本文關鍵詞： 格柵-空腔繞流 自激振蕩 振蕩頻譜 高速列車 通風格柵 車輛設備艙　出處：《北京交通大學》2017年博士論文　論文類型：學位論文

【摘要】：很多設備、建筑、載運工具都具有通風格柵,格柵與其內(nèi)側(cè)空間共同構(gòu)成格柵-空腔結(jié)構(gòu)。當流體沿切向流經(jīng)該結(jié)構(gòu)時即形成格柵-空腔繞流。一定條件下,此類流場會產(chǎn)生自激振蕩現(xiàn)象。流場自激振蕩是一類穩(wěn)定的周期性振蕩過程,能夠?qū)е陆Y(jié)構(gòu)振動、流動噪聲等問題,也會影響設備通風散熱或空調(diào)系統(tǒng)運行。同時,流場自激振蕩過程包含著復雜的流動現(xiàn)象和很多流體力學基本問題。對于該問題的研究具有重要的工程應用及理論研究意義。本文以地面載運工具為應用對象,使用數(shù)值模擬方法對格柵-空腔繞流流場自激振蕩現(xiàn)象進行研究。主要研究內(nèi)容有:格柵-空腔繞流流場自激振蕩產(chǎn)生機理、基本特征、激發(fā)條件、變化規(guī)律、控制方法及其在高速列車中的應用,以期加深對該流動現(xiàn)象產(chǎn)生原因的理解,明確流場自激振蕩的時頻特征及空間分布特征,提出流場自激振蕩頻率、幅值的預測方法,為解決流場自激振蕩在載運工具運行中所引起的一系列問題以及相關設計研究工作提供技術及理論依據(jù)。建立了格柵-空腔繞流數(shù)值模擬模型,使用粒子圖像測速法對模型進行了驗證。得到了流場變化過程,分析了流場自激振蕩的產(chǎn)生原因。使用頻譜分析方法,得到了不同流動參數(shù)的時頻特征及其空間分布規(guī)律,明確了自激振蕩基本特征。結(jié)果表明:大尺度渦團的運動導致格柵-空腔繞流流場產(chǎn)生自激振蕩;大尺度渦團的形成與格柵周圍渦量的聚集過程密切相關;不同位置的振蕩頻率相同;沿來流方向,壓力振蕩幅值呈現(xiàn)先增后減的變化趨勢。研究了流場自激振蕩的激發(fā)條件。得到的主要結(jié)論有:不同條件下,流場可能處于非振蕩狀態(tài)、過渡狀態(tài)及自激振蕩狀態(tài)。當流動處于相對穩(wěn)定的狀態(tài)時,若流場振蕩幅值大于零且振蕩幅值變化率接近零則表明流場中存在自激振蕩現(xiàn)象。當分離邊緣邊界層動量厚度δd較小,流動雷諾數(shù)Reδ較大,格柵間隔長高比G/H較大時,流場自激振蕩更容易被激發(fā)。當空腔相對長度Lc/L1.5,空腔相對高度Hc/L5時,空腔壁面不會對流場自激振蕩造成影響。對流場自激振蕩變化規(guī)律進行了研究,包括流動狀態(tài)研究及模式轉(zhuǎn)變研究。得到了不同流動狀態(tài)、振蕩模式下振蕩頻率、幅值的變化規(guī)律。主要結(jié)論有:格柵-空腔繞流流動狀態(tài)可以用參數(shù)λ=(Reδ)~(1/2)/(δd/G)進行區(qū)分。隨著λ的增加,流場將經(jīng)歷三種流動狀態(tài)。在不同流動狀態(tài)下,振蕩頻率、幅值的變化規(guī)律具有較大差異。隨著格柵間隔長高比G/H的增加,流動狀態(tài)轉(zhuǎn)變的臨界參數(shù)λ_1和λ_2均呈線性減小。隨著λ的增加,模式轉(zhuǎn)變發(fā)生的臨界參數(shù)(L/G)_j呈單調(diào)下降趨勢。兩者之間的關系可以用指數(shù)函數(shù)表示。對流場振蕩控制方法進行了分析。分別對兩種典型控制手段對于流場振蕩的抑制效果進行了評價。提出了改變格柵肋片角度控制流場振蕩的方法�？傮w來看,在分離邊緣添加斜面能夠有效降低格柵-空腔繞流流場的自激振蕩強度。而在沖擊邊緣切割斜面對流場振蕩的抑制效果不明顯。改變格柵肋片角度對流場振蕩的抑制效果較好。建立了考慮通風格柵影響的高速列車設備艙流動數(shù)值模擬模型,著重對通風格柵附近的流動情況進行了分析。模擬結(jié)果表明:高速列車設備艙通風格柵附近會產(chǎn)生流場自激振蕩現(xiàn)象。在其影響下,高速列車設備艙裙板受到周期性氣動載荷的作用。
[Abstract]:A lot of equipment, buildings, vehicles have ventilation grille grille, its inner space constitute the grille - cavity structure. When the fluid flows through the tangential structure is formed around the grille flow cavity. Under certain conditions, this kind of flow will produce self oscillation. The flow field is a kind of self-excited oscillation and stable periodic oscillation the process, can lead to structural vibration, flow noise and other issues, will also affect the equipment ventilation or air conditioning system operation. At the same time, the flow field oscillation process contains the basic problem of complex flow phenomena and many fluid mechanics. It has important engineering application and theoretical significance for the study of the problem. This article takes the ground vehicles for application the object, using numerical simulation method to study the grid - cavity flow around the self oscillation of the flow field. The main contents are: Grid - cavity flow oscillation generated The mechanism, basic characteristics, excitation conditions, variation, control method and its application in high speed train, in order to deepen the causes of the flow phenomena, clear flow self-excited oscillation frequency characteristics and spatial distribution characteristics, the flow field of self-excited oscillation frequency, amplitude value prediction method, to solve the technology and theory based on the flow field of self-excited oscillations in a series of problems caused by carrying tools in operation and related design work. A numerical simulation of flow around grid - cavity model, using particle image velocimetry