Fluids

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14 pages, 263 KiB

Open AccessArticle

Renormalization Group Approach as a Symmetry Transformation for an Analysis of Non-Newtonian Elastic Turbulence

by Andriy A. Avramenko, Igor V. Shevchuk, Nataliia P. Dmitrenko and Alina V. Konyk

Fluids 2025, 10(4), 79; https://doi.org/10.3390/fluids10040079 - 24 Mar 2025

Viewed by 147

Symmetry transformation methods are widely used in fluid flow problems. One such method is renormalization group analysis. Renormalization group methods are used to develop a macroscopic turbulence model for non-Newtonian fluids (Oldroyd-B type). This model accounts for the large-distance and large-time behavior of [...] Read more.

Symmetry transformation methods are widely used in fluid flow problems. One such method is renormalization group analysis. Renormalization group methods are used to develop a macroscopic turbulence model for non-Newtonian fluids (Oldroyd-B type). This model accounts for the large-distance and large-time behavior of velocity correlations generated by the momentum equation for a randomly stirred, incompressible flow and does not account for empirical constants. The aim of this mathematical study was to develop a k-ε RNG turbulence model for non-Newtonian fluids (Oldroyd-B type). For the first time, using the renormalization procedure, the transport equations for the large-scale modes and expressions for effective transport coefficients are obtained. Expressions for the renormalized turbulent viscosity are also derived. This model explains the phenomenon of the abrupt growth of the irregularity of velocity at low values of the Reynolds number. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

19 pages, 9368 KiB

Open AccessArticle

On the Effect of Gas Content in Centrifugal Pump Operations with Non-Newtonian Slurries

by Nicola Zanini, Alessio Suman, Mattia Piovan and Michele Pinelli

Fluids 2025, 10(1), 12; https://doi.org/10.3390/fluids10010012 - 8 Jan 2025

Viewed by 695

Abstract

Non-Newtonian fluids are widespread in industry, e.g., biomedical, food, and oil and gas, and their rheology plays a fundamental role in choosing the processing parameters. Centrifugal pumps are widely employed to ensure the displacement of a huge amount of fluids due to their [...] Read more.

Non-Newtonian fluids are widespread in industry, e.g., biomedical, food, and oil and gas, and their rheology plays a fundamental role in choosing the processing parameters. Centrifugal pumps are widely employed to ensure the displacement of a huge amount of fluids due to their robustness and reliability. Since the pump performance is usually provided by manufacturers only for water, the selection of a proper pump to handle non-Newtonian fluids may prove very tricky. On-field experiences in pump operations with non-Newtonian slurries report severe head and efficiency drops, especially in part-load operations, whose causes are still not fully understood. Several models are found in the literature to predict the performance of centrifugal pumps with this type of fluids, but a lack of reliability and generality emerges. In this work, an extensive experimental campaign is carried out with an on-purpose test bench to investigate the effect of non-Newtonian shear-thinning fluids on the performance of a small commercial centrifugal pump. A dedicated experimental campaign is conducted to study the causes of performance drops. The results allow to establish a relationship between head and efficiency drops with solid content in the mixture. Sudden performance drops and unstable operating points are detected in part-load operations and the most severe drops are detected with the higher kaolin content in the mixture. Performance drop investigation allows to ascribe performance drop to gas-locking phenomena. Finally, a critical analysis is proposed to relate the resulting performance with both fluids’ rheology and the gas fraction trapped in the fluid. The results here presented can be useful for future numerical validation and predicting performance models. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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12 pages, 2722 KiB

Open AccessArticle

Impact of Addition of a Newtonian Solvent to a Giesekus Fluid: Analytical Determination of Flow Rate in Plane Laminar Motion

by Irene Daprà, Giambattista Scarpi and Vittorio Di Federico

Fluids 2025, 10(1), 1; https://doi.org/10.3390/fluids10010001 - 24 Dec 2024

Viewed by 532

Abstract

In this study, the influence of the presence of a Newtonian solvent on the flow of a Giesekus fluid in a plane channel or fracture is investigated with a focus on the determination of the flow rate for an assigned external pressure gradient. [...] Read more.

