下?lián)舯┝鞯娘L(fēng)場特性以及其作用下高層建筑風(fēng)荷載研究
發(fā)布時間：2018-11-21 13:05
【摘要】：隨著全球氣候變暖,以下?lián)舯┝鞯葹榇淼膹?qiáng)對流天氣逐漸增多,使得對其的研究成為目前國際風(fēng)工程領(lǐng)域的熱點(diǎn)問題之一。下?lián)舯┝魇怯衫妆┨鞖庵行纬傻膹?qiáng)下沉氣流沖擊地面后,在地面加速擴(kuò)展開的一種氣流過程,由于下?lián)舯┝黠L(fēng)剖面與大氣邊界層風(fēng)剖面差異巨大,并且在距離地面很低處會產(chǎn)生強(qiáng)風(fēng)荷載,往往會導(dǎo)致結(jié)構(gòu)破壞。我國荷載規(guī)范只給出了大氣邊界層風(fēng)荷載,對下?lián)舯┝鞯倪@類極端風(fēng)并沒有考慮在內(nèi)。所以對下?lián)舯┝鞯难芯烤惋@得至關(guān)重要。本文基于沖擊射流模型建立下?lián)舯┝魅S模型,通過CFD數(shù)值方法對下?lián)舯┝鞯娘L(fēng)場進(jìn)行了定常數(shù)值模擬,對下?lián)舯┝鞯娘L(fēng)場特征進(jìn)行了重點(diǎn)分析。下?lián)舯┝鲝较蝻L(fēng)速在近地面附近達(dá)到最大值,之后隨著高度增大而迅速減小,徑向風(fēng)速剖面與大氣邊界層剖面有著顯著的差異。在下?lián)舯┝魃淞鞴芟路骄嚯x噴射中心半徑為1D的圓內(nèi)都存在著正壓,并且中心處壓力系數(shù)接近1。不同射流速度對無量綱化的徑向風(fēng)速剖面影響不大,不同的射流高度H對無量綱化的徑向風(fēng)速剖面有著一定的影響。下?lián)舯┝鞯倪吔鐚拥陌l(fā)展是呈非線性變化的。不同徑向位置r處,下?lián)舯┝黠L(fēng)剖面不同,建筑承受風(fēng)荷載作用亦不同。利用CFD方法對不同徑向位置處的高層建筑模型進(jìn)行了風(fēng)荷載特征分析。分別將模型置于距離下?lián)舯┝骱诵膔=OD,r=1D,r=1.5D,r=2D四個不同位置,利用SSTk-co湍流模型進(jìn)行定常數(shù)值模擬。不同徑向位置處模型周圍流場分析:在r=0D位置處,可以看到下沉的氣流垂直撞擊在高層建筑模型頂面,氣流撞擊頂面后向四周散開,并且在模型四個側(cè)面周圍氣流形成一個封閉的汽缸。在r=1D,r=1.5D,r=2D位置處,在模型迎風(fēng)面下部都存在一個氣流駐點(diǎn),在模型的側(cè)面中上部,流動在側(cè)面前端發(fā)生分離,在后端又發(fā)生了再附現(xiàn)象,而在模型下部沒有發(fā)生再附現(xiàn)象。不同徑向位置處模型表面風(fēng)壓系數(shù)分布分析:模型位于r=0D位置處時,模型各個表面均承受較大的壓力,此位置處,建筑結(jié)構(gòu)設(shè)計時應(yīng)有著足夠的抗壓強(qiáng)度。在r=1D,r=1.5D,r=2D位置處,模型迎風(fēng)面風(fēng)壓系數(shù)隨著徑向位置r的增大,峰值風(fēng)壓系數(shù)變小,并且在峰值風(fēng)壓系數(shù)附近區(qū)域風(fēng)壓系數(shù)變得不再飽滿。在側(cè)面與背面主要產(chǎn)生吸力,側(cè)面上部,前端吸力大于后端�？傮w來看,徑向位置對側(cè)面、背面壓力系數(shù)分布影響較小。
[Abstract]:With the global warming, the severe convective weather represented by the following storm currents is gradually increasing, which makes the research on it become one of the hot issues in the field of international wind engineering. The downburst flow is a kind of airflow process which is accelerated to expand on the ground after the strong sinking air flow formed by thunderstorm weather hits the ground. Because of the great difference between the downburst wind profile and the atmospheric boundary layer wind profile, Strong wind loads will occur at very low distances from the ground, which often lead to structural damage. The wind load of atmospheric boundary layer is only given in the load code of our country, and the extreme wind of downburst flow is not taken into account. Therefore, the study of downburst flow is very important. In this paper, based on impinging jet model, a three-dimensional model of downburst flow is established, and the wind field of downburst flow is simulated by CFD numerical method, and the wind field characteristics of downburst flow are analyzed emphatically. The radial wind speed of the downburst reaches its maximum near the ground and then decreases rapidly with the increase of height. The radial wind velocity profile is significantly different from the atmospheric boundary layer profile. The positive pressure exists in the circle where the radius of the jet center is 1 D below the jet tube, and the pressure coefficient is close to 1. Different jet velocities have little effect on the dimensionless radial wind profile, and different jet height H has a certain effect on the dimensionless radial wind velocity profile. The evolution of the boundary layer of the downburst flow is nonlinear. At different radial position r, the downburst wind profile is different, and the action of building bearing wind load is also different. The wind load characteristics of high-rise building models at different radial positions are analyzed by CFD method. The model was placed in four different positions at the core of storm flow at a distance. The SSTk-co turbulence model was used to carry out steady numerical simulation. Analysis of the flow field around the model at different radial positions: at rn0D position, it can be seen that the vertical impact of the sinking airflow is on the top surface of the model of the high-rise building, and the airflow impinges on the top surface and disperses around the top surface. A closed cylinder is formed around the four sides of the model. At the position of r ~ (1D) ~ r ~ (1) D ~ (1.5) D / r ~ (2 D), there is an airflow stop point in the lower part of the model's upwind surface. In the middle and upper side of the model, the flow is separated at the front end of the model, and the phenomenon of reattachment occurs at the back end. No reattachment occurred in the lower part of the model. Analysis of the distribution of wind pressure coefficient on the surface of the model at different radial positions: when the model is located at rn0D, each surface of the model is subjected to greater pressure. At this location, there should be sufficient compressive strength in the design of the building structure. The peak wind pressure coefficient decreases with the increase of radial position r, and becomes no longer full in the region near the peak wind pressure coefficient. Suction is mainly produced on the side and back, the upper side and the front end are larger than the back end. As a whole, the radial position has little effect on the distribution of the pressure coefficient on the side and back.