房间内强自然对流的两方程模型模拟研究

强自然对流是火灾时的主要流态之一,利用标准火灾房间内的基准实验数据,比较了工程上常用的3种两方程k-ε模型在预测大功率热源引起的强自然对流时的效果,即Standard(标准)k-ε模型,RNG(重整化)k-ε模型和Realizable(可实现)k-ε模型.研究发现火灾房间内存在垂直方向的下低上高的温度分层,且加热量越大,垂直温度分层的梯度也越大.Standard k-ε模型计算得到的热源附件的湍流动能最大,湍流黏性也最大.总体而言,Realizable k-ε模型的模拟效果稍好于Standard k-ε和RNGk-ε模型.3种k-ε模型预测的温度场准确度比自然对流速度场要高.在房间的中央位置,水平方向的室外流入气流与浮升力气流相互作用导致流态复杂,两方程模型在模拟这一现象时效果不佳.

Two equation Model based Simulation of Flow Characteristics in a Fire Room

Based on a set of experimental data from a benchmark test,a comparative study was made of the performance of three k-ε models,the standard k-ε model,RNG k-ε model,and realizable k-ε model,in the simulation of intensive natural convection.Temperature stratification is found to appear in the fire room.The more intensive the heat source is,the steeper the vertical temperature gradient becomes.The standard k-ε model offers the highest turbulence kinetic energy and turbulent viscosity.Generally speaking,realizable k-ε model performs better than the other two models.All the models predict the temperature field better than the velocity field.In the center of the room,due to the complicated interaction between the horizontal airflow from outside and buoyancy flow,the prediction from two-equation is poor.