Building Wall Surface Research Articles

Modeling the long-range transmission of airborne bioaerosol releases in a high-density urban environment

In this study, the effect of different meteorological conditions in four seasons on the flow field in a high-density urban environment was examined using numerical simulations. The effect of different thermal conditions on bioaerosol dispersion was evaluated. The dispersions of bioaerosol under three leakage scenarios, i.e., far from crowds (Release 1), close to crowds (Release 2), and simultaneous leakage at two locations, were analyzed. The flow field analysis shows that the wind speed is higher during the summer solstice than the other dates in the vertical direction. The concentration field analysis shows that compared with stable thermal conditions, the lateral dispersion range of bioaerosol in unstable thermal conditions is smaller and the dispersion distance is longer. Compared to Release 2, the Release 1 condition exhibits narrower lateral dispersion. In simultaneous releases, while the vertical concentration distribution trends remained unchanged, there were notable variations in concentration levels and dispersion range. The deposition analysis shows ground deposition in building areas surpasses building wall surface deposition across diverse leakage scenarios and meteorological conditions. Additionally, in Release 1, unstable thermal conditions enhance bioaerosol deposition on building walls but reduce it on the ground within the building area, compared to stable thermal conditions.

Parametrization of irregularity of urban morphologies for designing better pedestrian wind environment in high-density cities – A wind tunnel study

Breezeways are crucial for horizontal urban ventilation. However, their morphologies, which are highly irregular, still lack investigation. This study aims to gain a categorical understanding of how irregular breezeway morphologies affect pedestrian-level wind performance in high-density cities. Firstly, we extracted breezeway areas and centerlines by adopting different definitions of breezeways: Method 1 defining all near-ground open-spaces (i.e., roads, other non-building areas, and low-rise-building areas) as breezeways; Method 2 defining roads as breezeways. Secondly, multiple morphological parameters were developed to describe irregularity (i.e., fragmentation, angularity, and sinuosity) and permeability of 19 typical urban sites in Hong Kong. Thirdly, linear regression analysis was conducted to correlate the parameters with wind tunnel data. The results show that in a dense built environment, urban ventilation relies on morphologies of all near-ground open-spaces rather than only roads. The regression analysis reveals a negative correlation between pedestrian-level wind performance and urban irregularity, where fragmentation has the largest impact due to the increase of building wall surfaces and viscous friction. The regression analysis reveals a positive correlation between pedestrian-level wind performance and urban permeability, where the newly-defined parameter (i.e., open-space width), which incorporates fragmentation into calculation, achieves higher coefficient of determination than the widely-used parameter (i.e., open-space coverage ratio). The newly-developed regression model, which considers both urban permeability and irregularity, predicts wind speed with a simple mathematical manipulation and a comparable accuracy to models in previous studies. More importantly, it provides applicable spatial information of urban irregularity for design of open-spaces and improvement of urban ventilation.

Research on Image Recognition of Building Wall Design Defects Based on Partial Differential Equation

The detection of building wall surface defects is of great significance to eliminate potential safety hazards. In this paper, a research on building wall design defect image recognition based on partial differential equation is proposed. Collect the image data of building surface defects, sample and quantify the collected images, and preprocess the defect images such as digital threshold segmentation, filtering, and enhancement. Then, the improved partial differential equation is used to recognize the image as a whole. The second-order partial differential diffusion equation and the fourth-order partial differential equation are used to recognize the high-frequency and low-frequency bands of the image, respectively. The kernel principal component analysis algorithm is used to transfer the overall image input space to the high-dimensional feature space. The kernel function is used to calculate the inner product in different subband images of the high-dimensional feature space to reduce the dimension of the overall image. The processed coefficients are inversely transformed by nondownsampling contour wave to realize the overall image recognition and ensure that the edge information of the source image does not disappear. Experimental results show that compared with other algorithms, the proposed algorithm has better effect and better stability.

