Research Article  Open Access
FuBin Chen, XiaoLu Wang, Yun Zhao, YuanBo Li, QiuSheng Li, Ping Xiang, Yi Li, "Study of Wind Loads and Wind Speed Amplifications on HighRise Building with Opening by Numerical Simulation and Wind Tunnel Test", Advances in Civil Engineering, vol. 2020, Article ID 8850688, 24 pages, 2020. https://doi.org/10.1155/2020/8850688
Study of Wind Loads and Wind Speed Amplifications on HighRise Building with Opening by Numerical Simulation and Wind Tunnel Test
Abstract
Highrise buildings are very sensitive to wind excitations, and windinduced responses have always been the key factors for structural design. Facade openings have often been used as aerodynamic measures for windresistant design of highrise buildings to meet the requirement of structural safety and comfort. Obvious wind speed amplifications can also be observed inside the openings. Therefore, implementing wind turbines in the openings is of great importance for the utilization of abundant wind energy resources in highrise buildings and the development of green buildings. Based on numerical simulation and wind tunnel testing, the wind loads and wind speed amplifications on highrise buildings with openings are investigated in detail. The threedimensional numerical simulation for wind effects on highrise building with openings was firstly carried out on FLUENT 15.0 platform by SST model. The mean wind pressure coefficients and the wind flow characteristics were obtained. The wind speed amplifications at the opening were analyzed, and the distribution law of wind speed in the openings is presented. Meanwhile, a series of wind tunnel tests were conducted to assess the mean and fluctuating wind pressure coefficients in highrise building models with various opening rates. The variation of wind pressure distribution at typical measuring layers with wind direction was analyzed. Finally, the wind speed amplifications in the openings were studied and verified by the numerical simulation results.
1. Introduction
With the development of science and technology, new materials with light weight and high strength have been emerged. This promotes to the highrise buildings in the trend of light weight, high flexibility, and low damping. Highrise buildings are sensitive to wind excitations. Wind loads are the key factor for structural design of highrise buildings [1–4]. For super highrise buildings, the windinduced responses caused by acrosswind vibration will exceed those caused by alongwind force [5]. How to reduce wind effects on highrise buildings has always been the hot issue in wind engineering [6–11].
In recent years, openings have been adopted for wind loads reduction of highrise buildings [12–14]. Li et al. investigated wind load characteristics of highrise buildings with opening. Bearman believed that the opening directly directed the airflow to the side and back areas of the structure, which could break the regular vortex shedding system closely related to the acrosswind response [15]. Kikitsu and Okada showed that openings could reduce the structural dynamic response of highrise buildings [16]. Dutton and Isyumov conducted a wind tunnel testing on a tall building with a 9:1 aspect ratio of the square cross section and pointed out that openings can be effective in reducing the acrosswind excitation of tall buildings [17]. Okada and Kong carried out aeroelastic tests on square buildings with three opening modes and concluded that opening rate of 1.5% can reduce the dynamic displacement of the acrosswind direction by 20%–25% [18]. Zhang et al. indicated that the primary factor for the reduction of overall wind load on building models was the decrease of surface area due to opening [19]. Hu et al. pointed out that openings reduced the windinduced response significantly in the acrosswind direction [20]. With the increasing concerns on energy crisis, openings in the highrise buildings are getting more attraction for wind power generation. Li et al. pointed out that the openings could result in wind speed amplifications to some extent and would be of benefit for wind turbine installation for the purpose of wind energy utilization [21, 22]. Besides the reduction of aerodynamic forces, researchers began to focus on the flow characteristics around the highrise building with opening. Hassanli et al. investigated mean flow characteristics and the flow structure inside openings with five different layout configurations for wind energy harvesting [23]. Based on numerical simulation, Wang et al. analyzed the surface pressure contour and wind pressure coefficients of highrise building with openings [24].
Both numerical simulation and wind tunnel testing are adopted in this study to evaluate the effects of opening on highrise building. The mean wind pressure coefficients and the wind flow characteristics are discussed. The distribution law of wind speed in the openings is presented. Moreover, the wind speed amplifications at the opening are analyzed and comparatively studied. This study aims to provide useful information for windresistant design and wind energy utilization of highrise building with openings.
