计算流体力学研究人工体力作用下方形管中二次流的起源

O. Ayala, Thurston Humphries, Tyler Youells, Jahshawn Thomas, M. Ayala
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摘要

90°弯管可能是管道系统中最常用的管件。因此,在这种弯道中发生的二次流和相关损失具有相当大的工程重要性。然而,尽管许多研究者已经研究了这个问题,但尚不清楚二次流是如何发展和触发的。90度弯头的曲率诱导离心力,导致二次流的发展。二次流的强度取决于弯曲曲率半径(R)和雷诺数(Re)。本研究的目的是了解这种流动的触发机制和发展应该取决于R和Re。使用商用工具COMSOL Multiphysics来模拟在“离心”体力作用下的全直线管道中的流动。研究领域分为三个管道部分,入口管道,“弯头”管道(“离心”体力施加的地方)和出口管道。特别注意的是在弯头入口附近的“弯头”管道中的二次流。对不同层流雷诺数(Re = 10和100)和不同曲率半径(R/D = 2和5)进行了研究,发现流动横向压力梯度和流动“径向”平流对二次流现象的产生和传播都有影响。当采用滑动壁面条件时,二次流减弱,甚至旋涡运动消失。它还表明,旋涡型二次流的完全形成发生在相同的“弧长”距离上,而与具有代表性的“曲率半径”无关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Computational Fluid Dynamics to Study the Origin of Secondary Flows in Square Ducts With Straightened Elbow Concept Governed by Artificial Body Force
The 90° pipe bend is perhaps the most frequently used fitting in piping systems. The secondary flow and associated losses occurring in such bends are therefore of considerable engineering importance. However, although many investigators have studied the problem, it is still unclear how secondary flows develop, and get triggered. The curvature of the 90-degree elbow induces centrifugal force, causing the development of such secondary flow. The intensity of the secondary flow is dependent on the radius of the bend curvature (R) and Reynolds number (Re). The objective of this study is to gain an understanding of how of the triggering mechanism and development of this flow which should depend on R and Re. A commercial tool, COMSOL Multiphysics, is used to model the flow in a fully straight duct under the action of a “centrifugal” body force was studied. The domain of study was divided in three duct sections, the inlet duct, the “elbow” duct (where the “centrifugal” body force was applied), and the outlet duct. Special attention was paid to the secondary flows in the “elbow” duct near the elbow inlet. The study is conducted for different laminar Reynolds numbers (Re = 10 and 100), and different radius of curvatures (R/D = 2 and 5). It was found both the pressure gradient in the flow transversal direction and the flow “radial” advection appear to be responsible for the initiation of secondary flow phenomena and its propagation. When using slip wall conditions, the secondary flow gets weaker, or even its swirling motion disappears. It also appears to be that the full formation of the secondary flow of the vortex type occurs at the same “arc length” distance, regardless of the representative “radius of curvature.”
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