本文選題：高速水流 + 流激振動　； 參考：《武漢大學(xué)》2014年博士論文

【摘要】：高速水流和流激振動現(xiàn)象是水利工程中十分常見并且非常重要的問題,在建設(shè)高水頭、大流量水利工程時(shí),如果在設(shè)計(jì)、施工、運(yùn)行管理等環(huán)節(jié)上稍有不慎,就有可能因這兩個(gè)不利現(xiàn)象而威脅到整個(gè)樞紐的安全,因此對高速水流和流激振動現(xiàn)象進(jìn)行深入研究就顯得十分必要。國內(nèi)外關(guān)于這兩方面的研究也已經(jīng)積累了豐厚的成果,但是絕大部分都是在工程意義上的,這意味著無論在試驗(yàn)數(shù)據(jù)分析、還是數(shù)值模擬方面,基本都是以雷諾統(tǒng)計(jì)平均思想為理論基礎(chǔ)的,這種處理方法雖然在一定程度上能夠滿足工程上的需求,但它忽視了高速水流或者流激振動現(xiàn)象中所蘊(yùn)含的某種復(fù)雜規(guī)律性。因此將混沌理論引入到高速水流和流激振動的研究中來,是一種在工程意義下,將與湍流和振動有關(guān)的研究回歸到湍流以及流固耦合現(xiàn)象本源性質(zhì)的全新思想,并能為工程設(shè)計(jì)人員更好地理解高速水流和流激振動現(xiàn)象中的復(fù)雜性提供一定的理論基礎(chǔ),具有普遍的意義。論文首先研究了邊界條件對閘門振動特性的影響規(guī)律,隨后基于混沌理論,以模型試驗(yàn)中所測得的數(shù)據(jù)為研究背景,采用混沌初步識別方法、相空間重構(gòu)理論、混沌特征量的對比分析等方法,初步研究了窄縫式消能工、階梯式消能工、消力池底流消能以及平板閘門流激振動四種特定情況下高速水流脈動壓力或振動加速度響應(yīng)中所蘊(yùn)含的復(fù)雜性規(guī)律,并揭示了高速水流和流激振動中存在的混沌特性。以龍開口水電站深孔平板閘門為對象,通過Block Lanczos法進(jìn)行模態(tài)分析,采用約束剛度連續(xù)變化及附加質(zhì)量法研究了邊界支承條件和流固耦合兩方面因素對其自振特性的影響,發(fā)現(xiàn)順流向、側(cè)向及豎直向約束剛度的變化在某一范圍內(nèi)對閘門自振特性的影響非常顯著,其規(guī)律與矩形薄板橫向振動的規(guī)律一致；自振頻率與其振型振動方向所對應(yīng)的約束條件緊密相關(guān),與其他方向的約束條件基本無關(guān),通過分析閘門自振頻率隨約束變化的規(guī)律,可以推求其相應(yīng)振型的振動方向；在考慮流固耦合的情況下,門前水體通過附加質(zhì)量進(jìn)行模擬,結(jié)果表明水位在一定范圍內(nèi)的變化對閘門自振頻率的影響可以忽略,且約束條件的影響相對較小。隨后,在對四種不同模型試驗(yàn)中測量得到的試驗(yàn)數(shù)據(jù)進(jìn)行混沌特性分析時(shí),普遍得到了以下三條結(jié)論：(1)整體來看,對實(shí)測數(shù)據(jù)時(shí)間序列進(jìn)行混沌特征的初始判別時(shí),采用主分量分析法和0-1測試法是完全可行的,而且概念簡單、可操作性強(qiáng)、判別方法直觀有效。但這兩種方法只能定性判別時(shí)間序列是否具備混沌特性,而不能定量表示和區(qū)分混沌程度的強(qiáng)弱差異等。(2)相空間重構(gòu)的嵌入維數(shù)采用平均偽最近鄰域法(Cao方法)進(jìn)行計(jì)算,研究發(fā)現(xiàn)實(shí)測數(shù)據(jù)中包含一定水平的噪聲,可能對吸引子的重現(xiàn)和Lyapunov指數(shù)的計(jì)算造成影響,不過文獻(xiàn)[147]指出對于高維的時(shí)間演化過程,Cao方法對噪聲具有更好的魯棒性,該法在實(shí)測數(shù)據(jù)混沌分析的應(yīng)用中是完全可行的,后來在關(guān)聯(lián)維數(shù)的計(jì)算中也證明了這一點(diǎn)。(3)噪聲對Kolmogorov熵的計(jì)算有較明顯的影響,使得K只能對實(shí)測時(shí)間序列進(jìn)行定性的混沌特性識別,而不能反映混沌程度的大��；而最大Lyapunov指數(shù)在脈壓序列中也沒有很明顯的分布規(guī)律,但在加速度信號的分析中則存在明顯規(guī)律。在相空間重構(gòu)及混沌特征量的分布規(guī)律兩個(gè)方面,不同模型試驗(yàn)存在一定的差異,主要結(jié)論如下：(1)窄縫消能工選取一級收縮方案(FC)和二級收縮方案(SC)兩種體型進(jìn)行對比分析,得到相空間重構(gòu)嵌入?yún)?shù)τ在6-13之間,m在11-16之間,在FC方案中,τ口m隨流向都存在一定的規(guī)律性。飽和關(guān)聯(lián)維數(shù)D2更能反映出一定的規(guī)律性,表明在相同體型條件下,上游水位越高,流量越大,相應(yīng)的流動結(jié)構(gòu)越復(fù)雜,紊動隨機(jī)性更高；而在SC體型的第二個(gè)收縮段底板附近,水流紊動程度并不取決于水位、流量等初始條件,而取決于二級收縮段邊壁的突然轉(zhuǎn)折；窄縫消能工中邊墻的突然轉(zhuǎn)折使得底板附近水流結(jié)構(gòu)的復(fù)雜性及紊動程度比邊墻附近水流更加顯著,但收縮段并沒有從本質(zhì)上改變水流的動力結(jié)構(gòu),而只是微小的擾動。(2)階梯式消能工選取兩組階梯組合,并通過單寬流量和弗勞德數(shù)來控制來流條件,研究表明：相空間重構(gòu)的最佳嵌入?yún)?shù)范圍為τ-=7-18,m=8-17,結(jié)合關(guān)聯(lián)維數(shù)隨來流條件的變化規(guī)律,發(fā)現(xiàn)階梯式消能工上水流內(nèi)部結(jié)構(gòu)的演化過程并不直接取決于來流條件或者階梯體型,而是取決于階梯上的水流流態(tài),流態(tài)不同,水流狀態(tài)空間的演化規(guī)律就不同。豎直面凸角處的脈壓序列存在一定水平的噪聲或其附近流場的復(fù)雜度較高,可能由于跌落水流在豎直面凸角處存在較大空腔,空腔的脈動比水流脈動更復(fù)雜�；煦缣卣髁糠矫�,λ1的分布規(guī)律表明豎直面凸角測點(diǎn)的脈壓序列在跌落水流時(shí)比滑行水流更顯出隨機(jī)性,而水平面測點(diǎn)的脈壓序列在滑行水流時(shí)比跌落水流的混沌程度更大。D2的分布規(guī)律表明在滑行水流時(shí),豎直面和水平面凸角處的測點(diǎn)均有沿程下降的趨勢。(3)消力池中選取一種新型消能結(jié)構(gòu)為試驗(yàn)方案,擬定三組試驗(yàn)工況。結(jié)果表明,消力池底板測點(diǎn)的植整體上略大于消力中墩測點(diǎn),而m值則相反。D2總體分布在5.238-8.854之間,消力池底板測點(diǎn)數(shù)據(jù)的D2較消力中墩要�。辉诖罅髁抗r(2%)時(shí),消力池底板測點(diǎn)D2值有隨流向增大的趨勢；小流量工況(50%)時(shí),D2值呈現(xiàn)出隨流向減小的趨勢；中墩測點(diǎn)的D2值大小與來流條件無關(guān)；隨流量的減小,中墩前底板測點(diǎn)的D2值有先減后增的趨勢,中墩后測點(diǎn)則是遞減趨勢,這與該優(yōu)化方案的消能機(jī)理有關(guān)。在對λ1分布規(guī)律的分析中也間接表明了該優(yōu)化方案在較小流量時(shí)的消能效果更好。(4)研究了水彈性模型試驗(yàn)中所測量的閘門加速度響應(yīng)數(shù)據(jù),擬定了1/8～7/8共7個(gè)開度條件,上游水位控制在設(shè)計(jì)水位。除了1/8開度外,側(cè)向振動的m值比其他方向更大,而1/8和7/8開度在各振動方向時(shí)的m值比其他中間開度都要小。在該閘門的豎向振動與順流向振動中呈現(xiàn)出了較低維(3.342～5.130)的混沌吸引子,表明對閘門流激振動系統(tǒng)進(jìn)行建模,只需要更少的獨(dú)立控制變量,就可以基本描述閘門在振動過程中所呈現(xiàn)出來的復(fù)雜性和非線性規(guī)律。不同測點(diǎn)的λ1隨閘門開度的變化規(guī)律呈現(xiàn)“兩邊小中間大”的趨勢,表明除了1/8和7/8開度,在其他局部開啟條件下,閘門在水流激振影響下的振動復(fù)雜性更大,這就體現(xiàn)在實(shí)際工程中,閘門在2/8開度到6/8開度之間的振動情況存在更多不確定性,包括強(qiáng)烈振動的情況。
