Abstract
The results of an investigation into the application of LDA for measurement of two-phase flows are presented. It is determined that an important aspect of such measurement is the discrimination between the signals originating from different phases in the flow. It is shown that in the regions where the number density of the discrete phase is high, the error could become considerable. Existing methods of discrimination are investigated and shown to be inadequate. A novel method of signal discrimination is presented and is shown to be capable of complete removal of this error. A two-component LDA system is modified to incorporate the discriminator. Experimental data are presented in support of the method which are in good agreement with the calculated results.
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Abbreviations
- C :
-
constant, Eq. 3
- C sc :
-
particle scattering cross section
- d :
-
particle diameter
- i :
-
photodetector current
- E :
-
normalized threshold voltage
- M :
-
magnification factor of the receiving optics
- N :
-
data rate
- n :
-
defined in Eq. 5
- R :
-
radial position of the particle center defined in Eq. 2
- R0 :
-
R at 1/e 2 point
- R l , R u :
-
position R corresponding to V l V u
- S :
-
probe volume cross section area
- U :
-
mean velocity
- V :
-
signal amplitude
- V0:
-
signal amplitude for a seeding particle at Ro
- V l , V :
-
lower and upper threshold limits
- X, Y, Z :
-
coordinates
- ε0:
-
optical wave amplitude
- i:
-
particle arrival rate per unit area
- ψ:
-
discrete-phase/gas-phase mass ratio o density
- ϱ:
-
particle scattering amplitude function
- θ:
-
beam intersection half angle
- ν g :
-
volume of seeding particle
- ψ:
-
ratio of the discrete-phase to gas-phase data rate
- A :
-
auxiliary probe volume
- g :
-
continuous phase (gas or seeding particles)
- s :
-
discrete-phase (solid)
- Th :
-
threshold setting
References
Abramovich, G. N. 1970: The effect of admixture of solid particles, or droplets on the structure of a turbulent gas jet. Soviet Physics, Doklady, 15, 101–104
Durrani, T. S.; Greated, C. A. 1977: Laser systems in flow measurement, pp. 118–129. New York, London: Plenum Press
Girshovich, T. A.; Kartushiniskii, A. I.; Laats, M. K; Leonov, V. A.; Mul'gi, A. S. 1981: Experimental investigation of a turbulent jet carrying heavy particles of a disperse phase. Izvestiya Akademii Nauk USSR, Mekhanika Zhidkosti i Gaza. 5, 26–31
Lee, S. L.; Durst, F. 1982: On the motion of particles in turbulent duct flows. Int. J. Multiphase Flow, 8,125–146
Modarress, D.; Wuerer, J.; Elghobashi, S. 1982: An experimental study of a turbulent round two-phase jet. AIAA paper 82-0964
Modarress, D.; Tan, H.; Elghobashi, S. 1983: Two-component LDA measurement in a two-phase turbulent jet. AIAA paper 83-0052
Yeoman, M. L.; Azzopardi, B. J.; White, H. J.; Bates, C. J.; Roberts, P. J. 1982: Optical development and application of a two-colour LDA system for the simultaneous measurement of particle size and particle velocity. Presented at the Winter Annual Meeting of the Amer. Soc. Mech. Eng., Phoenix, Arizona, November 14–19
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Modarress, D., Tan, H. LDA signal discrimination in two-phase flows. Experiments in Fluids 1, 129–134 (1983). https://doi.org/10.1007/BF00272011
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DOI: https://doi.org/10.1007/BF00272011