Simulation and Analysis of Fluid Dynamic Behaviour of Foods during Filling Processes

2007 ◽  
Vol 2 (3) ◽  
Author(s):  
Eleonora Bottani ◽  
Roberto Rizzo ◽  
Giuseppe Vignali
Keyword(s):  
Dynamic Behaviour ◽  
Fluid Dynamic ◽  
Shear Thinning ◽  
High Viscosity ◽  
Inlet Section ◽  
Shear Thinning Fluids ◽  
Filling System ◽  
Time Required ◽  
Shear Thinning Fluid ◽  
Steady State Predictions

This research presents a model describing the behaviour of a non-Newtonian shear-thinning fluid during aseptic filling processes, in order to determine the influence of the behaviour of fluids on the performance of filling valves in aseptic beverage plants, mainly in terms of the time required to perform the filling process. The ultimate aim of the study is to explore the possibility of improving the accuracy of industrial filling processes, so as to be able to utilise them with high viscosity fluids.The numerical model, exploiting the Finite Elements Method (FEM), was designed using the commercial software Comsol Multiphysics, and validated by comparing the steady state predictions with outcomes of filling experiments performed in industrial laboratories. Hence, subsequent numerical simulations were performed to investigate the transition from laminar to turbulent flow for shear-thinning fluids under different pressure conditions, in 3D time-dependent configurations. Results of the simulations, performed on a low fat yoghurt, show that laminar flow subsists within the whole filling system when the Metzner-Reed Reynolds number at the inlet section of the valve is lower than approx 444.

scholarly journals Secondary instabilities in Taylor–Couette flow of shear-thinning fluids

2021 ◽  
Vol 933 ◽  
Author(s):  
S. Topayev ◽  
C. Nouar ◽  
J. Dusek
Keyword(s):  
Numerical Simulations ◽  
Couette Flow ◽  
Vortex Flow ◽  
Shear Thinning ◽  
Taylor Vortex ◽  
Shear Thinning Fluids ◽  
Taylor Vortex Flow ◽  
Viscous Shear ◽  
Taylor Couette ◽  
Shear Thinning Fluid

The stability of the Taylor vortex flow in Newtonian and shear-thinning fluids is investigated in the case of a wide gap Taylor–Couette system. The considered radius ratio is $\eta = R_1/R_2=0.4$ . The aspect ratio (length over the gap width) of experimental configuration is 32. Flow visualization and measurements of two-dimensional flow fields with particle image velocimetry are performed in a glycerol aqueous solution (Newtonian fluid) and in xanthan gum aqueous solutions (shear-thinning fluids). The experiments are accompanied by axisymmetric numerical simulations of Taylor–Couette flow in the same gap of a Newtonian and a purely viscous shear-thinning fluid described by the Carreau model. The experimentally observed critical Reynolds and wavenumbers at the onset of Taylor vortices are in very good agreement with that obtained from a linear theory assuming a purely viscous shear-thinning fluid and infinitely long cylinders. They are not affected by the viscoelasticity of the used fluids. For the Newtonian fluid, the Taylor vortex flow (TVF) regime is found to bifurcate into a wavy vortex flow with a high frequency and low amplitude of axial oscillations of the vortices at ${Re} = 5.28 \, {Re}_c$ . At ${Re} = 6.9 \, {Re}_c$ , the frequency of oscillations decreases and the amplitude increases abruptly. For the shear-thinning fluids the secondary instability conserves axisymmetry. The latter is characterized by an instability of the array of vortices leading to a continuous sequence of creation and merging of vortex pairs. Axisymmetric numerical simulations reproduce qualitatively very well the experimentally observed flow behaviour.

scholarly journals Modeling the motion of a Taylor bubble in a microchannel through a shear-thinning fluid

2021 ◽  
Vol 312 ◽  
pp. 05006
Author(s):  
Andrea Aquino ◽  
Davide Picchi ◽  
Pietro Poesio
Keyword(s):  
Shear Thinning ◽  
Current Theory ◽  
Continuous Phase ◽  
Bubble Velocity ◽  
Recent Theory ◽  
Taylor Bubble ◽  
Lubrication Film ◽  
Shear Thinning Fluids ◽  
Validity Range ◽  
Shear Thinning Fluid