[Abstract]:High speed water flow and flow excited vibration are very common and very important problems in water conservancy projects. In the construction of high water head and large flow water conservancy projects, if they are inadvertent in the design, construction, operation management and other links, it is possible to threaten the safety of the whole hub because of these two unfavorable phenomena. Therefore, the high speed flow and flow exciting vibration can be caused. It is very necessary to study the dynamic phenomena in depth. The research on these two aspects has also accumulated rich achievements, but most of them are in the engineering significance. This means that both the analysis of experimental data and the numerical simulation are basically based on the theoretical basis of the Reynolds statistical mean thought. Although the method can meet the needs of engineering to some extent, it ignores some kind of complex regularity contained in the phenomenon of high speed flow or flow induced vibration. Therefore, the introduction of chaos theory into the study of high speed water flow and flow excited vibration is a kind of research in engineering, which will return to the study of turbulence and vibration. The new idea of turbulence and the intrinsic properties of fluid solid coupling can provide a certain theoretical basis for engineering designers to better understand the complexity of high speed flow and flow excited vibration. The paper first studies the influence of boundary conditions on the vibration specificity of the gate, and then based on the chaos theory, the model is based on the theory of chaos. The data measured in the type test is the research background, the initial chaotic identification method, the phase space reconstruction theory and the chaotic characteristic comparison analysis are used to study the pulsating pressure or vibration of the high speed water flow under the four specific conditions of narrow slit energy dissipator, staircase type energy dissipator, stilling pool bottom current dissipation and flat gate flow induced vibration. The complex law contained in the acceleration response is presented, and the chaotic characteristics of the high speed water flow and the flow excited vibration are revealed. The modal analysis is carried out by the Block Lanczos method, taking the deep hole flat gate of the long shedding hydropower station as the object, and the two aspects of the boundary support conditions and the fluid solid coupling are studied by the continuous change of the constrained stiffness and the additional mass method. The influence of the factors on the natural vibration characteristics shows that the change of the lateral and vertical restraint stiffness has a very significant influence on the self vibration characteristics of the gate in a certain range. The law is consistent with the law of the transverse vibration of the rectangular plate, and the frequency of the vibration is closely related to the constraint conditions corresponding to the vibration direction of the vibration mode, and it is about the other direction. The beam condition is basically irrelevant. By analyzing the law of the vibration frequency of the gate, the direction of its corresponding vibration can be calculated. In the case of fluid solid coupling, the water body in front of the gate is simulated by the additional mass. The result shows that the influence of the change of the