【作者】 庄乃亮； 谭思超； 袁红胜； 杨博男；

【Author】 ZHUANG Nai-liang;TAN Si-chao;YUAN Hong-sheng;YANG Bo-nan;Fundamental Science on Nuclear Safety and Simulation Technology Laboratory,Harbin Engineering University;

【机构】 核安全与仿真技术重点学科实验室；

【摘要】 针对非稳态流动条件下矩形截面对称突缩管内流场分布与阻力特性进行了实验研究。采用粒子图像测速法(PIV)获得了简谐脉动流水平突缩管(突缩比2)瞬时流场分布信息,实验参数范围:300<Re<7500,脉动周期5~60s,幅值0.15~0.61。研究发现:定常流动条件下突缩管存在层流、层紊流过渡和紊流三个分区;在层流区和充分发展的紊流区,突缩管脉动流时均压降等于定常流动压降。在层流紊流过渡区,脉动流时均压降损失大于定常流动压降损失。且流量脉动幅值越大,脉动压降时均值越大,相对幅值也越大;流量脉动周期对脉动压降时均值无显著影响,突缩台阶上游角涡的大小随着流动的加、减速而减、增,尤其在层紊流过渡区较为显著。与定常流动相比,非稳态流动由于流动的加、减速导致突缩台阶附近角涡损失增加,从而导致突缩管时均压降损失有所增加。更多还原

【Abstract】 The flow field and resistance characteristics in sudden contraction channel of unsteady flow were investigated experimentally by 2D particle image velocimetry(PIV).Contraction ratio(upstream to downstream area ratio) of 4 and 2 were selected comparatively for the study.The instantaneous two dimensional velocity profile and flow resistance were obtained.The results of unsteady flow were compared with those of steady flow with the Reynolds number ranged from 300 to 7500,based on the upstream hydraulic diameter.The time averaged pulsatile pressure drop of sudden contraction channel is larger than that of steady flow in laminar-turbulent transition region,and the ratio of the former to the latter has positive correlation with pulsatile amplitude while the ratio is insensitive to the pulsatile frequency.The flow visualization shows that the size of corner eddy near the sudden contraction decreases with the acceleration increasing.It is the acceleration of pulsatile flow that intensifies the hydraulic loss of the sudden contraction.更多还原