A study on streetscape in harmony with Mozu-furuichi kofun group world heritage

This study aims at clarifying streetscape characteristics in harmony with kofun for planning urban area where kofun can be enjoyed while preserving the value of kofun in Mozu-Furuichi Kofun Group World Heritage by using landscape image taking a kofun as an object and a street crossing of residential urban district as a viewpoint place. This paper performed factor analysis by SD method using the words extracted from landscape plans, and understood the viewpoints of the evaluation. In addition, this paper organized the recognition elements in each target landscape, and understood the characteristics of landscape elements. Furthermore, harmony evaluation in streetscape with kofun in each landscape, and it was discussed what kind of landscape could be said the streetscape in harmony with kofun. From the results of these analyses, it can be understood that streetscape in harmony with kofun is evaluated from the three viewpoints of "regularity" "naturalness" and "history and culture" and that they are evaluated from the greenery along the streets, the color and design of wall surfaces of buildings, the walls and fences of buildings, and the pavement of roads and sidewalks, and their unity.

Small Object Detection in High-Resolution Images Based on Multiscale Detection and Re-training

Most of the current small object detection algorithms are designed for low-resolution images. They can neither directly process high-resolution images nor make full use of the information contained. In this paper, an algorithm is proposed to detect small objects in highresolution images directly. The process of the algorithm is as follows: Firstly, an original detection task is split logically into several relevant detection sub-tasks at different scales. Secondly, a corresponding low-resolution object detector is trained for each sub-task. Thirdly, the detectors are deployed to get detection results at different scales. Finally, the multi-scale detection results are logically combined to derive the final detection results of the small objects. Besides, the detector is re-trained at small scale by introducing negative samples. The algorithm proposed in this paper was tested in the task of defect detection on building wall surface. Experimental results show the reliability and efficiency of our approach.

Thermal Environment Design of Outdoor Spaces by Examining Redevelopment Buildings Opposite Central Osaka Station

Thermal environmental design in an outdoor space is discussed by focusing on the proper selection and arrangement of buildings, trees, and covering materials via the examination of redevelopment buildings in front of Central Osaka Station, where several heat island countermeasure technologies have been introduced. Surface temperatures on the ground and wall were calculated based on the surface heat budget equation in each 2 m size mesh of the ground and building wall surface. Incident solar radiation was calculated using ArcGIS and building shape data. Mean radiant temperature (MRT) of the human body was calculated using these results. Distribution of wind velocity was calculated by computational fluid dynamics (CFD) reproducing buildings, obstacles, trees, and the surroundings. The effect of MRT on SET* was greater than that of wind velocity at 13:00 and 17:00 on a typical summer day. SET* reduction was the highest by solar radiation shading, followed by surface material change and ventilation. The largest ratio of the area considered for the thermal environment was 83% on Green Garden, which consists of 44% of building shade, 21% of tree shade, 7% of water surface, and 11% of green cover. It is appropriate to consider the thermal environment design of outdoor space in the order of shade by buildings, shading by trees, and improvement of surface materials.

Environmentally friendly alternative to polyester polyol by corn straw on preparation of rigid polyurethane composite

Abstract Corn straw was transferred into straw powders (SPs) by physical treatment in order to prepare rigid polyurethane composite foams by one step method. The obtained foams were evaluated through mechanical properties, thermal properties and cellular structure. It was found that the compression strengths of composite foams sharply decreased compared to pure foam and powder size had no obvious influence on the compression strength in the growth direction. Flexural strengths of rigid polyurethane composite foams with corn straw decreased from 0.34 MPa (pure foams) to 0.22 MPa and 0.26 MPa, which decreased by 35.3% and 23.5%, respectively. The flexural strength of non-growth rigid polyurethane composite foam decreased slightly with the increase of powder size. SEM indicates that cellular foam was combined more tightly due to the addition of SPs. However, there were inhomogeneous distribution and more broken cells in all composite foams. Compared with pure foams, thermal properties of rigid polyurethane composite foams with corn straw were not changed, however, with SPs adding into the matrix, more heat flow was released compared with pure foams. All results indicate that polyol could be possibly replaced by corn straw in polyurethane industry, realizing environmentally friendly alternative to polyester polyol by corn straw in the preparation of rigid polyurethane composites. Rigid polyurethane foams have good thermal insulation effect, and is mainly used in the field of thermal insulation, such as refrigerator insulation filling material, chemical transportation pipeline insulation material, thermal insulation layer of building wall surface, etc.

