Dynamic integration between building energy simulation (BES) and computational fluid dynamics (CFD) simulation for building exterior surface

Different site conditions create a site specific microclimate which has great influence on building energy consumption. However, current energy simulation lacks a response to microclimate and buildings are treated with outdoor conditions based on weather data from nearest metrological site. This paper describes the coupling methodology between building energy simulation (BES) and computational fluid dynamics (CFD) simulation in order to analyze the impact of microclimate to building performance. A BES and a CFD exchange parameters in a dynamic time step base manner. The external surface of the building is the interface through which parameters are exchanged between BES and CFD. BES provides surface temperatures as the boundary conditions for CFD, while CFD calculates the heat transfer coefficients as the input to BES in each time step through a controller. This paper reviews the recent development in integration between BES and CFD methodologies. After an overview of coupling, the paper develops an approach of outdoor integration between BES and CFD. The proposed integration method is tested for case building and the result will be discussed.     

开放空间及周边的风环境历史变化分析——以南京为例

通过对南京三处开放空间及周边地区进行建筑体块建模和冬夏风场模拟,探求在1930-2000年间建筑密度增加、城市形态变化对风环境的影响,发现气流变化不确定性增加、部分地段户外活动舒适度下降、中观尺度的通风廊道受阻等.建议将开放空间及周边的风环境变化纳入城市规划设计和管理中,通过仿真模拟分析与可视化来协助建设管理决策和公共参与,确保高密度城区中开放空间在改善微气候方面的作用.     

Integrating neural network models with computational fluid dynamics (CFD) for site-specific wind condition

Most building energy simulations tend to neglect microclimates in building and system design, concentrating instead on building and system efficiency. Energy simulations utilize various outdoor variables from weather data, typically from the average weather record of the nearest weather station that is located in an open field, near airports and parks. The weather data may not accurately represent the physical microclimate of the site, and may therefore reduce the accuracy of simulation results. For this reason, this paper investigates utilizing computational fluid dynamics (CFD) with neural network (NN) model to predict site-specific wind parameters for energy simulation. The CFD simulation is used to find selected samples of site-specific wind conditions. Findings from CFD simulation are used as training data for NN. A trained NN predicts site-specific hourly wind conditions for a typical year. The outcome of the site-specific wind condition from the neural network is used as wind condition input for the energy simulation. The results of energy simulation using typical weather station data and site-specific weather data are compared in this paper, in order to find the possibility of using site-specific weather condition by NN with CFD to yield more realistic and robust ES results.     

Microclimatic coupling as a solution to improve building energy simulation in an urban context

To streamline the design of the energy efficient buildings, appropriate tools are needed to assess their energy performance taking into account the microclimatic context.Numerical simulation seems to be the most suitable issue, but none tool is dedicate to the direct evaluation of the microclimate influence on the building energy consumption. A complete solution could be to use both CFD and thermoradiative simulation tools complementary with the coupling technique perspective. This paper presents both a developed CFD-thermoradiative coupled simulation tool and a typical application on an urban fragment.The results lead to two kind of observations:

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Integration of the thermal model of a building in the microclimatic simulation platform enable a quantitative evaluation of the building energy demand regarding different urban design scenarii (e.g. mineralized vs vegetated).

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Different physical phenomena do not contribute as much in the energy balance and it is important to compute precisely each one to obtain the small scale microclimatic influence.

     

Urban microclimate and energy consumption: A multi-objective parametric urban design approach for dense subtropical cities

Climate change within the urban contexts is a crisis that cities are confronting globally. This issue poses numerous negative consequences such as thermal discomfort and increased energy usage within the building sector. This is especially the case in Western Sydney, Australia, where the average maximum temperature has risen by 7–8 °C within the past 30 years. This increase in temperature is highly concerning, since this region is witnessing rapid urban and infrastructural development and is proposed as the third-largest economy of Australia. Temperature changes in this region will also result in considerably increasing the electricity used for cooling purposes. This paper presents a parametric approach driven multi-objective optimization methodology to discover optimum design solution based on the urban microclimate and cooling energy demand of multi-functional buildings within this urban context. Mitigation measures including a range of design factors at both building (typology and window to wall ratio) and urban scales (aspect ratio and urban grid rotation) are further suggested for developing context sensitive optimum urban layouts. The resultant solutions indicate an improvement in urban thermal comfort, cooling and heating energy use by up to 25.85%, 72.76%, and 93.67%, respectively.     

