Investigation in Wind Tunnel Flow Interaction with Models of Two High-Rise Apartment Houses E.A

International Conference on Methods of Aerophysical Research, ICMAR 2008 INVESTIGATION IN WIND TUNNEL FLOW INTERACTION WITH MODELS OF TWO HIGH-RISE APARTMENT HOUSES E.A. Zikov1, A.V. Liabchuk1, A.D. Obukhovsky2, S.D. Salenko2, J.V. Telkova2 1Architect's office “Tectonics” LTD, 660018, Krasnoyarsk, Russia 2 Novosibirsk State Technical University, 630092, Novosibirsk, Russia During the design of buildings with height more than 75...100 m interaction the buildings with wind flow becomes the important factor. This factor determines safety of the upkeep of buildings and comfort of people situated inside and near the buildings [1, 5]. The purpose of the work is the wind-tunnel investigation of the flow around the two high-rise buildings under interference conditions, the determination of the total and distributed wind load acting on the building’s surface of housing estate, the investigation of influence of the high-rise buildings on the neighbouring buildings. The experiments were carried out in a wind tunnel T-503 at the industrial aerodynamics laboratory of NSTU. The department of aerohydrodynamics has many years experience of studies on the concerned research area [2, 3, 4]. In particular, the modeling technique of surface boundary layer in a wind tunnel was worked out by the staff of the department and damping devices for five bridge spans were developed. The high-rise buildings under consideration (Fig. 1) had a constant width of the facade Bb=32 м along the height and a variable width along the height at the side view. Height of the buildings was 104.7 m (above a ground apparatus floor); width of the maximum section was 22×32 m. Fig. 1. Overall view of the high-rise buildings models and experimental assembly © E.A. Zikov, A.V. Liabchuk, A.D. Obukhovsky, S.D. Salenko, J.V. Telkova Section 1 The models of the high-rise buildings were made from a plastic on 3D-printer according to given CAD-geometry. Accepted scale (1:250) and the application of 3D-printer technology promoted to reconstruct on the dummy a complex structure of the high-rise buildings surface including balconies, recessed balconies, jogs and other elements, important for shaping of flow. Lay of land, buildings and forest-plantations surrounded the high-rise complex were reproduced on the dummy. For simulation of the atmosphere boundary layer a grate with varied array spacing along a height was installed at the nozzle of wind tunnel. During the work a flow around the high-rise buildings was visualized by smoke stream technique, smoking wire method and wool-tuft technique using all-round blowing of the dummy. In this case a form of streamlines, characteristics of separated shear-layer areas and vortex flows were investigated. In ruling southwestern and opposite northeast wind directions one of the buildings is completely located in the wake of another (Fig. 2). In this case between the buildings throughout entire height is formed the stagnation zone with the intensive mixing inside the zone (Fig. 2b, Fig. 3) and the weak exchange with the external flow. This fact must be considered at design regimes of the work of the ventilation and conditioning systems of buildings. In the southeastern (Fig.4) and northwestern wind directions is observed the strong constriction of flow stream between the high-rise buildings, which causes an increase in the rate of flow and dynamic pressure. The growth of the latter can lead to the increased aerodynamic loadings on the attached facade systems of buildings in the sections of the minimum distance between the high-rises. In the wind of north (Fig. 5) and close to it directions high-rise buildings flow around, practically as unified whole, forming after themselves wide wake. In this case lower part of buildings and pedestrian zones fall into the wake, which appears with the flow around located above along the flow of city block construction. This must lead to decrease average wind speed and increase pulsating component in these zones. In the southern and close to it wind directions area relief renders essential influence to the nature of flow. The wind velocity profile above the relatively smooth aqueous surface becomes more filled, then with the flow upward along the slope of the bank of river occurs the compression of stream filaments and, therefore, should be expected increase in the speed in the lower part of the building and in the pedestrian zones. In this case, on the contrary, many buildings of city block fall into the aerodynamic shadow of high-rises. At streamlining of buildings (especially in the wind directions the approximately perpendicular to any wall) the extensive tear-off zone appears above the roofing (Fig. 6), in diagonal wind directions the pair of the vortices of counterrotation is formed above the roofing. These phenomena can present danger to the takeoff and landing maneuvers of helicopters. Flow pattern