2. Numerical Simulation
In order to investigate the wind effect of highrise building with openings, four rectangular models (B × D × H = 120 mm × 120 mm × 600 mm) were established in the numerical simulation software FLUENT 15.0, which are, respectively, named as L1 (fully enclosed), L2 (large openings in xdirection), L3 (large openings in both x and ydirections), and S1 (small openings in both x and ydirections). The opening heights are set at 0.51 H and 0.85 H, respectively, as shown in Figure 1.
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The computational domain was set as 7920 mm × 2040 mm × 1800 mm, as shown in Figure 2. In the height of the 0.51 H and 0.85 H of the L3 model, a total of 21 monitoring points, which were recorded as a_{1}–a_{11} and b_{1}–b_{11}, were used for wind speed monitoring, as shown in Figure 3. Monitoring points a_{1}–a_{11} are set in the xdirection openings, while monitoring points b_{1}–b_{11} are set in the ydirection openings. The wind direction was also defined in Figure 3.
2.1. Mean Wind Pressure Coefficients
Figure 4 illustrates the mean wind pressure coefficients of L1, L2, and L3 models under wind direction of 0°, respectively. It can be found that the mean wind pressure coefficients of the windward face are positive, and the fully enclosed model L1 reaches the maximum value 0.95 in the upper part of the building. After the openings are set, the local mean wind pressure coefficients increase at the top of the upper opening but decrease below the upper opening. The mean wind pressure coefficients are reduced near the lower opening. The other mean wind pressure coefficients away from the openings are almost unchanged.
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The mean wind pressure coefficients on the side faces are negative and change little along the elevation. Compared with the L1 model, the mean wind pressure coefficients on side faces of L2 model are reduced. As for the L3 model, the mean wind pressure coefficients decrease further, and the flow fields near the openings change. The wind pressure distribution at the inner openings changes.
The mean wind pressure coefficients on the leeward faces are also negative. For L1 model, the mean wind pressure coefficients at the bottom are the smallest and increase gently with elevation. After the openings are set, the negative pressures on the leeward tend to decrease as a whole. The mean wind pressure coefficients increase in circumferential direction far from the openings, and the maximum value of negative pressure appears near the openings.
Figures 5 and 6 show the mean wind pressure distribution in the openings of L2 model and L3 model, respectively. For L2 model, large negative pressures are generated at the leading edge of the openings. The absolute value of the negative pressure decreases along the incoming flow direction. The mean wind pressure coefficients in the trailing edge of the upper opening are uniformly maintained at about −0.5 while those of the lower opening are maintained at around −0.45. As for the L3 model, the absolute value of the negative pressures on the inner wall of the xdirection opening is significantly increased, indicating that the wind speed in the opening is further accelerated.
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2.2. Wind Flow Characteristics
2.2.1. Flow Field at the Same Elevation
The flow separation, vortex shedding phenomenon on the side face, and wake flow downstream the leeward can be visible in the numerical simulation. The mean velocity contour distributions with streamlines at height of 0.85 H for L1 model, L2 model, and L3 model under wind direction of 0° are, respectively, presented in Figure 7. For L1 model, flow separations are obviously found on the side faces, and regular largescale vortexes are observed downstream the leeward. For L2 model, the incoming flow is accelerated through the opening and disturbs the regular vortexes downstream leeward. New smallscale vortexes are formed near the opening. Moreover, the wind speeds along the side faces are decreased. When the openings are set at both xdirection and ydirection for L3 model, except for the complex flow characteristics emerged at ydirection openings, the regular vortexes downstream leeward are also disturbed. The sizes of vortexes on the side faces are decreased compared with L2 model.
