交变电场频率对弱导电液滴变形及融合的影响

Effect of alternating electric field frequency on deformation and coalescence of weakly conducting droplets

基于相场方法和电荷守恒模型,在OpenFOAM框架下发展了考虑电荷输运的两相流数值方法,系统研究了不同电物性参数条件下交变电场频率对弱导电的单个液滴变形和双液滴融合的影响。结果表明,交变电场频率对单个液滴变形具有显著影响,同时也会影响双液滴的融合时间。当介电常数比Q和导电率比R相等时,单个液滴在交变电场中的平均变形率和等效直流电场中液滴的稳态变形率相等,双液滴融合时间随着频率增加而增加。当Q>R时,随着频率增大,单个液滴的平均变形率不断增大,双液滴融合时间减少。当Q<R时,电场频率增大会导致单个液滴平均变形率的减小以及双液滴融合时间增加。

Based on the phase field method(PFM)and charge conservation equation,a numerical method is proposed for two-phase flows in an external electric field within the OpenFOAM framework.Under weakly conducting condition,the deformation of a single droplet and the coalescence of two droplets under alternating electric field are investigated.The results show that the frequency of the alternating electric field can effectively affect both the deformation rate of the single droplet and the coalescence efficiency of the two droplets.When the permittivity ratio Q equals to the electrical conductivity ratio R,the mean deformation resulting from the alternating electric field(AC field)is the same as the steady state deformation under the equivalent direct current electric field(DC field),and the coalescence time becomes longer with the increase of the AC field frequency.When Q>R,the mean deformation rate of the single droplet increases continuously and the coalescence time of two droplets reduces with the increase of the frequency of the AC field.When Q<R,the increase of AC field frequency leads to the decrease of the average deformation rate of single droplet and the increase of the fusion time of two droplets.