Turbulence Structure Modification and Drag Reduction by Microbubble Injections in a Boundary Layer Channel Flow

Turbulent boundary layer modification in a channel flow using injection of microbubbles as a means to achieve drag reduction was studied. The physical mechanism of this phenomenon is not yet fully understood. To obtain some information related to this phenomenon, single-phase (pure water) flow and two-phase (water and microbubbles) channel flow measurements are taken. The void fraction conditions were varied while maintaining a Reynolds number of 5128 based on the half channel height. The study indicates that the presence of microbubbles within the boundary layer modifies the turbulence structure such that variations in time and space turbulent scales are observed, as well as ejection and sweep phenomena.

[1]  Jinhee Jeong,et al.  On the identification of a vortex , 1995, Journal of Fluid Mechanics.

[2]  Steven Deutsch,et al.  Numerical Investigations Into the Mechanisms of Microbubble Drag Reduction , 1985 .

[3]  James M. Wallace,et al.  The wall region in turbulent shear flow , 1972, Journal of Fluid Mechanics.

[4]  Gretar Tryggvason,et al.  The effect of bubbles on the wall drag in a turbulent channel flow , 2005 .

[5]  M. S. Chong,et al.  A general classification of three-dimensional flow fields , 1990 .

[6]  Yoshiaki Kodama,et al.  A Research Project on Application of Air Bubble Injection to a Full Scale Ship for Drag Reduction , 2007 .

[7]  S. K. Robinson,et al.  Coherent Motions in the Turbulent Boundary Layer , 1991 .

[8]  Z. C. Liu,et al.  Analysis and interpretation of instantaneous turbulent velocity fields , 2000 .

[9]  M. D. Warholic.  Modification of Turbulent Channel Flow by Passive and Additive Devices , 1997 .

[10]  Akihiro Kanai,et al.  Direct numerical simulation of wall turbulent flows with microbubbles , 2001 .

[11]  George Em Karniadakis,et al.  Numerical simulation of turbulent drag reduction using micro-bubbles , 2002, Journal of Fluid Mechanics.

[12]  Marc Perlin,et al.  Influence of bubble size on micro-bubble drag reduction , 2006 .

[13]  W. Willmarth,et al.  Measurements of the structure of the Reynolds stress in a turbulent boundary layer , 1973, Journal of Fluid Mechanics.

[14]  S. Elghobashi,et al.  On the physical mechanisms of drag reduction in a spatially developing turbulent boundary layer laden with microbubbles , 2004, Journal of Fluid Mechanics.

[15]  Rameswar Bhattacharyya,et al.  DRAG REDUCTION OF A SUBMERSIBLE HULL BY ELECTROLYSIS , 1973 .

[16]  Javier Jiménez,et al.  The autonomous cycle of near-wall turbulence , 1999, Journal of Fluid Mechanics.