湿地降温增湿效应的数值模拟研究

采用数值模拟方法研究湿地对周边区域空气的降温增湿效应，建立了空气、水气的流动与扩散混合模型，描述给定空间的传热传质过程．控制方程包括连续方程、动量方程、能量方程和水气守恒方程．对每一相各自的流动，采用κ-ε双方程模型；对于两相的湍流流动，采用混合湍流模型．用FLUENT软件进行数值计算，得出给定区域的空气温度、相对湿度的空间分布．对实测案例进行了数值模拟，计算值与测定值符合良好，表明所建立的模型和计算方法可以很好地描述湿地对周边区域空气温度和湿度的影响．由等温线可以看到，低温空气的扩散在近湿地处，影响最大的区域距地面一定高度．冷空气从湿地边沿向远处及上下扩散，在温度最低区略有上升，到一定远处又下降至地面．对于相对湿度，在靠近湿地区域水气对地面附近的影响比气温影响明显，而远处水气对地面附近的影响不及气温影响大．

Numerical Simulation on Cooling and Humidifying Effects of Wetlands

A numerical simulation method is used to investigate the cooling and humidifying effects of wetlands. A mixture model was adopted to simulate the flow and diffusion of air and moisture, which describes the process of heat and mass transfer. The governing equations include the continuity equation, the momentum equation, the energy equation and the humidity conservation equation. The turbulent energy equation and the energy dissipation equation are used for each phase, and a mixture turbulence model for the two-phase turbulent flow. The distributions of the air temperature and moisture in the given region were calculated by the FLUENT software. The simulation for a case of the measurements in situ was carried out, and the calculation results agreed well with the field measurements data. From the isotherms, it can be seen that the most effective region of cold air is at a certain height above the ground near the wetland. The cold air diffuses up and down from the wetland edge while the coldest air rises slightly and comes down to the ground at the certain far place. The effect to the relative humidity near the ground is more evident than that of the temperature, and on the contrary, is not remarkable as the temper- ature at the distant place.