Pub Date : 2025-02-01DOI: 10.1016/j.jnnfm.2024.105378
Nan-Yang Zhao , Bin Xue , Ming-Yang Su , Zhong-Bin Xu , Qiong Wu , Jing Zhou
<div><div>The thorough analysis of thermal effects in the interior of molds enhances the understanding of the role and evolution of flow-thermal interactions during injection molding. However, current methods that incorporate heating and insulation devices for detecting melt within molds do not accurately reflect actual manufacturing environments. The non-isothermal conditions in molds also complicate the quantitative analysis of thermal effects, posing challenges for in-mold analysis. In this study, we proposed a comprehensive analytical and validation approach to investigate the significance of viscous dissipation in a non-adiabatic mold during injection molding. Channel dimensions (fixed length of 25 mm, radii of 0.75–1.5 mm) and melt velocities (25–150 mm s<sup>−1</sup>) were adjusted to observe pressure drop variations (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>en</mtext></msub></mrow></math></span>) in a special-designed mold. An equivalent pressure concept (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>vis</mtext></msub></mrow></math></span>) was proposed to assess temperature variations induced by viscous dissipation. Dimensionless indices related to channel dimensions (<span><math><msub><mi>I</mi><mrow><mi>P</mi><mo>_</mo><mi>R</mi></mrow></msub></math></span> and <span><math><msub><mi>I</mi><mrow><mtext>Pcor</mtext><mo>_</mo><mi>R</mi></mrow></msub></math></span>) and melt injection velocities (<span><math><msub><mi>I</mi><mrow><mi>P</mi><mo>_</mo><mi>v</mi></mrow></msub></math></span> and <span><math><msub><mi>I</mi><mrow><mtext>Pcor</mtext><mo>_</mo><mi>v</mi></mrow></msub></math></span>) were established to observe pressure drop (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>en</mtext></msub></mrow></math></span>) and corrected pressure drop (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>cor</mtext></msub></mrow></math></span>). The results indicate that the corrected pressure drop and viscosity curves (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>cor</mtext></msub></mrow></math></span> and <span><math><msub><mi>η</mi><mtext>cor</mtext></msub></math></span>) show more consistent variations versus channel dimensions and melt velocities when the viscous dissipation effect is quantitatively incorporated into melt pressure and viscosity analyses (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>en</mtext></msub></mrow></math></span> and <span><math><mi>η</mi></math></span>), aligning closely with observations under adiabatic conditions. Thermal-related dimensionless numbers (Eckert, Brinkman, and Peclet numbers) qualitatively confirm the significance of viscous dissipation. This study offers a comprehensive analysis and validation of thermal effects in mold, presenting a novel method for exploring specific melt behaviors and advancing the analysis of mold interiors in non-adiabatic environments.</div></div
{"title":"Significance of viscous dissipation effect during the rapid filling process in the non-adiabatic mold: A full analytical and validating solution","authors":"Nan-Yang Zhao , Bin Xue , Ming-Yang Su , Zhong-Bin Xu , Qiong Wu , Jing Zhou","doi":"10.1016/j.jnnfm.2024.105378","DOIUrl":"10.1016/j.jnnfm.2024.105378","url":null,"abstract":"<div><div>The thorough analysis of thermal effects in the interior of molds enhances the understanding of the role and evolution of flow-thermal interactions during injection molding. However, current methods that incorporate heating and insulation devices for detecting melt within molds do not accurately reflect actual manufacturing environments. The non-isothermal conditions in molds also complicate the quantitative analysis of thermal effects, posing challenges for in-mold analysis. In this study, we proposed a comprehensive analytical and validation approach to investigate the significance of viscous dissipation in a non-adiabatic