0
TECHNICAL PAPERS

Investigation of Microbubble Boundary Layer Using Particle Tracking Velocimetry

[+] Author and Article Information
Javier Ortiz-Villafuerte1

Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843-3133

Yassin A Hassan2

Department of Nuclear Engineering, Texas A&M University, College Station, TX 77843-3133y-hassan@tamu.edu

www.pivchallenge.org

1

Currently at Department of Nuclear Systems, National Institute for Nuclear Research, Ocoyoacac, Mexico 52045.

2

Corresponding author.

J. Fluids Eng 128(3), 507-519 (Oct 11, 2005) (13 pages) doi:10.1115/1.2174062 History: Received March 31, 2004; Revised October 11, 2005

Particle tracking velocimetry has been used to measure the velocity fields of both continuous phase and dispersed microbubble phase, in a turbulent boundary layer, of a channel flow. Hydrogen and oxygen microbubbles were generated by electrolysis. The average size of the microbubbles was 15μm in radius. Drag reductions up to 40% were obtained, when the accumulation of microbubbles took place in a critical zone within the buffer layer. It is confirmed that a combination of concentration and distribution of microbubbles in the boundary layer can achieve high drag reduction values. Microbubble distribution across the boundary layer and their influence on the profile of the components of the liquid mean velocity vector are presented. The spanwise component of the mean vorticity field was inferred from the measured velocity fields. A decrease in the magnitude of the vorticity is found, leading to an increase of the viscous sublayer thickness. This behavior is similar to the observation of drag reduction by polymer and surfactant injection into liquid flows. The results obtained indicate that drag reduction by microbubble injection is not a simple consequence of density effects, but is an active and dynamic interaction between the turbulence structure in the buffer zone and the distribution of the microbubbles.

FIGURES IN THIS ARTICLE
<>
Copyright © 2006 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Sketch of the PIV setup

Grahic Jump Location
Figure 2

Typical image from a two phase boundary layer measurement

Grahic Jump Location
Figure 3

Overlay of the velocity vectors from 40 consecutive instantaneous fields, and final velocity profile after dividing the velocity field into multiregions for optimum tracking

Grahic Jump Location
Figure 4

Comparison of the mean velocity profile in the single phase boundary layer, using the three different methods shown to compute the wall friction velocity

Grahic Jump Location
Figure 5

Microbubble size distribution at a liquid velocity of 10mm∕s

Grahic Jump Location
Figure 6

Distribution of the freely moving microbubbles in the boundary layer, for five different drag reduction values

Grahic Jump Location
Figure 7

Modification of the profiles of the streamwise component of the liquid mean velocity vector across the two phase boundary layer, for five different drag reductions, in physical coordinates

Grahic Jump Location
Figure 8

Modification of the profiles of the streamwise component of the liquid mean velocity vector across the two phase boundary layer, for five different drag reductions, in wall coordinates

Grahic Jump Location
Figure 9

Modification of the profiles of the normal component of the liquid mean velocity vector across the two phase boundary layer, for the highest and lowest cases of drag reduction, in physical coordinates

Grahic Jump Location
Figure 10

z component of the mean vorticity field for the drag reduction of 10.1% case

Grahic Jump Location
Figure 11

z component of the mean vorticity field for the drag reduction of 27.5% case

Grahic Jump Location
Figure 12

z component of the mean vorticity field for the drag reduction of 41.9% case

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In