风洞内非中性边界层风场和温度场耦合模拟

Numerical Simulation of Wind Field and Temperature Field in a Non-Neutral Atmospheric Boundary Layer using a Wind Tunnel Test

现有城市中性大气边界层只考虑风场忽略了温度场,无法研究大气昼夜温度分布对城市环境的影响。然而,温度场是对于城市环境研究的一个重要的因素,尤其在城市规划、城市热岛、污染物扩散等方面。城市非中性大气边界层包含风场和温度场,并分为稳定和不稳定两类,其风洞实验需要同时控制风场和温度场的模拟装置。文章采用数值模拟的方法模拟三角形尖劈、粗糙元、温度分层装置对风洞试验段的风场和温度场的影响规律,提出城市非中性稳定大气边界层风场和温度场在风洞内耦合形成时的控制策略,建议在稳定城市边界层的风洞试验时,先满足边界层速度、湍流度的风场特性要求,然后考虑风洞内的热损失,分段提高温度分层装置的温度梯度,从而同时实现目标风场和温度场。

The existing neutral atmospheric boundary layer (ABL), only taking the wind field into account, cannot appropriately study the effects of distribution of temperature during 24-h on urban environment. However, temperature field is a significant factor to study the urban environment, especially in term of urban planning, urban heat island, pollutant diffusion, etc. The non-neutral ABL includes wind and temperature fields, and it can be divided into stable type and unstable type. The wind tunnel testing of non-neutral ABL needs to simultaneously control the simulators of these two fields. In this study, a numerical simulation analysis with consideration of the effects of triangular split, rough element, and temperature stratification device (TSD) on wind and temperature fields in a wind tunnel test was carried out. Based on simulation results, a control strategy for the formation of wind and temperature fields in the non-neutral stable ABL was proposed. It is suggested to highly pay attention to the velocity and turbulence of wind field in wind tunnel testing of stable urban boundary layer to decrease heat loss in the wind tunnel and gradually increase of temperature gradient of TSD. This strategy can truly control the target temperature and wind fields.