Critical condition of electrohydrodynamic jetting from a polymer-solution droplet on a conductive wire

The deformation and breakup of a polymer solution droplet plays a key role in inkjet printing technology, tablet-coating process, and other spray processes. In this study, the bag breakup behavior of the polymer droplet is investigated numerically. The simple coupled level set and volume of fluid (S-CLSVOF) method and the adaptive mesh refinement (AMR) technique are employed in the droplet breakup cases at different Weber numbers and Ohnesorge numbers. The nature of the polymer solution is handled using Herschel–Bulkley constitutive equations to describe the shear-thinning behavior. Breakup processes, external flow fields, deformation characteristics, energy evolutions, and drag coefficients are analyzed in detail. For the bag breakup of polymer droplets, the liquid bag will form an obvious reticular structure, which is very different from the breakup of a Newtonian fluid. It is found that when the aerodynamic force is dominant, the increase of the droplet viscous force will prolong the breakup time, but has little effect on the final kinetic energy of the droplet. Moreover, considering the large deformation of the droplet in the gas flow, a new formula with the cross-diameter (Dcro) is introduced to modify the droplet drag coefficient.

Download Full-text

Magnetic Convection Inside a Polymer Solution Droplet on a Lyophobic Surface

Numerical Heat Transfer Part A Applications ◽

10.1080/10407782.2011.540962 ◽

2011 ◽

Vol 59 (2) ◽

pp. 98-113 ◽

Cited By ~ 2

Author(s):

Masayuki Kaneda ◽

Yusuke Matsushima ◽

Kazuhiko Suga

Keyword(s):

Polymer Solution ◽

Solution Droplet ◽

Magnetic Convection

Download Full-text

The growth of a bubble in a polymer solution and its critical condition.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.52.3146 ◽

1986 ◽

Vol 52 (481) ◽

pp. 3146-3151

Author(s):

Tomoji TSUJINO

Keyword(s):

Polymer Solution ◽

Critical Condition

Download Full-text

Role of polymer concentration and molecular weight on the rebounding behaviors of polymer solution droplet impacting on hydrophobic surfaces

Microfluidics and Nanofluidics ◽

10.1007/s10404-014-1518-4 ◽

2014 ◽

Vol 18 (5-6) ◽

pp. 1221-1232 ◽

Cited By ~ 19

Author(s):

Hyung Kyu Huh ◽

Sungjune Jung ◽

Kyung Won Seo ◽

Sang Joon Lee

Keyword(s):

Molecular Weight ◽

Polymer Solution ◽

Polymer Concentration ◽

Hydrophobic Surfaces ◽

Solution Droplet

Download Full-text

Numerical Simulations of Polymer Solution Droplet Impact on Surfaces of Different Wettabilities

Processes ◽

10.3390/pr7110798 ◽

2019 ◽

Vol 7 (11) ◽

pp. 798 ◽

Cited By ~ 5

Author(s):

Tembely ◽

Vadillo ◽

Soucemarianadin ◽

Dolatabadi

Keyword(s):

Polymer Solution ◽

Impact Analysis ◽

Contact Angle Hysteresis ◽

Polymer Concentration ◽

Dynamic Contact ◽

Droplet Impact ◽

Droplet Spreading ◽

Physically Based ◽

Solution Droplet ◽

Fluid Rheology

This paper presents a physically based numerical model to simulate droplet impact, spreading, and eventually rebound of a viscoelastic droplet. The simulations were based on the volume of fluid (VOF) method in conjunction with a dynamic contact model accounting for the hysteresis between droplet and substrate. The non‐Newtonian nature of the fluid was handled using FENE‐CR constitutive equations which model a polymeric fluid based on its rheological properties. A comparative simulation was carried out between a Newtonian solvent and a viscoelastic dilute polymer solution droplet. Droplet impact analysis was performed on hydrophilic and superhydrophobic substrates, both exhibiting contact angle hysteresis. The effect of substrates’ wettability on droplet impact dynamics was determined the evolution of the spreading diameter. While the kinematic phase of droplet spreading seemed to be independent of both the substrate and fluid rheology, the recoiling phase seemed highly influenced by those operating parameters. Furthermore, our results implied a critical polymer concentration in solution, between 0.25 and 2.5% of polystyrene (PS), above which droplet rebound from a superhydrophobic substrate could be curbed. The present model could be of particular interest for optimized 2D/3D printing of complex fluids.

Download Full-text

Effect of the Initial Solute Concentration on the Flow Pattern Inside an Evaporating Polymer Solution Droplet on a Substrate

ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference, Volume 1 ◽

10.1115/ht2007-32718 ◽

2007 ◽

Cited By ~ 1

Author(s):

Masayuki Kaneda ◽

Kentarou Hyakuta ◽

Hirotaka Ishizuka ◽

Jun Fukai

Keyword(s):

Contact Angle ◽

Polymer Solution ◽

Flow Pattern ◽

Laser Sheet ◽

Polymer Concentration ◽

Internal Flow ◽

Solute Concentration ◽

Initial Solute ◽

Solution Droplet ◽

Source Flow

The internal flow of an evaporating polymer solution droplet on a substrate is experimentally studied. The flow visualization is carried out. The effect of the initial polymer concentration is further investigated. A polystyrene-acetophenone (PS-Ap) and a polystyrene-anisole (PS-Ani) solution are employed as the droplet. A nylon powder is mixed with the droplet for the visualization by a YAG-laser sheet light. The droplet evaporates after the settlement on the substrate. Without the polymer dissolved in the solvent, complicated flow is observed in both droplets. For the cases with dissolved polymer, the flow pattern is rectified. In the PS-Ap droplet, the source flow is observed for the initial solute mass fraction c0 = 0.005 – 0.20. This convection becomes strong as c0 increases. The mechanism of the flow inside the PS-Ap droplet can be understood by the combination of the natural convection and Marangoni convection due to the differences of the temperature and the solute concentration. As for the PS-Ani droplet, the evaporation process and the flow pattern are affected by c0. For the dilute solution (0 < c0 < 0.03), the contact angle decreases during the contact line receding. The observed flow pattern becomes similar to that in the PS-Ap droplet. At c0 = 0.08 – 0.2, the decline of the contact angle is remarkable and the direction of the internal flow becomes inverse. This flow mechanism cannot be clarified, but it may have the relations with the decreasing contact angle.

Download Full-text