建筑高度对周围风场环境影响的数值模拟

建筑风环境作为建筑节能设计的一个重要方面,其对于区域气候与局部微气候的影响都不容忽视。本文应用基于RNG k-ε模型的CFD软件数值模拟研究不同的建筑高度差对建筑周围风场环境的影响,揭示有利于风流动的建筑因素,为进一步的住区建筑规划提供思路。模拟结果显示,在来流风速一定双体建筑高度差不同时,建筑间谷区风速与形成涡旋的中心位置和大小均不同。     

建筑与植物结合的城市生态设计

当前,我国城市绿地率已达相当高的比例,但环境恶化之势仍未得到根本扭转,其主要原因之一,在于城市景观综合生态机能的衰退。将建筑设计与城市植物群落结合,按照植物群落最小面积要求设置大中型绿地斑块、合理限定人为干扰并引导群落演替,就能减少绿地系统的人工维护,完善群落组织,改善城市小气候。而将建筑设计与绿地系统的生态补偿结合,兼顾绿地景观的关键生态过程和重要节点的保育,以绿地系统改善自然采光、通风与景观视觉,则能有效地弥补、修正城市绿地的格局与构成。最后,在建筑设计中结合绿地进行节能设计,利用绿地做功,还能降低建筑全生命周期的运营费用,有利于城市可持续健康发展。     

Optimization of variables in air conditioning control systems: Applications of simulations integrating CFD analysis and response factor method

The integration of three-dimensional spatial distributions into building simulations is of significant interest, and computational fluid dynamics (CFD) analysis is widely employed in building design processes. For example, based on the experience of architects and engineers, CFD analyses are often conducted under steady boundary conditions to determine the degree of attainment of indoor environments. However, CFD analyses have large calculation costs and cannot be often used for simulations with unsteady boundary conditions such as energy simulations in the building design processes. Thus, we developed a method that calculates sensitivities from heat sources to an arbitrary point in an indoor environment and integrates them into simulations with unsteady boundary conditions. In the proposed method, CFD analysis is employed under steady boundary conditions to calculate the response factors, and the resulting sensitivities are integrated into simulations under unsteady boundary conditions. In the present study, the proposed method was applied to optimize the variables of an air conditioning control system. With our method, temperature changes at a sensor over time are calculated from the time series of air supply temperature. In total, 800 calculations were conducted, and the optimal variables that allow the temperature at the sensor to reach the target value quickly were obtained. Except for the time required to calculate the response factors, the optimization in the present study took only a few seconds. If only CFD analysis was used for the optimization, the calculations would take a year. Thus, calculating the sensitivities via CFD analysis and utilizing the results in simulations is a useful approach for solving optimization problems. Moreover, the proposed method is applicable to simulations that require three-dimensional spatial distributions to enhance the accuracy of the calculation such as energy simulations.     

Simulation analysis of site design and layout planning to mitigate thermal environment of riverside residential development

The present study explains the application of a numerical simulation to investigate the thermal environment of a new riverside residential development in summer. The case study area consists of more than one hundred two-story detached houses built next to a river near Tokyo, Japan. According to the meteorological data, prevailing wind directions are at an angle to the northbound river flow affecting the microclimate of the study area in terms of surface temperature of land and buildings, air temperature and wind distribution at pedestrian height. These factors have been estimated using the stepwise CFD (computational fluid dynamics) simulation of radiation, conduction and convection. This method leads to an improvement of outdoor thermal environment by manipulating the site design and layout planning scenarios. The effect of river, permeable pavements and green space on thermal environment is examined by the site design options. Likewise, the impact of building arrangement is evaluated using alternative layout planning scenarios. In total, five scenarios have been simulated for the proposed sustainable development as explained in the paper. Above simulations provided an insight into the mitigation effects of each countermeasure. It is also shown that the management of inflow paths and the creation of wind paths for the interior of the site have the potentials to improve the outdoor thermal environment of riverside residential development.     

Would LEED-UHI greenery and high albedo strategies mitigate climate change at neighborhood scale in Cairo,Egypt?