Parameterization of Urban Sensible Heat Flux from Remotely Sensed Surface Temperature: Effects of Surface Structure

Sensible heat exchange has important consequences for urban meteorology and related applications. Directional radiometric surface temperatures of urban canopies observed by remote sensing platforms have the potential to inform estimations of urban sensible heat flux. An imaging radiometer viewing the surface from nadir cannot capture the complete urban surface temperature, which is defined as the mean surface temperature over all urban facets in three dimensions, which includes building wall surface temperatures and requires an estimation of urban sensible heat flux. In this study, a numerical microclimate model, Temperatures of Urban Facets in 3-D (TUF-3D), was used to model sensible heat flux as well as radiometric and complete surface temperatures. Model data were applied to parameterize an effective resistance for the calculation of urban sensible heat flux from the radiometric (nadir view) surface temperature. The results showed that sensible heat flux was overestimated during daytime when the radiometric surface temperature was used without the effective resistance that accounts for the impact of wall surface temperature on heat flux. Parameterization of this additional resistance enabled reasonably accurate estimates of urban sensible heat flux from the radiometric surface temperature.

Geosynthetics used to stabilize vegetated surfaces for environmental sustainability in civil engineering

Geosynthetics, factory-manufactured polymer materials, have been successfully used to solve many geotechnical problems in civil engineering. Two common applications are earth stabilization and erosion control. Geosynthetics used for earth stabilization include but are not limited to stabilized slopes, walls, embankments, and roads. Geosynthetics used for erosion control are mostly related to slopes, river channels and banks, and pond spillways. To enhance environmental sustainability, vegetation has been increasingly planted on the facing or surfaces of these earth structures. Under such a condition, geosynthetics mainly function as surficial soil stabilization while vegetation provides green appearance and erosion protection of earth surfaces. Recently, geosynthetic or geosynthetic-like material has been used to form green walls outside or inside buildings to enhance sustainability. Geosynthetics and vegetation are often integrated to provide combined benefits. The interaction between geosynthetics and vegetation is important for the sustainability of the earth and building wall surfaces. This paper provides a review of the current practice and research in the geosynthetic stabilization of vegetated earth and building surfaces for environmental sustainability in civil engineering with the emphases on geosynthetic used for erosion protection, geosynthetic-stabilized slopes, geosynthetic-stabilized unpaved shoulders and parking lots, and geosynthetic-stabilized vegetated building surfaces.

Three-dimensional flood routing of a dam break based on a high-precision digital model of a dense urban area

Dense buildings are the major factor affecting urban flood routing. Currently, the study of urban dam-break flood routing primarily focuses on a simplified terrain model and 2D shallow water equations, which ignore the effects of dense urban buildings. Furthermore, the complex interactions between the dam-break wave and the wall surfaces of buildings are not reflected in the results. To tackle these problems, three-dimensional flood routing with a high-precision digital model of an urban area is studied in this paper. Firstly, the vector data of various land types is extracted from a remote sensing image, and the NURBS algorithm based on the TIN algorithm is introduced to construct a three-dimensional terrain model. Coupled with the vector data and the terrain model, a three-dimensional digital model of the urban area is established. Next, a three-dimensional \(k{-}\varepsilon\) turbulence model is proposed for the flood routing simulation. A polyhedral grid with a second-order accuracy and a discrete format is used to divide the digital model of the urban area, and the governing equations are solved using the PISO algorithm. Finally, the superiority of the 3D mathematical model and the computational efficiency of the polyhedral mesh model are validated according to the urban flood routing experiments of Testa and Soares-Frazao. An urban reservoir, located in SZ City, China, is modelled to show that a dam-break flood in an urban area exhibits significant three-dimensional characteristics. Moreover, due to the surrounding buildings, the flood exhibits complex three-dimensional turbulence phenomena, including collision, reflection and vortices.

