本文關(guān)鍵詞： 龍卷風(fēng) CFD數(shù)值模擬 漩渦比 離散相模型 地面粗糙度 平移龍卷風(fēng)　出處：《東南大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：龍卷風(fēng)是一種超強的旋風(fēng),具有極大的破壞力。鑒于龍卷風(fēng)發(fā)生的概率非常小,現(xiàn)今國內(nèi)《建筑結(jié)構(gòu)荷載規(guī)范》中還沒有列出結(jié)構(gòu)抗龍卷風(fēng)設(shè)計的相關(guān)條款。然而,在設(shè)計核電廠等一些極其重要設(shè)施時,則必須明確考慮結(jié)構(gòu)遭遇龍卷風(fēng)的因素。地面粗糙度不僅是氣象學(xué)中常用的一個重要參數(shù),同時也是決定龍卷風(fēng)風(fēng)場結(jié)構(gòu)的一個重要參數(shù)。因此本文所研究的地面粗糙度對龍卷風(fēng)風(fēng)場特性及建筑表面荷載的影響可為后續(xù)研究龍卷風(fēng)提供一定的有用信息,也可為核電廠等極其重要的結(jié)構(gòu)抗龍卷風(fēng)設(shè)計及選址提供一定的參考。本文主要研究內(nèi)容如下：1、基于CFD數(shù)值模擬方法,對不同漩渦比作用下的龍卷風(fēng)風(fēng)場特性進行了研究。為研究多漩渦龍卷風(fēng)場結(jié)構(gòu)的特征,利用大型流體軟件FLUENT14.5的SSTk-ω湍流模型模擬了三種典型漩渦比值為0.28、0.5及1.0的龍卷風(fēng)場,通過離散相模擬技術(shù)得到了準(zhǔn)靜態(tài)龍卷風(fēng)的結(jié)構(gòu)形態(tài)圖。分析了不同漩渦比作用下龍卷風(fēng)切向速度曲線變化圖及速度矢量圖的分布特征。并對不同漩渦比龍卷風(fēng)場中的建筑物表面風(fēng)壓系數(shù)進行了模擬。結(jié)果表明,多漩渦龍卷風(fēng)作用下的結(jié)構(gòu)表面風(fēng)壓系數(shù)絕對值更小。2、同樣基于CFD數(shù)值模擬方法,研究了B類地形下的地面粗糙度(y0為0、0.1及0.25)對龍卷風(fēng)近地風(fēng)場產(chǎn)生的波動而對建筑物表面荷載所造成的影響。根據(jù)上文結(jié)果選取了漩渦比值為0.5,并把均勻砂粒模型作為等效地面粗糙度,較詳細(xì)地分析了地面粗糙度作用下龍卷風(fēng)風(fēng)場結(jié)構(gòu)特征及建筑物表面風(fēng)壓系數(shù)的分布情況。結(jié)果表明,地面粗糙度起到了減小龍卷風(fēng)核心半徑以內(nèi)的切向速度及增強龍卷風(fēng)核心半徑外的切向速度的作用,并造成龍卷風(fēng)的核心半徑變大；隨著粗糙度的增大建筑物表面風(fēng)壓系數(shù)的絕對值也隨之變大。3、為更加真實研究龍卷風(fēng)對結(jié)構(gòu)荷載的影響,研究了地面粗糙度對平移龍卷風(fēng)結(jié)構(gòu)荷載的影響。利用CFD數(shù)值模擬研究了平移龍卷風(fēng)與靜態(tài)龍卷風(fēng)場特征的區(qū)別,其中平移龍卷風(fēng)核心半徑處的最大切向速度明顯大于靜態(tài)龍卷風(fēng)；并分析了在地面粗糙度作用下的平移龍卷風(fēng)結(jié)構(gòu)表面風(fēng)壓系數(shù)的變化規(guī)律。結(jié)果表明,建筑物表面分布的風(fēng)壓系數(shù)都為負(fù)值,即表示龍卷風(fēng)中心在建筑表面產(chǎn)生了風(fēng)吸力；粗糙度長度越大的情況下,在建筑物靠近左側(cè)一方的位置處的風(fēng)壓系數(shù)絕對值越大,其它位置處的絕對值只是局部增大；而左右兩側(cè)中心位置處的風(fēng)壓系數(shù)的絕對值隨著粗糙度長度變大而變大。
[Abstract]:Tornadoes are super cyclones with great destructive power, given the very small probability of tornadoes occurring. At present, there are no relevant provisions on the tornado resistant design of structures in China. However, in the design of nuclear power plants and other extremely important facilities. The ground roughness is not only an important parameter in meteorology. It is also an important parameter to determine the structure of tornado wind field. Therefore, the influence of ground roughness on tornado wind field characteristics and building surface load can provide some useful information for further research on tornado. . It can also provide some reference for the design and site selection of the most important structures, such as nuclear power plant. The main contents of this paper are as follows: 1, based on CFD numerical simulation method. The characteristics of tornado wind field under different swirl ratios are studied. Using the SSTk- 蠅 turbulence model of the large-scale fluid software FLUENT14.5, the tornado fields with the ratios of 0.28g 0.5 and 1.0 are simulated. By means of discrete phase simulation technique, the structure shape diagram of quasi static tornado is obtained, and the distribution characteristics of tornado tangential velocity curve and velocity vector chart under the action of different swirl ratio are analyzed, and the tornadoes with different swirl ratios are analyzed. The wind pressure coefficient of the building surface in the field is simulated. The absolute value of the wind pressure coefficient of the structure surface under the action of multi-whirlpool tornado is smaller than that of the others. Based on the CFD numerical simulation method, the surface roughness of B type terrain is studied to be 0. The influence of 0.1 and 0.25) on the surface load of the building due to the fluctuation of the wind field near the ground. According to the above results, the swirl ratio is 0.5. Taking the uniform sand model as the equivalent surface roughness, the structure characteristics of tornado wind field and the distribution of wind pressure coefficient on the building surface under the action of ground roughness are analyzed in detail. The roughness of the ground reduces the tangential velocity within the core radius of the tornado and strengthens the tangential velocity outside the core radius of the tornado, and results in the increase of the core radius of the tornado. With the increase of roughness, the absolute value of wind pressure coefficient on the building surface also becomes larger. 3, in order to study the effect of tornado on the structure load more truly. The influence of ground roughness on the structural load of translational tornadoes is studied. The difference between the characteristics of translational tornadoes and static tornadoes is studied by CFD numerical simulation. The maximum tangential velocity of the translational tornado core radius is obviously larger than that of the static tornado. The variation law of wind pressure coefficient on the surface of the translational tornado structure under the action of surface roughness is analyzed. The results show that the wind pressure coefficients of the surface distribution of buildings are all negative. That is to say, the center of the tornado produces wind suction on the surface of the building; The bigger the roughness length is, the greater the absolute value of wind pressure coefficient is at the position near the left side of the building, while the absolute value at the other position is only local increase. The absolute value of the wind pressure coefficient at the center of the left and right sides increases with the length of roughness.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU312.1

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