平口管口处气泡行为特征数值模拟
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摘要
为研究平口管口处单个气泡行为特征,采用流体体积模型(Volume of Fluid,VOF)方法,数值模拟研究气泡的膨胀脱离过程,对比分析了浸没方式、管径、气体速度、液体密度和表面张力对气泡膨胀脱离时间和脱离直径的影响规律。研究结果表明:在3种不同管口浸没方式下,气泡膨胀脱离时间均随管口气体速度增大而降低,但降低速率逐渐减小;在底部和顶部浸没方式下,气泡膨胀脱离时间和脱离直径随表面张力增大而增加,随液体密度增大而降低;对于侧面浸没方式,气泡膨胀脱离时间和脱离直径随表面张力增大整体呈上升趋势,而受液体密度影响不大。气泡膨胀脱离时间与气泡脱离直径呈正相关。所建立的数学模型能够真实地模拟气泡形成及运动特征,从而提供一个有效的研究方法。
VOF( Volume of Fluid) model is employed to study the behavior of single bubble at nozzle of vertical flat pipe. The process of bubble expansion and detachment is simulated,and the influences of immersion mode,nozzle diameter,gas velocity,liquid density,and surface tension on bubble expansion detachment time and detachment diameter are comparatively analyzed. Results demonstrate that the bubble expansion and detachment time shortens with the increase of gas velocity at the nozzle,and then tends to be gentle gradually under three different nozzle immersion modes. In the bottom-immersion and top-immersion mode,the bubble expansion detachment time and detachment diameter both increase with the growth of surface tension,while decline with the climbing of liquid density. In the side-immersion mode,the bubble expansion detachment time and detachment diameter both increase with the growth of surface tension,whereas the effect of liquid density is subtle. There is a positive correlation between the bubble expansion and detachment time and the bubble detachment diameter. The established mathematical model offers an effective research approach by simulating the formation and motion of bubbles truly.
VOF( Volume of Fluid) model is employed to study the behavior of single bubble at nozzle of vertical flat pipe. The process of bubble expansion and detachment is simulated,and the influences of immersion mode,nozzle diameter,gas velocity,liquid density,and surface tension on bubble expansion detachment time and detachment diameter are comparatively analyzed. Results demonstrate that the bubble expansion and detachment time shortens with the increase of gas velocity at the nozzle,and then tends to be gentle gradually under three different nozzle immersion modes. In the bottom-immersion and top-immersion mode,the bubble expansion detachment time and detachment diameter both increase with the growth of surface tension,while decline with the climbing of liquid density. In the side-immersion mode,the bubble expansion detachment time and detachment diameter both increase with the growth of surface tension,whereas the effect of liquid density is subtle. There is a positive correlation between the bubble expansion and detachment time and the bubble detachment diameter. The established mathematical model offers an effective research approach by simulating the formation and motion of bubbles truly.
引文
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[15]吴晅,焦晶晶,梁盼龙,等.顶部浸没竖直向下平口管口气泡膨胀脱离特性[J].化工学报,2016,67(5):1868-1877.
[2] BESAGNI G,INZOLI F. Bubble Size Distributions and Shapes in Annular Gap Bubble Column[J]. Experimental Thermal and Fluid Science,2016,74:27-48.
[3]鞠花,陈刚,李国栋.静水中气泡上升运动特性的数值模拟研究[J].西安理工大学学报,2011,27(3):344-349.
[4] ZIEGENHEIN T,LUCAS D.Observations on Bubble Shapes in Bubble Columns under Different Flow Conditions[J].Experimental Thermal and Fluid Science,2017,85:248-256.
[5] LIOW J L. Quasi-equilibrium Bubble Formation During Top-submerged Gas Injection[J]. Chemical Engineering Science,2000,55(20):4515-4524.
[6] QU Chen,YU Yong,ZHANG Jian. Experimental Study of Bubbling Regimes on Submerged Micro-orifices[J].International Journal of Heat and Mass Transfer,2017,111:17-28.
[7] BARI S D,ROBINSON A J. Experimental Study of Gas Injected Bubble Growth from Submerged Orifices[J]. Experimental Thermal and Fluid Science,2013,44(1):124-137.
[8]徐玲君,陈刚,邵建斌,等.静水中单个气泡的动力学特性数值模拟[J].长江科学院院报,2011,28(9):18-20,29.
[9] PREMLATA A R,TRIPATHI M K,KARRI B,et al.Dynamics of an Air Bubble Rising in a Non-Newtonian Liquid in the Axisymmetric Regime[J]. Journal of NonNewtonian Fluid Mechanics,2017,239:53-61.
[10] GEORGOULAS A,KOUKOUVINIS P,GAVAISES M,et al. Numerical Investigation of Quasi-static Bubble Growth and Detachment from Submerged Orifices in Isothermal Liquid Pools:The Effect of Varying Fluid Properties and Gravity Levels[J]. International Journal of Multiphase Flow,2015,74:59-78.
[11] HUDA N,NASER J,BROOKS G,et al. CFD Modeling of Swirl and Nonswirl Gas Injections into Liquid Baths Using Top Submerged Lances[J]. Metallurgical and Materials Transactions B,2010,41(1):35-50.
[12]王冲,熊靓,朱道飞,等.贫化电炉气液混合顶吹的气泡群形态及搅拌效果[J].冶金能源,2014(2):30-33.
[13]吴晅,李铁,蔡杰,等.洗涤冷却室液池内气液流动特性的模拟研究[J].热力发电,2008,37(5):10-15,53.
[14] BRACKBILL J U,KOTHE D B,ZEMACH C. A Continuum Method for Modeling Surface Tension[J]. Journal of Computational Physics,1992,100(2):335-354.
[15]吴晅,焦晶晶,梁盼龙,等.顶部浸没竖直向下平口管口气泡膨胀脱离特性[J].化工学报,2016,67(5):1868-1877.