PLANE MATCHING WITH OBJECT-SPACE SEARCHING USING INDEPENDENTLY RECTIFIED IMAGES

Abstract. In recent years, the social situation in cities has changed significantly such as redevelopment due to the massive earthquake and large-scale urban development. For example, numerical simulations can be used to study this phenomenon. Such simulations require the construction of high-definition three-dimensional city models that accurately reflect the real world. Progress in sensor technology allows us to easily obtain multi-view images. However, the existing multi-image matching techniques are inadequate. In this paper, we propose a new technique for multi-image matching. Since the existing method of feature searching is complicated, we have developed a rectification method that can be processed independently for each image does not depend on the stereo-pair. The object-space searching method that produces mismatches due to the occlusion or distortion of wall textures on images is the focus of our study. Our proposed technique can also match the building wall surface. The proposed technique has several advantages, and its usefulness is clarified through an experiment using actual images.

Research on Method of Building Energy Conservation Based on Infrared Imaging Measurement

With the deepening of the energy conservation of the building, energy saving from the original design of building energy-saving gradually turned to the field detection and completion acceptance, which requires a corresponding energy-efficient means of detection. With the development of infrared technology, the combination of infrared technology and detection methods of building energy-saving, to further promote the development of building energy efficiency testing work. Compared to the traditional heat flow meter or hot-box method, infrared thermal imaging method has no effect on the measured object, detecting the surface temperature of quick reaction speed, accompanying with wide temperature range and high precision, is widely used in various fields of testing work, which has been particularly prominent in the thermal defect detection. In this paper, the method of infrared thermography is used to confirm whether the thermal defects exist in energy-saving construction or not. Testing results show that infrared thermography can accurately reflect the temperature distribution of building wall surface. Infrared thermal imaging to detect the building surface's energy efficiency, which is providing efficient and accurate means of detection for the evaluation of the building energy efficiency. This is to help carry out a comprehensive building energy-saving testing.

Experimental and numerical studies on convective heat transfer from various urban canopy configurations

This paper investigates the Convective Heat Transfer Coefficient (CHTC) variation of urban canopy surfaces for different urban canopy configurations by experimental and numerical simulation. The Weather Research Forecasting (WRF) model coupled with the Urban Canopy Model (UCM) is considered as an effective tool for prediction of urban heat island phenomena in urban areas. In the Single layer UCM of WRF, the CHTC of urban canopy surfaces and its dependence on urban parameters such as building coverage ratio and building height variations are not explicitly modeled. In UCM, the CHTC of urban canopy surfaces are evaluated from Jürges relation. In this relation, the local CHTC from building walls and the ground depends only on the wind velocity inside the canopy. However, this cannot be justified since other urban parameters like building coverage ratio and building height variation also contribute to the CHTC of urban canopy surfaces. Moreover, Jürges relation cannot distinguish the difference between CHTC of different building wall surfaces, i.e., windward, leeward and side walls, but expresses the CHTC for walls generally. In our study, wind tunnel experiments were firstly conducted to roughly grasp the dependence of urban parameters on bulk heat transfer from an urban canopy in a thermally stratified wind tunnel. However, it is not an easy task in wind tunnel experiments to evaluate local CHTC, which vary for individual canyon surfaces such as building roofs, walls and the ground. Numerical simulation validated by wind tunnel experiments can be an alternative for prediction of CHTC from building surfaces in an urban area. The authors conducted CFD simulation with a low-Reynolds number model to evaluate the CHTC from canopy surfaces. The calculated CFD results for velocity and temperature profile and bulk heat transfer from an urban canopy showed good agreement with experimental results. After this validation, the effects of urban canopy parameters on local convective heat transfer on individual surfaces were investigated by CFD simulation. Based on these results, the CHTC will be modified with respect to urban parameters, and will be incorporated into the UCM of the WRF model in our future study.

