On the application of LDA to bubbly flow in the wobbling regime

Abstract Considerations for applying LDA to bubbly flows with bubbles about 3 to 4 mm in diameter were investigated by means of detailed experiments in the model geometry of a train of bubbles. Both forward scatter and backscatter LDA were studied. The validity of phase discrimination via burst amplitude was tested and special attention was paid to the impact of bubble interface response to the laser beams.Forward and backscatter measurements can be compared well. In both configurations, predominantly the liquid phase is “seen” by LDA. A bubble itself only leads to a velocity realization in special conditions. In those cases the Doppler shift is determined by the motion of the bubble interface which consists of the motion of the center of gravity of the bubble as well as shape oscillations. In backscatter bubbles only give velocity realizations when their “cheeks” pass through the measuring volume virtually perpendicularly.It is shown that the bubble-caused velocity realization frequency is very low for bubbles of the size used. Phase discrimination on burst amplitude does not hold. In ambient cases such as bubble columns one can assume that only the liquid phase is being studied.

[1]  L.H.J. Absil,et al.  Analysis of the Laser Doppler Measurement Technique for Application in Turbulent Flows , 1995 .

[2]  P. F. Vassallo,et al.  Measurement of velocities in gas-liquid two-phase flow using laser Doppler velocimetry , 1992 .

[3]  R. Clift,et al.  Bubbles, Drops, and Particles , 1978 .

[4]  R. F. Mudde,et al.  Liquid velocity field in a bubble column: LDA experiments , 1997 .

[5]  G. A. Irons,et al.  A combined laser Doppler anemometry and electrical probe diagnostic for bubbly two-phase flow , 1991 .

[6]  W. W. Martin,et al.  The local measurement of the size and velocity of bubbles rising in liquids , 1982 .

[7]  Michel Lance,et al.  Homogeneous Turbulence in Bubbly Flows , 1991 .

[8]  J. Kuhlman,et al.  Three-component velocity measurements in a turbulent recirculating bubble-driven liquid flow , 1992 .

[9]  H. Tan,et al.  LDA signal discrimination in two-phase flows , 1983 .

[10]  R. S. Limaye,et al.  Velocity measurements in two‐phase bubble‐flow regime with laser‐doppler anemometry , 1976 .

[11]  Franz Durst,et al.  On the motion of particles in turbulent duct flows , 1982 .

[12]  Franz Durst,et al.  Characteristics of laser-doppler signals from bubbles , 1981 .

[13]  Robert F. Mudde,et al.  Coherent structures and axial dispersion in bubble column reactors , 1996 .

[14]  P.Y.W. Yu,et al.  Laser-Doppler measurement of the velocity and diameter of bubbles using the triple-peak technique , 1988 .

[15]  J. Joshi,et al.  Simultaneous measurements of gas and liquid phase velocities and gas hold-up using laser-doppler velocimeter , 1997 .

[16]  Liang-Shih Fan,et al.  Bubble wake dynamics in liquids and liquid-solid suspensions , 1990 .

[17]  Franz Durst,et al.  Experimental and numerical investigation a bubble-driven laminar flow in a axisymmetric vessel , 1984 .

[18]  INVESTIGATION OF THE USE OF LASER-DOPPLER VELOCIMETRY IN TWO-PHASE BUBBLY FLOWS , 1990 .

[19]  Eric Loth,et al.  STRUCTURE OF UNDEREXPANDED ROUND AIR JETS SUBMERGED IN WATER , 1989 .

[20]  I. G. Currie,et al.  Laser‐Doppler measurements of bubble dynamics , 1984 .

[21]  L. Drain.  The Laser Doppler Technique , 1980 .

[22]  M. Lance,et al.  Turbulence in the liquid phase of a uniform bubbly air–water flow , 1991, Journal of Fluid Mechanics.

[23]  J. L. Marié,et al.  Turbulence Measurements in Two-Phase Bubbly Flows Using Laser Doppler Anemometry , 1984 .

[24]  Jamshid M. Nouri,et al.  Particle motion and turbulence in dense two-phase flows , 1987 .

[25]  J. H. Whitelaw,et al.  Theorie und Praxis der Laser-Doppler-Anemometrie , 1987 .

[26]  V. P. Mishra,et al.  LDA Measurements of Flow in Stirred Gas-Liquid Reactors , 1992 .

[27]  S. L. Lee,et al.  An LDA technique for in situ simultaneous velocity and size measurement of large spherical particles in a two-phase suspension flow , 1982 .