共查询到18条相似文献,搜索用时 62 毫秒
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室内空气流动数值模拟的N点风口动量模型 总被引:7,自引:0,他引:7
为适应工程应用中快速、准确模拟室内空气流动的需要,提出N点风口动量模型,以简化描述利用计算流体动力学CFD方法模拟室内空气流动时百叶、多孔板类送风口的入流边界条件。百叶和多孔板风口的等温自由射流算例以及HESCO孔板类散流器在室内送风的算例和实验数据对比表明,N点风口动量模型可以较好地解决数值模拟室内空气流动的风口入流边界条件描述问题。 相似文献
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高速电梯运行时,井道内气压的快速变化会对轿厢运行的稳定性及安全性产生极大影响.为解决上述问题,提出了三种在井道壁面上开风口的设计方案,运用计算流体力学分析软件FLUENT对电梯运行过程中的空气流动状态进行数值仿真,同时改变风口形状以及数量,对井道内风速变化、轿厢所受气动阻力及气动力矩进行分析.分析结果表明,在提出的三种开风口方案中,上下圆形风口为最优,与未开风口时相比,轿厢气动阻力减小22.05 %,侧翻力矩减小29.87 %,俯仰力矩减小18.02 %.最后进行试验验证,表明了开风口方案的有效性,研究结果可为井道风口的设计提供理论依据. 相似文献
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针对型腔充填过程中的紊流流动,用代数应力模型研究紊流流动现象.成功地将代数应力模型引入PHOENICS软件中,完成了恒温流体充填过程三维时均速度和自由表面的计算模拟.与实验结果相比说明,本文基于PHOENICS软件开发的充填模拟具备了对复杂型腔充填过程的数值计算. 相似文献
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聚能装药可用来穿透装甲、岩石、混凝土等高强度日标,在国防工业以及石油工业有重要应用.质点类无网格法,如SPH和MPM,可以避免网格畸变,比基于网格的传统方法更适合聚能装药问题的模拟.该文针对物质点法中可能发生的数值断裂问题,提出了自适应分裂质点的方案.当质点在某一方向的累积应变达到一定阈值,即将质点一分为二,从而使物质点法可以更有效的表达射流形成过程中强烈的拉伸变形.采用C++语言编制了可自适应分裂质点的三维物质点法程序MPM3DPP,应用Johnson-Cook材料模型用来考虑应变率效应和热软化效应,Mie-Gruneisen状态方程用于金属在高压下的压力计算,Jones-Wilkins-Lee(JWL)状态方程用于描述爆炸产物等膨胀过程,并在压力项加入人工粘性用来处理冲击波.模拟并分析了爆炸飞片、聚能射流等问题,通过数值模拟,对射流形成过程中的变形情况以及温度、速度的分布进行分析.模拟结果和经验公式吻合. 相似文献
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为抑制跨超声速风洞扩散段的分离,提出了一种较为完备的设计方法。由于影响扩散段性能的参数较多,完全通过试验方法进行设计的成本过高,该方法通过数值模拟,结合适当的边界条件,详细描述了扩散段角度、分流锥角度与长度、孔板开孔率对扩散段性能的影响;从数值模拟的结果可以看出,孔板开孔率和扩开角对扩散段性能有显著影响,通过比较得出较为合理的参数匹配,提高了扩散段的防分离性能,并改善了出口气流质量。数值结果与试验结果结论一致,表明本文所用的方法用于扩散段气动设计是可行的,为数值模拟方法应用于风洞部段气动设计创造了一定的条件。 相似文献
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Shah M.E. Haque M.G. Rasul M.M.K. Khan A.V. Deev N. Subaschandar 《Experimental Thermal and Fluid Science》2009,33(2):322-328
The influence of the velocity profile at the inlet boundary on the simulation of air velocity distribution inside an electrostatic precipitator is presented in this study. Measurements and simulations were performed in a duct and an electrostatic precipitator (ESP). A four-hole cobra probe was used for the measurement of velocity distribution. The flow simulation was performed by using the computational fluid dynamics (CFD) code FLUENT. Numerical calculations for the air flow were carried out by solving the Reynolds-averaged Navier–Stokes equations coupled with the realizable k-ε turbulence model equations. Simulations were performed with two different velocity profiles at the inlet boundary – one with a uniform (ideal) velocity profile and the other with a non-uniform (real) velocity profile to demonstrate the effect of velocity inlet boundary condition on the flow simulation results inside an ESP. The real velocity profile was obtained from the velocity measured at different points of the inlet boundary whereas the ideal velocity profile was obtained by calculating the mean value of the measured data. Simulation with the real velocity profile at the inlet boundary was found to predict better the velocity distribution inside the ESP suggesting that an experimentally measured velocity profile could be used as velocity inlet boundary condition for an accurate numerical simulation of the ESP. 相似文献
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In this paper, simple and consistent open boundary conditions are presented for the numerical simulation of viscous incompressible laminar flows. The present approach is based on an arbitrary Lagrangian-Eulerian particle method using upwind interpolation. Three kinds of inlet/outlet boundary conditions are proposed for particle methods, a pressure specified inlet/outlet condition, a velocity profile specified inlet/outlet condition, and a fully developed flow outlet condition. These inlet/outlet conditions are realized by using boundary particles and modification to the physical value such as velocity. Poiseuille flows, flows over a backward-facing step, and flows in a T-shape branch are calculated. The results are compared with those of mesh-based methods such as the finite volume method. The method presented herein exhibits accuracy and numerical stability. 相似文献
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Forming and breaking the ceiling of inlet gas velocity regarding to separation efficiency of cyclone
《Particuology》2023