in the pedestrian zones has very complex nature. It is possible to mark the stagnation zones (Fig. 3), the sections of direct and reverse flows, vortex and screw flows. Into flow in the pedestrian zones has a strong effect the contraction of stream filaments with the air flow between the high-rises (Fig. 4), the horseshoe vortices in the lower part of the buildings, downflows along the windward walls (Fig. 7). The knowledge of flow structure in the environment of the buildings in different wind directions will make it possible to more deliberately solve the problems of the calculation of the local stiffenings of wind loads with the design of attached facade systems, ventilation of buildings, guarantee of safe operation of helicopter areas, comfort in the pedestrian zones. International Conference on Methods of Aerophysical Research, ICMAR 2008 a) b) Fig. 2. Flow visualization around the high-rise buildings in the southwestern wind direction a) b) Fig. 3. Flow visualization around the high-rise buildings in the southwestern wind direction Fig. 4. Flow visualization in Fig. 5. Flow visualization in the southeastern wind direction under northern wind direction Section 1 a) b) Fig. 6. Flow visualization above the roofing of buildings in horizontal (a) and vertical (b) arrangement of the smoking wire a) b) Fig. 7. Flow visualization in the lower part of the buildings in northern (a) and northwestern (b) wind direction. As is known, regular eddy formation from the bluff body surface can lead to appearance of one of the forms of the aeroelastic oscillations of construction - wind resonance. It occurs when the frequency of trailing vortexes it coincides with one of the natural frequencies of the construction. In this case the intensive oscillations of construction across the flow appear. Trailing vortex from the surface of the bluff bodies is characterized by Strouhal number: Sh=fB/V, where f - the frequency of trailing vortexes, V - velocity of incident flow, B - width of the matter across the flow. For determining characteristic Strouhal numbers the measurements of the stream-velocity fluctuations in the environment of buildings with the circular scavengings were made. The pulsations of speed were measured with the aid of the double hot-wire anemometer of the fixed resistance, whose the sensor was established usually on the 0.75 of buildings height. The results of studies showed that independent of wind direction in the environment of the pair of buildings the frequency spectrum of the pulsations was washed away (Fig. 8c), that it does not make it possible to clearly mark one prevailing frequency and number Sh corresponding to it. It is known that after the single cylindrical body, located perpendicularly to the direction of the steady flow, is formed the Karman vortex street, and in the spectrum the clear peak of the frequency of trailing vortexes is observed. However, many factors influence the spectrum of the frequencies of two high-rise buildings being investigated: the exponential low of the distribution of vertical speed, the increased flow turbulence, the underlying surface, surrounding urban building, the variable the buildings section width at the height, and also the interference of two closely spaced buildings. Therefore for the development of the major factors, which lead to “erosion” of frequency spectrum, it was decided to conduct the number of additional studies with the similar prismatic body. Measurements were conducted on the screen in the flow without the grate and after the grate. Thus, the influence all of factors enumerated above consecutively was excluded. Experiments were International Conference on Methods of Aerophysical Research, ICMAR 2008 conducted at Reynolds numbers Re = 0.5·105 – 1.4·105. It was established that in the flow after the single prism in the uniform flow is observed the clear peak of frequency corresponding to Strouhal numbers Sh = 0..09, when prism was established across the flow and Sh = 0.15, when prism was established along the flow. These results will agree rather well with literature data, given for the prisms of small lengthening and similar cross section. Analogous results are obtained also for the single high-rise building, which has in comparison with the prismatic body the section variable on the height (Fig. 8b). For determining the influence of the distribution of the flow parameters, typical for the atmospheric boundary layer, prismatic body was investigated in the flow above the screen after the irregular grate with Reynolds numbers Re = 0,4·105 – 1,1·105. Results showed that in the frequency spectrum also was present the clearly expressed peak, which corresponds to Strouhal numbers Sh = 0.11, when prism was established across the flow and Sh = 0,13, when prism was established lengthwise. Model of one of the high-rise buildings, which has section variable on the height in comparison with the prismatic body, was investigated at the same conditions.

Load more