本文關(guān)鍵詞：海洋立管渦激振動頻域和時域預(yù)報(bào)方法研究　出處：《上海交通大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 渦激振動 強(qiáng)迫振蕩實(shí)驗(yàn) 旋轉(zhuǎn)實(shí)驗(yàn) 頻域預(yù)報(bào) 時域預(yù)報(bào)

【摘要】：隨著海洋石油開采不斷向深海發(fā)展，立管的安全性對于石油工業(yè)的發(fā)展以及海洋環(huán)境的維護(hù)至關(guān)重要。洋流中立管兩側(cè)交替泄渦引起的渦激振動現(xiàn)象是立管疲勞損傷的主要因素，嚴(yán)重威脅著立管的安全。因此，準(zhǔn)確的估算立管在實(shí)際海洋環(huán)境中的渦激載荷及動力響應(yīng)，不斷優(yōu)化立管的結(jié)構(gòu)設(shè)計(jì)一直是海洋工程領(lǐng)域中的重要課題。 本文首先開展了系列海洋立管模型實(shí)驗(yàn)，通過高雷諾數(shù)下剛性圓柱體強(qiáng)迫振蕩實(shí)驗(yàn)研究，為頻域和時域預(yù)報(bào)模型提供高雷諾數(shù)升力系數(shù)數(shù)據(jù)庫，提高實(shí)尺度立管渦激振動響應(yīng)預(yù)報(bào)精度；同時，通過柔性立管在均勻流和剪切流下自激振蕩實(shí)驗(yàn)，研究立管主導(dǎo)模態(tài)的時域特性；然后利用頻域方法對立管模型渦激振動響應(yīng)進(jìn)行預(yù)報(bào)、并與實(shí)驗(yàn)結(jié)果進(jìn)行對比，探究頻域方法的適用性和局限性；最后本文提出了一種半經(jīng)驗(yàn)性的時域預(yù)報(bào)方法，期望解決立管遇到的變軸向力、立管-土壤耦合等非線性問題，并將時域預(yù)報(bào)結(jié)果與實(shí)驗(yàn)結(jié)果進(jìn)行了對比。論文內(nèi)容主要包括以下幾個方面： 1.對均勻來流下剛性圓柱體做不同幅值和頻率強(qiáng)迫振蕩時的水動力特性進(jìn)行了實(shí)驗(yàn)研究，得到了升力系數(shù)、阻力系數(shù)和相位角等與無因次振蕩頻率、振幅之間的關(guān)系曲線，從而為頻域和時域預(yù)報(bào)模型提供高雷諾數(shù)升力系數(shù)數(shù)據(jù)庫，提高實(shí)尺度立管渦激振動響應(yīng)預(yù)報(bào)精度；并通過對比本試驗(yàn)數(shù)據(jù)與低雷諾數(shù)試驗(yàn)數(shù)據(jù)得到了在亞臨界區(qū)域雷諾數(shù)對渦激振動特性的影響。研究發(fā)現(xiàn)，在亞臨界區(qū)域，雷諾數(shù)對渦激振動特性的影響很小，因此用低雷諾數(shù)試驗(yàn)數(shù)據(jù)來預(yù)報(bào)實(shí)際海洋環(huán)境下的立管渦激振動是合理的，但只限于實(shí)際海洋環(huán)境的雷諾數(shù)處于亞臨界區(qū)域的情況。 2.通過拖曳試驗(yàn)和旋轉(zhuǎn)實(shí)驗(yàn)?zāi)M了立管模型在均勻流和剪切流下的渦激振動響應(yīng)情況，分別利用模態(tài)疊加法和小波方法對兩種流場下立管在橫向和流向上的幅值響應(yīng)特性和主導(dǎo)頻率的時域響應(yīng)特性進(jìn)行了分析；此外，本文還利用逆有限元方法將柔性立管位移響應(yīng)作為輸入條件計(jì)算出了附加質(zhì)量系數(shù)在立管上的分布情況，期望能夠?qū)︻l域和時域經(jīng)驗(yàn)?zāi)Ｐ椭懈郊淤|(zhì)量系數(shù)的選擇提供科學(xué)依據(jù)。研究發(fā)現(xiàn)了一些有趣的現(xiàn)象，對于均勻流工況，雖然流向上的主導(dǎo)模態(tài)對應(yīng)的固有頻率并不是橫向上2倍，但是兩個方向上的鎖定頻率卻總是呈2倍關(guān)系，原因可能在于流向和橫向上的附加質(zhì)量系數(shù)能夠自己調(diào)整、直至兩個方向上的主導(dǎo)模態(tài)對應(yīng)的固有頻率正好為2倍關(guān)系；此外，無論在均勻流還是在剪切流工況下，均發(fā)現(xiàn)了主導(dǎo)模態(tài)的“間歇”特性，在剪切流中該性質(zhì)則更加明顯，對于這種工況，頻域方法已經(jīng)基本不再適用。 3.對頻域理論預(yù)報(bào)過程進(jìn)行了詳細(xì)的闡述，并利用頻域方法對均勻流和剪切流工況下的柔性立管渦激振動進(jìn)行了預(yù)報(bào)。與試驗(yàn)結(jié)果進(jìn)行對比發(fā)現(xiàn)，對于剪切流下單模態(tài)渦激振動，頻域方法十分適用，預(yù)報(bào)準(zhǔn)確度很高；但是對于均勻流工況和剪切流下多頻耦合工況，頻域理論預(yù)報(bào)結(jié)果比較差。此外，本文還通過頻域數(shù)值計(jì)算方法研究發(fā)現(xiàn)，軸向預(yù)張力對立管渦激振動的模態(tài)和幅值都會產(chǎn)生較大的影響，從而可以推斷出渦激振動導(dǎo)致的軸向力變化會進(jìn)行反饋、對渦激振動響應(yīng)又產(chǎn)生影響，而且影響極有可能不可忽略；因此，對于剪切流單模態(tài)渦激振動宜采用頻域方法，對于均勻流、剪切流多模態(tài)以及考慮變軸向力等非線性因素時，則需要研究新的時域預(yù)報(bào)方法。 4.通過研究發(fā)現(xiàn)，頻域預(yù)報(bào)方法對于多頻耦合響應(yīng)因素的簡化處理以及對于變軸向力因素的忽略，會導(dǎo)致較大的預(yù)報(bào)誤差；因此本文提出半經(jīng)驗(yàn)性的時域預(yù)報(bào)方法對立管在均勻流、剪切流和階梯流下的渦激振動響應(yīng)進(jìn)行了預(yù)報(bào)，并與實(shí)驗(yàn)結(jié)果和頻域預(yù)報(bào)結(jié)果進(jìn)行了對比，，發(fā)現(xiàn)與實(shí)驗(yàn)結(jié)果吻合很好，從而證明了該時域預(yù)報(bào)方法的可行性和可靠性。理論上，這種時域預(yù)報(bào)研究方法基本上適用于解決海管中遇到的絕大多數(shù)非線性問題。
[Abstract]:With the continuous development of ocean oil exploitation to the deep sea, vertical pipe safety for the development of the petroleum industry, it is crucial to maintain the marine environment. The riser VIV currents on both sides of the turn of vortex shedding is the main factor caused by riser fatigue damage, a serious threat to the safety of the riser. Therefore, the accurate estimation of vortex shock load and dynamic response in real marine environment, constantly optimize the structure design of tube has been an important topic in the field of marine engineering.
This paper carried out a series of marine riser model experiment, through the high Reynolds number of rigid cylinder forced oscillation experiment, provide high Reynolds number of lift coefficient database for frequency domain and time domain prediction model, improve the real scale riser VIV response prediction accuracy; at the same time, through flexible risers in uniform flow and shear flow oscillation experiment self study, riser time-domain characteristics of dominant mode; then using frequency method of riser VIV response prediction model, and compared with the experimental results, the applicability and limitations of the method in frequency domain; finally this paper proposes a time domain prediction method of a semi empirical, expected to solve the variable axial force vertical pipe encountered the vertical pipe soil coupling nonlinear problems, and the time-domain prediction results are compared with the experimental results. The main research contents are as follows:
1. to do under the uniform flow rigid cylinder with different amplitudes and frequencies of the forced oscillation hydrodynamic characteristics are studied experimentally. The lift coefficient, drag coefficient and phase angle and the dimensionless oscillation frequency, the relationship between the amplitude of the curve, thus providing high Reynolds number database for the lift coefficient in frequency domain and time domain prediction model, improve full scale riser VIV response prediction accuracy; and the influence on the vibration characteristics of the vortex in the subcritical Reynolds number is obtained by comparing the regional test data and test data of low Reynolds number. The study found that in the subcritical region, the Reynolds number effect of vortex excited vibration is very small, so a low Reynolds number test data to predict the actual ocean environment of vortex induced vibration is reasonable, but only a Reynolds number of actual marine environment in the subcritical region.
2. by towing test and rotating experimental simulation of vortex induced vibration model in uniform flow and shear flow response, respectively, using the modal superposition method and the wavelet method of two kinds of flow in the horizontal and vertical pipe flow on the amplitude response characteristics of the time domain and the dominant frequency is analyzed; in addition, this paper also uses inverse finite element method of the displacement response of flexible riser as input to calculate the added mass coefficient in vertical distribution on the tube, expect that the added mass coefficients in frequency domain and time domain experience model selection to provide a scientific basis. The study found some interesting phenomena, for uniform flow conditions, although the dominant the corresponding flow mode natural frequency is not horizontal 2 times, but the frequency locking in two directions but always is 2 times, the reason may lie in the flow and the additional quality The amount of their natural frequency coefficients can be adjusted, the dominant mode corresponding to the two directions until just 2 times; in addition, both in uniform flow or in shear flow conditions were found in the dominant mode of "intermittent" characteristics, the nature is more obvious in shear flow, in this condition, the frequency domain method is no longer applicable.
3. of the frequency domain prediction process in detail, and the use of frequency domain method for uniform flow and shear flow conditions of the flexible riser vortex induced vibration was predicted. Compared with the experimental results showed that the shear flow for single modal vortex induced vibration, the frequency domain method is very applicable, the forecast accuracy is very high; but for uniform flow and shear flow conditions under multi frequency coupling condition, frequency domain theory prediction results are relatively poor. In addition, this paper also through the frequency domain numerical calculation method research found that the vortex induced vibration of axial pre tension riser mode and amplitude will have a greater impact, which can be inferred from the axial force changes of vortex induced vibration will lead to feedback, but also have an impact on the vortex induced vibration, and the impact is likely not to be ignored; therefore, the shear flow of vortex induced vibration of single mode should be adopted for the frequency domain method, uniform flow, shear flow It is necessary to study the new method of time domain prediction when multimodal and nonlinear factors such as variable axial force are considered.
4. through the study found that the frequency domain prediction method for multi frequency response coupling simplified factors and neglect of variable axial force factors, will lead to larger forecast errors; therefore this time prediction method of semi empirical in uniform flow in the riser, vortex induced vibration shear flow and step flow responses of the forecast, and compared with the experimental results and the frequency-domain prediction results, that are in good agreement with the experimental results, which proves the feasibility and reliability of the time domain prediction method. In theory, the time domain prediction research method basically applicable to solve pipe sea most nonlinear problems.

【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：P742;P751

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