In this study, the influence of the presence of a Newtonian solvent on the flow of a Giesekus fluid in a plane channel or fracture is investigated with a focus on the determination of the flow rate for an assigned external pressure gradient. The pressure field is nonlinear due to the presence of the normal transverse stress component. As expected, the flow rate per unit width

Q^{'}

is larger than for a Newtonian fluid and decreases as the solvent increases. It is strongly dependent on the viscosity ratio

ε

(

0 \leq ε \leq 1

), the dimensionless mobility parameter

β

(

0 \leq β \leq 1

) and the Deborah number

D e

, the dimensionless driving pressure gradient. The degree of dependency is notably strong in the low range of

ε

. Furthermore,

Q^{'}

increases with

D e

and tends to a constant asymptotic value for large

D e

, subject to the limitation of laminar flow. When the mobility factor

β

is in the range

[0.5 \div 1]

, there is a minimum value of

ε

to obtain an assigned value of

D e

. The ratio

U_{N} / U

between Newtonian and actual mean velocity depends only on the product

\sqrt{β} D e

, as for other non-Newtonian fluids. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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28 pages, 7378 KiB

Open AccessArticle

Effects of Channelling a Peripherally Inserted Central Venous Catheter on Blood Flow

by Laura Hernández-Cabré, Marta Ulldemolins-Rams, Judit Vilanova-Corsellas and Carles Torras

Fluids 2024, 9(11), 245; https://doi.org/10.3390/fluids9110245 - 22 Oct 2024

Cited by 1 | Viewed by 1239

Abstract

A catheter is a device that is inserted into the venous system to infuse treatment with controlled doses per unit of time. The study of its interaction with blood flow cannot be easily analysed with common analytical methods or different visualization techniques in [...] Read more.

A catheter is a device that is inserted into the venous system to infuse treatment with controlled doses per unit of time. The study of its interaction with blood flow cannot be easily analysed with common analytical methods or different visualization techniques in real life. Computational Fluid Dynamics has become a very useful tool in a wide variety of fields of scientific study and has allowed access to the understanding of the anatomical and physiological functioning of the human body. In this work, Computational Fluid Dynamics is used to study the effects of inserting a catheter on blood flow and the quality of the mixture of blood with the various substances infused through this device. Results show that the insertion of the catheter not only does not worsen the blood circulation but improves it by reducing stagnant zones. Regarding mixture, a homogenization of the fluids in the venous area before their entrance to the heart was observed. Highest quality mixtures correspond to fewer infused fluids and at lower velocity. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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12 pages, 4128 KiB

Open AccessArticle

CFD Analysis of Ultra-High-Performance Concrete Rheological Tests

by Tomáš Jirout, Adam Krupica and Alexandr Kolomijec

Fluids 2024, 9(2), 45; https://doi.org/10.3390/fluids9020045 - 11 Feb 2024

Cited by 3 | Viewed by 2101

Abstract

This study connects and compares the results from two different rheological measurement techniques, namely, the slump test and rotational rheometry, on UHPC (Ultra-High-Performance Concrete) through the use of commercially available numerical simulation software ANSYS Fluent 2022 R2. The workability and resulting mechanical properties [...] Read more.

