【摘要】 用旋涡强度法对PIV测得的湍流泡状流混合层流动进行研究,混合层高低侧流速之比为4∶1,基于速度差和管道水力直径的Reynolds数范围为4400～132000。气泡分别从隔板尾部混合层的中心起始位置与低速侧注入流体,直径为0.5～2mm。利用旋涡强度法分析流场清楚地显示出排除了剪切作用的涡结构主要集中在混合层中心的锥形区域,随着Reynolds数的增大,旋涡强度的值不断增大而锥形区域不断变窄。在同一Reynolds数下,沿主流方向旋涡强度先增大、后减小。从混合层中心注气时气泡主要分布在隔板下游旋涡强度值较大的区域,而低速侧注入的气泡主要分布在低速侧,但由于涡结构的卷吸作用,低速侧注入的气泡也会进入隔板下游的中心区域。与单相流动相比,低Reynolds数情况下气泡的加入可以加剧流场本身的变化,而高Reynolds数时则对旋涡强度产生的影响较弱。更多还原

【Abstract】 Turbulent bubbly mixing layer was experimentally investigated by PIV and analyzed by using the swirling strength method.The velocity ratio between high speed and low speed was 4∶1 and the Reynolds number based on the velocity difference of two streams and hydraulic channel diameter ranged from 4400 to 132000.Bubbles with a diameter from 0.5 mm to 2 mm were injected into the flow field at the end of the splitter and in the low speed side separately.By using the swirling strength method,the vortex structures excluded the effect of shear were shown clearly,and were concentrated in the coniform area of the central mixing flow field.With increasing Reynolds number,swirling strength increased and the coniform area became narrow.Swirling strength first increased and then decreased along the downstream direction at the same Reynolds number.When injected at the end of the splitter,most of the bubbles were distributed in the downstream area of the mixing layer where swirling strength was larger.However,when the bubbles were injected in the low speed side,bubbles were mainly concentrated in the low speed side,but some of them could also be trapped by the vortex structures and move to the central part of the mixing layer.Compared with the single phase case,the results indicated that swirling strength was strengthened when the bubbles were injected at a low Reynolds number,while it was weakened at a high Reynolds number.更多还原