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2.2.2. Flow Field at Different Elevations
Figure 8 shows the mean wind pressure contour distributions on windward and leeward faces at different elevations for L1 model, L2 model, and L3 model under wind direction of 0°, respectively. For L1 model, the wind flow strikes the windward and creates a stagnation point at about 2/3 height of model. The maximum positive pressure is emerged near the stagnation point. After the openings are set, the flow at the opening position is introduced into the leeward face, and the positive pressure near the opening is decreased. The single vortex on the top from the leeward is shattered and reduced to four different vortexes, which results in the phenomenon that the mean wind pressure coefficients on the leeward face decrease in circumferential direction away from the openings. The flow field characteristics of L3 model are consistent with those of L2 model on the windward and leeward. However, the absolute values of the negative pressure in the opening are significantly increased. The minimum negative pressure at the upper opening appears on the bottom of the leading edge of the opening, while the minimum negative pressure at the lower opening appears on the top of the leading edge of the opening. This phenomenon should be paid attention to by the structural designers.
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Figure 9 illustrates the mean wind pressure distributions on side faces at different elevations for L1 model, L2 model, and L3 model under wind direction of 0°, respectively. For L1 model, it can be found that the flow around side faces is mainly separated. The minimum negative pressure appears on the side faces. For L2 model, the area with a wind pressure coefficient of −0.7 at the top of the building is enlarged, while the area with a mean wind pressure coefficient of −0.65 and −0.6 near the upper and lower openings is reduced. By continuing to add the opening of the ydirection, it can be found that the area with a mean wind pressure coefficient of −0.7 at the upper opening and the area with a mean wind pressure coefficient of −0.6 at the lower opening are further reduced. There are two reasons for this phenomenon. On the one hand, the opening on the windward face reduces the flow energy of vorticities, resulting in the reduction of wind pressure on the side surface. On the other hand, the opening on the ydirection changes the flow field characteristics near the opening. The uniform vertical mixing component caused by the vortex on the original building surface and flow in the side opening strikes the upper side of the opening, which together cause a significant reduction in the negative pressure (absolute value) above the opening.
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2.3. Wind Speed Amplification Effect of Upper and Lower Openings
The relationship between wind energy and wind speed is defined as follows:where is the power of the wind, is the air density (kg/m^{3}), A is the swept area of rotor (m^{2}), and is the mean wind speed (m/s) of incoming flow. It can be observed that the wind energy is proportional to the cube of the wind speed. The wind speed ratio is introduced to describe the amplification effect of the mean wind speed in the opening:in which is the mean speed in the direction of the axis of the opening and is the reference wind speed of an approaching location away from the model at the same height.
The numerical simulation can obtain the wind speed ratio at any position. The reference wind speeds are 7.75 m/s at 0.85 H and 7.16 m/s at 0.51 H, respectively. The reference wind speeds in the large opening models keep the same as those in the small opening models.
Tables 1 and 2 present the wind speed ratios of a_{1}–a_{11} monitoring points of the L3 model and S1 model under the wind direction of 0°, respectively. For L3 model, all the wind speed ratios are larger than 1.0, indicating that all the wind speeds have been amplified in the opening. Moreover, the wind speed ratios firstly increase and then decrease along with the opening. The bold values in Tables 1 and 2 represent the maximum wind speed ratios for upper opening and lower opening, respectively. The maximum wind speed ratio occurs at a_{3} point. The variation of wind speed ratios along with the opening in the lower opening keeps the same as that in the upper opening. The wind speed ratios in the lower opening are larger than those in the upper opening, implying that the opening position is important for wind speed amplification. For S1 model, the wind speed ratios are larger than 1.0 from monitoring points a_{2} to a_{6}. The variation of wind speed ratios with the position of monitoring point keeps the same pattern with that in L3 model. The maximum wind speed ratio occurs at a_{2} point.
 
The bold values represent the maximum wind speed ratios for upper opening and lower opening, respectively. 
 
The bold values represent the maximum wind speed ratios for upper opening and lower opening, respectively. 
