本文關(guān)鍵詞：海底管道與樁柱受力特性數(shù)值模擬　出處：《浙江大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 地質(zhì)災(zāi)害 海底滑坡 海底管道 樁 CFD 流體與結(jié)構(gòu)相互作用 數(shù)值模擬 拖曳力 湍流模型

【摘要】：海底滑坡等地質(zhì)災(zāi)害是引起海洋結(jié)構(gòu)物(海底管線、樁柱等)破壞的主要原因之一。海底油氣管道是深海油氣輸運(yùn)的重要生命線,由于海底管道長距離輸運(yùn),經(jīng)歷的海底地形崎嶇、起伏變化大,海底管道容易形成局部懸跨段,而這些懸跨段所在的海溝、海槽等低洼區(qū)域往往是海底滑坡泥流的主要輸運(yùn)通道,嚴(yán)重威脅著管道的在位穩(wěn)定性。海底滑坡泥流的流速極快,改變了周圍水域的流動(dòng),極易造成影響區(qū)域內(nèi)的海洋結(jié)構(gòu)物的破壞。由于海洋結(jié)構(gòu)物(樁柱)的存在,對(duì)水流的阻流作用,其周圍流場發(fā)生改變,形成樁前水流下降、馬蹄渦以及尾渦等現(xiàn)象,這些現(xiàn)象造成樁柱周圍海床的局部沖刷,因此,對(duì)樁柱的穩(wěn)定性提出了更高的要求。 目前關(guān)于地質(zhì)災(zāi)害對(duì)海洋結(jié)構(gòu)物影響的研究主要以模型試驗(yàn)和數(shù)值模擬(CFD)為主,其中模型試驗(yàn)是在巖土力學(xué)和流體力學(xué)兩大理論的指導(dǎo)下研究流體與結(jié)構(gòu)的相互作用,而數(shù)值模擬作為技術(shù)手段再現(xiàn)模型試驗(yàn)的結(jié)果,相互驗(yàn)證其可靠性和適用性。本文的研究主要是以有關(guān)文獻(xiàn)的模型試驗(yàn)結(jié)果為依據(jù),從數(shù)值模擬角度研究了海洋結(jié)構(gòu)物與流體的相互作用,并將數(shù)值分析結(jié)果與實(shí)驗(yàn)結(jié)果進(jìn)行了對(duì)比分析。 本文關(guān)于海洋結(jié)構(gòu)物(海底管線、樁柱)與流體相互作用方面完成了以下工作： 1.在數(shù)值計(jì)算中采用赫巴模型模擬海底滑坡泥流,得到了與實(shí)驗(yàn)相近的結(jié)果,證明了計(jì)算模型的合理性,進(jìn)一步優(yōu)化了無量綱拖曳力系數(shù)與非牛頓流體雷諾數(shù)之間的關(guān)系,得到了管道拖曳力系數(shù)隨非牛頓流體雷諾數(shù)的增大而減小的規(guī)律,研究了不同懸跨高度下管道拖曳力系數(shù)的變化,發(fā)現(xiàn)管道拖曳力系數(shù)隨著管道懸跨高度的增大而增大,最后保持穩(wěn)定；在Renon-Newtonian一定的情況下,存在臨界懸跨高度比(H/D)Critical,在小于此值時(shí),管道拖曳力系數(shù)隨之增大,大于此值時(shí),管道拖曳力系數(shù)保持穩(wěn)定；給出了海底管道法向拖曳力系數(shù)與管道懸跨高度之間的關(guān)系,提出了更為合理的管道拖曳力計(jì)算方法； 2.采用三種湍流模型對(duì)樁柱周圍流場的變化做了數(shù)值模擬分析,得到了與前人研究相近的結(jié)果,證明了計(jì)算模型和湍流模型的合理性,詳細(xì)分析了群樁樁間距、湍流模型、床面類型及粗糙度、水流速度變化及其水深變化對(duì)樁柱周圍流場變化的影響,得出以下結(jié)論：樁間距S/D4時(shí),樁柱周圍流場變化的相互影響越小；湍流模型對(duì)樁周流場分布影響較大；光床時(shí)樁周流速要比粗床時(shí)的大；床面粗糙度D/Ks越小,對(duì)樁周靠近床面附近的流場分布影響越大；來流速度越大,樁前下降水流速度增大,樁前馬蹄渦現(xiàn)象有增強(qiáng)趨勢(shì),樁前形成順壓梯度區(qū)；樁側(cè)流速增大,發(fā)生流動(dòng)分離,樁柱兩側(cè)分離角向后移動(dòng)；樁后流速減小,形成逆壓梯度區(qū)；樁前出現(xiàn)馬蹄渦現(xiàn)象,樁前0.5D范圍內(nèi)受到馬蹄渦的影響。
[Abstract]:Submarine landslide and other geological hazards are one of the main causes of damage to marine structures (submarine pipelines, piles, etc.). Submarine oil and gas pipeline is an important lifeline of deep sea oil and gas transportation, because of long distance transportation of submarine pipeline. The undersea topography is rugged and fluctuating greatly, and the submarine pipeline is easy to form local overhanging section, and the trench and trough in which the overhanging section is located are often the main transport channel of the submarine landslide mudflow. It is a serious threat to the stability of pipeline. The velocity of mud flow in submarine landslide is very fast, which changes the flow of surrounding waters. It is easy to cause the damage of ocean structure in the affected area. Because of the existence of the ocean structure (pile column), the flow field around the water flow changes and the flow in front of the pile drops. The phenomena such as horseshoe vortex and wake vortex cause the local erosion of the seabed around the pile column, so the stability of the pile column is required higher. At present, the research on the influence of geological hazards on marine structures mainly consists of model test and numerical simulation (CFDs). The model test is based on the two theories of rock and soil mechanics and fluid mechanics to study the interaction between fluid and structure, and numerical simulation