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU973.213
本文編號：2347033
[Abstract]:With the global warming, the severe convective weather represented by the following storm currents is gradually increasing, which makes the research on it become one of the hot issues in the field of international wind engineering. The downburst flow is a kind of airflow process which is accelerated to expand on the ground after the strong sinking air flow formed by thunderstorm weather hits the ground. Because of the great difference between the downburst wind profile and the atmospheric boundary layer wind profile, Strong wind loads will occur at very low distances from the ground, which often lead to structural damage. The wind load of atmospheric boundary layer is only given in the load code of our country, and the extreme wind of downburst flow is not taken into account. Therefore, the study of downburst flow is very important. In this paper, based on impinging jet model, a three-dimensional model of downburst flow is established, and the wind field of downburst flow is simulated by CFD numerical method, and the wind field characteristics of downburst flow are analyzed emphatically. The radial wind speed of the downburst reaches its maximum near the ground and then decreases rapidly with the increase of height. The radial wind velocity profile is significantly different from the atmospheric boundary layer profile. The positive pressure exists in the circle where the radius of the jet center is 1 D below the jet tube, and the pressure coefficient is close to 1. Different jet velocities have little effect on the dimensionless radial wind profile, and different jet height H has a certain effect on the dimensionless radial wind velocity profile. The evolution of the boundary layer of the downburst flow is nonlinear. At different radial position r, the downburst wind profile is different, and the action of building bearing wind load is also different. The wind load characteristics of high-rise building models at different radial positions are analyzed by CFD method. The model was placed in four different positions at the core of storm flow at a distance. The SSTk-co turbulence model was used to carry out steady numerical simulation. Analysis of the flow field around the model at different radial positions: at rn0D position, it can be seen that the vertical impact of the sinking airflow is on the top surface of the model of the high-rise building, and the airflow impinges on the top surface and disperses around the top surface. A closed cylinder is formed around the four sides of the model. At the position of r ~ (1D) ~ r ~ (1) D ~ (1.5) D / r ~ (2 D), there is an airflow stop point in the lower part of the model's upwind surface. In the middle and upper side of the model, the flow is separated at the front end of the model, and the phenomenon of reattachment occurs at the back end. No reattachment occurred in the lower part of the model. Analysis of the distribution of wind pressure coefficient on the surface of the model at different radial positions: when the model is located at rn0D, each surface of the model is subjected to greater pressure. At this location, there should be sufficient compressive strength in the design of the building structure. The peak wind pressure coefficient decreases with the increase of radial position r, and becomes no longer full in the region near the peak wind pressure coefficient. Suction is mainly produced on the side and back, the upper side and the front end are larger than the back end. As a whole, the radial position has little effect on the distribution of the pressure coefficient on the side and back.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU973.213
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