CAJ | 학술논문

对扩缩通道内流动与换热进行了数值模拟并探讨了其中的非线性特性。通过对不同突扩比ER、不同长宽比AR及不同雷诺数Re下通道内流场和温度场进行分析，给出在一定工况下对称通道内流体的流动和换热会出现偏斜等非线性现象的情况。数值模拟结果表明，存在临界雷诺数Rec使流体流动和换热形态发生转变，当Re超过Rec时，流体流动和换热不仅有对称解，还有非对称解；当Re继续增大时，流体流动和换热出现振荡。通道的几何尺寸及后缩段（表现为ER及AR）都对Rec产生影响。分析结果表明，当Re超过临界雷诺数Rec时，同一截面处上下壁面的局部努塞尔数Nu也由对称向非对称转变，上下壁面出现最大局部Nu的位置也不同。
대확축통도내류동여환열진행료수치모의병탐토료기중적비선성특성。통과대불동돌확비ER、불동장관비AR급불동뢰낙수Re하통도내류장화온도장진행분석，급출재일정공황하대칭통도내류체적류동화환열회출현편사등비선성현상적정황。수치모의결과표명，존재림계뢰낙수Rec사류체류동화환열형태발생전변，당Re초과Rec시，류체류동화환열불부유대칭해，환유비대칭해；당Re계속증대시，류체류동화환열출현진탕。통도적궤하척촌급후축단（표현위ER급AR）도대Rec산생영향。분석결과표명，당Re초과림계뢰낙수Rec시，동일절면처상하벽면적국부노새이수Nu야유대칭향비대칭전변，상하벽면출현최대국부Nu적위치야불동。
The Newtonian fluid flow in a rectangular channel with sudden expansion followed by sudden contraction was simulated numerically for the whole flow region.The nonlinear characteristics and temperature field were investigated with various Reynolds numbers and geometrical dimensions.The results show that the temperature field will evolve from symmetric state to asymmetric state with the increase of Re .When Re <Re c (critical Reynolds number),the symmetric state is stable.However,when Re ≥Re c ,the flow loses stability and develops from symmetric state to asymmetric state via a symmetry-breaking bifurcation.The expansion ratio and aspect ratio can affect the value of the critical Reynolds number.The analysis results show that when the Re number is greater than the critical Re ,Nu number will change significantly,and then affect the heat transfer of the pipeline.