is used as a technical means to reproduce the results of the model test. The research in this paper is mainly based on the model test results of relevant literature and studies the interaction between ocean structures and fluids from the point of view of numerical simulation. The numerical results are compared with the experimental results. In this paper, the following work has been done on the interaction between ocean structures (submarine pipelines, piles and columns) and fluids: 1. In the numerical calculation, the Herba model is used to simulate the mudflow of submarine landslide, and the results are close to those of the experiment, which proves the rationality of the calculation model. The relationship between the dimensionless drag force coefficient and the Reynolds number of non-Newtonian fluid is further optimized, and the law that the drag force coefficient decreases with the increase of the Reynolds number of non-Newtonian fluid is obtained. The variation of towing force coefficient under different suspended span heights is studied. It is found that the towing force coefficient increases with the increase of the suspended span height of the pipeline and remains stable at last. In the case of Renon-Newtonian, the critical ratio of suspended span to height is H / D critical, and when it is less than this value, the drag coefficient of the pipeline increases. When the value is greater than this value, the drag force coefficient of the pipeline remains stable. The relationship between the normal drag force coefficient and the suspended span height of the pipeline is given, and a more reasonable method for calculating the towing force of the pipeline is put forward. 2. Three kinds of turbulence models are used to simulate the flow field around the pile column, and the results are similar to those of the previous researches, and the rationality of the calculation model and the turbulence model is proved. The influences of pile spacing, turbulence model, bed surface type and roughness, flow velocity and water depth on the flow field around the pile column are analyzed in detail. The following conclusions are drawn: when the pile spacing is S / D _ 4. The interaction of the flow field around the pile column is smaller; The turbulence model has a great influence on the distribution of flow field around the pile. The velocity of pile circumference in bare bed is higher than that in thick bed. The smaller the bed roughness D / Ks, the greater the influence on the distribution of the flow field near the bed surface. The larger the velocity of flow is, the greater the velocity of descending flow in front of pile is, and the phenomenon of horseshoe vortex in front of pile is increasing, and the gradient region is formed in front of pile. The flow separation occurs when the velocity of the pile side increases, and the separation angle moves backward on both sides of the pile column. The velocity of flow behind the pile decreases and the inverse pressure gradient zone is formed. The horseshoe vortex appears in front of the pile and is affected by the horseshoe vortex in the range of 0.5 D in front of the pile.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P756.2;TU470

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本文編號(hào)：1379663