2.4. The Variation of Flow Field with Wind Direction
Tables 3 and 4 illustrate the variation of wind speed of monitoring points b_{1} and b_{11} on the L3 model with the wind direction, respectively. It can be seen that due to the influence of openings the wind velocities in the direction of parallel and vertical entrances at the side center point vary with the wind direction. For example, the wind speed in the ydirection of the b_{11} point is increased from the negative value (downward) with the increase of the wind direction. The separation bubble and the incoming flow separating the corners are directly introduced into the opening, and the airflow is introduced and discharged to change the original flow field. The streamlined diagram of wind speed from 0° to 45° shows the same pattern. The vortices of the side faces are clearly separated to form several smaller vortices, indicating that the frequency of vortex shedding is also reduced.


3. Wind Tunnel Test
According to the influence of surface distribution on wind, the surface roughness is divided into four different categories: A, B, C, and D [25]. The model and wind field simulated in the wind tunnel are shown in Figure 10. The mean wind velocity profile and turbulence intensity of the terrain B are simulated. This terrain type specifies a mean wind speed profile with a power law exponent of = 0.22. The wind tunnel geometric scale ratio is 1:300.
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The 1:300 scaled model corresponds to the actual structure dimension with length, width, and height of 36 m × 36 m × 180 m. The model has openings in four surfaces at the heights of 0.5 H and 0.85 H, and the openings run through the wall and are connected with each other. Two models with different opening rates were made: model M1 has a larger opening with a size of 12 m × 12 m; model M2 has a smaller opening with a size of 6 m × 6 m. The ratio of section area of single opening to the area of the facade is defined as opening rate. The opening rates of larger opening and smaller opening are 2.22% and 1.11%, respectively. In each model, there are 22 measurement layers and totally 512 measuring points, of which layers H, J, K, T, U, and V are 32 measuring points in each layer. The remaining 16 layers are the standard measuring layer, and each standard layer has 20 measuring points. Detailed descriptions of the model façade and measurement points are shown in Figures 11 and 12.
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The wind pressure coefficient in this study is expressed by the incoming wind pressure at the height of the building top (180 m) as the reference wind pressure. The expression is defined as follows:where is the wind pressure coefficient time history of a certain measurement point i on the model; is the wind pressure value of the singlesided measuring point i on the model; is the static pressure; is the mean wind speed at the reference height; and is air density and equals 1.25 kg/m^{3}.
After the time history of the wind pressure coefficient is recorded, the mean wind pressure coefficient and the standard deviation of the fluctuating wind pressure can be obtained by the following equations:where is the mean wind pressure coefficient of the pressure measuring point i, is the standard deviation of the fluctuating wind pressure, and N is the number of samples of the measuring point and equals 10,000 in the wind tunnel test.
3.1. Distribution Characteristics of Wind Pressure Coefficient on the Façade and Inner Wall of the Opening
In order to further discuss the wind pressure distribution, the inner wall of the opening is unfolded along the axis and named as A, B, C, and D faces, respectively, as shown in Figure 13. The mean wind pressure coefficient and fluctuating wind pressure coefficient distributions of different façades and different inner walls in the L1, L2, and L3 model wind direction of 0° are presented in Figures 14 and 15. After analysis, the following conclusions can be drawn:(1)The mean wind pressure coefficients on the windward surface of L1, L2, and L3 models are all positive. With the increase of height, the positive pressures increase and reach their maximum in the middle and upper altitude and then decrease owing to the threedimensional flow around the top of model. For L2 model with xdirection opening, the wind pressure coefficients change near the opening. The wind pressure coefficients near the upper and lower openings decrease slightly. For L3 model with both x and ydirection openings, the mean wind pressure distribution on the windward surface is almost the same as that in L2 model. The fluctuating wind pressure on the windward surface gradually increases along the height for L1 model. The overall variation of fluctuating wind pressure with opening is very small.(2)Due to the horseshoe vortex phenomenon, the mean wind pressure coefficients on the side faces tend to be uniform along the height for L1 model. The L3 model can change the flow field characteristics of the side faces on the basis of L2 and further reduce the mean and fluctuating wind pressure on the side faces. The fluctuating wind pressure coefficients of side faces change substantially uniformly along the height but gradually increase along the incoming flow direction. However, the fluctuating wind pressure coefficients are significantly reduced at the opening position.