mold during injection molding. Channel dimensions (fixed length of 25 mm, radii of 0.75–1.5 mm) and melt velocities (25–150 mm s<sup>−1</sup>) were adjusted to observe pressure drop variations (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>en</mtext></msub></mrow></math></span>) in a special-designed mold. An equivalent pressure concept (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>vis</mtext></msub></mrow></math></span>) was proposed to assess temperature variations induced by viscous dissipation. Dimensionless indices related to channel dimensions (<span><math><msub><mi>I</mi><mrow><mi>P</mi><mo>_</mo><mi>R</mi></mrow></msub></math></span> and <span><math><msub><mi>I</mi><mrow><mtext>Pcor</mtext><mo>_</mo><mi>R</mi></mrow></msub></math></span>) and melt injection velocities (<span><math><msub><mi>I</mi><mrow><mi>P</mi><mo>_</mo><mi>v</mi></mrow></msub></math></span> and <span><math><msub><mi>I</mi><mrow><mtext>Pcor</mtext><mo>_</mo><mi>v</mi></mrow></msub></math></span>) were established to observe pressure drop (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>en</mtext></msub></mrow></math></span>) and corrected pressure drop (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>cor</mtext></msub></mrow></math></span>). The results indicate that the corrected pressure drop and viscosity curves (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>cor</mtext></msub></mrow></math></span> and <span><math><msub><mi>η</mi><mtext>cor</mtext></msub></math></span>) show more consistent variations versus channel dimensions and melt velocities when the viscous dissipation effect is quantitatively incorporated into melt pressure and viscosity analyses (<span><math><mrow><mstyle><mi>Δ</mi></mstyle><msub><mi>P</mi><mtext>en</mtext></msub></mrow></math></span> and <span><math><mi>η</mi></math></span>), aligning closely with observations under adiabatic conditions. Thermal-related dimensionless numbers (Eckert, Brinkman, and Peclet numbers) qualitatively confirm the significance of viscous dissipation. This study offers a comprehensive analysis and validation of thermal effects in mold, presenting a novel method for exploring specific melt behaviors and advancing the analysis of mold interiors in non-adiabatic environments.</div></div","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"336 ","pages":"Article 105378"},"PeriodicalIF":2.7,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.jnnfm.2024.105380
Evgeniy Boyko
Viscous flows through configurations fabricated from soft materials exert stresses at the solid–liquid interface, leading to a coupling between the flow field and the elastic deformation. The resulting fluid–structure interaction affects the relationship between the pressure drop and the flow rate , or the corresponding flow resistance . While the flow resistance in deformable configurations has been extensively studied for Newtonian fluids, it remains largely unexplored for non-Newtonian fluids even at low Reynolds numbers. We analyze the steady low-Reynolds-number fluid–structure interaction between the flow of a non-Newtonian fluid and a deformable tube. We present a theoretical framework for calculating the leading-order effect of the complex fluid rheology and wall compliance on the flow resistance, which holds for a wide class of non-Newtonian constitutive models. For the weakly non-Newtonian limit, our theory provides the first-order non-Newtonian correction for the flow resistance solely using the known Newtonian solution for a deformable tube, bypassing the detailed calculations of the non-Newtonian fluid–structure-interaction problem. We illustrate our approach for a weakly viscoelastic Oldroyd-B fluid and a weakly shear-thinning Carreau fluid. In particular, we show analytically that both the viscoelasticity and shear thinning of the fluid and the compliance of the deformable tube decrease the flow resistance in the weakly non-Newtonian limit and identify the physical mechanisms governing this reduction.