water level in a certain range on the vibration frequency of the gate can be ignored, and the restraint bar can be ignored. The influence of the parts is relatively small. Then, in the analysis of the chaotic characteristics of the experimental data obtained from four different model tests, the following three conclusions are generally obtained: (1) in the whole, the principal component analysis and the 0-1 test method are completely feasible for the initial discrimination of the chaotic characteristics of the measured data time series. The two methods can only determine whether the time series has chaotic characteristics, but can not quantify and distinguish the difference of the intensity of chaos. (2) the embedding dimension of the phase space reconstruction is calculated by the average pseudo nearest neighborhood method (Cao method), and the actual number is found. The noise in a certain level may affect the recurrence of the attractor and the calculation of the Lyapunov exponent. However, literature [147] points out that the Cao method has better robustness to the noise in the time evolution process of the high dimension. The method is completely feasible in the application of the measured data chaos analysis, and later in the calculation of the correlation dimension. It is also proved that (3) noise has a significant influence on the calculation of Kolmogorov entropy, so that K can only identify the qualitative chaotic characteristics of the measured time series, but can not reflect the size of chaos, but the maximum Lyapunov exponent has no obvious distribution in the pulse pressure sequence, but it is stored in the acceleration signal analysis. There are certain differences in the two aspects of the phase space reconstruction and the distribution law of the chaotic characteristic quantity. The main conclusions are as follows: (1) the narrow slit energy dissipator selects the first order contraction scheme (FC) and the two stage contraction scheme (SC) for the analysis of the ratio, obtains the phase space reconstruction embedding parameter tau between 6-13, and m in 11- 16, in the FC scheme, the m of the tau port has a certain regularity with the flow direction. The saturation correlation dimension D2 can reflect a certain regularity. The higher the water level, the greater the flow, the more complex the flow structure and the higher turbulence, and the turbulence in the second contraction segments of the body shape. The degree does not depend on the initial conditions such as water level, flow and other initial conditions, but it depends on the abrupt turning of the side wall of the two stage contraction section. The sudden turning of the side wall of the narrow gap energy dissipator makes the complexity and turbulence degree of the flow structure near the floor more significant than the flow near the side wall, but the contraction section does not have the dynamic structure that essentially changes the flow of the flow, but only the dynamic structure of the flow is not essentially changed. It is a small disturbance. (2) the ladder type energy dissipator selects two sets of ladder combinations and controls the flow condition through the single wide flow and Froude number. The study shows that the optimum embedding parameter range of phase space reconstruction is tau -=7-18, m=8-17, combining the relation dimension with the changing law of the flow condition, it is found that the internal structure of the water flow in the staircase energy dissipator is shown. The process does not depend directly on the flow condition