Neighborhood has always been of significant interest to built environment stockholders as a basic planning unit. However, any discussion in these concerns, without drawing attention to sustainable microclimate approaches, would still in a mess at a time of increasing population and climate change. Emergence of the sustainable development concept at the mid-20th century and its emphasis led to increasing crucial role that the urban green infrastructure along with reflective materials can play in mitigating neighborhood microclimate’s symptoms of climate change. Considering the lack of studies for urban heat island (UHI) in hot arid regions, particularly in Egypt and the limited number of studies concerning the numerical simulation of all mitigation strategies incorporated, this research studies the mitigation of UHI phenomenon in a case study in Cairo in present and future (2020, 2050 and 2080) through applying the criteria of tree lines, green roofs, high albedo pavements and shading structures within the neighborhood sustainability assessment tool (Leadership in Energy and Environmental Design for Neighborhood; LEED-ND). The microclimatic numerical CFD simulations of ENVI-met 4.0 was used following the measurement of LAI and Albedo of selected Egyptian trees to assess UHI through air and radiant temperature differences before and after applying mitigation strategies. Results demonstrate a considerable ability to acclimatize the microclimate in terms of better conditions in present and future.     

基于计算流体力学数值模拟的城市绿地温湿效应及室外热舒适评价研究进展

近年来随着计算机与各学科领域交叉研究的发展,计算流体力学数值模拟方法在城市环境的微气候研究方面得到较多应用,为研究绿地在有限面积内更有效地实现其降温效应提供了新的思路。回顾计算流体力学(CFD)数值模拟方法在不同尺度的城市绿地温湿效应及室外热舒适度评价研究中的应用,在此基础上,总结目前存在的问题及不足,对未来该领域的研究方向提出3点展望,以期为未来城市绿地微气候研究提供参考:1)多平台与尺度扩展研究;2)微气候特征指标的综合交叉分析;3)高适配度模拟模型的及时更新。     

Das städtische Mikroklima: Analyse für die Stadt‐ und Gebäudeplanung

In the face of global warming, human thermal comfort has become an increasing important aspect in applied urban planning. As the urban heat island is not a homogenous factor the microclimate conditions play an important role also for single buildings and the situation inside. For a better consideration of this aspect in the planning process, qualitative and especially quantitative assessment tools are required. To get a better knowledge about the quantitative dimension of urban climates investigations on thermal comfort in outdoor and indoor spaces are carried out in selected city quarters in the city of Kassel in Germany. These studies consist of experimental investigations including field interviews about usage of urban open spaces and thermal sensation and numerical simulations on thermal comfort under recent as well as future regional climate conditions. The added‐value of the interdisciplinary research project is based on the correlation of findings from human‐biometeorology with the outcomes from sociologic questionnaires and building physics, which will be used to plan and design structures in a high spatial resolution. The thermal conditions outside continue inside the building, a combination of internal and external climate considerations must be made. The aim of a research at the University of Kassel is the examination and presentation of different microclimate and its influence on the thermal behavior of buildings.     

沿海城市住宅小区风环境研究

随着城市的飞速发展,住宅小区风环境问题日益突出。沿海地区受海陆风影响明显,全年风速一般较大,其住宅小区的风环境研究需特别考虑。本文通过IECM CFD10.0建立数值风洞,采用SSTK-ω湍流物理模型求解住宅小区内风速的方法来研究某沿海城市住宅小区的群体建筑风环境。研究表明,数值方法能准确模拟小区风流场,建筑布局和来流方向对小区风环境影响明显,可结合城市风玫瑰图合理规划建筑布局。采用数值方法,可以对己建小区提出措施改进不良风环境,还可以指导、优化未建小区的规划与设计,以营造健康舒适的居住区微气候环境。     

Thermal simulation: Response factor analysis using three-dimensional CFD in the simulation of air conditioning control