(3)For L1 model, the mean wind pressure coefficients on the leeward surface are negative. The wind pressure coefficients reach their maximum value at the bottom of model and increase in the circumferential direction. Once the opening is set, the mean and fluctuating wind pressure coefficients keep increasing from the inside to the outside along the circumferential direction. The fluctuating wind pressure coefficients on the leeward surface are obviously increased, which needs to be paid more attention to.(4)The mean and fluctuating wind pressure coefficients of inner wall AB and wall CD in both xdirection and ydirection are illustrated from Figures 16–19. It can be found that all the mean internal pressure coefficients of the opening wall are negative. The absolute value of the negative pressure coefficient at the front of the opening in xdirection is the largest and decreases rapidly along the flow approaching direction. The minimum negative pressure of the building appears at the front of the openings in the model of L3. The distribution law of the fluctuating wind pressure keeps the same as the law of the mean wind pressure distribution. The fluctuating wind pressure coefficients reach its maximum value at the leading edge of the opening but decrease rapidly along the flow approaching direction and then become steady. The distribution of fluctuating wind pressure coefficients on the wall CD in the ydirection is different. Due to the influence of accelerated flow in the opening, the maximum fluctuating wind pressure coefficient appears near the middle opening and its value can reach 0.44. The fluctuating wind pressure coefficients on the wall of D decreases gradually from inside to outside along the circumferential direction. The fluctuating wind pressure on the surface C decreases gradually along the height.
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3.2. Analysis of Wind Pressure Coefficients of Typical Measuring Layers
The mean wind pressure coefficients are quantitatively analyzed by taking the typical measurement layers of the large and small openings model. Among them, layer P is the measurement layer far from the openings, layer S is the measurement layer under the upper opening, and layer W is the measurement layer above the upper opening. Figure 20 presents the mean and fluctuating wind pressure coefficients of all measurement points in P, S, and W measurement layers near the upper opening of models L1, L2, and L3 at the wind direction of 0°.
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It can be found that the mean wind pressure coefficients of the windward surface measurement points increase after the openings are set. Compared with the S and W layers near the opening, the mean wind pressure coefficients on the windward surface of P layer increase slightly. The mean wind pressure coefficients in both side faces and leeward surfaces in L2 and L3 models are smaller than those in L1 model. Moreover, the mean and fluctuating wind pressure coefficients in L3 model are smaller than those in L2 model, indicating that the mean wind pressure coefficients decrease dramatically in the model L3 than in the model L2.
3.3. The Variation of Wind Pressure Distribution of Typical Measuring Layers with Wind Direction
The typical measuring layers S and T at the heights of 0.81 H and 0.825 H are selected as the research objects to investigate the variation of the wind pressure coefficients of the measuring points with wind direction. Figure 21 shows the variation of the mean and fluctuating wind pressure coefficients of the measuring layers S with the wind direction. In the direction of the incoming flow, the measuring points on each façade are divided into an upwind direction and a downwind direction. For example, at 0° wind direction, the measuring points of S1–S2 are at the upwind direction while the measuring points of S4–S5 are at the downwind direction. By analyzing Figure 21, the following conclusions can be obtained:(1)For the model L1, as the wind direction increases, the absolute value of the mean wind pressure for measuring points S1–S5 first increases and then decreases. The maximum negative pressure occurs near the wind direction of 10°. At the measurement points of the downwind direction, the absolute value of the mean wind pressure decreases as the wind direction increases. After openings are set in the model L3, the mean wind pressure values of the measuring points S1 and S5 are slightly reduced. Measuring points S2 and S3 on both sides of the opening are most affected. Compared with the fully enclosed L1 model, the absolute value of negative pressure and positive pressure decrease at the same wind direction. As for the influence of the opening on the fluctuating wind pressure, it can be observed that although the S1–S5 measuring points of the L1 model have some undulations, the fluctuating wind pressure generally increases and then decreases. The position of the maximum fluctuating wind pressure gradually moves from the downwind direction to the upwind direction as the wind direction increases, which also indicates that the position with the strongest turbulence action moves to upwind direction with the change of wind direction. After openings are set, it can be clearly seen that this variation has not been changed. The fluctuating wind pressure coefficients of all the measuring points are significantly reduced. The measuring points S1 and S5 at the edge are obviously reduced at the wind direction of 0°∼15°. The maximum reduction of S1 at the wind direction of 0° is up to 25%. The fluctuating wind pressure coefficients of the measurement points S2 and S3 are reduced at all wind directions. The maximum reduction and the occurrence angles were 27% for 30° and 16% for 0°, respectively.