低含液率气液两相钝体绕流实验与机理
Experimental and Mechanistic Study on Vortex Flow Around a Bluff Body in Gas-Liquid Flow with Low Liquid Fraction

气液两相钝体绕流现象广泛存在于生产实践和社会生活中，其中气相中含少量液体是常见的两相流现 象．通过实验，研究了常压下 50,mm 口径水平圆管中低含液率气液两相钝体绕流的涡街现象，就含液率对涡街信号 的频率与幅值的影响进行比较分析，应用消除趋势波动法(DFA)对涡街信号进行处理，得到液相体积含率 0.1%,左右 是本实验条件下能产生稳定涡街的分界点．对实验流型――环状流进行了动力学分析，得到气、液相惯性力之比和 液相韦伯数随含液率的变化规律，并从液相的分布与运动及气相夹带液滴对漩涡能量影响两方面，分析了涡街失稳 的机理．最后利用拟合的两相斯特劳哈尔数和含液率之间的线性关系，使涡街在湿气及低含液率下的测量误差从 6.37%,减小到 2.03%,，对实际工程测量有一定的指导意义．
The gas-liquid two-phase flow around a bluff body is widely encountered in the production practices and social lives．In this study，the vortex flow around a bluff body in 50,mm-caliber horizontal gas-liquid two-phase flow with low liquid fractions at normal pressure was investigated by experiments．The effects of liquid fractions on the frequency and amplitude of vortex signal were discussed，and then，vortex signals were processed by detrended fluc- tuation analysis(DFA)．A characteristic liquid volume fraction around 0.1%, for the stability of vortex street was at- tained．The relationship of liquid fractions with gas-liquid phase inertia forces and the liquid Weber number were dis- cussed respectively by the dynamics analysis for annular flow．The law of vortex street instability was analyzed．It was found that the energy of vortex street would be dissipated by liquid phase and entrained droplets．The error of gas- liquid two phase flow with low liquid fractions and moisture measure decreased from 6.37%, to 2.03%, by setting up the linear relationship of two-phase Strouhal number and liquid fractions，which is instructional in actual engineering