Applications of multiphase flows in microchannels as chemical and biological reactors and cooling systems for microelectronic devices typically present liquid slugs alternated with bubbles of elongated shape, the Taylor bubbles. These occupy almost entirely the cross-section of the channel and present a hemispherical front and a liquid layer, the lubrication film, which separates the gas from the tube wall. The Taylor bubble perturbs the surrounding fluids activating many transport mechanisms in the proximity of the gas-liquid interface; therefore, the bubble motion significantly influences the heat and mass transfer rates. Although many works deeply investigate the bubble hydrodynamics in Newtonian fluids, the knowledge about the relation between bubble hydrodynamics and rheological properties is insufficient, and studies where the continuous phase exhibits a shear-thinning behavior are missing. Our numerical analysis tries to fill this gap by investigating the motion of a Taylor bubble in a non-Newtonian shear-thinning fluid, modeled by the Carreau viscosity model. First, we validate the results against the Newtonian case and a recent theory for shear-thinning fluids (Picchi et al., Journal of Fluid Mechanics, 2021, 918). Then, we investigate the bubble hydrodynamics far from the validity range of the current models. Finally, we study the scaling of the bubble velocity and lubrication film thickness, extending the current theory to shear-thinning fluids.

scholarly journals Squirming through shear-thinning fluids

2015 ◽  
Vol 784 ◽  
Author(s):  
Charu Datt ◽  
Lailai Zhu ◽  
Gwynn J. Elfring ◽  
On Shun Pak
Keyword(s):  
Asymptotic Analysis ◽  
Numerical Simulations ◽  
Rheological Properties ◽  
Reynolds Numbers ◽  
Shear Thinning ◽  
Fundamental Question ◽  
Low Reynolds Numbers ◽  
Shear Thinning Fluids ◽  
Micro Organisms ◽  
Shear Thinning Fluid

Many micro-organisms find themselves immersed in fluids displaying non-Newtonian rheological properties such as viscoelasticity and shear-thinning viscosity. The effects of viscoelasticity on swimming at low Reynolds numbers have already received considerable attention, but much less is known about swimming in shear-thinning fluids. A general understanding of the fundamental question of how shear-thinning rheology influences swimming still remains elusive. To probe this question further, we study a spherical squirmer in a shear-thinning fluid using a combination of asymptotic analysis and numerical simulations. Shear-thinning rheology is found to affect a squirming swimmer in non-trivial and surprising ways; we predict and show instances of both faster and slower swimming depending on the surface actuation of the squirmer. We also illustrate that while a drag and thrust decomposition can provide insights into swimming in Newtonian fluids, extending this intuition to problems in complex media can prove problematic.

scholarly journals Computational fluid dynamic studies of mixers for highly viscous shear thinning fluids and PIV validation

2018 ◽  
Vol 179 ◽  
pp. 133-149 ◽  
Author(s):  
Marti Cortada-Garcia ◽  
Weheliye Hashi Weheliye ◽  
Valentina Dore ◽  
Luca Mazzei ◽  
Panagiota Angeli
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Shear Thinning ◽  
Shear Thinning Fluids ◽  
Dynamic Studies ◽  
Viscous Shear

Wetting phenomena during processing of high-viscosity shear-thinning fluid

2011 ◽  
Vol 166 (12-13) ◽  
pp. 723-733 ◽  
Author(s):  
Kanthi Latha Bhamidipati ◽  
Sima Didari ◽  
Prince Bedell ◽  
Tequila A.L. Harris
Keyword(s):  
Shear Thinning ◽  
High Viscosity ◽  
Wetting Phenomena ◽  
Shear Thinning Fluid

scholarly journals Analysis of Power Input of an In-Line Rotor-Stator Mixer for Viscoplastic Fluids

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 916
Author(s):  
Mehmet Ayas ◽  
Jan Skocilas ◽  
Tomas Jirout
Keyword(s):  
Experimental Data ◽  
Shear Rate ◽  
Shear Thinning ◽  
Power Input ◽  
Rotor Speed ◽  
Shear Thinning Fluids ◽  
Power Draw ◽  
Rate Profile ◽  
Shear Thinning Fluid

In this work, the power draw and shear profile of a novel in-line rotor-stator mixer were studied experimentally and the laminar flow regime was simulated. The power draw of the rotor-stator mixer was investigated experimentally using viscoplastic shear-thinning fluid and the results of the obtained power consumptions were verified through simulations. The power draw constant and Otto-Metzner coefficient were determined from the result of experimental data and through simulations. A new method is suggested for the determination of the Otto-Metzner coefficient for the Herschel–Bulkley model and the term efficiency is introduced. It was shown that the proposed method can be applied successfully for the prediction of the Otto-Metzner coefficient for the mixing of viscoplastic shear-thinning fluids. The effect of geometry and rotor speed on power consumption and shear rate profile in the investigated mixer is discussed from the results of the simulations. It was found that numerical methods are a convenient tool and can predict the power draw of the in-line rotor-stator mixer successfully.

