|
|
The minimum record time for PIV measurement in a vessel agitated by a Rushton turbine
Šulc, R. ; Ditl, P. ; Fořt, I. ; Jašíková, D. ; Kotek, M. ; Kopecký, V. ; Kysela, Bohuš
In PIV studies published in the literature focusing on the investigation of the flow field in an agitated vessel the record time is ranging from the tenths and the units of seconds. The aim of this work was to determine minimum record time for PIV measurement in a vessel agitated by a Rushton turbine that is necessary to obtain relevant results of velocity field. The velocity fields were measured in a fully baffled cylindrical flat bottom vessel 400 mm in inner diameter agitated by a Rushton turbine 133 mm in diameter using 2-D Time Resolved Particle Image Velocimetry in the impeller Reynolds number range from 50 000 to 189 000. This Re range secures the fully-developed turbulent flow of agitated liquid. Three liquids of different viscosities were used as the agitated liquid. On the basis of the analysis of the radial and axial components of the mean- and fluctuation velocities measured outside the impeller region it was found that dimensionless minimum record time is independent of impeller Reynolds number and is equalled N. t(Rmin) = 103 +/- 19.
|
|
|
Local velocity scaling in T400 vessel agitated by Rushton turbine in a fully turbulent region
Šulc, R. ; Ditl, P. ; Fořt, I. ; Jašíková, D. ; Kotek, M. ; Kopecký, V. ; Kysela, Bohuš
The hydrodynamics and flow field were measured in an agitated vessel using 2-D Time Resolved Particle Image Velocimetry (2-D TR PIV). The experiments were carried out in a fully baffled cylindrical flat bottom vessel 400 mm in inner diameter agitated by a Rushton turbine 133 mm in diameter. The velocity fields were measured in the zone in upward flow to the impeller for impeller rotation speeds from 300 rpm to 850 rpm and three liquids of different viscosities (i.e. (i) distilled water, ii) a 28% vol. aqueous solution of glycol, and iii) a 43% vol. aqueous solution of glycol), corresponding to the impeller Reynolds number in the range 50 000 < Re < 189 000. This Re range secures the fully-developed turbulent flow of agitated liquid. In accordance with the theory of mixing, the dimensionless mean and fluctuation velocities in the measured directions were found to be constant and independent of the impeller Reynolds number. On the basis of the test results the spatial distributions of dimensionless velocities were calculated. The axial turbulence intensity was found to be in the majority in the range from 0.388 to 0.540, which corresponds to the high level of turbulence intensity.
|
|
| |
|
|
Comparison of measured instantaneous velocities and a calculated flow in an agitated vessel
Kysela, Bohuš ; Pešava, V. ; Konfršt, Jiří ; Chára, Zdeněk ; Kotek, M.
Proces míchání je řízen změnami rychlostního pole a tvorbou vírových struktur v průběhu pracovního cyklu. V této studii porovnáváme výsledky CFD výpočtů s výsledky měření střední prostorově průměrované rychlosti, a také polohově závislé rychlosti odpovídající otáčivému pohybu míchadla, při kterém vznikají vírové struktury. Experimentální data časových řad dvourozměrných vektorových map rychlostí byly získány pomocí TR PIV měření v oblasti míchadla. Pro získání hodnot okamžitých rychlostí a vírových struktur bylo použito modelování pomocí LES v kombinaci s SM simulací pohybu oblasti s míchadlem. Získané výsledky jsou zde porovnány a aplikace použité metody diskutována.
|
guest ::
