圆柱壁面上液滴凝固相变对其运动行为的影响
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摘要
采用CLSVOF耦合焓-多孔介质方法对单液滴撞击低温光滑圆柱壁面的现象进行数值模拟研究,揭示了壁面温度、壁面浸润性和液滴撞击速度等因素对液滴撞击低温光滑圆形壁面后动力学行为及相变特性的影响,研究中主要关注两个重要参数的变化规律:液膜高度变化和液滴对壁面的润湿特性。研究表明:提高壁面疏水性能可有效减小液滴碰撞圆柱的铺展润湿面积,从而减小冻结面积,降低结冰的危害程度;由于圆柱壁面的曲率作用,液滴撞击疏水圆柱壁面会出现液膜断裂,但在极低温度下,可抑制液膜在圆形壁面上的分裂,导致液膜在壁面上的铺展面积有所增加,防结冰性能下降。
The prevention and control of ice accumulation has important applications in aviation,building construction and power grid construction. A deep physical insight of the ice forming on the cylindrical surface would give an instruction to the ice-removal strategies for energy conversion devices. Simulations were performed using CLSVOF(coupled level-set and volume of fluid) to track the air-water interface and an enthalpy-porosity method to capture the phase transition. The effects of learning behavior and phase transition characteristics are mainly concerned with the variation of two important parameters: the change of liquid film height and the wetting characteristics of droplets on the wall. The results showed that improve the wall hydrophobicity performance, which could effectively reduce the spreading wetted area of the droplet impact cylinder, thereby reducing the frozen area and decreasing the damage degree of icing. Due to the curvature of the cylinder, the liquid film breaks when the droplet hits the hydrophobic cylindrical wall. However, at extremely low temperature, it can inhibit the splitting of the liquid film on the circular wall surface, resulting in an increase in the spreading area of the liquid film on the wall surface, and the icing phenomenon becomes more serious.
The prevention and control of ice accumulation has important applications in aviation,building construction and power grid construction. A deep physical insight of the ice forming on the cylindrical surface would give an instruction to the ice-removal strategies for energy conversion devices. Simulations were performed using CLSVOF(coupled level-set and volume of fluid) to track the air-water interface and an enthalpy-porosity method to capture the phase transition. The effects of learning behavior and phase transition characteristics are mainly concerned with the variation of two important parameters: the change of liquid film height and the wetting characteristics of droplets on the wall. The results showed that improve the wall hydrophobicity performance, which could effectively reduce the spreading wetted area of the droplet impact cylinder, thereby reducing the frozen area and decreasing the damage degree of icing. Due to the curvature of the cylinder, the liquid film breaks when the droplet hits the hydrophobic cylindrical wall. However, at extremely low temperature, it can inhibit the splitting of the liquid film on the circular wall surface, resulting in an increase in the spreading area of the liquid film on the wall surface, and the icing phenomenon becomes more serious.
引文
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[26]杨国敏,郭开华,李宁.过冷水滴碰撞导线表面结冰机理的实验研究[J].制冷学报,2011,32(5):37-41.Yang G M,Guo K H,Li N,et al.Experimental study on the freezing mechanism of super-cooled water droplets impacting on a wire[J].Journal of Refrigeration,2011,32(5):37-41.
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[29]Liang G,Shen S,Mu X.Numerical analysis and insight of drop impacting dynamics upon a liquid film[J].Acta Mechanica,2017,228(2):385-400.
[30]Ding B,Wang H,Zhu X,et al.How supercooled superhydrophobic surfaces affect dynamic behaviors of impacting water droplets[J].International Journal of Heat and Mass Transfer,2018,124:1025-1032.
[2]胡琴,于洪杰,徐勋建,等.分裂导线覆冰扭转特性分析及等值覆冰厚度计算[J].电网技术,2016,40(11):3615-3620.Hu Q,Yu H J,Xu X J,et al.Study on torsion characteristic and equivalent ice thickness of bundle conductors[J].Power System Technology,2016,40(11):3615-3620.
[3]殷水清,赵珊珊,王遵娅,等.全国电线结冰厚度分布及等级预报模型[J].应用气象学报,2009,20(6):722-728.Yin S Q,Zhao S S,Wang J Y,et al.National wire icing thickness distribution and grade prediction model[J].Journal of Applied Meteorological Science,2009,20(6):722-728.
[4]范瑶,王宏,朱恂,等.壁面曲率及过冷度对液滴铺展特性的影响[J].化工学报,2016,67(7):2709-2717.Fan Y,Wang H,Zhu X,et al.Effect of curvature and undercooling degree of surface on behavior of droplet spreading[J].CIESC Journal,2016,67(7):2709-2717.
[5]Worthington A M.A second paper on the forms assumed by drops of liquids falling vertically on a horizontal plate[J].Proceedings of the Royal Society of London,1876,25(171-178):261-272.
[6]Mao T,Kuhn D C S,Tran H.Spread and rebound of liquid droplets upon impact on flat surfaces[J].AIChE Journal,1997,43(9):2169-2179.