Thermal Effect on Pollutant Dispersion in an Urban Street Canyon

This investigation was carried out to reveal the impact of solar radiation on wind flow structure and pollutant dispersion in an urban street canyon of aspect ratio of one using the computational fluid dynamic (CFD) technique. The simulation results (velocity and concentration data) show that heating from building wall surfaces and ground lead to strong buoyancy forces as the air is heated by the wall surface when receiving direct solar radiation. This thermally induced buoyancy plays a significant role in determining flow fields within street canyon. When the sun shines on the leeward side of the building and the ground, the airflow structure and pollutant dispersion patterns are similar to that without solar radiation, the buoyancy flux adds to the upward advection flux along the wall strengthening the original vortex. When the windward wall is warmer than the air, an upward buoyancy flux opposes the downward advection flux along the wall, and divides the flow structure into two counter-rotating vortices indicating a clockwise top vortex and a reverse lower vortex within the canyon. Further, the impact of various temperature differences on the windward heating and different velocities for inlet velocity has been examined. The relative influence of the thermal effect can be estimated by bulk Richardson number (R b ).

Impact of non-uniform urban surface temperature on pollution dispersion in urban areas

Airflow pattern through street canyons has been widely studied to understand the nature of pollution dispersion in order to develop guidelines for urban planners. One of the major contributing parameters in pollution dispersion is thermal-induced flow caused by surface and air temperature difference. However, most of the previous studies assumed isothermal condition for street canyons. Those addressed the thermal-induced flow, have assumed a uniform wall surface temperature distribution. The external building wall surface temperature distribution is not uniform, and is influenced by many factors including the wall surface characteristics, and shading. The non-uniform temperature distribution significantly impacts on 3-dimensional airflow within street canyons. Moreover, effect of intersection is barely considered in the literature where L/H<3 (L and H are respectively length and height of street canyon). This Paper reports the development of a 3-dimensional model to study the effect of non-uniform wall surface temperature distribution on the pollution dispersion and flow pattern within the short street canyons (L/H<3). For this purpose, a computational fluid dynamics (CFD) model is developed to investigate these effects on pollution dispersion in various prevailing wind velocities and directions. Moreover, active and passive techniques to reduce the level of concentration are examined. The study clearly shows that thermal-induced flow dominates during fair-weather condition.

Rule-based Mamdani-type fuzzy modelling of thermal performance of multi-layer precast concrete panels used in residential buildings in Turkey

Heat insulation applied on outer wall surfaces of buildings for the purpose of conserving energy, can be analyzed experimentally, mathematically and by using simulation modelling. In this study, simulation modelling of insulation layer (d2), for residential buildings in 81 cities classified into four climatic regions in Turkey was investigated. This stimulus model is constructed into rule-based Mamdani-type fuzzy modelling (RBMTF), using input parameters (Uw,Te) and output parameter d2, described by RBMTF if-then rules. RBMTF has been designed using the MATLAB 7.04 fuzzy logic toolbox. The d2 was predicted using two input parameters: Uw and Te. The values for Uw ranged from 0.4 to 0.7. The values for Te ranged from −43°C to −3°C. The values for d2 ranged from 0.07 to 0.21. Seven linguistic terms were considered for each of the input and output variables, namely Very Low (L1), Low (L2), Negative Medium (L3), Medium (L4), Positive Medium (L5), High (L6), Very High (L7). R2 for the testing data were about 97.4%. Overall, RBMTF can be used as a reliable modelling method for thermal performance of multi-layer precast concrete panels used in residential buildings’ studies.