This study connects and compares the results from two different rheological measurement techniques, namely, the slump test and rotational rheometry, on UHPC (Ultra-High-Performance Concrete) through the use of commercially available numerical simulation software ANSYS Fluent 2022 R2. The workability and resulting mechanical properties of the UHPC (a material used in construction) are highly dependent on its rheology and, hence, also on the composition and level of homogeneity of the assessed mixture. It is generally understood that the most suitable rheological model for concrete mixtures is the Hershel–Bulkley model. However, obtaining reliable rheological data is complicated as the wide-gap rotational rheometers developed for concrete show bias in their measurements even on precise laboratory equipment, while common industrial tests, such as the slump test, do not produce the usual shear rate–shear stress relation and, hence, do not allow for more complex analysis. Recently, a new methodology for the rheological measurement of non-Newtonian fluids that utilises a simple power input–rotation speed measurement was published. However, in this study, only model liquids were evaluated, and the method was not validated for more complex fluids such as pastes. Therefore, it was the goal of this study to show this method’s suitability for fine pastes through a comparison with the slump test, using numerical simulation. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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15 pages, 7964 KiB

Open AccessArticle

Numerical Analysis of Non-Newtonian Fluid Effects on the Equilibrium Position of a Suspended Particle and Relative Viscosity in Two-Dimensional Flow

by Keiya Tomioka and Tomohiro Fukui

Fluids 2024, 9(2), 37; https://doi.org/10.3390/fluids9020037 - 1 Feb 2024

Cited by 4 | Viewed by 2084

Abstract

A solvent in suspension often has non-Newtonian properties. To date, in order to determine these properties, many constitutive equations have been suggested. In particular, power-law fluid, which describes both dilatant and pseudoplastic fluids, has been used in many previous studies because of its [...] Read more.

A solvent in suspension often has non-Newtonian properties. To date, in order to determine these properties, many constitutive equations have been suggested. In particular, power-law fluid, which describes both dilatant and pseudoplastic fluids, has been used in many previous studies because of its simplicity. Then, the Herschel–Bulkley model is used, which describes fluid with yield stress. In this study, we considered how a non-Newtonian solvent affected the equilibrium position of a particle and relative viscosity using the regularized lattice Boltzmann method for fluid and a two-way coupling scheme for the particle. We focused on these methods so as to evaluate the non-Newtonian effects of a solvent. The equilibrium position in Bingham fluid was closer to the wall than that in Newtonian or power-law fluid. In contrast, the tendency of relative viscosity in Bingham fluid for each position was similar to that in power-law fluid. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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17 pages, 7920 KiB

Open AccessArticle

Computational Fluid Dynamics Modeling of Concrete Flows in Drilled Shafts

by Jesudoss Aservitham Jeyaraj, Anthony Perez, Abla Zayed, Austin Gray Mullins and Andres E. Tejada-Martinez

Fluids 2024, 9(1), 13; https://doi.org/10.3390/fluids9010013 - 31 Dec 2023

Cited by 1 | Viewed by 2653

Abstract

Drilled shafts are cylindrical, cast-in-place concrete deep foundation elements. During construction, anomalies in drilled shafts can occur due to the kinematics of concrete, flowing radially from the center of the shaft to the concrete cover region at the peripheral edge. This radial component [...] Read more.

Drilled shafts are cylindrical, cast-in-place concrete deep foundation elements. During construction, anomalies in drilled shafts can occur due to the kinematics of concrete, flowing radially from the center of the shaft to the concrete cover region at the peripheral edge. This radial component of concrete flow develops veins or creases of poorly cemented or high water-cement ratio material, as the concrete flows around the reinforcement cage of rebars and ties, jeopardizing the shaft integrity. This manuscript presents a three-dimensional computational fluid dynamics (CFD) model of the non-Newtonian concrete flow in drilled shaft construction developed using the finite volume method with interface tracking based on the volume of fluid (VOF) method. The non-Newtonian behavior of the concrete is represented via the Carreau constitutive model. The model results are encouraging as the flow obtained from the simulations shows patterns of both horizontal and vertical creases in the concrete cover region, consistent with previously reported field and laboratory experiments. Moreover, the flow exhibits the concrete head differential developed between the inside and the outside of the reinforcement cage, as exhibited in the physical experiments. This head differential induces the radial component of the concrete flow responsible for the creases that develop in the concrete cover region. Results show that the head differential depends on the flowability of the concrete, consistent with field observations. Less viscous concrete tends to reduce the head differential and the formation of creases of poorly cemented material. The model is unique, making use of state-of-the-art numerical techniques and demonstrating the capability of CFD to model industrially relevant concrete flows. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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20 pages, 5906 KiB

