Macro-instabilities of velocity field in stirred vessel:

Hasal, P.; Montes, J.-L.; Boisson, H. C.; Fořt, Ivan

doi:10.1016/s0009-2509(99)00334-6

Cited by 65 publications

(57 citation statements)

References 29 publications

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“…Consequently, an explicit value of the dominant MI frequency could not be determined. Similar types of difficulties in determining the dominant MI peak have been noted in the works of Montes et al (1997), Hasal et al (2000), Nikiforaki et al (2003) and Khan (2005). However, this was not crucial in the analysis.…”

Section: Macro-instabilitiessupporting

confidence: 74%

PIV study of the flow field generated by a sawtooth impeller

Unadkat

Rielly

Nagy

2011

Chemical Engineering Science

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Stereoscopic and high-speed particle image velocimetry (PIV) techniques have been employed to study the flow field induced by a sawtooth (EkatoMizer) impeller, operated in the fully turbulent flow regime at an impeller speed of 1500 rpm.Ensemble-averaged mean flow fields and turbulence quantities were calculated for a region close to the impeller blades. The flow was found to be anisotropic near the impeller and exhibited return-to-isotropy behaviour further away from it. Macroinstabilities were found to have a high probability of occurrence in the discharge stream. All three velocity components from the stereo-PIV measurements were used to estimate the dissipation rate, by adopting a large eddy simulation (LES) analogy.Spurious vectors distorting the dissipation rate calculation were identified, and various standard deviation filters were applied for vector validation. By evaluating the filtered dissipation rate profiles against the multi-fractal intermittency model of Meneveau and Sreenivasan (1991), the global standard deviation filter was found to be the most suitable type. The ratio of the maximum to the mean dissipation rate for the EkatoMizer discharge stream was found to be similar to that reported for Rushton disk turbine and pitched-blade turbine impellers in the literature, raising questions about the reported high-shear advantage of sawtooth impellers.

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Section: Macro-instabilitiessupporting

confidence: 74%

PIV study of the flow field generated by a sawtooth impeller

Unadkat

Rielly

Nagy

2011

Chemical Engineering Science

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“…The mechanism is complex and three-dimensional but the large vortices clearly appear in a regular way, with a well defined frequency. Hasal et al (2000) used the proper orthogonal decomposition to analyse LDA data observed for a PBT and found a f' = 0.087 for Re = 750 and Re = 1,200, and a value of 0.057 for Re = 75,000. In addition they noticed that the fraction of the total kinetic energy carried by the flow instabilities (relative magnitude) varied with the location inside the stirred vessel, they being stronger in the central and wall regions below the impeller but weaker in the discharge flow from the impeller.…”

Section: Jet Impingement Macro-instabilities (J-mis)mentioning

confidence: 99%

Flow Instabilities in Mechanically Agitated Stirred Vessels

Galletti¹,

Brunazzi²

2011

Hydrodynamics - Advanced Topics

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“…Any periodic disturbance or instabilities, e.g., Macro Instabilities (MI), of the flow field in a stirred tank using hydrofoil impellers should, therefore, be a consequence of geometry. MI are low frequency phenomena with time and length scales far greater than the turbulence scales [3]. The MI in the system will be derived from a combination of Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) measurements.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics in a Stirred Square Tank Investigated Using a 3‐D PIV LES Decomposition Approach and LDA Measurements

Kilander¹,

Rasmuson²

2004

Chem Eng & Technol

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In this study, the hydrodynamics and turbulence in a square tank stirred with the hydrofoil impeller Lightnin A310 is investigated using a large eddy particle image velocimetry approach. Particle image velocimetry data are used as the large scale part of a large eddy simulation and the small scales are modelled by direct calculation of the turbulent stress tensor using filtered particle image velocimetry data. The spatial distribution of the calculated dissipation rate showed agreement with previous work. The macro instabilities of the flow structure were investigated by means of spectral analysis. Low frequency phenomena separated from the mean flow were detected. The cause of these could partly be explained by the circulation time for the tank.

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Macro-instabilities of velocity field in stirred vessel:

Cited by 65 publications

References 29 publications

PIV study of the flow field generated by a sawtooth impeller

PIV study of the flow field generated by a sawtooth impeller

Flow Instabilities in Mechanically Agitated Stirred Vessels

Hydrodynamics in a Stirred Square Tank Investigated Using a 3‐D PIV LES Decomposition Approach and LDA Measurements

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