小型绿化带对局部微气候影响的数值模拟

Numerical simulation of the local microclimate affected by small green belts

以垂直于来流方向和沿来流方向布置的绿化区组成的小型绿化带为研究对象,将绿化带简化为多孔介质模型,采用数值模拟的方法研究了在0.5 m/s、1.0m/s和1.5 m/s风速下绿化带对局部微气候的影响,并对比分析了两种布置形式对绿化区的影响范围。结果表明,当风速从0.5 m/s增加到1.5 m/s时,相同温降、湿增的影响范围均逐渐扩大;并且随绿化带下风向距离的增大,温度逐渐回升,湿度不断减小。在同一风速下,当温降、湿增的数值变化为一定值时,垂直于来流方向布置的绿化区的影响范围明显大于沿来流方向布置的绿化区的影响范围。

In the article, we would like to introduce a numerical sim- ulation method to analyze the impact of the green belt on the local mi- eroelimate under different wind velocities. The small green belt men- tioned in this article is composed of two kinds of artificial green ar- eas, including green area formed in the airflow direction and that built in the perpendicular direction. The size of green area of the former is 20 m × 10 m × 10 m whereas that of the latter is supposed to be of an area of 50 m × 10 m × 10 m. And the influential seope of two kinds of green areas of stated forms has been compared with each other in this paper. The green belt we proposed is supposed to be as the porous medium model, whose porosity is taken as 0.8. The simula- tion results show that the influential scope on the humidity and tem- perature of the green belt gradually is expected to expand with the in- crease of the wind velocity from O. 5 m/s to 1.5 m/s in the downward wind region of the green belt. What is more, the heat and mass transfer would oceur constantly between the green belt and the atmo- sphere through the transpiration, which helps to lower the surrounding temperature and increase the mass fraction of water vapor. In addi- tion, with the increase of the influential scope of the green belt, the surrounding temperature would be able to tlse gradually, with the continuous decrease of the surrounding humidity. When lowering the given temperature and increasing the given humidity, the influential scope of the green area decorated in the perpendicular direction on the local microchmate is expected to be obviously greater than the one of green area designated in the airflow direction under the same wind velocity. Therefore, the green area built up in the air-current direc- tion can be expected to prevent heat and mass transfer between the vegetation and the atmosphere. Hence, when defining the green belt, it is necessary to reduce appropriately the quantity of vegetation to be planted in the local summer prevalent wind direction in order to take full advantage of the vegetation to regulate the local microclimate.