Open AccessArticle

A Constructal-Theory-Based Methodology to Determine the Configuration of Empty Channels Used in the Resin Impregnation of a Square Porous Plate

by Glauciléia Maria Cardoso Magalhães, Jeferson Avila Souza and Elizaldo Domingues dos Santos

Fluids 2023, 8(12), 317; https://doi.org/10.3390/fluids8120317 - 10 Dec 2023

Cited by 2 | Viewed by 1857

Abstract

Liquid composite molding techniques are largely used to produce pieces such as truck cabins or wind turbine blades. The liquid resin infusion processes use a network of injection channels to improve the resin flow through a porous-reinforced medium. The present numerical study predicts [...] Read more.

Liquid composite molding techniques are largely used to produce pieces such as truck cabins or wind turbine blades. The liquid resin infusion processes use a network of injection channels to improve the resin flow through a porous-reinforced medium. The present numerical study predicts the positioning of empty channels by applying constructal theory to an idealized problem. The channels’ position and size were not predefined but instead constructed (made to grow) from an elemental channel. Two strategies were tested for channel growth: each new elemental channel was placed next to the region with the lowest or highest resistance to resin flow. The geometric configuration of the channels was constructed using a control function instead of using pre-defined shapes. The conservation of mass and momentum and an additional transport equation for the resin volume fraction were solved using the finite volume method. The volume of the fluid model was used for the treatment of the multiphase flow (air + resin). The growth of an empty channel with the lowest resistance strategy led to a decrease in the injection time and waste of resin. The size (resolution) of the elemental channel also affected the performance indicators and geometric configuration of the injection channels. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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10 pages, 7655 KiB

Open AccessArticle

Improving Homogeneity of 3D-Printed Cementitious Material Distribution for Radial Toolpath

by Mingyang Li, Zhixin Liu, Jin Yao Ho and Teck Neng Wong

Fluids 2023, 8(3), 87; https://doi.org/10.3390/fluids8030087 - 1 Mar 2023

Cited by 1 | Viewed by 1916

Abstract

The 3D cementitious material printing method is an extrusion-based additive manufacturing strategy in which cementitious materials are extruded through a dynamic nozzle system to form filaments. Despite its ability to fabricate structures with high complexity and efficiency, the uneven material distribution during the [...] Read more.

The 3D cementitious material printing method is an extrusion-based additive manufacturing strategy in which cementitious materials are extruded through a dynamic nozzle system to form filaments. Despite its ability to fabricate structures with high complexity and efficiency, the uneven material distribution during the extrusion and deposition process is often encountered when a radial toolpath is introduced. This limits the design freedom and printing parameters that can be utilized during radial toolpath printing. Here, we report a facile strategy to overcome the existing challenges of cementitious material non-homogeneity by rationally developing new nozzle geometries that passively compensate the differential deposition rate encountered in conventional rectangular nozzles. Using two-phase numerical study, we showed that our strategy has the potential of achieving a homogeneous mass distribution even when the nozzle travel speed is unfavorably high, while filament from a rectangular nozzle remains highly non-homogenous. The material distribution unevenness can be reduced from 1.35 to 1.23 and to 0.98 after adopting trapezoid and gaussian nozzles, indicating improvements of 34.3% and 94.2%, respectively. This work not only outlines the methodology for improving the quality of corner/curved features in 3DCMP, but also introduces a new strategy which can be adopted for other extrusion-based fabrication techniques with high material inertia. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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17 pages, 4812 KiB

Open AccessArticle

Numerical Study of the Effects of Asymmetric Velocity Profiles in a Curvilinear Channel on Migration of Neutral Buoyant Particle

by Ryo Naito and Tomohiro Fukui

Fluids 2023, 8(2), 69; https://doi.org/10.3390/fluids8020069 - 16 Feb 2023

Cited by 1 | Viewed by 1949

Abstract

The microstructure and suspended particle behavior should be considered when studying the flow properties exhibited by particle suspension. In addition, particle migration, also known as Segré–Silberberg effects, alters the microstructure of the suspension and significantly affects the viscosity properties of the suspension. Therefore, [...] Read more.