or the staircase shape, but depends on the flow pattern on the ladder, the flow state is different, the evolution law of the flow state space is different. The pulse pressure sequence at the convex angle of the vertical face has a certain level of noise or the complexity of the flow field near the vertical plane, which may be due to the falling flow at the convex angle of the vertical face. There is a larger cavity, the pulsation of the cavity is more complex than the flow pulsation. In the aspect of chaotic characteristic, the distribution of lambda 1 shows that the pulse pressure sequence of the vertical plane convex angle measuring point is more random than the gliding flow in the fall flow, and the distribution law of the pulse pressure sequence of the horizontal point measuring point is larger than the falling water flow in the gliding flow. It is shown that in the sliding flow, the measuring points at the vertical and horizontal angles all have a downward trend along the distance. (3) a new energy dissipation structure is selected as the test scheme in the stilling pool, and the three sets of test conditions are drawn up. The results show that the planting of the bottom plate of the floor of the stilling pool is slightly larger than the stilling piers, while the m value is generally distributed in the 5.238-8.85 4, the D2 of the bottom plate of the stilling pool is small, and the D2 value of the bottom plate of the stilling pool has a tendency to increase with the flow direction in the large flow condition (2%); when the small flow condition (50%), the value of the D2 value decreases with the flow direction; the size of the piers measuring point is independent of the flow condition; as the flow rate decreases, the front bottom plate measurement of the middle pier is measured. The D2 value of the point has a tendency to decrease and increase first, and the post test point of the middle pier is the decreasing trend, which is related to the energy dissipation mechanism of the optimization scheme. In the analysis of the distribution law of the lambda 1, the energy dissipation effect of the optimized scheme is better. (4) the acceleration response data measured in the hydroelastic model test are studied. A total of 7 opening conditions of 1/8 to 7/8 are determined. The upstream water level is controlled at the design water level. In addition to the 1/8 opening, the m value of the lateral vibration is larger than that in the other directions, while the m value of 1/8 and 7/8 opening is smaller than the other intermediate opening degrees in each direction of vibration. The lower dimension (3.342 to 5.130) of the chaos is presented in the vertical and downstream vibration of the gate. The attractor indicates that only less independent control variables are needed to model the gate flow excited vibration system. The complexity and the nonlinear law of the gate in the vibration process can be described basically. The trend of the change of the gate opening of the different measuring points with the opening of the gate is "small in the middle of the two sides", which shows the 1/8 and 7/8 opening. Under the conditions of other local opening, the vibration of the gate is more complex under the influence of the flow excitation, which is reflected in the actual engineering. There are more uncertainties in the vibration of the gate between the 2/8 opening and the 6/8 opening, including the strong vibration.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TV131.3
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本文編號：1901095