压缩机叶轮内三维粘性流动的数值计算 总被引:2,自引:0,他引:2
采用指数插值方法来生成离心叶轮内部复杂流道的三维贴体网格。在流场计算中运用有限解析法对叶轮机械内部流场的统一方程进行离散。通过采用交错网格系统实现各计算点压力值的紧密相关,并用SIMPLER算法进行求解,采用改进的jacobi线迭代法求解代数方程组,实现了对离心叶轮内部复杂流场的数值模拟,以某实际离心叶轮为例,将数值计算结果与其测量值相比,两者吻合较好,表明了该数值求解方法的有效性。 相似文献
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Chang- Hyun Sohn Chang-Soo Kim Ui-Hyun Jung B. H. L Lakshmana Gowda 《Journal of Mechanical Science and Technology》2006,20(3):418-425
The present investigation deals with the study of the internal flow phenomena of the counter flow type vortex tube using experimental
testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex
tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure
was varied from 0.1 MPa to 0.3 MPa. The experimentally visualized results on the tube show that there is an apparent sudden
changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the
stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase
in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow
information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex
tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar
to that observed in experiments. 相似文献
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A numerical model was developed to investigate dynamic instability in fossil fired once through boilers and the influence of the dynamics of tube and membrane structure furnace wall tubes on the stability boundary was examined. In order to predict density wave oscillation (DWO), the most common type of dynamic instability, a time domain nonlinear analysis approach was used to give a transient flow field in the tubes. The tubes were divided into one-dimensional finite volumes along their lengths and equations of conservation of mass, momentum and energy were discretized to give algebraic equations. The SIMPLE algorithm was adopted to solve these equations. Analysis of two-dimensional transient conduction across a tube-membrane section of each volume was performed concurrently and the resulting heat transfer between tube inner wall and fluid was included in the source term of the energy equation. After verification with results in available literature, the model was applied to a wall tube section of a 700 MW boiler furnace in subcritical once-through condition. The stability boundaries for three types of tube configuration were predicted, and it was found that the dynamics of tube configuration can have a significant effect on the flow instability in the boiler furnace wall tubes. 相似文献
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Young-Ryoul Back Jae-Heon Lee Byung-Ha Kang Myung-Do Oh 《Journal of Mechanical Science and Technology》1994,8(3):219-230
Characteristics of fluid flow and convective heat transfer of a pulsating flow in a curved tube have been investigated numerically.
The tube wall is assumed to be maintained at a uniform temperature peripherally in a fully developed pulsating flow region.
The temperature and flow distributions over a cross-section of a curved tube with the associated velocity field need to be
studied in detail. This problem is of particular interest in the design of Stirling engine heat exchangers and in understanding
the blood flow in the aorta. The time-dependent, elliptic governing equations are solved, employing finite volume technique.
The periodic steady state results are obtained for various governing dimensionless parameters, such as Womersley number, pulsation
amplitude ration, curvature ratio and Reynolds number. The numerical results indicate that the phase difference between the
pressure gradient and averaged axial velocity increases gradually up to π/2 as Womersley number increases. However, this phase
difference is almost independent of the amplitude ratio of pulsation. It is also found that the secondary flow patterns are
strongly affected by the curvature ratio and Reynolds number. These, in turn, give a strong influence on the convective heat
transfer from the pipe wall to the pulsating flow. The results obtained lead to a better understanding of the underlying physical
process and also provide input that may be used to design the relevant system. The numerical approach is discussed in detail,
and the aspects that must be included for an accurate simulation are discussed. 相似文献
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以直管式Coriolis质量流量计为例,从理论上研究了非线性对测量管振动特性的影响。建立了考虑非线性的测量管振动方程;用Galerkin法对振动方程进行了离散化处理,将连续体的偏微分方程简化为关于广义坐标的二自由度非线性振动方程;用多尺度法对离散化的振动方程进行定性理论分析,指出了非线性对测量管振动的影响,给出了非线性引起的附加振动成份。所得结论与有关文献给出的实验结果一致,对测量管的设计和输出信号处理具有理论指导意义。 相似文献
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采用3阶精度的迎风格式及2阶精度的中心差分格式,直接求解二维非定常N-S方程组,研究狭缝节流空气静压轴承压降恢复之后区域的流场特性。使用雷诺方程计算相同位置气膜中心处的流场状态,并与直接数值模拟方法的计算结果进行对比。结果表明:雷诺方程与N-S方程在计算域内计算结果基本一致,两者压力偏差为0.173%,速度偏差为1.217%;流场压力、密度沿气流方向逐渐减小,但在气膜方向几乎不变;流场速度、压力梯度沿气流方向逐渐增加,速度在流场出口处达到最大值;直接数值模拟方法得到了流场的温度变化,即整个流场的温度变化很小,温度整体呈上下高、中心低的分布,而雷诺方程无法计算得出整个流场的温度变化情况;采用雷诺方程计算轴承压降恢复之后区域的流场是合理的。 相似文献
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Laila S. Bayoumi 《International Journal of Mechanical Sciences》2001,43(11):770
An analytical solution is obtained for the problem of cold drawing through flat idle rolls of regular polygonal metal tubular sections from round tube. The solution is based on obtaining a compatible velocity field that satisfies kinematic conditions to yield the strain-rate components. The stresses are obtained by combining the material constitutive law with Levy–Mises flow rule and integrating the equations of equilibrium. The solution is applied to the case of a low-carbon steel standard round pipe to investigate the effects of drawn section shape, friction at the roll interface, roll radius and wall thickness on the roll load and drawing force. The results obtained have shown that for different section shapes the roll load and drawing force decrease with the increase of the number of sides and increase with the decrease of corners radius. Surface friction has no appreciable effect on the loads which allows dry drawing. An increase in the roll radius increases the roll load but the drawing force remains unchanged. Increasing the wall thickness does not proportionally increase the roll load and drawing force; the tube wall behaves as a thin shell subjected to biaxial combined membrane and bending stresses. 相似文献
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The analysis for the three-dimensional fluid flow past tube banks arranged in equilateral-triangular form at Remax=4,000 is carried out using a large eddy simulation technique. The governing equations for the mass and momentum conservation
are discretized using the finite volume method. Parallel computational techniques using MPI (Message Passing Interface) are
implemented in the present computer code. The computation time decreases linearly proportional to the number of used CPUs
in the present parallel computation. We obtained the time-averaged streamwise and cross-streamwise velocities and turbulent
intensities. The present numerical results are compared with the PIV experimental data and agree generally well with the experimental
data. 相似文献