[7]Heungsup P,Carr W W,Zhu J,et al.Single drop impaction on a solid surface[J].AIChE Journal,2010,49(10):2461-2471.
[8]Rioboo R,Marengo M,Tropea C.Time evolution of liquid drop impact onto solid,dry surfaces[J].Experiments in Fluids,2002,33(1):112-124.
[9]Hung L S,Yao S C.Experimental investigation of the impaction of water droplets on cylindrical objects[J].International Journal of Multiphase Flow,1999,25(8):1545-1559.
[10]Liang G T.Special phenomena of droplet impact on an inclined wetted surface with experimental observation[J].Acta Physica Sinica,2013,62(8):084707.
[11]梁超,王宏,朱恂,等.液滴撞击不同浸润性壁面动态过程的数值模拟[J].化工学报,2013,64(8):2745-2751.Liang C,Wang H,Zhu X,et al.Numerical simulation of droplet impact on surfaces with different wettability[J].CIESC Journal,2013,64(8):2745-2751.
[12]杨宝海,王宏,朱恂,等.速度对液滴撞击超疏水壁面行为特性的影响[J].化工学报,2012,63(10):3027-3033.Yang B H,Wang H,Zhu X,et al.Effect of velocity on behavior of droplet impacting on superhydrophobic surface[J].CIESC Journal,2012,63(10):3027-3033.
[13]Liang G,Guo Y,Yang Y,et al.Liquid sheet behaviors during a drop impact on wetted cylindrical surfaces[J].International Communications in Heat and Mass Transfer,2014,54(5):67-74.
[14]Flemings M C.Solidification Processing[M].New York:McGrawHill,1974.
[15]Schiaffino S,Sonin A A.Molten droplet deposition and solidification at low Weber numbers[J].Physics of Fluids,1998,9(11):3172-3187.
[16]Jung S,Tiwari M K,Doan N V,et al.Mechanism of supercooled droplet freezing on surfaces[J].Nature Communications,2012,3:615.
[17]Alavi S,Passandideh-Fard M,Mostaghimi J.Simulation of semimolten particle impacts including heat transfer and phase change[J].Journal of Thermal Spray Technology,2012,21(6):1278-1293.
[18]Yao Y,Li C,Zhang H,et al.Modelling the impact,spreading and freezing of a water droplet on horizontal and inclined superhydrophobic cooled surfaces[J].Applied Surface Science,2017,419:52-62.
[19]冷梦尧,常士楠,丁亮.不同浸润性冷表面上水滴碰撞结冰的数值模拟[J].化工学报,2016,67(7):2784-2792.Leng M Y,Chang S N,Ding L,et al.Numerical simulation of droplet impinging and freezing on cold surfaces with different wettability[J].CIESC Journal,2016,67(7):2784-2792.
[20]Liang G,Yang Y,Guo Y,et al.Rebound and spreading during a drop impact on wetted cylinders[J].Experimental Thermal and Fluid Science,2014,52(52):97-103.
[21]Liu Y,Andrew M,Jing L,et al.Symmetry breaking in drop bouncing on curved surfaces[J].Nature Communications,2015,6:10034.
[22]Andrew M,Liu Y,Yeomans J.Variation of the contact time of droplets bouncing on cylindrical ridges with ridge size[J].Langmuir,2017,33(30):7583-7587.
[23]Li H,Roisman I V,Tropea C.Influence of solidification on the impact of supercooled water drops onto cold surfaces[J].Experiments in Fluids,2015,56(6):133.
[24]Yao Y,Li C,Tao Z,et al.Experimental and numerical study on the impact and freezing process of a water droplet on a cold surface[J].Applied Thermal Engineering,2018,137:83-92.
[25]Yang G,Guo K,Li N.Experimental study on the freezing mechanism of super-cooled water droplets impacting on a wire[J].Journal of Refrigeration,2011,32(5):37-41.
[26]杨国敏,郭开华,李宁.过冷水滴碰撞导线表面结冰机理的实验研究[J].制冷学报,2011,32(5):37-41.Yang G M,Guo K H,Li N,et al.Experimental study on the freezing mechanism of super-cooled water droplets impacting on a wire[J].Journal of Refrigeration,2011,32(5):37-41.
[27]Sussman M,Puckett E G.A coupled level set and volume-offluid method for computing 3D and axisymmetric incompressible two-phase flows[J].Journal of Computational Physics,2000,162(2):301-337.
[28]Voller V R,Prakash C.A fixed grid numerical modelling methodology for convection-diffusion mushy region phase-change problems[J].International Journal of Heat and Mass Transfer,1987,30(8):1709-1719.
[29]Liang G,Shen S,Mu X.Numerical analysis and insight of drop impacting dynamics upon a liquid film[J].Acta Mechanica,2017,228(2):385-400.
[30]Ding B,Wang H,Zhu X,et al.How supercooled superhydrophobic surfaces affect dynamic behaviors of impacting water droplets[J].International Journal of Heat and Mass Transfer,2018,124:1025-1032.