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題 名 | 三維環形噴流層流流場之數值模擬=Numerical Simulation of Three Dimensional Annular Swirling Laminar Jet Flow |
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作 者 | 廖清標; 盧泰成; 吳銘順; 施慶忠; | 書刊名 | 力學 |
卷 期 | 17:2 2001.12[民90.12] |
頁 次 | 頁151-161 |
分類號 | 440.137 |
關鍵詞 | 環形噴流; 圓柱擋體; 投影法; 渦漩數; Annular swirling jet flow; Central body; Projection method; Swirl number; |
語 文 | 中文(Chinese) |
中文摘要 | 本文主要利用數值計算方法探討環形噴流於一圓柱擋體後之流場結構。以有限差分法求解二維時變的 Navier-Stokes方程式。首先利用投影法導出壓力的Poisson方程式,使得連續方程式能自動滿足。速度場則採用顯式 Adams-Bashforth法及Crank-Nicloson法的混合計算方法,網格採 MAC 交錯網格,使得壓力及速度在求解過程不必疊代程序,流場解答不論在時間或空間的離散上,都能獲得二階精確度。影響流場的主要參數為雷諾數及渦漩數,本文之數值模擬針對數種不同低雷諾數及渦漩數進行流場特性探討,入流之邊界條件由實驗量測給定,出流之邊界條件則採軸向線性對流邊界條件。與林之實驗比較,初步結果顯示流場型態與實驗大致相符。對無漩流之流場發現當 Re=405 時流況變為非軸對稱之渦流釋放,當增加雷諾數至500時將無渦漩產生。 |
英文摘要 | A numerical investigation is presented to study the flow structures behind an axially mounted center-body of a confined annular swirling jet flow. Based on the time-dependent, three-dimensional Navier-Stokes equations, a semi-implicit projection method is employed to obtain the pressure Poisson equation such that the equation of continuity satisfies automatically. The velocity can be solved then form the equation of motion by using a compound method. An implicit Crank-Nicolson scheme for second derivative terms in θ and explicit Adams-Bashforth scheme for the other terms are used. Therefore, the strict restriction of increment of computing time step can be released. The MAC staggered grid system is adopted in the numerical model. The characteristics of this numerical scheme are decoupled the velocity and pressure in the solution solver without iterating procedures, and having second order accuracy in both time and space discretization. The inflow boundary conditions are provided from the experimental measurements by LDA and the convective outflow boundary condition is used in the numerical model. The flow structures are dependent on Reynolds number and swirl number. Numerical simulations for the cases of several different Reynolds number and swirl strengths of inflow are described. The present numerical results are in reasonable agreement with those of the experiment obtained by LDA measurements and smoke visualization of Lin. In the case of non-swirling flow, the flow becomes nonaxisymmetric with vortex shedding for Re = 405. If we increase Reynolds number to 500, the vortex shedding will be choked. |
本系統中英文摘要資訊取自各篇刊載內容。