本文選題：復(fù)式斷面　切入點(diǎn)：SERC-FCF　出處：《西安理工大學(xué)》2017年碩士論文

【摘要】：天然河道多為復(fù)式河道,其橫斷面通常由灘地和主槽兩部分組成。在枯水季節(jié),水流主要集中在河道的主槽中流動;當(dāng)洪水來臨時,水流會漫過河道灘地,形成漫灘水流。相比單一斷面,復(fù)式斷面的水流運(yùn)動更加復(fù)雜。當(dāng)水流漫灘后,主槽與灘地上兩部分水體之間相互作用,斷面水流的流速分布、床面剪切應(yīng)力和阻力等水力因素都將發(fā)生變化,單一斷面的水流計算公式已經(jīng)不再適用,需要研究新的方法來描述復(fù)式斷面的水流運(yùn)動,因此研究復(fù)式斷面的水力學(xué)特性具有重要意義。本文結(jié)合英國科學(xué)工程研究協(xié)會洪水水槽設(shè)施(SERC-FCF)的試驗資料,對復(fù)式斷面的垂向平均流速、床面剪切應(yīng)力、達(dá)西—魏斯巴哈阻力系數(shù)和曼寧系數(shù)進(jìn)行了分析。本文在查閱大量文獻(xiàn)的基礎(chǔ)上,總結(jié)了適用于計算復(fù)式斷面過流能力的12種方法,其中包括6種經(jīng)驗法和6種理論分析法,通過這些方法的計算值與實測值的對比分析,得出了每種方法的計算精度。另外本文還介紹了用于水流數(shù)值模擬的HEC-RAS、CES和MIKE 21三種模型,并結(jié)合試驗數(shù)據(jù)驗證了這三種模型在復(fù)式斷面水流運(yùn)動研究中的適應(yīng)性。本文所得的主要結(jié)論如下:(1)復(fù)式斷面主槽部分的流速大,灘地部分的流速小,垂向平均流速在橫向上存在流速梯度,尤其是在灘槽交界面處梯度最大;床面剪切應(yīng)力的分布趨勢與平均流速的分布相似,其變化規(guī)律與水深和灘槽過水面積之比有關(guān);達(dá)西-魏斯巴哈阻力系數(shù)和曼寧系數(shù)的變化與床面條件、灘槽寬度比和水深都有一定的關(guān)系。(2)在12種復(fù)式斷面過流能力的計算方法中,對角線分割法(DCM)、水平分割法(HDM)和Huthoff法(HCM)的計算精度都較高,可應(yīng)用于復(fù)式斷面的過流能力計算,而單一斷面法的計算精度最差,因此不宜應(yīng)用于復(fù)式斷面過流能力的計算。由于Huthoff法具有一定的理論基礎(chǔ),所以該方法更具有普適性。(3)HEC-RAS的主槽部分計算值偏大,而灘地部分的計算值偏小;相比較HEC-RAS的計算結(jié)果,CES和MIKE 21的計算結(jié)果與實測值比較吻合,模擬效果較好,說明這兩種數(shù)學(xué)模型可以應(yīng)用于復(fù)式斷面水流的研究。
[Abstract]:The natural channel is mostly duplex channel, and its cross section is usually composed of beach and main channel.In the dry season, the flow of water is mainly concentrated in the main channel of the river, and when the flood comes, the flow will overrun the channel beach and form the floodplain flow.Compared with a single section, the flow motion of the composite section is more complex.When the flow overruns, the interaction between the main channel and the two parts of the water body on the beach, the velocity distribution of the cross-section flow, the shear stress of the bed surface and the resistance will all change, and the formula for calculating the flow of a single section is no longer applicable.It is necessary to study a new method to describe the flow motion of a composite section, so it is of great significance to study the hydraulic characteristics of a composite section.Based on the experimental data of SERC-FCF, the vertical average velocity, bed shear stress, Darcy Weissbach resistance coefficient and Manning coefficient of the composite section are analyzed.On the basis of consulting a large number of literatures, this paper summarizes 12 methods suitable for calculating the overcurrent capacity of compound cross section, including 6 kinds of empirical methods and 6 kinds of theoretical analysis methods. Through the comparison and analysis between the calculated values and the measured values of these methods,The calculation accuracy of each method is obtained.In addition, three models, HEC-RASN CES and MIKE 21, which are used for numerical simulation of water flow, are introduced, and the adaptability of these three models in the study of the flow motion of complex cross-section is verified by combining the experimental data.The main conclusions obtained in this paper are as follows: (1) the velocity of the main channel of the composite section is large, the velocity of the beach is small, and the vertical average velocity of velocity exists in the transverse direction, especially at the interface of the beach and trough.The distribution trend of shear stress on bed surface is similar to that of average velocity, and its variation law is related to the depth of water and the ratio of water area of beach trough, and the change of resistance coefficient and Manning coefficient of Daxi-Weisbach coefficient is related to the bed condition.There is a certain relationship between the width ratio of beach and channel and the depth of water. (2) among the 12 methods for calculating the overcurrent capacity of composite cross section, the diagonal division method (DCM), the horizontal partition method (HDM) and the Huthoff method (HCM) have higher calculation accuracy, which can be applied to the calculation of the overcurrent capacity of the composite cross section.The calculation accuracy of single section method is the worst, so it is unsuitable to be applied to the calculation of overcurrent capacity of compound cross section.Because the Huthoff method has a certain theoretical foundation, the method is more general. The calculation value of the main slot part of HEC-RAS is larger than that of the beach part, and the calculated results of HEC-RAS and MIKE 21 are in good agreement with the measured values.The simulation results show that these two mathematical models can be applied to the study of complex cross section flow.
【學(xué)位授予單位】：西安理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TV133

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