發(fā)布時(shí)間：2018-06-05 09:02

  本文選題：顆粒離散元 + 點(diǎn)球浸入邊界法��； 參考：《天津大學(xué)》2014年碩士論文

【摘要】：泥沙顆粒在三維紊流場中的輸移是典型兩相流問題。本文采用基于有限體積法的高效能紊流并行計(jì)算程序——CgLES,結(jié)合點(diǎn)球浸入邊界法和基于“事件驅(qū)動”模型和“彈簧—阻尼”模型的顆粒離散元法,對泥沙輸移問題進(jìn)行數(shù)值模擬研究,可以模擬百萬甚至千萬量級的泥沙顆粒運(yùn)動,需要的計(jì)算資源較少,適合研究較大空間尺度的泥沙演變過程,更接近于工程應(yīng)用,同時(shí)具有較高精度,對于泥沙顆粒的輸移研究具有重要意義。本文應(yīng)用上述方法對明渠紊流邊界層中泥沙顆粒的運(yùn)動與分布,明渠床面沙紋的演變以及直立樁柱周圍的局部沖刷三種典型的泥沙輸移問題進(jìn)行了數(shù)值模擬。研究發(fā)現(xiàn):明渠中顆粒的輸運(yùn)對紊流的統(tǒng)計(jì)特征有影響,其運(yùn)動與近壁區(qū)紊流擬序結(jié)構(gòu)密切相關(guān)。慣性顆粒在明渠紊流邊界層中分布存在不均勻性,易聚集形成順流向條帶結(jié)構(gòu),這種不均勻性主要受St數(shù)的影響,當(dāng)St≈O(1)時(shí),不均勻性最為顯著。明渠紊流中沙紋會發(fā)生合并,在沙紋數(shù)量不變的條件下,沙紋高度近似呈線性增長,而沙紋的長度的平均值卻保持恒定。隨著沙紋高度的增大,輸沙率逐漸降低并趨于穩(wěn)定。當(dāng)沙紋發(fā)生合并時(shí),沙紋的高度快速增加,輸沙率也隨之大幅降低。直立樁柱周圍的局部沖刷首先發(fā)生在與展向?qū)ΨQ面呈40°左右的樁柱兩側(cè),此處的沖刷深度在整個沖刷過程中一直保持最大。隨著沖刷發(fā)展,沖刷區(qū)域和淤積區(qū)域逐漸向下游延伸,沖淤變化速度減小,最終達(dá)到?jīng)_淤平衡。
[Abstract]:The transport of sediment particles in three-dimensional turbulent flow is a typical two-phase flow problem. In this paper, a parallel computation program of high efficiency turbulent flow based on finite volume method, CgLES, is adopted, and the particle discrete element method based on event-driven model and "spring-damping" model is combined with point-ball immersion boundary method. A numerical simulation study on sediment transport can simulate the movement of millions or even tens of millions of sediment particles, which requires less computing resources. It is suitable for studying the sediment evolution process on a large spatial scale and is closer to engineering application. At the same time, it has high precision, which is of great significance for the study of sediment transport. In this paper, the motion and distribution of sediment particles in turbulent boundary layer of open channel, the evolution of sand grain on open channel bed and the local scour around vertical pile column are numerically simulated. It is found that the transport of particles in the open channel has an effect on the statistical characteristics of turbulent flow, and its motion is closely related to the quasi-sequence structure of turbulent flow near the wall. The distribution of inertial particles in the turbulent boundary layer of open channel exists inhomogeneity, and it is easy to gather and form a stripe structure along the direction of flow. This inhomogeneity is mainly affected by St number, and the inhomogeneity is the most obvious when St 鈮，

本文編號：1981438