The microstructure and suspended particle behavior should be considered when studying the flow properties exhibited by particle suspension. In addition, particle migration, also known as Segré–Silberberg effects, alters the microstructure of the suspension and significantly affects the viscosity properties of the suspension. Therefore, particle behavior with respect to the changes in mechanical factors should be considered to better understand suspension. In this study, we investigated the particle behavior in asymmetric velocity profiles with respect to the channel center numerically using the lattice Boltzmann method and a two-way coupling scheme. Our findings confirmed that the final equilibrium position of particles in asymmetric velocity profiles converged differently between the outer and inner wall sides with respect to the channel center. This indicates that the mechanical equilibrium position of particles can be changed by asymmetric velocity profiles. In addition, centrifugal force acting on the particles is also important in the study of equilibrium position. These results suggest that the microstructure and viscosity characteristics of a suspension in a pipe could be handled by changes in velocity profiles. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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18 pages, 1940 KiB

Open AccessArticle

A New Rheological Model for Phosphate Slurry Flows

by Zeineb Ghoudi, Souhail Maazioui, Fayssal Benkhaldoun and Noureddine Hajjaji

Fluids 2023, 8(2), 57; https://doi.org/10.3390/fluids8020057 - 8 Feb 2023

Cited by 1 | Viewed by 2330

Abstract

In this paper, a new rheological model for the flow of phosphate-water suspensions is proposed. The model’s ability to replicate the rheological characteristics of phosphate-water suspensions under different shear rate conditions is evaluated using rheometric tests, and it is found to be in [...] Read more.

In this paper, a new rheological model for the flow of phosphate-water suspensions is proposed. The model’s ability to replicate the rheological characteristics of phosphate-water suspensions under different shear rate conditions is evaluated using rheometric tests, and it is found to be in good agreement with experimental data. A comprehensive methodology for obtaining the model parameters is presented. The proposed model is then incorporated into the OpenFoam numerical code. The results demonstrate that the model is capable of reproducing the rheological behavior of phosphate suspensions at both low and high concentrations by comparing it with suitable models for modeling the rheological behavior of phosphate suspensions. The proposed model can be applied to simulate and monitor phosphate slurry flows in industrial applications. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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20 pages, 908 KiB

Open AccessArticle

Shear Flows of Dilatant Fluids with Limited Shear Rates: Analytical Results and Linear Stability Analysis

by Lorenzo Fusi

Fluids 2023, 8(1), 25; https://doi.org/10.3390/fluids8010025 - 9 Jan 2023

Viewed by 2619

Abstract

In this paper, we study the simple shear flows of a class of dilatant fluids with a limited shear rate. This class of fluids is characterized by shear thickening behavior in which the apparent viscosity tends to infinity as the modulus of the [...] Read more.

In this paper, we study the simple shear flows of a class of dilatant fluids with a limited shear rate. This class of fluids is characterized by shear thickening behavior in which the apparent viscosity tends to infinity as the modulus of the stress approaches a finite threshold. The apparent viscosity function is a logarithmic type with two material parameters. We considered this specific form because it fits very well with the flow curves of some granular suspensions for specific values of the material parameters. Despite the nonlinearity of the constitutive law, it is possible to determine explicit steady-state solutions for a simple shear flow, namely (i) the channel flow; (ii) the flow between coaxial cylinders, and (iii) the flow down an inclined plane. We performed a two-dimensional linear stability analysis to investigate the onset of possible instabilities of the steady basic flow, putting into evidence the dependency of the critical Reynolds number on the material parameters. Full article

(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)

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