压差对含裂缝硐室氡运移影响的数值模拟研究

为研究地下硐室存在裂缝下的氡运移规律,依据某人防工程的构造和物理几何尺寸,建立了适合裂缝网络渗流特性的数学模型和氡运移方程,采用计算流体力学方法,研究了不同室内外压差条件下含裂缝硐室内氡的运移规律。结果表明:分形裂缝网络的渗流模型来表征墙体裂缝的渗流特性具有可行性;随压差从5 Pa增至30 Pa,压差抑制了氡从裂缝中扩散到室内的运移,裂缝处流出的氡质量流量总减少76.5%;压差对排氡起促进作用,从排风口处流出的质量流量总增加了186.2%。硐室在滤毒通风状况下,压差为20 Pa时排氡效率最高,最有利于室内氡的控制。压差的增大可等效为换气次数的增加,顶送下回的送风方式容易造成靠近送风口处氡的堆积且在室内易产生涡流。

Numerical Simulation Study on the Influence of Pressure Difference on Radon Migration in Underground Chambers with Cracks

In order to study the migration law of radon in underground chamber with cracks, according to the structure and physical geometry size of a civil air defense project, mathematical model for seepage characteristics of fracture network and radon migration equation was established. CFD was adopted in this paper to make the numerical simulation of the migration law of radon in the chamber under different pressure difference conditions. The results indicate that based on the basic theory and method of porous media fractal, it is feasible to use the fractal fracture network seepage model to characterize the seepage characteristics of wall cracks. The model has been verified to be accurate and reliable. With the increase of pressure difference from 5 Pa to 30 Pa, the pressure difference inhibits the migration of radon from the cracks to the room, and the total mass flow rate of radon flowing out of the cracks was reduced by 76.5%; The pressure difference promotes the radon exhaust,the total mass flow from out of the exhaust port increased by 186.2%. When the pressure difference is 20 Pa, the mass flow reduction rate at the crack and the mass flow increase rate at the air outlet both reach the maximum. Therefore, in the chamber under the condition of poison filtering and ventilation, when the pressure difference is 20 Pa, the radon removal efficiency is the highest, which is most conducive to the control of indoor radon. The increase in pressure difference can be equivalent to an increase in the number of air changes. Under the condition of ensuring a constant pressure difference, the top-supply bottom-return mode is likely to cause the accumulation of radon near the air inlet and the two sides of the air supply port are likely to produce eddy currents indoors.