Multi-Dimensional Flow Characteristics of Bubbly Flows.

气泡流的多维流动特性。

• 批准号: 08458119
• 负责人: ARITOMI Masanori
• 金额: $ 4.86万
• 依托单位: TOKYO INSTITUTE OF TECHNOLOGY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08458119/
• 关键词: Multiphase flow; Babbly flow; Ultrasonic pulse; Doxpler effect; Velocity profile; Void fraction profile; Turbulence intersity; Flow arround bubbles; 乱流強度分布; 気泡二相流; 多次元的流動特性; ボイド率; 計測技術; 画像処理; 気液二相流

(1) A measurement system using Doppler effect of ultrasonic pulse and data processing has been developed. The proposed measurement system can measure instantaneous mixture velocity profiles of bubbly flows in the channel. By treating statistically the measured instantaneous mixture velocity profiles, the velocity profiles of both phases, the void fraction profile and turbulence intensity of the liquid phase in the channel and the liquid velocity field surrounding a bubble can be obtained.(2) Flow structure in fully developed bubbly flows is governed by the flow profile of a liquid continuous phase which is flatter than that of liquid single phase flows. Since bubbles go up due to the difference between buoyancy and interfacial shear stress, the relative velocity between both phases are almost constant in the channel.(3) Void fractions in the channel are almost constant except for those near the wall.(4) The two-phase multiplier of turbulence in bubbly flows is defined as a ratio of tur … More bulence intensity in bubbly flows to that in water single phase flows. The exist of bubbles has both effects of turbulence promotion and dispassion. For void fraction less than 0.3%, the dispassion effect is superior than the promotion effect. In the case of void fraction larger than 0.5%, the promotion effects becomes greater with an increase in void fraction.(5) The liquid flow field surrounding bubbles can be classified into three regions ; a boundary layer, a transition region and a main flow region. The boundary layer is strongly dependent on the bubble rising motion and the flow is not influenced with changes in air and water flow rates. The transition regions influenced by both effect of the bubble motion and the main liquid flow. Velocity fluctuation is high in this region because the mixing of these two effects exists. The main flow region is located far from bubbles and the bubble motion does not affect the flow.(6) The boundary layer thickness is dependent strongly on the bubble diameter and slightly on the distance between bubbles and its empirical correlation is proposed. The distance from the bubble surface to this region changes according to both bubble Reynolds number and the average void fraction and its empirical correlation is also proposed. Less

(1)研制了一种利用超声脉冲多普勒效应和数据处理的测量系统。所提出的测量系统可以测量通道内气泡流的瞬时混合速度分布。通过对实测的瞬时混合速度分布进行统计处理，可以得到两相的速度分布、通道内液相的空隙率分布和湍流强度以及气泡周围的液体速度场。(2)充分发育气泡流的流动结构受液体连续相流型的支配，该流型比液体单相流型平坦。由于气泡由于浮力和界面剪切应力的差异而上升，因此两相之间的相对速度在通道中几乎是恒定的。(3)除槽壁上的空隙外，槽内空隙率基本不变。(4)气泡流湍流度的两相乘数定义为气泡流与水单相流的湍流度之比。气泡的存在既有促进湍流的作用，也有平抑湍流的作用。当孔隙率小于0.3%时，冷静效果优于促进效果。在孔隙率大于0.5%的情况下，随着孔隙率的增加，促进作用越来越大。(5)气泡周围的液体流场可分为三个区域；一个边界层，一个过渡区和一个主流区。边界层强烈依赖气泡上升运动，流动不受空气和水流速变化的影响。过渡区受气泡运动和主液流的共同影响。由于这两种影响的混合存在，该地区的速度波动很大。主要流动区域远离气泡，气泡运动不影响流动。(6)边界层厚度与气泡直径关系密切，与气泡间距关系不大，并提出了边界层厚度与气泡直径的经验相关关系。给出了气泡表面到该区域的距离随气泡雷诺数和平均空隙率的变化规律及其经验相关性。少

项目成果

M.Aritomi, et al.: "Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit, (II) Flow Characteristics of Bubbly Countercurrent Flow" J.Nucl.Sci.Technol.Vol.34. 783-791 (1997)

M.Aritomi等人：“使用超声波速度分布监视器和视频数据处理单元的气泡流测量系统，(II)气泡逆流流的流动特性”J.Nucl.Sci.Technol.Vol.34。

S.Zhou, M.Aritomi, et al.: "Measurement System of Bubbly Flow Using Ultrasonic Velocity Profile Monitor and Video Data Processing Unit, (III) Comparison of Flow Characteristics between Bubbly Cocurrent and Countercurrent Flows" J.Nucl.Sci.Technol.Vol.35.

S.Zhou，M.Aritomi，等：“使用超声波速度分布监视器和视频数据处理单元的气泡流测量系统，（III）气泡顺流和逆流流动特性的比较”J.Nucl.Sci.Technol

M. Aritomi, et al.: "Flow Characteristics of Bubbly Countercurrent Flour" Proceedings of NTHAS98. 1. 31-38 (1998)

M. Aritomi 等人：“起泡逆流面粉的流动特性”NTHAS98 论文集。

M.Aritomi, 他5名: "Measuremert System of Bubbly Flow Using Ultrasonic Velocity Profile Motion and Video Data Processing Unit,(II)" Journal of Nuclear Science and Technolozy. 34・8. 915-923 (1997)

M.Aritomi 等 5 人：“使用超声波速度分布运动和视频数据处理单元的气泡流测量系统，（II）”核科学技术杂志 34・8（1997）。

M.Aritomi 他: "Measurement System and Flow Characterisrtics of Bubbly Countercurrent Flow" Proceedings of Japan-US Seminar on Two-Phase Flow Dynamics. 401-408 (1996)

M.Aritomi 等：“气泡逆流的测量系统和流动特性”日美两相流动力学研讨会论文集 401-408 (1996)。