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

The Korean Society of Mechanical Engineers (대한기계학회)
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Modification of Particle Dispersion in Isotropic Turbulence by Free Rotation of Particle

등방성 난류에서 입자의 회전에 의한 분산 특성의 변화

  • 박용남 (연세대학교 기계공학과) ;
  • 이창훈 (연세대학교 기계공학과)
  • Received : 2008.12.26
  • Accepted : 2010.06.04
  • Published : 2010.07.01
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Abstract

The effect of a particle's spin is investigated numerically by taking into account the effect of lift forces originating due to difference between the rotations of a particle and of a fluid, such as the Saffman and Magnus lift forces. These lift forces have been ignored in many previous studies on particle-laden turbulence. The trajectory of the particles can be changed by the lift forces, resulting in a significant modification of the stochastic characteristics of heavy particles. Probability density functions and autocorrelations are evaluated from the velocity of solid particle, acceleration of solid particles, and acceleration of fluid at the position of solid particle. Changes in velocity statistics are negligible but statistics related with acceleration are affected by the rotation of particle. When a laden particle encounters coherent structures during its motion, the particle's rotation might significantly affects the motion due to intermittently large fluid acceleration near the coherent structures.

등방성 난류에서 부유된 무거운 입자의 운동에서, 입자의 회전이 고려되었을 때 입자의 분산 특성에 나타난 변화를 살펴보았다. 입자의 회전을 고려함으로 인해 추가로 고려되는 양력은 그 크기가 작은 것으로 알려져 있고, 따라서 많은 연구에서 회전에 의한 효과는 무시되었다. 본 연구에서는 라그랑지안 기법으로 추적한 입자의 궤적에 미치는 양력의 크기를 속도와 가속도의 자기상관함수 및 확률밀도함수를 통해 정량적으로 살펴보았다. 속도 통계량에서는 양력에 의한 효과가 무시할 만 했으나, 가속도와 관련된 통계는 양력에 의한 영향이 있는 것으로 확인되었다. 난류의 가속도는 간헐성을 띄며, 간헐적인 특성은 난류 구조와 관련이 있다는 것이 알려져 있다. 따라서 입자에 작용하는 양력과 난류구조에 연관성이 있다는 유추가 가능하다.

Keywords

References

  1. Pope, S.B., 2000, Turbulent Flow, CambridgeUniversity press, Cambridge, p.184.
  2. Jung, J.D, Yeo, K.M. and Lee, C, 2008, “Behavior ofHeavy Particles in Isotropic Turbulence,” PhysicalReview E, Vol.77, 016307. https://doi.org/10.1103/PhysRevE.77.016307
  3. Eswaran, V. and Pope, S.B, 1988, “An Examinationof Forcing in Direct Numerical Simulation ofTurbulence,” Comp. Fluids, Vol.16, p.257. https://doi.org/10.1016/0045-7930(88)90013-8
  4. Choi, J. I. and Lee, C., 2003, “Lagrangian Statisticsin Turbulent Channel Flow,” Phys. Fluids, Vol.26,pp.883. https://doi.org/10.1063/1.864230
  5. Maxey, M. R. and Riley, J. J., 1983, “Equation ofMotion for a Small Rigid Sphere in a Non-UniformFlow,” Phys. Fluids, Vol.26, No.4, p.883. https://doi.org/10.1063/1.864230
  6. Happel, J. and Brenner, H., 1973, Low ReynoldsNumber Hydrodynamics, Noordhoff Intl. Pub. Leiden.
  7. Rubinow, S. I. and Keller, J. B., 1961, TheTransverse Force on Spinning Sphere Moving in aViscous Fluid, J. Fluid Mech., Vol.11, p.447. https://doi.org/10.1017/S0022112061000640
  8. Saffman, P. G., 1965, “The Lift on a Small Sphere ina Slow Shear Flow,” J. Fluid Mech., Vol.22, p.385. https://doi.org/10.1017/S0022112065000824
  9. Mclauhglin, J. B., 1991, “Inertial Migration of aSmall Sphere in Linear Shear Flow,” J. Fluid Mech.,Vol.224, p.262.
  10. Mei, R., 1992, “An Approximate Expression for theShear Lift on a Spherical Particle at Finite ReynoldsNumber,” Intl. J. Nultiphase Flow, Vol.18, p.145. https://doi.org/10.1016/0301-9322(92)90012-6
  11. Crowe, C., Sommerfeld, M. and Tsuji, Y., 1998,Multiphase Flows with Droplets and Particles, CRCpress.
  12. Lee, S. and Lee, C., 2005, “Intermittency ofAcceleration in Isotropic Turbulence,” PhysicalReview E, Vol. 71, 056310. https://doi.org/10.1103/PhysRevE.71.056310