{"title":"Interplay between complex fluid rheology and wall compliance in the flow resistance of deformable axisymmetric configurations","authors":"Evgeniy Boyko","doi":"10.1016/j.jnnfm.2024.105380","DOIUrl":"10.1016/j.jnnfm.2024.105380","url":null,"abstract":"<div><div>Viscous flows through configurations fabricated from soft materials exert stresses at the solid–liquid interface, leading to a coupling between the flow field and the elastic deformation. The resulting fluid–structure interaction affects the relationship between the pressure drop <span><math><mrow><mi>Δ</mi><mi>p</mi></mrow></math></span> and the flow rate <span><math><mi>q</mi></math></span>, or the corresponding flow resistance <span><math><mrow><mi>Δ</mi><mi>p</mi><mo>/</mo><mi>q</mi></mrow></math></span>. While the flow resistance in deformable configurations has been extensively studied for Newtonian fluids, it remains largely unexplored for non-Newtonian fluids even at low Reynolds numbers. We analyze the steady low-Reynolds-number fluid–structure interaction between the flow of a non-Newtonian fluid and a deformable tube. We present a theoretical framework for calculating the leading-order effect of the complex fluid rheology and wall compliance on the flow resistance, which holds for a wide class of non-Newtonian constitutive models. For the weakly non-Newtonian limit, our theory provides the first-order non-Newtonian correction for the flow resistance solely using the known Newtonian solution for a deformable tube, bypassing the detailed calculations of the non-Newtonian fluid–structure-interaction problem. We illustrate our approach for a weakly viscoelastic Oldroyd-B fluid and a weakly shear-thinning Carreau fluid. In particular, we show analytically that both the viscoelasticity and shear thinning of the fluid and the compliance of the deformable tube decrease the flow resistance in the weakly non-Newtonian limit and identify the physical mechanisms governing this reduction.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"336 ","pages":"Article 105380"},"PeriodicalIF":2.7,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.jnnfm.2024.105350
Abdallah Ghazal , Ida Karimfazli
We analyze the injection of a heavy viscoplastic fluid into a closed-end, two-dimensional vertical channel filled with a Newtonian fluid, focusing on flow dynamics across a wide range of density differences. Three distinct flow regimes are identified. At low density differences, the displacement flow below the injector is minimal. At high density differences, the injected fluid behaves like a free-falling jet, rapidly giving rise to advective instabilities near the advancing front. In the moderate density range, the injected fluid forms a finger-like interface and displaces the Newtonian fluid beneath the injector. Yet this flow also becomes unstable due to interfacial instabilities near the injection point. Surprisingly, we demonstrate that the heavy fluid ultimately flows upwards, regardless of the density difference. This counterintuitive behavior is attributed to the formation of a progressively more stable, density-stratified layer beneath the injector, which inhibits the downward movement of the heavy fluid. We further characterize the transient displacement flow at moderate density differences, where the front velocity initially becomes steady before re-accelerating at higher density differences. Our findings show that the front velocity is controlled by a balance between local density differences and viscous stresses, and we explain the mechanisms driving the re-acceleration at higher density differences. Remarkably, the interface shape remains consistent across all density differences.
{"title":"Defying gravity: Injection of viscoplastic fluids in vertical channels","authors":"Abdallah Ghazal , Ida Karimfazli","doi":"10.1016/j.jnnfm.2024.105350","DOIUrl":"10.1016/j.jnnfm.2024.105350","url":null,"abstract":"<div><div>We analyze the injection of a heavy viscoplastic fluid into a closed-end, two-dimensional vertical channel filled with a Newtonian fluid, focusing on flow dynamics across a wide range of density differences. Three distinct flow regimes are identified. At low density differences, the displacement flow below the injector is minimal. At high density differences, the injected fluid behaves like a free-falling jet, rapidly giving rise to advective instabilities near the advancing front. In the moderate density range, the injected fluid forms a finger-like interface and displaces the Newtonian fluid beneath the injector. Yet this flow also becomes unstable due to interfacial instabilities near the injection point. Surprisingly, we demonstrate that the heavy fluid ultimately flows upwards, regardless of the density difference. This counterintuitive behavior is attributed to the formation of a progressively more stable, density-stratified layer beneath the injector, which inhibits the downward movement of the heavy fluid. We further characterize the transient displacement flow at moderate density differences, where the front velocity initially becomes steady before re-accelerating at higher density differences. Our findings show that the front velocity is controlled by a balance between local density differences and viscous stresses, and we explain the mechanisms driving the re-acceleration at higher density differences. Remarkably, the interface shape remains consistent across all density differences.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"336 ","pages":"Article 105350"},"PeriodicalIF":2.7,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143154452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.jnnfm.2024.105375
Jinrong Zhang , Dadong Yan , Li Peng , Xianbo Huang
As well known, in the simulation process of wind tunnel, as long as the Reynolds number is kept constant, a small-sized model wing can be used to simulate a large-sized real wing and obtain similar flow fields. We draw inspiration from it that in the flow of viscoelastic fluid, such as the process of polymer melt injection, the mold corresponds to a wind tunnel, and there is also a flow field. Since the polymer melt is a viscoelastic fluid and is different from air, there should be another physical quantity corresponding to the Reynolds number. By dimensional analysis, we find that it is the Weissenberg number, . If remains constant, changing the injection speed , changing the relaxation time of the polypropylene melt , or changing the size of the mold will result in a similar geometric shape of the flow field. In fact, changing the size of the mold in polymer processing is not an easy task. Therefore, we first conduct mesoscopic scale dimensional analysis and then perform mesoscopic scale molecular dynamics simulation. The simulation results verify the conclusion of the dimensional analysis, so we have reason to believe that the conclusion is correct at the macroscopic scale, and we expect to verify it in the future by changing the mold size and injection speed. In the future, we will use this method to understand the flow of polymer melt in the mold, which may enhance our understanding of melt flow instability within the mold.
