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Experiments in Fluids

, Volume 34, Issue 5, pp 556–565 | Cite as

Experiments on the flow of a thin liquid film over a horizontal stationary and rotating disk surface

Article

Abstract

Experiments on characterization of thin liquid films flowing over stationary and rotating disk surfaces are described. The thin liquid film was created by introducing deionized water from a flow collar at the center of an aluminum disk with a known initial film thickness and uniform radial velocity. Radial film thickness distribution was measured using a non-intrusive laser light interface reflection technique that enabled the measurement of the instantaneous film thickness over a finite segment of the disk. Experiments were performed for a range of flow rates between 3.0 lpm and 15.0 lpm, corresponding to Reynolds numbers based on the liquid inlet gap height and velocity between 238 and 1,188. The angular speed of the disk was varied from 0 rpm to 300 rpm. When the disk was stationary, a circular hydraulic jump was present in the liquid film. The liquid-film thickness in the subcritical region (downstream of the hydraulic jump) was an order of magnitude greater than that in the supercritical region (upstream of the hydraulic jump) which was of the order of 0.3 mm. As the Reynolds number increased, the hydraulic jump migrated toward the edge of the disk. In the case of rotation, the liquid-film thickness exhibited a maximum on the disk surface. The liquid-film inertia and friction influenced the inner region where the film thickness progressively increased. The outer region where the film thickness decreased was primarily affected by the centrifugal forces. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. At high rotational speeds, spiral waves were observed on the liquid film. It was also determined that the angle of the waves which form on the liquid surface was a function of the ratio of local radial to tangential velocity.

Keywords

Reynolds Number Film Thickness Liquid Film Centrifugal Force Disk Surface 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

g

Gravitational acceleration, m/s2

\( \dot Q \)

Flow rate, m3/s

r

Local disk radius from its center, m

ri

Radius at which the liquid enters the disk surface, m

rHJ

Location of the hydraulic jump, m

Rei

Reynolds number, (V i δ i /v), (\( \dot Q \)/2πr i v)

Vr

Local radial velocity, (\( \dot Q \)/2πrδ), m/s

Vi

Radial velocity component at the exit of the collar, (\( \dot Q \)/2πr i δ i ), m/s

Greek letters

α

The angle between the tangent to the wave and radial direction, degree

δ

Local film thickness, m

δi

Initial gap height, m

δsub

Film thickness in the subcritical region at the hydraulic jump location, m

ν

Kinematic viscosity at the inlet conditions, m2/s

ω

Rotational speed, rad/s

Notes

Acknowledgements

Funding of this work was provided by the NASA Microgravity Fluids Physics Program, Glenn Research Center, Cleveland, Ohio, under contract NCC3–789.

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUniversity of ConnecticutStorrsUSA

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