(2)For the L3 model, the measuring points S6–S10 are transferred from the leeward surface to the side surface as the wind direction increases. The absolute value of the negative pressure of the measured points increases with the increase of wind direction. After the openings are set, the absolute value of negative pressure decreases greatly. The maximum reduction of S6–S10 occurs at the wind direction of 0°, and the maximum reduction is 16%, 18%, 26%, 20%, and 21%, respectively. The fluctuating wind pressure gradually decreases with the increase of the wind direction; the variation remains unchanged after the openings are set. The fluctuating wind pressure decreases greatly under the same wind direction.(3)The measuring points of S11–S15 of the L1 model are transferred from the side surface to the leeward surface. As the wind direction increases, the absolute values of the negative pressures of the measuring points first decrease and then increase. After the openings are set, the regularity of the measured points on the side surface shows fluctuation, and the mutation occurred at the wind directions of 10° and 25°. The absolute value of the negative pressure is greatly reduced. The maximum reductions of S11–S15 are all emerged at the wind directions of 45°, which is 19%, 19%, 23%, 19%, and 22%, respectively. The fluctuating wind pressure in the L1 model decreases with the increasing of the wind direction. The variation remains unchanged after the openings are set. The amplitude decreases greatly within the wind direction range of 0°–15°.(4)In the fully enclosed model L1, the measuring points S16–S20 are transferred from the windward surface to the side surface as the wind direction increases. The positive pressure of the windward measuring point first increases and then decreases as the wind direction increases. The maximum positive pressure of the windward surface appears at the wind direction of 20° for the measuring point S19. The maximum positive pressure of the middle measuring point S18 appears at the wind direction of 5°. After the openings are set, the positive pressure increases at the wind direction of 0° of the measuring point in the upwind direction. The mean wind pressure coefficients are greatly reduced within the wind direction range of 0°–20° due to the influence of the openings. The fluctuating wind pressure of the measuring point of the L1 model keeps decreasing as the wind direction increases, except for the upwind direction edge measuring point S20. After the opening is set, the variation of the fluctuating wind pressure coefficients with the wind direction keeps the same as before. The fluctuating wind pressure coefficients of the upwind direction measuring point increase and are larger than those of the L1 model in many wind directions.
Figure 22 shows the variation of the mean and fluctuating wind pressure coefficients of the measuring layers T with the wind direction. Compared the results of the L1 model with those of the L3 model, it can be found that the windward surface of the measuring points T27T8 is transferred to the side surface with the increase of the wind direction. The side surface of the measuring point T1T10 is transferred to the leeward surface with the increase of wind direction. The variation of mean and fluctuating wind pressure coefficients with the wind direction is the same as that of layer S. The measuring points T19 and T26 are transferred from the side surface to the leeward surface as the wind direction increases. The mean negative pressures of measurement point T20 in downwind direction at some wind directions are greater than the maximum negative pressures at the side surface without openings. The measurement point T20 is in the downwind position and its fluctuating wind pressure increases obviously at the wind direction of 45°, which is 39% higher than that of L1 model. The measuring points T11 and T8 are transferred from the leeward surface to the side surface as the wind direction increases. T17 and T12 on both sides of the opening are affected by the opening. The absolute values of the mean wind pressure and the fluctuating wind pressure of T12 in the upwind direction within the wind direction range of 0°–20° after the opening are greatly increased when comparing to the unopened working condition. The mean negative pressures of T17 in the downwind direction at most wind directions are greater than negative pressures in the side surface of L1 model. After the wind direction increases to 10°, the fluctuating wind pressure of measurement point T17 in the downwind position is significantly increased. At the wind direction of 28°, it increases by 28% compared with the fully enclosed condition.
