Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
권호 표지
DOI QR코드

DOI QR Code

Relative Viscosity of Emulsions in Simple Shear Flow: Temperature, Shear Rate, and Interfacial Tension Dependence

전단유동에서 온도, 전단속도, 계면장력 변화에 따른 에멀전의 유변학적 특성

  • Received : 2015.02.08
  • Accepted : 2015.06.08
  • Published : 2015.08.01
Download PDF
⟨ Previous Next ⟩

Abstract

We simulate an emulsion system under simple shear rates to analyze its rheological characteristics using the lattice Boltzmann method (LBM). We calculate the relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, and surfactant concentration. The relative viscosity of emulsions decreased with an increase in temperature. We observed the shear-thinning phenomena, which is responsible for the inverse proportion between the shear rate and viscosity. An increase in the interfacial tension caused a decrease in the relative viscosity of the decane-in-water emulsion because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.

격자 볼츠만 기법(Lattice Boltzmann method)을 사용하여 에멀전의 유변학적 특성을 파악하기 위한 시뮬레이션을 수행하였다. 간단한 전단 유동하에서 온도와 전단속도, 계면장력에 변화를 주어 에멀전(decane-in-water)의 상대점도를 계산하고 이를 분석하였다. 에멀전의 상대점도는 온도가 증가함에 따라 감소하였고, 전단속도가 증가함에 따라 감소하는 전단박하(Shear thinning) 현상을 보여주었다. 이는 크로스 모델(Cross model)을 통해 검증하였고 일치하는 경향을 보여주었다. 계면에 존재하는 계면활성제(Surfactant)를 통해 제어되는 계면장력이 증가할수록 상대점도는 감소하는 경향을 보여주었다. 이것은 큰 계면장력에서는 기름방울의 변형이 억제되고 점도가 상대적으로 높은 기름방울의 표면적이 감소하면서 나타난다고 해석할 수 있다.

Keywords

References

  1. Edwards, D. A., Brenner, H. and Wasan, D. T., 1991, "Interfacial Transport Processes and Rheology," Butterworth-Heinemann, Philadelphia.
  2. Langevin, D., 2014, "Rheology of Adsorbed Surfactant Monolayers at Fluid Surfaces," Annu. Rev. Fluid Mech., Vol. 46, pp. 47-65. https://doi.org/10.1146/annurev-fluid-010313-141403
  3. Janssen, J. J. M., Boon, A. and Agterof, W. G. M., 1994, "Influence of Dynamic Interfacial Properties on Droplet Breakup in Simple Shear Flow," AIChE Journal, Vol. 40, No. 12, pp. 1929-1939. https://doi.org/10.1002/aic.690401202
  4. Bos, M. A. and van Vliet, T., 2001, "Interfacial Rheological Properties of Adsorbed Protein Layers and Surfactants: a Review," Adv. Colloid Interface Sci., Vol. 91, No. 3, pp. 437- 471. https://doi.org/10.1016/S0001-8686(00)00077-4
  5. Farhat, H. and Lee, J. S., 2011, "Suppressing the Coalescence in the Multi-component Lattice Boltzmann Method," Microfluidics and Nanofluidics, Vol. 11, No. 2, pp. 137-143. https://doi.org/10.1007/s10404-011-0780-y
  6. Choi, S. B., Kondaraju, S. and Lee, J. S., 2014, "Study for Optical Manipulation of a Surfactant-covered Droplet using Lattice Boltzmann Method," Biomicrofluidics, Vol. 8, No. 2, pp. 024104-1-15. https://doi.org/10.1063/1.4868368
  7. Stone, H. A. and Leal, L. G., 1990, "The Effects of Surfactants on Drop Deformation and Breakup," J. Fluid Mech., Vol. 220, pp. 161-186. https://doi.org/10.1017/S0022112090003226
  8. Eggleton, C. D., Tsai, T. and Stebe, K. J., 2001, "Tip Streaming from a Drop in the Presence of Surfactants," Phys. Rev. Lett., 87, pp. 048302-1-4. https://doi.org/10.1103/PhysRevLett.87.048302
  9. Feigl, K., Megias-Alguacil, D., Fischer, P. and Windhab, E.J., 2007, "Simulation and Experiments of Droplet Deformation and Orientation in Simple Shear Flow with Surfactants," Chem. Eng. Sci., Vol. 62, No. 12, pp. 3242-3258. https://doi.org/10.1016/j.ces.2007.02.008
  10. Kondaraju, S., Farhat, H. and Lee, J. S., 2012, "Study of Aggregational Characteristics of Emulsions on their Rheological Properties using the Lattice Boltzmann Approach," Soft Matter, 8, pp. 1374-1384. https://doi.org/10.1039/C1SM06193C
  11. Choi, S. B. and Lee, J. S., 2014, "Film Drainage Mechanism between Two Immiscible Droplets," Microfluid Nanofluid.
  12. Gunstensen, A. K. and Rothman, D. H., 1991, "Lattice Boltzmann Model of Immiscible Fluids," Phys. Rev. A, 43, pp. 4320-4327. https://doi.org/10.1103/PhysRevA.43.4320
  13. Lishchuk, S., Care, C. and Halliday, I., 2003, "Lattice Boltzmann Algorithm for Surface Tension with Greatly Reduced Microcurrents," Phys. Rev. E, 67, pp. 036701-1-5. https://doi.org/10.1103/PhysRevE.67.036701
  14. Guo, Z., Sheng, C. and Shi, B., 2002, "Discrete Lattice Effects on the Forcing Term in the Lattice Boltzmann Method," Phys. Rev. E, 65, pp. 046308-1-6. https://doi.org/10.1103/PhysRevE.65.046308
  15. He, X., Chen, S. and Doolen, G. D., 1998, "A Novel Thermal Model for the Lattice Boltzmann Method in Incompressible Limit," J. Comput. Phys., 146, pp. 282-300. https://doi.org/10.1006/jcph.1998.6057
  16. Guo, Z. and Zhao, T.S., 2005, "Lattice Boltzmann Simulation of Natural Convection with Temperature-Dependent Viscosity in a Porous Cavity," Prog. Comput. Fluid Dyn., 5, pp. 110-117. https://doi.org/10.1504/PCFD.2005.005823
  17. Stone, H. A., 1990, "A Simple Derivation of the Time-dependent Convective-diffusion Equation for Surfactant Transport along a Deforming Interface," Phys. Fluids A, 2, pp. 111-112. https://doi.org/10.1063/1.857686
  18. Farhat, H., Celiker, F., Singh T. and Lee, J. S., 2011, "A Hybrid Lattice Boltzmann Model for Surfactant-covered Droplets," Soft Matter, 7, pp. 1968-1985. https://doi.org/10.1039/c0sm00569j
  19. Chhabra, R. P. and Richardson, J. F., 2008, "Non-Newtonian Flow and Applied Rheology: Engineering Applications," Butterworth-Heinemann, Burlington.
  20. Escudier, M. P., Gouldson, I. W., Pereira, A. S., Pinho, F. T. and Poole, R. J., 2001, "On the Reproducibility of the Rheology of Shear-thinning Liquids," J. Non-Newtonian Fluid Mech., Vol. 97, No. 2-3, pp. 99-124. https://doi.org/10.1016/S0377-0257(00)00178-6