{"title":"Dimensional analysis and the validation by molecular dynamics simulation of polymer melt flow","authors":"Jinrong Zhang , Dadong Yan , Li Peng , Xianbo Huang","doi":"10.1016/j.jnnfm.2024.105375","DOIUrl":"10.1016/j.jnnfm.2024.105375","url":null,"abstract":"<div><div>As well known, in the simulation process of wind tunnel, as long as the Reynolds number is kept constant, a small-sized model wing can be used to simulate a large-sized real wing and obtain similar flow fields. We draw inspiration from it that in the flow of viscoelastic fluid, such as the process of polymer melt injection, the mold corresponds to a wind tunnel, and there is also a flow field. Since the polymer melt is a viscoelastic fluid and is different from air, there should be another physical quantity corresponding to the Reynolds number. By dimensional analysis, we find that it is the Weissenberg number, <span><math><mrow><mi>W</mi><mi>i</mi></mrow></math></span> <span><math><mrow><mo>(</mo><mo>=</mo><mi>v</mi><mi>τ</mi><mo>/</mo><mi>z</mi><mo>)</mo></mrow></math></span>. If <span><math><mrow><mi>W</mi><mi>i</mi></mrow></math></span> remains constant, changing the injection speed <span><math><mi>v</mi></math></span>, changing the relaxation time of the polypropylene melt <span><math><mi>τ</mi></math></span>, or changing the size of the mold <span><math><mi>z</mi></math></span> will result in a similar geometric shape of the flow field. In fact, changing the size of the mold in polymer processing is not an easy task. Therefore, we first conduct mesoscopic scale dimensional analysis and then perform mesoscopic scale molecular dynamics simulation. The simulation results verify the conclusion of the dimensional analysis, so we have reason to believe that the conclusion is correct at the macroscopic scale, and we expect to verify it in the future by changing the mold size and injection speed. In the future, we will use this method to understand the flow of polymer melt in the mold, which may enhance our understanding of melt flow instability within the mold.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"336 ","pages":"Article 105375"},"PeriodicalIF":2.7,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143154450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.jnnfm.2025.105382
Vladimir Shelukhin
A mathematical model for two-phase granular fluids is developed for capillary suspensions and it satisfies the basic principles of thermodynamics. A detailed analysis is given for steady Couette flows between two cylinders. The model is checked by experimental benchmarks: capillary forces prevent the phase separation. The greater the capillary forces the stronger the resistance to phase separation. It has been long recognized that yield stress is attributable to the surface tension between particles and interstitial fluid. We discuss such an issue. It is proved that the particles can outrun or lag behind the liquid depending on the rheological properties of the capillary suspension.
