本文關鍵詞：彎道中流體流動及對流換熱的數(shù)值模擬　出處：《華東理工大學》2016年碩士論文　論文類型：學位論文

  更多相關文章： 彎道 對流換熱 網格獨立解 邊界條件

【摘要】：本文以彎道中的牛頓流體和非牛頓冪律流體的流動與對流換熱問題為研究對象,采用高精度算法進行了數(shù)值模擬。網格獨立解是對流換熱數(shù)值研究的前提,而邊界條件的恰當處理則是模擬結果準確性的關鍵,本文著重分析了速度場和溫度場的網格獨立解。針對牛頓流體湍流流動,本文結合第二類邊界條件(熱流密度條件),并改變網格密度,對比分析其兩種邊界處理方式對數(shù)值解準確性的影響。對于冪律流體層流流動,本文分析了Dn數(shù)、流動指數(shù)n和Pr數(shù)對流動及對流換熱的影響。對于牛頓流體和冪律流體,本文算法均良好地模擬了彎道中流體的流動與對流換熱。網格獨立解的研究結果表明：由于不可壓縮流動中速度場和溫度場之間的耦合關系較弱,獲得網格獨立解所需的網格數(shù)目存在差別,溫度場對網格密度要求更高。另外對于冪律流體而言,當二次流出現(xiàn)四渦結構現(xiàn)象后,流動更為復雜,這種情況下,速度場對網格密度要求相對較高。對于牛頓流體湍流流動,兩種熱流密度邊界條件的處理方式的對比結果表明,Kader(1981)的代數(shù)方法可以在網格粗糙的情況下仍然能夠較好地吻合實驗值,具有更好的通用性和網格適應性。但由于壁面處溫度梯度對于計算Nu數(shù)的準確性有較大的影響,此時仍應盡可能采用y+值小的網格。對于冪律流體層流流動,盡管Dn數(shù)具有不穩(wěn)定性,二次流從二渦突變成四渦結構時的Dn數(shù)不固定,但當四渦結構現(xiàn)象出現(xiàn)后,相同的Dn數(shù)下,本文速度場分布與前人結果吻合良好,且隨著Dn數(shù)增大,其對速度場影響減弱；而溫度場分布主要受到Dn數(shù)和Pr數(shù)的影響。
[Abstract]:In this paper, the flow and convection heat transfer problems of Newtonian fluid and non-Newtonian power-law fluid in curved channel are studied, and the numerical simulation is carried out by using high-precision algorithm. The independent solution of grid is the premise of the numerical study of convection heat transfer. The proper treatment of boundary conditions is the key to the accuracy of the simulation results. In this paper, the grid independent solutions of velocity field and temperature field are analyzed, especially for the turbulent flow of Newtonian fluid. Combining the second kind of boundary condition (heat flux condition), and changing the grid density, the effect of two kinds of boundary treatment methods on the accuracy of numerical solution is analyzed, and the laminar flow of power law fluid is studied. In this paper, the effects of Dn number, flow exponent n and pr number on flow and convection heat transfer are analyzed, for Newtonian fluid and power law fluid. The numerical results show that the coupling relationship between velocity field and temperature field in incompressible flow is weak. There are differences in the number of meshes needed to obtain the independent solution of the grid, and the temperature field requires higher grid density. In addition, for power-law fluids, the flow becomes more complex when the secondary flow has a four-vortex structure phenomenon. For the turbulent flow of Newtonian fluid, the results of two heat flux boundary conditions are compared. The algebraic method of Kaderian 1981is able to agree well with the experimental data even when the grid is rough. It has better generality and mesh adaptability, but the temperature gradient on the wall has a great influence on the accuracy of the calculation of Nu number. In the case of laminar flow of power-law fluid, the number of Dn is not fixed when the secondary flow changes from two vortices to four vortices, despite the instability of Dn number. However, when the phenomenon of four-vortex structure appears, the distribution of velocity field in this paper is in good agreement with the previous results under the same Dn number, and with the increase of Dn number, its influence on the velocity field weakens. The distribution of temperature field is mainly affected by Dn number and pr number.
【學位授予單位】：華東理工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TK124

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本文編號：1363909