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Direct Numerical Simulation (DNS) is the most accurate, but also the most expensive, way of computing turbulent flow. To cut the costs of DNS we consider a family of second-order, explicit one-leg time-integration methods and look for the method with the best linear stability properties. It turns out that this method requires about two times less computational effort than Adams–Bashforth. Next, we discuss a fourth-order finite-volume method that is constructed as the Richardson extrapolate of a classical second-order method. We compare the results of this fourth-order method and the underlying second-order method for a DNS of the flow in a cubical driven cavity at Re= 104. Experimental results are available for comparison. For this example, the fourth-order results are clearly superior to the second-order results, whereas their computational effort is about twenty times less. With the improved simulation method, a DNS of a turbulent flow in a cubical lid-driven flow at Re = 50,000 and a DNS of a turbulent flow past a square cylinder at Re = 22,000 are performed. 相似文献
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目的研究电流体动力学近场直写的射流成形机理及其规律,探索电流体动力学近场直写射流成形的影响因素。方法首先对电流体动力学近场直写的射流成形机理进行理论分析,并构建数学模型,然后以去离子水为溶剂配成质量分数为13%~17%的聚氧化乙烯作为模拟材料,采用有限元数值模拟方法进行仿真试验验证。结果在电场力作用下,液滴会发生流变形成弯液面,随着电荷密度的增大,弯液面逐渐形成泰勒锥,当电荷密度进一步增加,电场力克服了液体表面张力,在泰勒锥顶端产生射流;电压、喷射高度和入口压力等工艺参数会影响射流形态。结论电压越大或喷射高度越小,射流受到的电场力越大;入口压力越大,锥形越长;通过调整工艺参数可以改善射流形态;电流体动力学近场直写方法可实现聚合物溶液高分辨率的喷墨印刷。 相似文献
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为研究二维水槽内无旋、无粘流体在分段激励下的自由面波高和非线性,本文运用势流方程的Crank-Nicolson有限差分方法,通过改变激励参数,画出不同激励条件下自由面的波高.数值结果表明,在单一水平激励下,不同激励频率下的波高表现出规律的周期拍的现象.在分段激励下,当水平激励消失时,自由面波高拍的现象亦消失.当自由面波高为小振幅时,自由面以驻波形式作自由振动.当自由面波高为大振幅时,波峰与波谷衰减,非线性现象出现,并且波高的振幅越大,非线性现象越明显. 相似文献
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A mathematical model and results of numerical calculation of the process of interaction between a swirling jet and drift flow are presented in the paper. The structure of flow and the process of chemical reactions are investigated under conditions of transverse injection of a swirling jet of combustion products into a flow of fuel-air mixture. Inferences are made of the possibility of using a transversely injected jet to provide for a gasdynamic stabilization of flame in combustors of gas-turbine engines. 相似文献
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The numerical simulation of time-dependent, 2-D compressible boundary-layer flow containing a region of separation is studied. The separation is generated by the introduction of an adverse pressure gradient along the freestream boundary. In order to validate the numerical method, a low Mach-number laminar separation bubble flow is considered, which enables an extensive comparison with incompressible results. The generation of an adverse pressure gradient along the freestream boundary can be realized in various ways. An imposed decelerating flow boundary is compared with a suction technique. The effects of the strength of the pressure gradient and the presence of small upstream perturbations on the separation bubble are also investigated. The time-averaged characteristics of the flow are in good quantitative agreement with incompressible approximate theories predicting the condition for separation. The appearance of self-excited vortex shedding in unperturbed flows under a sufficiently strong adverse pressure gradient is consistent with incompressible flow simulations reported in the literature. The satisfactory result achieved in the calculation of the low-Mach-number flow encourages the application of the numerical method to flows with strong compressibility effects. 相似文献