{"title":"Particulate suspensions with capillary force: The micropolar fluid theory approach","authors":"Vladimir Shelukhin","doi":"10.1016/j.jnnfm.2025.105382","DOIUrl":"10.1016/j.jnnfm.2025.105382","url":null,"abstract":"<div><div>A mathematical model for two-phase granular fluids is developed for capillary suspensions and it satisfies the basic principles of thermodynamics. A detailed analysis is given for steady Couette flows between two cylinders. The model is checked by experimental benchmarks: capillary forces prevent the phase separation. The greater the capillary forces the stronger the resistance to phase separation. It has been long recognized that yield stress is attributable to the surface tension between particles and interstitial fluid. We discuss such an issue. It is proved that the particles can outrun or lag behind the liquid depending on the rheological properties of the capillary suspension.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"336 ","pages":"Article 105382"},"PeriodicalIF":2.7,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143154451","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jnnfm.2024.105354
Andrew Clarke, Mahdi Davoodi
A drilling process comprises a drill-pipe rotating within a borehole where fluid is pumped down the pipe and returns, with drilled cuttings, along the annulus. Predominantly the axis of the system is horizontal. Thus, in the absence of axial flow the process geometry is that of a Taylor–Couette flow. Formulated drilling fluids themselves are usually regarded as Bingham or Hershel-Bulkley in nature, but nevertheless encompass elastic behaviour. We have thus studied the distribution of dense (i.e. sedimenting) non-Brownian solid particles in Taylor–Couette flow of model drilling fluids as a function of center body rotation speed. In all cases Taylor vortices are formed above some critical, fluid dependent, Taylor number. However, depending on the fluid properties, particles decorate the vortices differently: particles in a polymeric fluid move to the centroids of the vortices, whereas in a colloidal fluid they move to the outer periphery of the vortices, as previously observed for Newtonian fluids. With a mixed fluid, a clear transition between the two regimes is found. We postulate that this behaviour is a result of a balance between elastically derived lift forces and inertially driven Saffman lift forces acting antagonistically on the particles.
{"title":"The movement of particles in Taylor–Couette flow of complex fluids","authors":"Andrew Clarke, Mahdi Davoodi","doi":"10.1016/j.jnnfm.2024.105354","DOIUrl":"10.1016/j.jnnfm.2024.105354","url":null,"abstract":"<div><div>A drilling process comprises a drill-pipe rotating within a borehole where fluid is pumped down the pipe and returns, with drilled cuttings, along the annulus. Predominantly the axis of the system is horizontal. Thus, in the absence of axial flow the process geometry is that of a Taylor–Couette flow. Formulated drilling fluids themselves are usually regarded as Bingham or Hershel-Bulkley in nature, but nevertheless encompass elastic behaviour. We have thus studied the distribution of dense (i.e. sedimenting) non-Brownian solid particles in Taylor–Couette flow of model drilling fluids as a function of center body rotation speed. In all cases Taylor vortices are formed above some critical, fluid dependent, Taylor number. However, depending on the fluid properties, particles decorate the vortices differently: particles in a polymeric fluid move to the centroids of the vortices, whereas in a colloidal fluid they move to the outer periphery of the vortices, as previously observed for Newtonian fluids. With a mixed fluid, a clear transition between the two regimes is found. We postulate that this behaviour is a result of a balance between elastically derived lift forces and inertially driven Saffman lift forces acting antagonistically on the particles.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"335 ","pages":"Article 105354"},"PeriodicalIF":2.7,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.jnnfm.2024.105342
Daniel J. Curtis, Francesco Del Giudice, Karl M. Hawkins
{"title":"Editorial to the Commemorative Special Issue of JNNFM in honour of Professor Ken Walters FRS","authors":"Daniel J. Curtis, Francesco Del Giudice, Karl M. Hawkins","doi":"10.1016/j.jnnfm.2024.105342","DOIUrl":"10.1016/j.jnnfm.2024.105342","url":null,"abstract":"","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"334 ","pages":"Article 105342"},"PeriodicalIF":2.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143099701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1016/j.jnnfm.2024.105351
Hua Zhang , Chang Shu , Lian-Ping Wang , Yaguang Liu
In this work, a viscoelastic lattice Boltzmann flux solver (VLBFS) with log-conformation representation is proposed for simulating the incompressible flows of a viscoelastic fluid at high Weissenberg number conditions. Compared with the original lattice Boltzmann flux solver (LBFS), the present method has two main new features. First, the method solves the polymer constitutive equations with log-conformation representation. Second, an upwind-biased scheme is incorporated in the interpolation when performing flux reconstructions at the cell interface. With the aid of these two treatments, the numerical stability of VLBFS is significantly improved, making it capable of solving high Weissenberg number problems (HWNP). Compared with using the lattice Boltzmann method (LBM) to solve the viscoelastic fluid flow, VLBFS inherits the advantages of LBFS, such as flexible mesh generation, decoupling of the grid spacing and time interval, and low memory requirement. VLBFS can also precisely recover the macroscopic constitutive equation. The present method has been critically validated using three benchmark cases, namely, the plane Poiseuille flow, lid-driven cavity flow, and 4:1 abrupt planar contraction flow. The numerical results fully demonstrate the solver’s powerful ability in simulating HWNP.