The heat generated from an air-conditioning equipment or other thermal loads is distributed throughout a room by a three-dimensional airflow. This three-dimensional airflow creates a three-dimensional heat distribution in a room. To better understand building performance, we must integrate this spatial distribution into building simulations. Thus, three-dimensional computational fluid dynamics (CFD) analysis is necessary in design process because most conventional building energy simulations still employ a temperature that is averaged across the space of a room. However, usually only a few cases of CFD analyses are executable in real design process because of the large computational load they require. This paper presents a new, simplified method to calculate heat transport phenomena in rooms, based on a few cases of CFD analysis, and to integrate data into a nodal analysis. This method can be used to calculate an indoor environment, including the spatial distribution of temperature, with a computational load that is much lighter than it is in a simulation using CFD alone. Furthermore, in terms of precision, it is a far more reliable method than the conventional simulation, which assumes the perfect mixing of heat in a room. In the paper, we apply this method to simulate the control of air conditioning. Ordinarily, the reproduction of the phenomena shown in the calculation examples requires substantial manpower and costly computing resources for experimentation or CFD analysis. With our calculation method, it is possible to reproduce the same calculation results in a very short time with a PC. And we checked the potential to the practical use through a verification calculation with CFD analysis.     

气候条件驱动下建筑计算性设计方法研究

适应气候的建筑形态是降低建筑能耗以及营造舒适微气候的主要方法之一。通过计算性设计方法,可以在方案设计阶段对建筑性能进行优化。将设计条件与决策过程向数据和算法进行转化,是实现这一优化过程的关键。以建筑体量为研究对象,基于既往气候驱动下计算性设计的相关研究,针对工作流程中气候驱动因子的多维度整合、环境性能的多元化评价以及影响因子的参数化建构三个核心环节,建立了由“特征认知-逻辑转化-方法择取”构成的决策框架,并对其中关键性技术方法进行解析。最终结合工程实践,验证计算性设计方法在气候适应性设计中的应用价值。     

场地微气候综合分析方法

绿色建筑的设计最重要的就是因地制宜,与自然环境和谐共生。要做到这一点,在建筑规划设计阶段,少不了对场地微气候环境的分析,目前普遍采用的计算机模拟分析或经验总结分析的方式还有其局限性,综合地分析场地微气候环境各因素,得出综合的分析结论,更有利于指导建筑师进行场地设计。     

浅谈夏热冬冷地区办公建筑的微气候设计策略

对夏热冬冷地区办公建筑在使用中能耗大,人体的舒适度低的情况进行了分析,从外部环境设计、建筑单体设计和颜色方面介绍了微气候设计策略,以改善办公建筑微气候,达到提高人体舒适度的效果。     

济南奥林匹克体育中心自然通风设计

采用CFD技术对整个体育中心进行了微气候模拟分析,分析了各场馆自然通风的策略,并进行了自然通风的系统设计.     

基于夏季小气候效应的杭州街道适应性设计策略研究

随着城市热岛效应日趋严重,小尺度公共空间的气候研究已成为风景园林学科的研究热点之一。选取杭州市文一西路和古墩路作为实测对象,于2017年8月对各测点空间的空气温度、相对空气湿度、太阳辐射强度、风速风向进行测定,分析小气候因子日变化趋势,并运用Rayman 1.2模型评价人体舒适度,针对性提出街道空间小气候适应性设计策略。研究表明,尽可能设定与城市主导风平行或接近的街道朝向,通过人为增建遮阴空间、调控街道界面小气候一致、采用植物或绿色建筑材料、增设道路中央景观界面,且当人行道及机非分隔绿带分别种植落叶、常绿乔木,设五条绿带,选用乔—灌—草复层结构,同时增设垂直绿化时,能够有效缓解夏季极端热感受,从而营建舒适健康的城市街道空间。     

动·静·显·隐:大数据在城市设计中的四种应用模式

伴随着信息化技术的不断进步,城市设计实践中也呈现出大尺度化、高颗粒化、人本量化、经验量化等新特征趋势,尤其是大数据引领的数字化技术飞速发展,在城市设计的转型与提升中具有重要的现实意义.阐述了城镇化实践对于城市设计的大数据诉求特征,在大量规划实践探索的基础上,凝练大数据面向城市设计的四种应用维度,分别为:追踪即时人群活动潮汐波动规律的动态大数据应用;精确到建筑空间基准单元的静态大数据应用;体现出民生真实空间场所感受的显性大数据应用;衍射市场营运内在规律的隐性大数据应用.并结合具体案例,说明四种维度大数据的内涵特征与应用方法,初步建立大数据在城市设计中的应用模式,并对其未来应用进行前瞻.