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为了实现聚能战斗部对水下目标的高效毁伤,在传统聚能战斗部的基础上设计了一种采用不同材料的球缺罩与偏心亚半球形罩组合的聚能战斗部。阐述了复合材质组合式聚能战斗部的结构设计及作用原理,利用有限元软件AUTODYN数值模拟了其成型及侵彻水下靶板的过程,并与传统的偏心亚半球缺式和单一材质组合式战斗部的毁伤效果进行了对比。研究表明,复合材质组合式战斗部形成的前级杆式射流侵彻水介质过程中可以为后级杆式射流开辟无耗能通道;在相同炸高下,侵彻相同厚度的水介质与靶板后,与传统杆式射流相比,复合材质杆式射流的动能衰减率最小,剩余动能提升了28.59%。该复合材质组合式聚能战斗部可以实现对水下目标的高效毁伤。 相似文献
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S. A. Dvinin A. P. Ershov I. B. Timofeev V. A. Chernikov V. M. Shibkov 《High Temperature》2004,42(2):171-182
This study is devoted to the investigation of a dc discharge in a transverse gas flow. It is shown that the discharge may exist in several forms depending on the gas flow velocity. The standard stationary discharge similar to a discharge in still gas is realized if the displacement rate of the plasma boundary exceeds the gas flow velocity. The displacement rate of the plasma boundary in a diffusion model is defined by the relation V
f
= 2
, where D
a
is the ambipolar diffusion coefficient, and
i
is the frontal ionization frequency. Otherwise, the discharge assumes the form of two plasma wakes formed by the cathode and anode, respectively. The surface of the plasma wakes is oriented at an angle to the flow velocity C
s
(sin = V
f
/C
s
). If sin is smaller than the ratio of the discharge sustaining voltage in the stationary regime U
st
to the breakdown voltage U
bk
, the discharge transforms into the pulse–periodic form, when the formation of a structure of the cathode and anode plasma wakes is interrupted by a new gas breakdown. A numerical simulation of the discharge properties is performed. The numerical simulation results are compared to the experimental ones. 相似文献
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本文运用了有限体积方法模拟了低压有机金属化学气相外延生长室的二维流场和热场的分布情况,分析了生长室内压力和基座转速对于流场和热场影响,指出了低压金属有机化学气相外延的优点所在. 相似文献
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为预测和预防压气机叶轮磨损,基于多相流理论对超音速压气机内的三维气固两相流场进行数值模拟。在分析中将压气机内的流场按可压缩气体处理,同时考虑温度对颗粒运动轨迹的影响。模拟结果表明,叶片出口端部前缘,温度达到最大,颗粒的运动速度也达到最大值。由此判明叶轮磨损最严重处位于叶片端部。 相似文献
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Studies on the motion of particles in turbulence and interactions between particles and turbulence are extremely significant, which can help us to improve the efficiency of industrial processes. In this article, we investigated the particle distribution and particle-turbulence interaction in a solid-liquid channel flow with the Euler-Lagrange two-way model. The liquid phase was solved using direct numerical simulation (DNS), and the particle motion was tracked by Newtonian equations of motion considering effects of drag force, pressure gradient force, and gravity. Two-way coupling was used to explain the effect of particles on the turbulence structure. The results show that the local void fraction of particles indicates the wall-peaked profile, particles scatter uniformly in the spanwise direction, and the injection of particles suppresses the turbulence activities in the near wall region. Suppression of the liquid turbulence is mainly caused by vortexes decay of different sizes. 相似文献
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介绍了多元平行流冷凝器的结构特点和前人的研究成果,对平行流冷凝器的流动和传热特点进行了深入分析,在此基础上运用分布参数法建立了稳态数学模型,对某种规格的平行流冷凝器在一定工况下数值模拟,计算得到不同迎面风速下平行流冷凝器流动换热情况。结果表明,多元平行流冷凝器在冷凝换热时较常规换热器具有显著优越性,迎面风速对冷凝换热的影响存在一个临界范围。 相似文献
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数值模拟采用的模型对计算结果有较大影响,本文利用LVEL紊流模型、标准k-ε模型和RNGk-ε模型等三种模型对喷流诱导通风系统进行了数值模拟,并与实测数据进行了比较,得到了各模型的一些应用特点。 相似文献