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IntroductionRecentlytheauthorspresentedanewdynamicsmodelfortrafficflow[1].Themodelcomprisesacontinuumequationandadynamicsequation k/ t+ (ku) / x=0 ,( 1 ) u t+u u x=ue(k) -uT +a u x,( 2 )wherekistrafficdensity ;uismeanspeed ;x ,tarespaceandtimecoordinatesrespectively .Tisrel… 相似文献
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It is necessary to understand the features of air pressure in a drainage stack of a high-rise building for properly designing and operating a drainage system. This paper presents a mathematical model for predicting the stack performance. A step function is used to describe the effect of the air entrainment caused by the water discharged from branch pipes. An additional source term is introduced to reflect the gas-liquid interphase interaction (GLII) and stack base effect. The drainage stack is divided into upper and base parts. The air pressure in the upper part is predicted by a total variation diminishing (TVD) scheme, while in the base part, it is predicted by a characteristic line method (CLM). The predicted results are compared with the data measured in a real-scale high-rise test building. It is found that the additional source term in the present model is effective. It intensively influences the air pressure distribution in the stack. The air pressure is also sensitive to the velocity-adjusting parameter (VAP), the branch pipe air entrainment, and the conditions on the stack bottom. 相似文献
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通过用时间分裂算法求解Navier-Stokes方程,对中等Reynolds数下靠近排列的两个交错方柱三维绕流进行了数值模拟,其中,中间速度场用四阶Adams格式计算,压力场通过结合近似因子分解方法AF1与稳定的双共轭梯度方法Bi-CGSTAB进行迭代求解.数值模拟发现当两个方柱靠得较近时,有互相吸引趋势,而且上游方柱的Strouhal数较大.方柱的交错排列方式对绕流影响明显.计算结果与实验定性吻合,而且比用MAC-AF1方法计算的结果好. 相似文献
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Swirling-strength based large eddy simulation of turbulent flow around single square cylinder at low Reynolds numbers 总被引:1,自引:0,他引:1
In view of the fact that large scale vortices play the substantial role of momentum transport in turbulent flows, large eddy simulation(LES) is considered as a better simulation model. However, the sub-grid scale(SGS) models reported so far have not ascertained under what flow conditions the LES can lapse into the direct numerical simulation. To overcome this discrepancy, this paper develops a swirling strength based the SGS model to properly model the turbulence intermittency, with the primary characteristics that when the local swirling strength is zero, the local sub-grid viscosity will be vanished. In this paper, the model is used to investigate the flow characteristics of zero-incident incompressible turbulent flows around a single square cylinder(SC)at a low Reynolds number range Re ∈ [103, 104]. The flow characteristics investigated include the Reynolds number dependence of lift and drag coefficients, the distributions of time-spanwise averaged variables such as the sub-grid viscosity and the logarithm of Kolmogorov micro-scale to the base of 10 at Re = 2 500 and 104, the contours of spanwise and streamwise vorticity components at t = 170. It is revealed that the peak value of sub-grid viscosity ratio and its root mean square(RMS) values grow with the Reynolds number. The dissipation rate of turbulent kinetic energy is larger near the SC solid walls.The instantaneous factor of swirling strength intermittency(FSI) exhibits some laminated structure involved with vortex shedding. 相似文献
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