{"title":"A lattice Boltzmann flux solver with log-conformation representation for the simulations of viscoelastic flows at high Weissenberg numbers","authors":"Hua Zhang , Chang Shu , Lian-Ping Wang , Yaguang Liu","doi":"10.1016/j.jnnfm.2024.105351","DOIUrl":"10.1016/j.jnnfm.2024.105351","url":null,"abstract":"<div><div>In this work, a viscoelastic lattice Boltzmann flux solver (VLBFS) with log-conformation representation is proposed for simulating the incompressible flows of a viscoelastic fluid at high Weissenberg number conditions. Compared with the original lattice Boltzmann flux solver (LBFS), the present method has two main new features. First, the method solves the polymer constitutive equations with log-conformation representation. Second, an upwind-biased scheme is incorporated in the interpolation when performing flux reconstructions at the cell interface. With the aid of these two treatments, the numerical stability of VLBFS is significantly improved, making it capable of solving high Weissenberg number problems (HWNP). Compared with using the lattice Boltzmann method (LBM) to solve the viscoelastic fluid flow, VLBFS inherits the advantages of LBFS, such as flexible mesh generation, decoupling of the grid spacing and time interval, and low memory requirement. VLBFS can also precisely recover the macroscopic constitutive equation. The present method has been critically validated using three benchmark cases, namely, the plane Poiseuille flow, lid-driven cavity flow, and 4:1 abrupt planar contraction flow. The numerical results fully demonstrate the solver’s powerful ability in simulating HWNP.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"335 ","pages":"Article 105351"},"PeriodicalIF":2.7,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142744985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1016/j.jnnfm.2024.105355
E. Fernández-Díaz , F.J. Rubio-Hernández , J.F. Velázquez-Navarro
The feasibility of applying quasi-linear large amplitude oscillatory shear (QL-LAOS) approach to a shear thickening (ST) fumed silica suspension was tested. While the characteristic time has been used as the parameter for the original QL-LAOS analysis of shear thinning fluids, we obtained that a description based upon increasing stiffness is more appropriate for ST fumed silica suspensions. Very low third to first harmonics ratio were obtained indicating the need of alternative criteria to identify QL-LAOS behavior in ST suspensions. Consequently, a method based upon the best fit of an ellipse to the experimental Lissajous-Bowditch curves was proposed. Compliances were obtained from areas of viscous and elastic fitted ellipses. The dependence of the material functions obtained by using a Jeffrey´s mechanical viscoelastic framework with angular frequency supports the idea of ST microstructure evolves by increasing with shear the number of small hydroclusters.
