复杂地貌特征下的城市风环境与污染物扩散研究

Abstract: In recent years, with the rapid development of the urbanization process, many cities in China and in the world are facing more and more serious wind environment problems, e.g., the pedestrian comfort and pollutant accumulation, which trigger widespread concerns. However, since there is a lack of theoretics and methods on resolving these problems, the scientific planning in the urban expansion faces huge challenges. Based on the full comprehension of the drawbacks and limitations of previous studies, this project will be carried out by taking a typical morphologically complex city district as the research prototype through Computational Fluid Dynamics (CFD) and wind tunnel tests to analyze the detailed district wind field . The main work includes:.1) Develop a high precision pocket anemometer, pollution source generator, and pollution concentration monitoring device;.2) By combining the methods of pressure measurement and force measurement, the urban canopy resistant characteristics will be analyzed with considering different urban spatial morphologies;.3) The Unmanned Aerial Vehicle (UAV) oblique aerial photography and three dimensional cloud points reverse fitting technique will be used to establish the complex building geometric modeling;.4) Based on the multi-scale coupling method, the velocity down-scaling issues of the coupling surface between WRF and CFD will be analyzed;.Finally, a high effective and precise analysis framework on urban wind environments and pollutant dispersion by combining the numerical simulation and wind tunnel tests will be established. This framework can provide technical supports for the rational urban planning and sustainable development of cities.

摘要：近年来，随着高强度的城市开发，由风环境引起的行人舒适度与污染物积聚等问题愈发严重，引起了广泛关注。而目前对该问题研究的理论与方法还非常缺乏，使得城市扩张过程中的科学规划问题面临着严峻的挑战。本项目将针对现有研究的不足，拟以复杂地貌特征下的典型城区为研究背景，利用风洞试验与数值模拟相结合的方法对其关键问题进行探索，主要内容包括：1）研发高精度袖珍型风速仪、污染源发生器与污染物浓度监测装置；2）采用测力和测压法分别对冠层模型进行风洞试验，揭示冠层内阻力系数的分布规律；3）基于倾斜摄影测量技术，结合三维点云逆向拟合法，提出复杂城区几何模型的高精度生成方法；4）基于多尺度耦合数值模拟，实现WRF与CFD风场数据的高精度交换；最后结合风洞试验与数值模拟对典型城区风环境及污染物扩散进行综合分析，从而提出一套高效率、高精度的研究方法，为城市扩张的合理规划与可持续发展提供技术支撑。

随着我国城市人口所占的比重不断增大，风环境，热环境带来的负面影响日益激烈。大量机动车排放的有害气体容易在城市街道、小区等建筑物密集区域积聚，得不到扩散，导致了严重的空气污染，一系列问题的出现对城市小区的通风能力和自净化能力提出了更高要求。本项目针对当前风环境与污染物扩散研究中面临的痛点问题，历时三年（2019.01.01-2021.12.31），利用CFD数值模拟和风洞试验相结合的方法对其关键问题进行了精细化研究。主要研究成果如下：在风洞试验方面，研发了高精度风速探针、污染源发生器和污染物浓度监测仪；开展了城市冠层模型风洞试验，研究了冠层阻力系数的沿高度方向分布；建立了典型城区风洞试验模型，揭示了风环境的分布特点和污染物扩散规律。在数值模拟方面，搭建了倾斜摄影测量平台，生成了城区复杂地貌几何模型，并对风场进行了多尺度耦合分析，建立了速度场高阶降尺方法，最后对典型城区风环境与污染物扩散进行了大涡模拟研究，提出了复杂地形风环境高精度数值模拟流程。为日后准确预报小区污染物浓度，评估小区风环境，改善小区通风能力和自净化能力提供了科学支撑，具有广泛的应用前景。基于项目研究成果，申请并授权发明专利3项；在国内外重要期刊上发表高水平论文12篇，培养了硕士3名，协助培养博士1名，较好完成了项目任务和各项考核指标。