Modification of the ultrasound induced activity by the presence of an electrode in a sono-reactor working at two low frequencies (20 and 40 kHz). Part II: Mapping flow velocities by particle image velocimetry (PIV).

Sonoelectrochemical experiments differ from sonochemical ones by the introduction of electrodes in the sonicated reaction vessel. The aim of the study is to characterize the changes in the ultrasonic activity induced by the presence of an electrode located in front of the transducer. The scope of our investigations concerns two low frequency vibration modes: 20 and 40 kHz. For this purpose, two laser visualization techniques have been used. The first part of the study, described in a previous paper (Part I), deals with the laser tomography technique which provides an accurate picture of the reactor active zones, related to numerous cavitation events. The second part of the paper (Part II) will describe the particle image velocimetry (PIV) technique used to measure the velocity vector field in the fluid portion between the horn and the electrode. As for the previous study, two parameters were studied: the electrical power supplied to the transducer and the electrode/transducer distance. The velocity vector fields show a main flow in the reactor axis. This flow seems to correspond to the conical cavitation bubbles structure which is observed on the laser tomography pictures. When an electrode is introduced into the reactor, two additional symmetric transversal flows can be quantified on both sides of the electrode.

[1]  Chao Sun,et al.  Particle image velocimetry measurement of the velocity field in turbulent thermal convection. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[2]  C. Bernard,et al.  Sonoelectrochemistry: transient cavitation in acetonitrile in the neighbourhood of a polarized electrode , 1995 .

[3]  J. Buick,et al.  PIV applied to eckart streaming produced by a medical ultrasound transducer. , 2001, Ultrasonics.

[4]  M. Angioletti,et al.  CFD turbulent modelling of jet impingement and its validation by particle image velocimetry and mass transfer measurements , 2005 .

[5]  Jean-Louis Luche,et al.  Synthetic Organic Sonochemistry , 1998 .

[6]  Yoshimichi Hagiwara,et al.  An experimental study on turbulent swirling water flow with immiscible droplets , 2006 .

[7]  Kuang-An Chang,et al.  Vortex generation and evolution in water waves propagating over a submerged rectangular obstacle: Part II: Cnoidal waves , 2001 .

[8]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[9]  Bertrand Dubus,et al.  Experimental and theoretical investigation of the mean acoustic pressure in the cavitation field. , 2005, Ultrasonics sonochemistry.

[10]  T. Leighton.  The Acoustic Bubble , 1994 .

[11]  B. Dubus,et al.  Cone-like bubble formation in ultrasonic cavitation field. , 2003, Ultrasonics sonochemistry.

[12]  R. Compton,et al.  Voltammetry in the presence of ultrasound: mass transport effects , 1996 .

[13]  Nick Lanier,et al.  Feasibility of fluorescence-based imaging of high-energy-density hydrodynamics experiments , 2003 .

[14]  E. Kimmel,et al.  Preliminary investigations of ultrasound induced acoustic streaming using particle image velocimetry. , 2001, Ultrasonics.

[15]  Randy H. Ewoldt,et al.  Turbulent and transitional velocity measurements in a rectangular microchannel using microscopic particle image velocimetry , 2003 .

[16]  R. Adrian.  Particle-Imaging Techniques for Experimental Fluid Mechanics , 1991 .

[17]  Wesley Le Mars Nyborg,et al.  11 - Acoustic Streaming , 1965 .