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

2007 ◽  
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.

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

Processes ◽  
2019 ◽  
Vol 7 (11) ◽  
pp. 798 ◽  
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.

Internal Flows in Microscopic Polymer Solution Droplets Evaporating on Flat Surfaces

2010 ◽  
Author(s):  
Shohei Yasumatsu ◽  
Narumi Nanri ◽  
Yu Yoshitake ◽  
Koichi Nakaso ◽  
Jun Fukai
Keyword(s):  
Mathematical Model ◽  
Surface Tension ◽  
Free Surface ◽  
Polymer Solution ◽  
Local Minimum ◽  
Flow Direction ◽  
Solute Concentration ◽  
Internal Flows ◽  
Initial Solute ◽  
The Mathematical Model

To control the formation process of polymer thin films from polymer solution droplets using inkjet printings, internal flows of the droplets on substrates are studied. In our previous study [1], internal flow of polymer solution droplets receding on a lyophobic surface was experimentally visualized. It was found that the direction of the circulation flow in the droplet depended on the solvent and the initial solute concentration. In particular, the flow direction of polystyrene-anisole solution was reversed as the initial solute concentration increased. In this study, to clarify this reason, the conservation equations of momentum, energy and mass on two-dimensional cylindrical coordinate are numerically solved using a finite element method. The mathematical model considers the free convections derived by the dependencies of the density and surface tension on the solute concentration. As a result, the dependences of the calculated velocities on the initial solute concentration agree qualitatively with the experiments. The mathematical model predicts that double circulation flows appear after a single flow develops at high initial solute concentrations, while double circulations do not develop at low concentrations. It is concluded that the difference between the flow directions investigated experimentally is due to such a change of the flow structure. The distribution of the surface tension on the free surface is also discussed. When a local minimum of the surface tension appears on the free surface, the double circulations develop. According to the result for a low contact angle, the local minimum point shifts toward the axis of symmetry with a lapse of time, and finally erases the double circulations.

Drag Reducing Polymer in Helicoidal Flow

1981 ◽  
Vol 103 (4) ◽  
pp. 491-496 ◽  
Author(s):  
J. T. Kuo ◽  
L. S. G. Kovasznay
Keyword(s):  
Drag Reduction ◽  
Polymer Solution ◽  
Ph Value ◽  
Flow Behavior ◽  
Superposition Principle ◽  
Polymer Concentration ◽  
Second Phase ◽  
Additional Parameter ◽  
Solution Flow ◽  
Screw Pump

A novel flow configuration was explored for the study of the behavior of drag reducing polymers. A screw pump consisting of a smooth cylinder and a concentrically placed screw was used to create a strongly three-dimensional but essentially laminar flow. In the first phase of the study, the static pressure head developed by the screw pump was measured as a function of polymer concentration (polyox 10 to 100 ppm in water). A large increase of the developed head was observed that behaved in an analogous manner to drag reduction as far as concentration and straining of the polymer solution was concerned. In the second phase of the study, a new apparatus was constructed and the additional parameter of a superimposed through flow was included and the degree of failure of the superposition principle was established. Sensitivity of the phenomenon to chemicals like HCl, HNO3, and NaOH in the polymer solution was also studied. When the effect of these chemicals on the polymer solution flow behavior was presented in terms of the pH value of the polymer solution, it showed a similar trend to those observed in drag reduction.

Macroscopic characteristics and internal flow pattern of dimethyl ether flash-boiling spray discharged through a vertical twin-orifice injector

Energy ◽  
2016 ◽  
Vol 114 ◽  
pp. 1240-1250 ◽  
Author(s):  
Dehao Ju ◽  
Zhong Huang ◽  
Xiaoxu Jia ◽  
Xinqi Qiao ◽  
Jin Xiao ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Dimethyl Ether ◽  
Internal Flow ◽  
Flash Boiling

Effect of Process Parameters on Jet Length in Electrospraying of Thermoplastic Polymer

2012 ◽  
Vol 535-537 ◽  
pp. 1146-1150 ◽  
Author(s):  
Amit Jadhav ◽  
Li Jing Wang ◽  
Carl Lawrence ◽  
Rajiv Padhye
Keyword(s):  
Polymer Solution ◽  
Process Parameters ◽  
Thermoplastic Polyurethane ◽  
Polymer Concentration ◽  
Spray Angle ◽  
Thermoplastic Polymer ◽  
Coating Quality ◽  
Jet Length ◽  
Series Of Experiments ◽  
Insight Into

Electrospraying is inexpensive and an effective way to produce submicron range coating. Spray Angle and Jet Length are important characteristics that affect coating quality while polymer solution subjected to electrospraying. It was of interest to determine the effect of the process parameters on Jet Length. In this paper, an attempt was made to apply the electrospraying concept for coating textile surfaces. Series of experiments were carried out employing different settings of process parameters such as voltage, nozzle-collector distance and polymer concentration. Thermoplastic polyurethane dissolved in tetrahydrofluran was used as a solution. The results provide some insight into the effect of electrospraying process parameters on Jet Length

Temperature Dependence of the Shear-Thinning Behavior o Partially Hydrolyzed Polyacrylamide Solution for Enhanced Oil Recovery

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Pan-Sang Kang ◽  
Jong-Se Lim ◽  
Chun Huh
Keyword(s):  
Temperature Dependence ◽  
Polymer Solution ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Polymer Concentration ◽  
Shear Thinning ◽  
Temperature Model ◽  
Polyacrylamide Solution ◽  
Partially Hydrolyzed Polyacrylamide ◽  
Hydrolyzed Polyacrylamide

Abstract The viscosity of injection fluid is a critical parameter that should be considered for the design and evaluation of polymer flood, which is an effective and popular technique for enhanced oil recovery (EOR). It is known that the shear-thinning behavior of EOR polymer solutions is affected by temperature. In this study, temperature dependence (25–70 °C) of the viscosity of a partially hydrolyzed polyacrylamide solution, the most widely used EOR polymer for oil field applications, was measured under varying conditions of the polymer solution (polymer concentration: 500–3000 ppm, NaCl salinity: 1000–10,000 ppm). Under all conditions of the polymer solution, it was observed that the viscosity decreases with increasing temperature. The degree of temperature dependence, however, varies with the conditions of the polymer solution. Martin model and Lee correlations were used to estimate the dependence of the viscosity of the polymer solution on the polymer concentration and salinity. In this study, we proposed a new empirical model to better elucidate the temperature dependence of intrinsic viscosity. Analysis of the measured viscosities shows that the accuracy of the proposed temperature model is higher than that of the existing temperature model.

scholarly journals A Numerical Investigation on Droplet Bag Breakup Behavior of Polymer Solution

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2172
Author(s):  
Guidong Chu ◽  
Lijuan Qian ◽  
Xiaokai Zhong ◽  
Chenlin Zhu ◽  
Zhongli Chen
Keyword(s):  
Polymer Solution ◽  
Adaptive Mesh Refinement ◽  
Gas Flow ◽  
Aerodynamic Force ◽  
Adaptive Mesh ◽  
Droplet Breakup ◽  
Viscous Force ◽  
Solution Droplet ◽  
New Formula ◽  
Breakup Time

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.

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