Estimation of turbulence dissipation rate by Large eddy PIV method in an agitated vessel

Kysela, Bohuš; Jašíková, Darina; Konfršt, Jiří; Šulc, Radek; Ditl, Pavel

doi:10.1051/epjconf/20159202045

Cited by 5 publications

(6 citation statements)

References 11 publications

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“…In our case, the impeller revolution frequency is Nimp = 6.67 s −1 , then the corresponding blade tip velocity, Vtip, was 2.01 ms −1 , water viscosity ν = 10 −6 m 2 s −1 , impeller diameter D = 9.6 × 10 −2 m, and the Reynolds mixing number ReM = 1.93 × 10 5 .…”

mentioning

confidence: 85%

“…It is obvious that all of these aspects contribute to lowering of mixing expenses (which, globally, reach up to several million dollars yearly). There are both experimental [1][2][3][4][5] and mathematical studies in the literature. The mathematical modelling typically uses the turbulence modelling approach [6], but recently, there are attempts to apply the direct numerical simulation technique [7].…”

Section: Introductionmentioning

confidence: 99%

“…The time-resolved Particle Image Velocimetry (hereinafter PIV) method is the natural choice for the applied experimental technique, as we need to study both topology and dynamics of the flow. Several examples of application of this method on mixing process could be found in the literature, e.g., References [4,5,8].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Low-Frequency Phenomena within Flow Pattern in Standard Mixing Vessel Induced by Pitched Blade Impeller

2021

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An experimental study on the flow pattern dynamics in a standard mixing vessel with radial baffles filled with water and induced by a pitched blade impeller pumping downward is presented. Investigation is mainly focused on detection and analysis of quasi-periodical or periodical low-frequency phenomenon connected with time- and length-scales considerably exceeding the Blade Passage Frequency (hereinafter BPF) and common turbulent eddies. This phenomenon, which is expressed as large-scale mean-flow variations, is generally known as flow Macro-Instability (hereinafter MI). It could break-down just below the liquid surface, or it crashes to the liquid surface and causes its Macro-Swelling (hereinafter MS). Our investigation was based on classical two-dimensional (2D) Particle Image Velocimetry (hereinafter PIV) measurement within 3 selected vertical planes in the vessel and subsequent analysis of the velocity field. The dominant frequencies evaluated in the selected points and overall analysis of the quasi-periodical macro-flow pattern behavior is to be shown. Identification of the quasi-periodical substructures appeared within the flow pattern was performed using the Oscillation Pattern Decomposition (hereinafter OPD) method. Observation of the macro-flow patterns confirmed presence of the macro-flow structures detected within flow pattern at the identical mixing pilot plant setup by previous investigations of the MIs phenomenon, i.e., the primary circulation loop and strong impeller discharge jet located in the lower vessel segment and the strong ascending wall current at the baffle, which break-down below the surface very often. A further important contribution of the presented work is the investigation of both flow pattern within the baffles vicinity and in the middle of the sector far from the baffle, showing a significant difference. Low-frequency periodical (or quasi-periodical) behavior of the investigated macro-structures was qualitatively confirmed by the presented results and it was quantified using the velocity dominant frequencies evaluation, as noted below. This frequency analysis brings insight into the supposed and detected interconnections between dynamics of the adjacent flow structures. Detected different flow patterns within the main plane near the baffles and in the inclined plane reveal a strong influence of the baffle presence to the local vertical flow, especially within the upper part of the vessel. Quite a different flow pattern appears tangentially in front of and behind the baffle, where a wake is revealed, indicating significant influence of the baffle on the local tangential flow. The new findings represent a contribution to better understanding the physical phenomena behind the standard mixing process.

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confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Investigation of Low-Frequency Phenomena within Flow Pattern in Standard Mixing Vessel Induced by Pitched Blade Impeller

2021

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“…It is obvious that all of these aspects contribute to lowering of mixing expenses (which, globally, reach up to several million dollars yearly). There are both experimental [1,3,13,20,22] and mathematical studies in the literature. The mathematical modelling typically uses the turbulence modelling approach [12], but recently, there are attempts to apply the Direct numerical simulation(DNS) technique [21].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Low-Frequency Phenomena within Flow Pattern in Standard Mixing Vessel Induced by Pitched Blade Impeller

Bruha¹,

Procházka²,

Uruba³

2022

Which Factors Contribute to Innovative Performance? A Case Study Applied to the Food and Beverage Industry

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“…Figura 3.9.-Tasa de disipación obtenida mediante (a) evaluación directa, (b) análisis dimensional y (c) evaluación LES[22].En esta investigación se utilizaron las ecuaciones (3.3) y (3.6) para calcular 𝒌 y 𝜺, respectivamente. Esta elección se tomó con base en que el sistema de velocimetría es bidimensional, y que la resolución de la cámara fotográfica no es suficiente para capturar la información en la escala de Kolmogorov (𝜼).En este sentido la formulación de la ecuación (3.6), toma en cuenta la resolución de las imágenes obtenidas mediante la técnica PIV, y en los casos donde está es mayor a la escala de Kolmogorov, la ecuación modela la información faltante, lo que resulta en una mejor aproximación de 𝜺[22],[28],[96],[97],[99],[101],[105],[107].…”

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Análisis de patrones turbulentos de un tanque agitado, utilizando dinámica de fluidos computacional y velocimetría por imágenes de partículas

González-Neria¹

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In the present investigation, the hydrodynamic behavior in the stirring tank was analyzed. Taking a special interest in the turbulent patterns derived from the generation of turbulent kinetic energy and its dissipation rate. As well as its variation when modifying the surfaces of a 45° pitched 4 blade turbine, when using U and V grooves. Measurements of the velocity fields were carried out with the technique of particle image velocimetry in different planes, with the aim of applying the methodology of angle resolved. The system consists of a double pulse laser with a wavelength of 532nm and 75mJ, a camera with a resolution of 2360 X 1776 pixels and a frequency of 16 frames per second. The agitation tank used is made of acrylic with a diameter of 25cm (T), with four baffles 3mm thick and 2.5cm wide, mounted equidistant on the internal walls. The impeller was placed concentrically at a height from the bottom of the tank equal to C= 1/3T. The working fluid is water and about 12 liters are used to fill the tank to a height of 25cm (H). In addition, the commercial software ANSYS® Fluent® was used to implement the Large Eddy Simulation, in order to investigate the affinity of these results with those obtained experimentally. The implementation of the grooves on the surfaces of the blades led to a reduction in the power number and the pumping number. Furthermore, the distributions of the dissipation rate and of turbulent kinetic energy were modified.

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Estimation of turbulence dissipation rate by Large eddy PIV method in an agitated vessel

Cited by 5 publications

References 11 publications

Investigation of Low-Frequency Phenomena within Flow Pattern in Standard Mixing Vessel Induced by Pitched Blade Impeller

Investigation of Low-Frequency Phenomena within Flow Pattern in Standard Mixing Vessel Induced by Pitched Blade Impeller

Investigation of Low-Frequency Phenomena within Flow Pattern in Standard Mixing Vessel Induced by Pitched Blade Impeller

Análisis de patrones turbulentos de un tanque agitado, utilizando dinámica de fluidos computacional y velocimetría por imágenes de partículas

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