3.4. Wind Speed Amplification Effects in the Openings
The wind speed amplification effects in the openings are studied for model with openings in xdirection and the model with openings in both xdirection and ydirections. Figures 23 and 24 show the variation of the wind speed ratio with the wind direction of the model with large and small openings. For the L2 model with large openings, the wind speed ratio increases steadily with the increasing wind direction and reaches the maximum value between the wind direction range of 25°–35°, but then it decreases rapidly. The maximum wind speed ratio appears at an oblique angle with the incoming flow. This phenomenon is consistent with the conclusions of Li et al. [26] and Zhang et al. [27]. For the L3 model, the wind direction corresponding to the maximum value of wind speed ratio changes, all of which occur at the wind direction of 0°. The wind speed ratio keeps steady between wind directions of 0°–15°. However, it decreases rapidly after exceeding wind direction of 15°. Setting openings in both xdirection and ydirection can obtain a larger wind speed ratio than that obtained from the model of openings only in xdirection between the wind direction range of 0°–10°. The wind speed ratio can be increased by 8.3% when the maximum value appears at the wind direction of 0° in the model with large openings and by 9.2% when the maximum value appears at the wind direction of 0° in the model with small openings. This shows that at a wind direction of 0°–10°, setting openings in both xdirection and ydirection can obtain a larger wind speed ratio than that with openings only in xdirection. The model L2 can keep the wind speed ratio greater than 1.0 in the wind direction range of 0°–45°, while the model L3 can obtain a larger wind speed ratio than that obtained from model L2 in the range of 0°–10°. But the wind speed ratio decreases rapidly with the increase of wind direction. The wind speed ratio is less than 1.0 when wind direction exceeds 20°.
4. Conclusions
Based on numerical simulation and wind tunnel testing, this study investigated the wind loads and wind speed amplifications on highrise buildings with openings. The main conclusions are listed as follows:(1)The numerical simulation results of highrise buildings with opening are almost consistent with those of wind tunnel study, showing good verification with each other.(2)The wind pressure distribution on the highrise building surfaces is changed after openings are set. Although the mean wind pressure coefficients of the windward surface increase at local position, they are reduced overall. Setting openings in both xdirection and ydirection can further reduce the mean and the fluctuating wind pressure coefficients compared to only setting openings in xdirection. However, the inner walls of the openings are subjected to larger negative pressure in the xdirection.(3)For the large and small openings, the model L2 with openings only in xdirection can maintain the wind speed ratio greater than 1.0 in the wind direction range of 0°～45°. The model L3 can obtain a wind speed ratio of 8.3%～9.2% higher than that of model L2 in the wind direction range of 0°–10° of the wind direction, indicating that wind energy can be utilized more effectively in highrise buildings with opening in the xdirection.(4)When the openings are set in xdirection, the airflow on the windward surface is introduced into the leeward surface, changing the flow field characteristics of the position of the original opening and the leeward surface. The openings in the ydirection can further change the flow field distribution. Compared with the model L2, the vortex size in side surface is decreased and the peripheral wind speed is decreased.(5)Once the openings are set, the single vortex from the top of the leeward surface is scattered and reduced to four vortexes of different sizes. The model L3 produces a larger negative pressure in the opening compared to the model L2. The extreme wind pressure values in the opening of the model L2 appear on the bottom of the upper opening and the top of the lower opening respectively, indicating that the position of the opening has important influence on the wind load of highrise building.
Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.
Conflicts of Interest
The authors declare that they have no conflicts of interest regarding the publication of this paper.
Acknowledgments
This work was fully supported by the grants from the National Natural Science Foundation of China (project nos. 51778072, 51708207, and 51408062), a grant from Hunan Provincial Natural Science Foundation (project no. 2020JJ5176), and a grant from Hunan Provincial Education Department (project no. 18B206).
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