The maximum-efficiency inlet velocity (MEIV) is a ceiling of inlet gas velocity that defines separation efficiency during cyclone design and operation. Experiment and computational fluid dynamics (CFD) simulation exhibited that an apex cone at the dust outlet can break the ceiling and improve the separation efficiency. The phenomenon is closely related to the effect of excessive high inlet gas velocity on the back-mixing escape of fine particles, which is the final result of back mixing, entrainment by the rapid upward airflow, and secondary separation of the inner vortex. In the center of the inner vortex, the airflow rotates slowly and moves rapidly upward. This elevator type of airflow delivers re-entrained particles to the vortex finder. A higher inlet gas velocity accelerates the elevator, causing more entrained particles to escape. This explains the decrease in efficiency at an excessively high inlet gas velocity. When an apex cone is installed at the dust outlet, the back-mixing is significantly weakened because the vortex core is bounded to the center of separator, while the transport effect of rapid upward airflow is weakened by the decrease in axial velocity in the center. Therefore, particle escape is weakened even at excessive high inlet gas velocities. Instead, the centrifugal effect is enhanced because of increased tangential velocity of the gas and particles. Consequently, the ceiling of inlet gas velocity is broken. 相似文献
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提出了一个新的气核-液膜耦合模型来求解垂直上升气液环状流在充分发展段的流动参数.本模型考虑了液膜、气核以及它们之间的相互影响和作用.模型中基本的气核区域和液膜区域的质量和动量方程由Fluent6.3.26进行求解,而液滴方程以及相界面上的夹带和沉积作用通过用户自定义接口函数UDF(User Defined Functi... 相似文献
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Reza Maddahian Azadeh Kebriaee Bijan Farhanieh Bahar Firoozabadi 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(4):489-501
In this research, the developing turbulent swirling flow in the entrance region of a pipe is investigated analytically by
using the boundary layer integral method. The governing equations are integrated through the boundary layer and obtained differential
equations are solved with forth-order Adams predictor-corrector method. The general tangential velocity is applied at the
inlet region to consider both free and forced vortex velocity profiles. The comparison between present model and available
experimental data demonstrates the capability of the model in predicting boundary layer parameters (e.g. boundary layer growth,
shear rate and swirl intensity decay rate). Analytical results showed that the free vortex velocity profile can better predict
the boundary layer parameters in the entrance region than in the forced one. Also, effects of pressure gradient inside the
boundary layer is investigated and showed that if pressure gradient is ignored inside the boundary layer, results deviate
greatly from the experimental data. 相似文献
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Oliver T. Stein Benjamin B?hm Andreas Dreizler Andreas M. Kempf 《Flow, Turbulence and Combustion》2011,87(2-3):425-447
Turbulent opposed jet (TOJ) burners are an interesting test case for fundamental combustion research and a good benchmark for the available modelling approaches. However, these opposed jet flames strongly depend on the turbulence generation inside the nozzle, which is usually achieved through a perforated plate upstream of the nozzle exit. The present work investigates the flow from these perforated plates and the subsequent turbulence generation in great detail. We present results from highly-resolved large eddy simulations (LES) of the in-nozzle flow in turbulent opposed jets alongside state-of-the-art particle image velocimetry (PIV) at standard and high repetition rates taken inside a glass nozzle. The in-nozzle PIV data provides the LES inflow conditions with unprecedented detail, which are used to follow the initial jet development behaviour known from PIV, before jet coalescence, turbulence production and decay further downstream in the nozzles are successfully predicted. In regions where the PIV experiment suffers from inherent limitations like reflections and the velocity bias, the LES data is available to still obtain a detailed picture of the flow. The sensitivity of the simulations to various physical and numerical parameters is discussed in detail. Results from LES and PIV are compared qualitatively and quantitatively in terms of first and second moments of velocity, temporal autocorrelations, and energy density spectra. Significant deviations are found in the frequency (20%) and strength of vortex shedding from the inlet plane only, whereas the qualitative and quantitative agreement between simulation and experiment is otherwise excellent throughout, implying that a successful large eddy simulation of a turbulent opposed jet can be performed in a domain that includes the perforated plates. 相似文献