Flow Regime Transition of Accelerated （Decelerated） Flow in Rectangular Channel
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摘要: 针对恒压差变化率下矩形通道内的流态转捩特性进行理论和实验研究。通过理论研究,得到恒压差变化率下的层流速度分布。以层流速度分布为基础,应用能量梯度法,对加速和减速情况下的转捩雷诺数(Re)进行计算,并分析影响转捩Re的因素。分析结果表明:加速过程中转捩Re低于稳态情况下的转捩Re和减速过程中的转捩Re高于稳态情况下的转捩Re;初始稳态压差越接近稳态转捩时的压差,转捩Re偏离稳态转捩Re就越小;压差变化率对转捩Re几乎没有影响。通过加减速实验研究得到的转捩Re变化规律和理论结果基本一致,但在压差变化率影响方面存在差异。Abstract: Flow regime transition under constant pressure drop rate in rectangular channel is investigated by theoretical and experimental study. Laminar velocity distribution and the method to determine the critical Reynolds number is obtained by theoretical study. The factors that affect the critical Reynolds is analyzed.The results show that the critical Reynolds number of accelerated（decelerated） flow is smaller（larger） than that of the steady flow. The pressure drop rate has little effect on the critical Reynolds number while the starting steady part pressure drop does. The critical Reynolds number approaches to the steady condition value while the steady part pressure drop approaches to the steady condition value. The pressure drop rate hardly affects the critical Reynolds number.The experimental data supports the smaller（larger） critical Reynolds number in accelerated（decelerated） flow, but is not consistent with the effect of pressure drop rate.
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