TURBULENCE ENERGY SPECTRA IN BAFFLED MIXING VESSELS

Turbulence energy spectra were measured for longitudinal and lateral components of fluctuating velocity, in baffled mixing vessels keeping geometrical similarity, by using a hot-film anemometer. From the comparison of the spectra, it was confirmed that the turbulence in the impeller stream deviated largely from both homogeneity and isotropy, especially in the lower wave-number range. However, these deviations were so small for the turbulence in other regions that the assumption of local isotropy would be applicable and that the homogeneity was implied to exist in the higher wave-number range. Energy spectra normalized by microscale λ and fluctuating velocity component u''i showed good similarity and were not affected by location in the vessel, agitator speed and size of the mixing vessel. Then, effects on energy spectra by agitator speed and by the size were fairly represented by u''i and by λ respectively. The Kolmogoroff''s universal similarity of spectrum was not observed except in the very high wave-number range.