method to validate the model. The flow field change process, analyzes the causes of the self-excited oscillation flow. Using spectrum analysis method. The different flow parameters and spatial distribution features of time-frequency, clear the basic characteristics of the self-excited oscillation. The results show that the movement of vortexes in Grid - cavity flow The flow field of self-excited oscillation; closely related to the formation and accumulation of vorticity around the grille vortexes at the different positions of the same; oscillation frequency; along the flow direction, pressure oscillation amplitude showed a trend of first increase and then decrease. The excitation conditions flow self-excited oscillation. The main conclusions are: different conditions under the field in a non oscillatory state, transition state and self-excited oscillation. When the flow is in a relatively stable state, if the flow oscillation amplitude is greater than zero and the oscillation amplitude change rate is close to zero indicates that the self-excited oscillation phenomenon in the flow field. When the separation edge boundary layer momentum thickness Reynolds number D is small, Re 8 the larger, taller than G/H large grid spacing, flow field oscillation is excited easily. When the relative length of the Lc/L1.5 cavity, the cavity relative height of Hc/L5, the cavity surface will not affect the flow field of self-excited oscillation Ring. The flow field oscillation changes were studied, including the change of flow state and study mode. Under different flow conditions, oscillation frequency of the oscillation mode, the amplitude of variation. The main conclusions are: Grid - cavity flow around the state with parameter = (Re delta) ~ (1/2) / (8 d/G) were distinguished. With lambda increases, the flow field will experience the three flow. Under different flow conditions, the oscillation frequency, with larger differences in variation amplitude. With the increase of G/H grid interval height, flow state transition critical parameters of a _1 and a _2 were decreased linearly with lambda. Increase the critical parameters change mode (L/G) _j is a monotone decreasing trend. The relationship between the two can be expressed by exponential function. The flow field oscillation control methods are analyzed respectively. Two kinds of typical control methods for the inhibitory effect of flow oscillation The evaluation method is put forward. The change of fin angle control grid flow oscillation. Overall, add a bevel can effectively reduce the intensity of the self-excited oscillation cavity flow around the grille in the separation edge. With the impact of the cutting edge oblique face the inhibitory effect of flow oscillation is not obvious. The best inhibition grille rib angle convection field oscillation the change. A high-speed train equipment cabin numerical flow simulation model considering the influence of ventilation grille, especially near the flow situation of the ventilation grille is analyzed. The simulation results show that near the high-speed train compartment ventilation grid will have a flow of self oscillation. Under its influence, the high-speed train equipment cabin apron by action cycle of the aerodynamic load.

【學位授予單位】：北京交通大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：U270.1

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本文編號：1539723