Summary
The following turbulence properties of a bubble column bioreactor were measured using a constant temperature anemometer with wedge shaped probes: intensity, autocorrelation function, micro and macro scales, energy dissipation rate, power spectra and energy dissipation spectra. The influence of the medium, aerator type and gas flow rate on the turbulence properties were considered. The turbulence which prevails in bubble columns is swarm turbulence and cannot be described by grid turbulence when perforated plates are used. The gas flow rate and medium properties exert only slight influences on the shape of the power spectra and energy dissipation spectra. In systems with porous plates, the turbulence has a much finer structure and the maximum of the energy dissipation spectra is closer to the gas dispersion range than in systems with perforated plates. The efficiency of energy utilization for gas dispersion in the former is therefore higher.
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Abbreviations
- E:
-
Energy dissipation rate (Poise s−2)
- E1(k):
-
One dimensional wave number power spectrum (cm3 s−2)
- E1(n):
-
One dimensional frequncy power spectrum (cm2 s−1)
- EG :
-
Mean relative gas hold up
- g:
-
Acceleration of gravity (m s−2)
- H:
-
Longitudinal distance from aerator (cm)
- k:
-
Wave number (cm−1)
- m:
-
Constant
- n:
-
Frequency (cycle; s−1)
- R:
-
Correlation coeffient
- RE :
-
(Euler) autocorrelation coefficient
- rx :
-
Point distance in x-direction (cm; mm)
- r:
-
Transverse position (centre at r=0) (cm)
- T:
-
Measuring time (s)
- TEL :
-
Macrotime scale (s)
- t:
-
Time (h, s)
- U:
-
Velocity (cm s−1)
- Ū:
-
Mean flow velocity (cm s−1)
- \(\overline{\overline {\text{U}}} \) :
-
Mean flow velocity (Eq. (21)) (cm s−1)
- u:
-
Velocity measured by anemometer (cm s−1)
- ux, uy :
-
Turbulence velocity fluctuations (cm s−1)
- u′:
-
Turbulence intensity (cm s−1)
- u ′x, y :
-
Mixed turbulence intensity (Eq. (17)) (cm s−1)
- wSG :
-
Superficial gas velocity (cm s−1)
- wSL :
-
Superficial liquid velocity (cm s−1)
- x:
-
Coordinate (here flow direction) (cm)
- y:
-
Coordinate perpendicular to wedge edge of probe and flow direction (cm)
- z:
-
Coordinate parallel to the wedge edge of probe (cm)
- εG:
-
Mean relative gas hold up
- η:
-
Kolmogoroff length scale (mm)
- Λf:
-
Macro scale (mm)
- λf:
-
Micro scale (mm)
- μ:
-
Dynamic liquid viscosity (P)
- ν:
-
Kinematic liquid viscosity (St)
- ρ:
-
Liquid density (g cm−3)
- τ:
-
Time lag (s)
- τE:
-
Dissipation time scale (s)
- φ1:
-
Dissipation spectrum (s−2)
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Zakrzewski, W., Lippert, J., Lübbert, A. et al. Investigation of the structure of two-phase flows in bubble column bioreactors. European J. Appl. Microbiol. Biotechnol. 12, 150–156 (1981). https://doi.org/10.1007/BF01008335
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DOI: https://doi.org/10.1007/BF01008335