管内幂律液/气三维流动特性和湍流调制机理的实验研究

The researches on the flow characteristics of liquid-gas two-phase flow in the fields of energy, chemicals and transportation have an important theoretical significance. With the development of new energy and new materials, a variety of engineering applications from power-law non-Newtonian fluid have been more widely used. Because of the liquid-gas two-phase flow instability and the complexity of phase interface and interaction between the liquid and gas two phases in pipe with intricately rheological properties of power-law fluid, the flow characteristics and turbulence control become increasingly urgent and arduous tasks. In this project by synthesizing the theory of the flow stability or turbulence mechanism and the experimental technique of synchronized measurement with the laser-induced fluorescence and the three-dimensional synthetic aperture images, the study on three-dimensional transient flow characteristics (velocity, pressure field)of the power-law liquid-gas two-phase flow in pipe, moreover the space-time evolution of the liquid-gas interfaces(three-dimensional structure sizes, spatial distributions, etc.) and the morphology of liquid film on the wall will be proceeded.The effects of the rheological parameters including the power-law and rheological index on the pipe flow will be researched. At the same time the parametric study on the mechanism of the flow pattern transition is carried out in order to discover the parameterized criterion on the transition. The interaction mechanism among the liquid film,bubble and vortex shedding by bubble's wakes will be analyzed. Under the perturbations of the released parameterized bubbles in the power-law liquid pipe flow, the mechanism of the turbulence modulation and the optimal control strategy will be investigated by experiments so as to reduce friction and increase the efficiency of the flow transport and mass transfer.

管内气液两相流动特性的研究在能源、化工和交通等领域具有重要理论意义；随着新能源、新材料的发展，各种幂律型非牛顿流体在工程中应用越发广泛。鉴于气液两相流动的不稳定性、相界面分布与作用力和幂律流体流变特性的复杂性，使管内幂律液/气两相流动特性和对湍流控制的研究成为日益紧迫而艰巨的课题。本项目拟通过流动稳定性和湍流机理分析、三维合成孔径图像与激光诱导荧光同步测量实验技术相结合的方法，进行管内幂律液/气两相瞬时三维流动特性(速度场、压力场等)、气液相界面(三维结构尺寸、空间分布等)和管壁液膜形态的时空运动演化规律的研究，探讨幂律液体流变参数(幂律和流变指数)对管内流动特性的影响，开展管内幂律液/气两相流流型转换机理和判据的参数化研究，获得包括液膜、气泡及其尾流诱导涡脱落之间的相互作用机制，研究施加气泡扰动下管内幂律液/气流动的湍流调制机理和优化控制策略，实现降低摩阻，提高流动输运和传质效率的目的。

管内气液两相流动特性的研究在能源、化工和交通等领域具有重要理论意义；随着新能源、新材料的发展，各种幂律型非牛顿流体在工程中应用越发广泛。鉴于气液两相流动的不稳定性、相界面分布与作用力和幂律流体流变特性的复杂性，使管内幂律液/气两相流动特性和对湍流控制的研究成为日益紧迫而艰巨的课题。本项目通过流动稳定性和湍流机理分析、三维粒子图像测速相结合的方法，进行管内幂律液/气两相瞬时三维流动特性、气液相界面的时空运动演化规律的研究，探讨幂律液体流变参数(幂律和流变指数)对管内流动特性的影响，开展管内幂律液/气两相流流型转换机理、施加气泡扰动下管内幂律液/气流动特性的研究，以达到提高流动输运和传质效率的目的。. 采用课题组自行研制的角位移机构和管道内幂律液/气两相流动实验测量装置，依据Scheimpflug准则，分别对水、甘油和卡波姆液体的管道内气液两相流动进行三维粒子图像测速技术研究,观测施加微气泡流和大气泡对幂律流动特性的影响。综合黏度、表面张力、流体密度等参量，提出气泡抬升运动模型，采用气泡尺度预测模型，对幂律液/气两相流动进行了数值模拟；通过对幂律液/气界面稳定性的理论研究和数值求解，得出了液体表面波的不稳定形式，结果表明液体的黏性力始终是抑制液相破碎成液滴的重要因素；表面张力在瑞利和泰勒模式下，液相表面张力所起的作用正好相反，即表面张力在瑞利模式下是促进液相破碎的重要因素，而在泰勒模式下，是抑制液相破碎的因素；泰勒模式下最大扰动增长率、占优波数及截止波数都大于瑞利模式，液/气相界面更不稳定，更易破碎；幂律指数增加会导致最大扰动增长率减小，占优波数略减，截止波数基本不变，说明幂律指数的增加不利于液相的破碎。幂律指数越大，流体的剪切变稠特征越显著，黏性越大，从而更不容易破碎；稠度系数表征的是幂律流体的稠度大小，反映了液体的黏性，是抑制幂律流相破碎的重要因素。