Asymptotics of slow flow of very small exponent power-law shear-thinning fluids in a wedge

1995 ◽  
Vol 6 (6) ◽  
pp. 559-571 ◽  
Author(s):  
M. E. Brewster ◽  
S. J. Chapman ◽  
A. D. Fitt ◽  
C. P. Please
Keyword(s):  
Boundary Layers ◽  
Power Law ◽  
Outer Region ◽  
Shear Thinning ◽  
Similarity Solutions ◽  
Explicit Solutions ◽  
Slow Flow ◽  
Small Power ◽  
Shear Thinning Fluids ◽  
Shear Thinning Fluid

The incompressible slow viscous flow of a power-law shear-thinning fluid in a wedge-shaped region is considered in the specific instance where the stress is a very small power of the strain rate. Asymptotic analysis is used to determine the structure of similarity solutions. The flow is shown to possess an outer region with boundary layers at the walls. The boundary layers have an intricate structure consisting of a transition layer 0(ɛ) adjoining an inner layer O(ɛlnɛ), which further adjoins an inner-inner layer 0(ɛ) next to the wall. Explicit solutions are found in all the regions and the existence of ‘dead zones’ in the flow is discussed.

scholarly journals Mixing Enhancement of Non-Newtonian Shear-Thinning Fluid for a Kenics Micromixer

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1494
Author(s):  
Abdelkader Mahammedi ◽  
Naas Toufik Tayeb ◽  
Kwang-Yong Kim ◽  
Shakhawat Hossain
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Reynolds Numbers ◽  
Shear Thinning ◽  
Navier Stokes ◽  
Mixing Enhancement ◽  
Pressure Losses ◽  
Shear Thinning Fluids ◽  
Wide Range

In this work, a numerical investigation was analyzed to exhibit the mixing behaviors of non-Newtonian shear-thinning fluids in Kenics micromixers. The numerical analysis was performed using the computational fluid dynamic (CFD) tool to solve 3D Navier-Stokes equations with the species transport equations. The efficiency of mixing is estimated by the calculation of the mixing index for different cases of Reynolds number. The geometry of micro Kenics collected with a series of six helical elements twisted 180° and arranged alternately to achieve the higher level of chaotic mixing, inside a pipe with a Y-inlet. Under a wide range of Reynolds numbers between 0.1 to 500 and the carboxymethyl cellulose (CMC) solutions with power-law indices among 1 to 0.49, the micro-Kenics proves high mixing Performances at low and high Reynolds number. Moreover the pressure losses of the shear-thinning fluids for different Reynolds numbers was validated and represented.

scholarly journals GALERKIN LEAST-SQUARES APPROXIMATIONS FOR FLOWS OF CASSON FLUIDS THROUGH AN EXPANSION

2006 ◽  
Vol 5 (2) ◽  
pp. 82
Author(s):  
F. S. F. Zinani ◽  
S. Frey
Keyword(s):  
Least Squares ◽  
Continuum Mechanics ◽  
Complex Geometry ◽  
Shear Thinning ◽  
High Viscosity ◽  
Industrial Applications ◽  
Material Behavior ◽  
Sudden Expansion ◽  
Shear Thinning Fluids ◽  
Viscosity Function

Among non-Newtonian fluid models, purely viscous constitutive equations play an important role in industrial applications regardless their lack of accuracy in non-viscometric flows. In this work we are concerned with the flow of viscoplastic shear-thinning fluids in complex geometry. Viscoplastic fluids are those that behave as extremely high viscosity materials when submitted to low stresses and that flow when submitted to stresses higher than a yield stress value. Usually, they also present shearthinning behavior. Fluids such as molten chocolate, xanthan gum solutions, blood, wastewater sludges, muds, and polymer solutions present viscoplastic shear-thinning features. In order to approximate numerically viscoplastic shear-thinning flows we first describe a mechanical model based on continuum mechanics conservation laws of mass and momentum. The description of material behavior is such as to respect certain principles of objectivity and generality in continuum mechanics. The Generalized Newtonian Liquid constitutive equation with Casson viscosity function is able to predict viscoplasticity and shear-thinning. The numerical approximation of the equations is performed by a finite element method. To prevent the model from pathologies known for the classic Galerkin method, we employ a stabilized method based on a Galerkin least-squares (GLS) scheme, which is designed to circumvent Babuška-Brezzi condition and deal with the asymmetry of the advective operator. We present approximations for the flow through a planar 4:1 sudden expansion. We investigate the influence of Reynolds and Casson numbers on the flow dynamics.

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