Dynamic airflow simulation within an isolation room

In many hospitals, isolation rooms are used to contain patients who are highly infectious, and the spread of air and bacteria within the isolation room is closely relates to room air distribution. This article uses the computational fluid dynamics (CFD) method to investigate the effects of a moving person and the opening and closing of a sliding door on room air distribution, including velocity, pressure and contaminant fields. Dynamic meshes are employed to simulate the movement of the walking person and sliding door. According to numerical results, the impact of those moving objects on room air distribution is addressed in this study.     

Verification of a CFD model for indoor airflow and heat transfer

The SST k–ω based model is applied to calculate air-flow velocities and temperatures in a model office room. Calculations are compared with experiments and with the results of the standard k–ε, the RNG k–ε model and the laminar model. It is concluded that (a) all the three tested turbulent models predict satisfactorily the main qualitative features of the flow and the layered type of temperature fields and (b) computations with the SST k–ω based model show the best agreement with measurements. The use of this model is proposed combined with a suitable grid.     

基于CFD的有害气体泄漏扩散的数值模拟

在实验室建立系统模型的基础上，利用计算流体力学（CDF）软件Fluent对有害气体泄漏扩散过程进行了数值模拟，整个模拟计算过程的稳定性和收敛性均较好。研究结果表明：出口处的平均速度在迭代116次后达到稳定，迭代过程中的残差收敛标准为1e-5；流场中的速度分布较为明显，不同的颜色代表了不同的速度等高线，且流场中的最大速度为1．561256m／s，最小速度为0．021359m／s；获得模拟计算的最关键技术参数CO2浓度的空间分布，并与试验中的实测数据进行了对比，简单分析了产生误差的原因。研究对泄漏事故扩散趋势做出准确的预测，建立有针对性的应急救援预案，实施有效的现场控制，具有一定的科学参考价值。     

A computational and experimental study of ultra fine water mist as a total flooding agent

Computational fluid dynamics (CFD) calculations were carried out to design total flooding fire tests in a 28 m³ compartment for an ultra fine water mist (<10 μm). The exit momentum of the mist produced by a proprietary ultrasonic generator technology was extremely low with a mist discharge velocity below 1 m/s. The mist was discharged with multiple floor outlets equally spaced around the centrally located 120 kW pool-like gas fire. The transport of mist and its interaction with the fire was simulated by Fluent, a commercial CFD model. Lagrangian Discrete Phase Model (DPM) was used for droplets. Simulation predicted extinguishment within 10 s with a mist delivery rate of 1 l/min. However, in total flooding fire tests conducted, extinction times were more than 5 min. Additional computations approximating the ultra fine mist (UFM) as a dense gas agreed well with the observed transport timescales of minutes indicating that UFM behaves like a gas. Further, the mist–fire interaction needs a multi-phase Euler–Euler approach with a droplet vaporization model.     

类锥形组合群膜结构的风荷载探讨

风荷载是张拉膜结构设计中的控制荷载,利用流体力学的数值计算方法研究了复杂形态的类锥形组合群膜结构的风场特征,根据计算结果探讨了膜结构表面风压系数的分布规律并用于实际工程的风荷载确定。     

大跨度单层网壳结构风振响应的流固协同分析

风振计算是结构设计中的一项重要内容,该方法在进行复杂结构风振计算时的准确性值得商榷.利用风洞试验进行风振响应分析存在成本高、周期长、试验复杂等缺点.研究了运用计算流体动力学(Computational Fluid Dynamic,CFD)中的非稳态计算,获取建筑物表面风荷载时程,通过网格数据插值,将风荷载直接作用于有限元模型的相应节点进行动力时程分析,提出了适合此类结构使用的风振系数简化计算公式.采用该方法对某一大跨单层悬索式网壳结构的风振响应进行了计算.结果表明,流体动力学与固体有限元程序之间的协同分析,不但支持不同软件不同节点之间的匹配,而且可以考虑自然风的时空相关性以及结构高阶振型的影响,更加精确地反映结构实际的风振情况.     

CFD simulation of VOCs concentrations in a resident building with new carpet under different ventilation strategies

This paper investigates the effect of ventilation strategies on the concentrations of volatile organic compounds (VOCs) emitted from a new carpet in an apartment with the VOCs emission characteristics taken from chamber test data. The commercial software FLUENT 6 has been employed to solve the continuity, momentum, turbulence and concentration equations under five different ventilation strategies. Numerical results show that ventilation strategies have a small effect on VOCs emission from carpet. Continuous ventilation keeps a low level of VOCs concentration in the air. Flushing ventilation has a significant effect on the VOCs concentration in the air. During a period without ventilation, VOCs concentration in the air usually increases to a high level. Thus, the ventilation should be carried out before the arrival of residents to ensure a low level of VOCs concentration. At the startup of ventilation run, the sudden flow strongly promotes the mixing of VOCs, which may lead to local high concentration.     

Numerical simulation of backdraft phenomena

This paper reports preliminary computational fluid dynamics (CFD) simulations of backdraft observed in an experimental rig at Lund University. The analysis was performed with the CFX software using the Detached Eddy Simulation (DES) turbulence model, a hybrid of Large Eddy Simulation (LES) and RANS, in combination with the EDM combustion model. The DES model uses a RANS formulation in wall proximity to avoid computationally expensive grid resolution that is necessary for realistic LES predictions in wall layers.     

头支撑下空化器外形对通气超空泡的影响

目前,空化器外形对超空泡形态的影响研究都是在空化器前的流场未被干扰时进行的,当水洞试验因采用头部支撑方式而影响了空化器前的流场时,通气超空泡形态随空化器外形的变化规律尚不明确。本文应用计算流体力学(CFD)仿真软件FLUENT,参照头支撑下通气超空泡生成的试验模型,建立了随空化器直径、连接杆直径和空化器锥角变化的仿真模型。在通气量一定的情况下,通气超空泡的长度和长径比随头支撑连接杆的增大而增大,随空化器直径的增大而减小,随空化器锥角的减小而增大,并深入研究了空化器外形对空泡尺寸的影响规律,为水洞超空泡试验在头支撑方式下空化器外形的设计提供参考。     

Research on Performance of U Separator in Sand and Dust Test System

Sand/dust test is one of the key projects to examine the environmental adaptability of ordnance equipment.In order to decrease the abrasion of test facility caused by the sand/dust particles,the particles contained in the airflowneed to be reclaimed effectively.Amathematical model of Useparator is established.The flowfield and the trajectories of particles inside the separator are obtained using a numerical simulation method,and the separation efficiency and pressure drop of separator with different rows of separate components are also obtained at various flowvelocities.The simulation results indicate that the efficiency of U inertia separator is affected by the flowvelocity evidently,and a reasonably designed separator can meet the requirement of the separation efficiency in particular situation.The results can be use as reference for the design and test of sand/dust separate systems.