Characterizing urban surface cover and structure with airborne lidar technology

Urban and landscape planners are becoming increasingly aware of the potential of light detection and ranging (lidar) technology to produce height and structural information over large geographic areas in both an economic and time-efficient fashion. In urban environments where the structural complexity is high, for example, lidar is seen as a critical and innovative dataset to improve the characterization of both vegetation and building attributes. Using a small-footprint, first- and last-return lidar dataset of Vancouver, Canada, we demonstrate the potential to derive a suite of attributes important for describing the interactions of the urban surface and atmosphere in weather forecasting, air pollution, and urban dispersion modelling. Two levels of attributes were defined. First, primary attributes such as building shape, size, and location and tree classification were calculated. Building extent and size were computed using an object-based approach based on connectivity and height rules. The classification of tree crown areas was derived from the location of last-return data, filtered to remove the incidence of last returns caused by the interaction of the lidar beam with building edges, and height rules. Validation showed that building areas derived from lidar compared well with aerial photography estimates (r2 = 0.96, p < 0.001, n = 98). The percentage difference between estimates was equal to 16% (n = 83) when buildings were discriminated from the surrounding features. However, the percentage difference between estimates increased to 35% (n = 98) when commission errors were considered, as lidar often overestimated building areas due to closely spaced buildings (gaps less than 1–2 m) not being separated. Similarly, the height and area of lidar-extracted trees were highly correlated with field-based measurements (r2 = 0.84 and 0.76, respectively, p < 0.001, n = 50). Once these primary attributes were derived, we demonstrate the extraction of a number of secondary attributes including building mean height, normalized building volume, building wall surface area, and interelement spacing. Of significance, this research has shown that lidar can provide spatially detailed estimates of urban structure and cover which characterize the aerodynamic and energetic properties of urban areas.

Frequency selective surfaces on building materials – air gap impact

It is demonstrated how frequency selective surfaces (FSSs) can be deployed on conventional building materials, so as the FSS frequency response is not affected by the building material. This effectively means that the two surfaces, the FSS and the building wall surface, will affect radio propagation independently based on their own characteristics. When FSSs are attached to building walls, they can suffer significant detuning, compared to free-standing frequency response, which appears to fade away as the air gap between the two surfaces increases. Simulations and anechoic chamber measurements demonstrate that a 'break-point' air gap exists, beyond which the FSS response is not affected by the presence of the building wall.

Improvement of building wall surface temperature measurements by infrared thermography

By using quantitative thermal scanning of building surface structures, it is possible to access the temperature field. For further calculation of the heat flux exchanged by these structures with the environment, one must quantify as finely as possible the temperature field on the bodies surfaces. For this purpose we have to take into account that real bodies are not black, which implies that a part of the ambient radiation received by the infrared camera detectors is reflected radiation. In this paper, we present a method to quantify the reflected flux by using an infrared mirror, which allows large surface temperature measurements by infrared thermography under near-ambient conditions with improved accuracy. In order to validate the method, an experimental study was carried out on a multi-layer wall, which simulated an insulation default. A good agreement was noticed between the thermocouple temperatures and the infrared corrected ones. Then, the method is applied to outdoor measurements.

Thermal effects on vehicle emission dispersion in an urban street canyon

The impact of the thermal effects on vehicle emission dispersion within street canyons is examined. The results show that heating from building wall surfaces and horizontal surfaces lead to strong buoyancy forces close to surfaces receiving direct solar radiation. This thermally induced flow is combined with mechanically induced flows formed in the canyon where there is no solar heating, and affects the transport of pollutants from the canyon to the layer aloft. The relative influence of each of these effects can be estimates by Gr/ Re 2. When the windward wall is warmer than the air, an upward buoyancy flux opposes the downward advection flux along the wall; if Gr/ Re 2 > 2, the flow structure is divided into two counter-rotating cells, and pollutants are accumulated on the windward side of the canyon. When the horizontal surface is heated, and Gr/ Re 2 > 4, the flow structure is divided into two counter-rotating cells by upward buoyancy flux. Pollutants are accumulated at the windward side of the canyon. When the leeward side is heated, the buoyancy flux adds to the upward advection flux along the wall strengthening the original vortex and pollutant effects of transport compared to the isothermal case.