{"title":"Analysis of the shear thickening behavior of a fumed silica suspension using QL-LAOS approach","authors":"E. Fernández-Díaz , F.J. Rubio-Hernández , J.F. Velázquez-Navarro","doi":"10.1016/j.jnnfm.2024.105355","DOIUrl":"10.1016/j.jnnfm.2024.105355","url":null,"abstract":"<div><div>The feasibility of applying quasi-linear large amplitude oscillatory shear (QL-LAOS) approach to a shear thickening (ST) fumed silica suspension was tested. While the characteristic time has been used as the parameter for the original QL-LAOS analysis of shear thinning fluids, we obtained that a description based upon increasing stiffness is more appropriate for ST fumed silica suspensions. Very low <span><math><mrow><mo>(</mo><mrow><mo>≤</mo><mn>1.5</mn></mrow><mo>)</mo></mrow></math></span> third to first harmonics ratio were obtained indicating the need of alternative criteria to identify QL-LAOS behavior in ST suspensions. Consequently, a method based upon the best fit of an ellipse to the experimental Lissajous-Bowditch curves was proposed. Compliances were obtained from areas of viscous and elastic fitted ellipses. The dependence of the material functions obtained by using a Jeffrey´s mechanical viscoelastic framework with angular frequency supports the idea of ST microstructure evolves by increasing with shear the number of small hydroclusters.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"335 ","pages":"Article 105355"},"PeriodicalIF":2.7,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142744986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-19DOI: 10.1016/j.jnnfm.2024.105353
Yixuan Hou , Zhao Jin , Xinzhe Que , Yongchao Zhou , Yiping Zhang
Bubble behaviors in structured fluids are of great interests in industrial applications, while there is currently a lack of understanding regarding the effect of thixotropic microstructure on the bubble formation process. To this end, this study explores the influence of thixotropy on bubble growth in thixotropic yield stress fluids by numerical simulations using the Arbitrary Lagrangian-Eulerian (ALE) method. The numerical results reveal that, with the increase in the thixotropy number, the bubbles at detachment transform from inverted conical to spherical shapes at lower gas flow rates, and from spindle to conical shapes at higher gas flow rates, along with the decreased detachment volume and time. It is also found that the effect of gas flow rate varies with different thixotropy numbers. The flow field of the structured fluid reveals that the increases in gas flow rate primarily promote the structural destruction near the bubble tip, while the increase in thixotropy number facilitate the fluid flow around the bubble, with the significant reduction of the low-shear zones and expansion of the yielded zones near the equatorial plane. As a result, modulating the fluid flow with thixotropy number mainly influences the hydrodynamic pressure on the bubble. Based on a force balance model, the forces acting on the bubble are then calculated by integrating the stress on the interface, and it is found that thixotropy number controls the bubble detachment state with the drag effect. Accordingly, the mechanisms governing the influence of thixotropy on drag effect are discussed considering the flow field characteristics and the correlations of drag coefficients. This work helps to deepen the understanding of the bubble behaviors in structured fluids.
{"title":"The influence of thixotropy on bubble growth in thixotropic yield stress fluids: Insights from numerical simulations","authors":"Yixuan Hou , Zhao Jin , Xinzhe Que , Yongchao Zhou , Yiping Zhang","doi":"10.1016/j.jnnfm.2024.105353","DOIUrl":"10.1016/j.jnnfm.2024.105353","url":null,"abstract":"<div><div>Bubble behaviors in structured fluids are of great interests in industrial applications, while there is currently a lack of understanding regarding the effect of thixotropic microstructure on the bubble formation process. To this end, this study explores the influence of thixotropy on bubble growth in thixotropic yield stress fluids by numerical simulations using the Arbitrary Lagrangian-Eulerian (ALE) method. The numerical results reveal that, with the increase in the thixotropy number, the bubbles at detachment transform from inverted conical to spherical shapes at lower gas flow rates, and from spindle to conical shapes at higher gas flow rates, along with the decreased detachment volume and time. It is also found that the effect of gas flow rate varies with different thixotropy numbers. The flow field of the structured fluid reveals that the increases in gas flow rate primarily promote the structural destruction near the bubble tip, while the increase in thixotropy number facilitate the fluid flow around the bubble, with the significant reduction of the low-shear zones and expansion of the yielded zones near the equatorial plane. As a result, modulating the fluid flow with thixotropy number mainly influences the hydrodynamic pressure on the bubble. Based on a force balance model, the forces acting on the bubble are then calculated by integrating the stress on the interface, and it is found that thixotropy number controls the bubble detachment state with the drag effect. Accordingly, the mechanisms governing the influence of thixotropy on drag effect are discussed considering the flow field characteristics and the correlations of drag coefficients. This work helps to deepen the understanding of the bubble behaviors in structured fluids.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"335 ","pages":"Article 105353"},"PeriodicalIF":2.7,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142744983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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