The Eulerian-Lagrangian approach is employed to simulate droplet trajectories due to the large-velocity gradient between two solid surfaces: a stationery block (slider) and a rotating plane (disk). Sudden expansion after the extremely small spacing will trap the particles in the open spaces. The fluid phase flowfield is obtained by solving Navier-Stokes equations with slip boundary correction in the Eulerian approach, and the droplet trajectories are calculated by integrating equations of motion with slip correction in the Lagrangian approach. Because of the extremely small spacing and the droplet size, Brownian motion effectively increases the probability of slider-head collisions, especially for extremely small particles. This study demonstrates that the effect due to particle size is the dominant factor in determining the probability of particle-slider collision, especially for particle sizes comparable with the air mean free path and the flowfield immediately adjacent to the solid surfaces. The results also show that lowering the flying height of the slider and increasing the disk velocity attracts the particles toward the gap between the disk and the slider.

1.
Bird, G. A., (ed.), 1976, Molecular Gas Dynamics, Clarendon Press.
2.
Burgdorfer
A.
,
1959
, “
The Influence of the Molecular Mean Free Path on the Performance of Hydrodynamic Gas Lubricated Bearings
,”
ASME Journal of Basic Engineering
, Vol.
81
, pp.
94
94
.
3.
Dahneke
B.
,
1974
, “
Diffusional Deposition of Particles
,”
Journal of Colloid & Interface Engineering Science
, Notes, Vol.
48
, pp.
983
992
.
4.
Davies
C. N.
,
1995
, “
Definitive Equations for the Fluid Resistance of Spheres
,”
Proceedings of the Physical Society
, Vol.
57
, Part 4, pp.
259
270
.
5.
Davis
M. H.
,
1972
, “
Collisions of Small Cloud Droplets: Gas Kinetic Effects
,”
Journal of Atmospheric Sciences
, Vol.
29
, pp.
91
92
.
6.
Decker, R., and Shafer, C. F. (eds), 1989, “Mixing and Demixing Processes in Multiphase Flows with Application to Propulsion Systems,” NASA CP-3006.
7.
Durst
F.
,
Milojevic
D.
, and
Schonung
B.
,
1984
, “
Eulerian and Lagrangian Predictions of Particular Two-Phase Flows: a Numerical Study
,”
Applied Mathematical Modelling
, Vol.
8
, pp.
101
115
.
8.
Happel, J., and Brenner, H., 1965, Low Reynolds Number Hydrodynamics, Prentice-Hall, Englewood Cliffs, N.J., pp. 983–992.
9.
Patankar, S. V., 1981, Numerical Heat Transfer and Fluid Flow, Hemisphere Publishing, Washington.
10.
Saffman
P. G.
,
1965
, “
The Lift on a Small Sphere in a Slow Shear Flow
,”
Journal of Fluid Mechanics
, Vol.
22
, pp.
385
400
.
11.
Saffman
P. G.
,
1968
,
Corrigendum to “The Lift on a Small Sphere in a Slow Shear Flow
,”
Journal of Fluid Mechanics
, Vol.
31
, pp.
624
624
.
12.
Schaaf
S. A.
, and
Sherman
F. S.
,
1953
, “
Skin Friction in Slip Flow
,”
Journal of Aeronautical Sciences
, Vol.
21
, No.
2
, pp.
85
90
.
13.
Stevens
L. D.
,
1981
, “
The Evolution of Magnetic Storage
,”
IBM Journal of Research and Development
, Vol.
25
, No.
5
, pp.
663
675
.
This content is only available via PDF.
You do not currently have access to this content.