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K e y w o r d s : Architectural design; Airflow around Buildings; Air Stagnation; Bioclimatic Architecture; Environmental Wind Engineering; Urban climate; Wind Comfort. 4/2019 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 51 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T The Si les ian Univers i ty of Technology No. 4/2019 d o i : 1 0 . 2 1 3 0 7 / A C E E 2 0 1 9 0 5 1 K . Z i e l o n k o J u n g The following paper concerns the possibility of including the above mentioned issues in the process of urban and architectural design in case of designing medium-high urban building developments, on the example of a particular project. In accordance with the current legal situation in Poland, aerodynamic analyses are required only for high-rise building projects, as well as for building developments located in aeration corridors. The paper is aimed to test the validity of the application of aerodynamic tests also while designing dense urban development units. Moreover, it concerns the possibility of introduction of such tests in the concept phase of a project, when basic decisions regarding the shape of buildings and their arrangement are made. Design methods based on the factual data concerning common practices and legal conditions in Poland have been juxtaposed to research methods in the field of aerodynamics. The subject of the research concerns a conceptual design of a building development that is intended to fill the urban quarter at the junction of Street Woronicza and Aleja Niepodległości (Independence Avenue) in Warsaw. In the process of forming buildings, experimental studies in wind tunnel, using oil visualization method have been applied. The method allows for a relatively prompt qualitative identification of the airflow around the building on the pedestrian level (the studies were conducted at the Department of Aerodynamics, Faculty of Power and Aeronautical Engineering, Warsaw University of Technology). 2. THE ISSUE ASSUMED AGAINST THE BACKGROUND OF THE PRESENT RESEARCH CONDITION Research in the field of environmental wind engineering has been intensively developed since the second half of the 20th century. Such studies belong with the field of physics known as fluid dynamics (FD). It is believed that a research which led to a breakthrough in connecting environmental wind engineering directly to architecture was the study by Gandemer, who, in 1975, identified and described the twelve so-called aerodynamic effects created around detached buildings and buildings arranged in the form of simple systems [5]. This study provided the basis for creating design guidelines for architects and urban planners. Gandemer applied tunnel experiments, which were then developed at the turn of the 80s and 90s by subsequent researchers (Hussain and Lee, Brown and DeKay, and, especially, Oke). The experiments helped to understand the nature of wind phenomena in a three-dimensional system and were acknowledged as an important element of the pro-ecological approach to design in the 1990’s [6]. The importance of phenomena occurring in arrangements known as street canyons, namely the spaces between two parallel lengthened buildings, the typical street layouts in cities, has been emphasised in the experiments. Simultaneously, studies on numerical methods of wind simulation (computational fluid dynamics CFD) were being developed [7].The first achievements concerning space ventilation between buildings in the area of CFD include there search in 1993 by Walker, Shao and Willscoroft. This research method continues to be explored till the present day [8], especially in the scope of the connection between building development geometry and the airflow around it. Especially complex systems corresponding to the actual geometric characteristics of cities pose a great challenge [2, 9]. Despite the significant development in research methods, also numerical ones, with certain exceptions, aerodynamic research still fails to be included in spatial planning processes, whereas the level of knowledge displayed by architects and urban planners on this subject is insignificant. The issues raised in the present paper concern wind conditions that occur between buildings and create wind comfort for pedestrians (it was assumed to appear at 1.5 m above the ground). The presence of the comfort requires protection against both, violent gusts of wind and against wind turbulence (the phenomena occur at building edges or in building narrowing). Moreover, it is crucial to prevent air stagnation from occurring. The latter leads to an insufficient ventilation in the spaces between buildings, overheating in the summer, the retention of unpleasant odours and air pollution. From the research quoted by, among other researchers, Daniels [6], it stems that in the wind direction perpendicular to the street axis, uninterrupted ventilation in street space occurs when the parameter h/w (“h” is the height of buildings and “w” is the distance between them) is less than 0.37. As the value of the parameter is increased, the air ventilation gradually reduces, whereas above the h/w value equal to 0.74, the air exchange stops completely. Similar data is also provided in publications by further authors (namely, Oke, Harmana, Okamoto, Castro and Robins). Observing the implementations of contemporary development housing estates, as well as the buildings that fill of the existing downtown development of large Polish cities, it is easy to identify buildings with geometry posing such a risk [4]. 52 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 4/2019 ANALYSIS OF WIND CONDITIONS AROUND A BUILDING DEVELOPMENT AS A PART OF ITS FORM DESIGNING PROCESS, A CASE STUDY A R C H I T E C T U R E 4 /2019 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 53 a In the present paper, attempt is made to verify, using a particular example, whether by means of designing buildings to fill of an urban quarter in accordance with the principles commonly applied in development investments in Poland, a risk of uncomfortable aerodynamic phenomena arises and whether such risks can be counteracted by introducing proper improvements in the shape of buildings. 3. RESEARCH ASSUMPTIONS First, a building structure concept was created for the building development that was intended to fill the selected plot. The function assumed for the building was of residential and service nature. During the research, the plot was not subject to the local development scheme, which would provide design guidelines. Thus, the form of the building was shaped according to the following criteria: • maximum use of the spatial potential of the plot so as to get as much useable space as possible in the designed building (it was the initial criterion, analogically to what is most often the case in the practice of development investments), • obtaining the required conditions for the location of the building, • creating a harmonious spatial composition with neighbouring buildings. Once the urban conditions had been analysed, a comb-shaped building was formed (Figure 1). In such a way, courtyards were formed that open towards the south, thus provided with good access of light. The presence of courtyards offers a possibility to develop a continuity with the existing green areas and introduce such areas into the interior of the projected building development quarter. Moreover, such a shape of the designed building makes it possible to provide a good lighting of rooms in it. Bearing in mind the existing residential building situated to the west (38 m high), the designed building development has been moved away from the plot border by a distance of over 7 m. A distance of about 30 m between the buildings was obtained in this way. This allowed to maintain the current conditions of insolation for the existing building. A varied height of the building was assumed (36, 28 and 20 m in order to harmonize it better with the heights of neighbouring buildings) and two wide gates were introduced (for the sake of a better communication between the street and the courtyards) As a result, an initial concept for the building development shape was created. In the form a layout that covers also neighbouring buildings, the structure was subjected to tests in the wind tunnel. The research resulted in a general diagnosis of wind conditions and in identification of problem areas. On the basis of the test, the shape of the designed building development was adjusted and subjected again to experimental research in the tunnel. The research resulted in the decision to introduce another modification to the shape of the building. The resulting version of the Figure 1. Situational plan (on the left) and axonometric view of the designed building (on the right), together with the surroundings. The designed building is marked in grey; author’s own study K . Z i e l o n k o J u n g project was considered final and thus it was evaluated. The scheme of the described action plan is shown in Fig. 2. Experimental studies in the aerodynamic tunnel of medium-speed were used. The oil visualization method was selected [4, 10, 11, 12], as it provides qualitative results. The picture presenting the results, although it fails to provide reference to numerical values, makes it possible to identify the nature of wind conditions prevailing at the pedestrian level, which is an important zone, due to the presence of both, too violent gusts of wind and air stagnation. It is therefore an adequate method for the initial phases of the project. At the same time, the method is relatively simple and not that time-consuming, as compared to other experimental methods. The research was conducted in a tunnel of 1 mx 1m measuring space cross-section. The model of the designed building with the surrounding building developments, made on 1:500 scale, was attached to the base, made of black