Journal of Non-Newtonian Fluid Mechanics最新文献

{"title":"A multiscale framework for polymer modeling applied in a complex fluid flow","authors":"Kosar Khajeh,&nbsp;Deboprasad Talukdar,&nbsp;Gentaro Sawai,&nbsp;Hitoshi Washizu","doi":"10.1016/j.jnnfm.2024.105200","DOIUrl":"10.1016/j.jnnfm.2024.105200","url":null,"abstract":"<div><p>Understanding polymer dynamics under shear flow is crucial for studying their rheological behavior in diverse applications. However, conventional micro analyses provide limited insights into polymer elongation and conformation. To address this, we propose a hybrid model combining the Lattice Boltzmann method and Langevin Dynamics technique, which captures the multiscale nature of polymer dynamics. Using the coarse-grain bead-spring method, we optimize computational efficiency and model polymers as chains with specific mass and charge. Our hybrid model integrates Navier-Stokes equations with external drag force modified based on segment velocities from Brownian Dynamics simulations.</p><p>In our study, we investigated the effects of chain structure and solvent properties on polymer solutions under shear flow through numerical simulations. We observed that in high shear rate flows, a viscous solvent promotes polymer elongation, while low shear rate flows lead to chain insolubility in the base oil. Longer chains have a greater overall impact on the fluid due to increased contact points with the solvent. The size of the polymer coil over time is influenced by shear rate, chain length, and solvent viscosity. Moreover, solvent density, particle mass, and radius locally affect fluid flow. The higher viscosity fluids result in amplified hydrodynamic and random forces acting on the chains. These findings have implications for applications involving polymer additives that alter the properties of the host solvent in natural and artificial processes. Our study represents an initial step towards a comprehensive understanding of polymer dynamics, taking into account the diverse factors that influence them.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"325 ","pages":"Article 105200"},"PeriodicalIF":3.1,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139892762","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}

{"title":"The steady and unsteady regimes in a cubic lid-driven cavity with viscoplastic fluid solved with the lattice Boltzmann method","authors":"Marco A. Ferrari,&nbsp;Admilson T. Franco","doi":"10.1016/j.jnnfm.2024.105198","DOIUrl":"10.1016/j.jnnfm.2024.105198","url":null,"abstract":"<div><p>This work builds upon the previously published analysis of a lid-driven cavity filled with viscoplastic fluid. We extend the study from a two-dimensional case to a three-dimensional one, employing the moment representation of the lattice Boltzmann method to obtain numerical results. The findings expand the existing dataset, which can potentially serve as benchmark results for inertial regimes of viscoplastic flows. In this study, we investigate the Reynolds and Bingham numbers until the flow transition from stationary to a transient regime. The results reveal that, similarly to the Newtonian case, there is an effective Reynolds number for the bifurcation, approximately Re^⁎ = Re₀ (1 + Bn), where Re₀ represents the bifurcation point for a Newtonian fluid. Like the Newtonian cases, there were instances where the Taylor-Görtler-like vortices moved toward the cavity's side periodically. In other cases, more than two vortices simultaneously formed, with their number changing over time. Finally, similar to the two-dimensional case, the bifurcation initiated after the Moffat eddies in the downstream corner broke down into plugs.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"325 ","pages":"Article 105198"},"PeriodicalIF":3.1,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139664956","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}

{"title":"Multiscale simulations for polymer melt spinning process using Kremer–Grest CG model and continuous fluid mechanics model","authors":"Yan Xu,&nbsp;Yuji Hamada,&nbsp;Takashi Taniguchi","doi":"10.1016/j.jnnfm.2024.105195","DOIUrl":"10.1016/j.jnnfm.2024.105195","url":null,"abstract":"<div><p>We succeeded in developing a <u>m</u>ulti<u>s</u>cale <u>s</u>imulation (MSS) method for a spinning process of a polymer melt. A previous work by Sato and Taniguchi (2017) developed a MSS method where the microscopic model and macroscopic model for the spinning process are respectively modeled by using a slip-link model and a continuous fluid mechanics model. Here we replace the microscopic model with the Kremer–Grest <u>c</u>oarse-<u>g</u>rained (CG) model, and investigate the state of the polymer chains at steady state in the spinning process, by changing the <u>d</u>raw <u>r</u>atio <span>Dr</span>. Unlike the previous MSS, where the microscopic simulator is a slip-link model, in which polymer chains are simulated in virtual space and entanglements are treated by virtual links, in the present MSS, a real space molecular dynamics simulator is used as the microscopic simulator. The replacement brings the advantage that we can obtain more information on the state of polymer chains, but also brings two computational difficulties, (I) the requirement of a huge computational cost, and (II) the simulation box problem related to the periodic boundary condition in the microscopic system. To deal with (I), we considered a micro-macro coupling method different from previous MSS. To resolve problem (II), we used the UEF (uniform extensional flow) method developed by Nicholson and Rutledge (2016) and Murashima et al. (2018) for a polymer melt system. By using these two ideas, we performed MSS simulations, and established a correspondence between the macroscopic flow and the microscopic polymer conformations at any position along the spinning line. Furthermore, we investigated the influence of <span>Dr</span> on the stretching and orientation of polymers chains and the spatial correlation between polymer chains.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"325 ","pages":"Article 105195"},"PeriodicalIF":3.1,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139649109","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}

{"title":"Elastoviscoplasticity intensifies the unstable flows through a micro-contraction geometry","authors":"A. Chauhan,&nbsp;C. Sasmal","doi":"10.1016/j.jnnfm.2024.105186","DOIUrl":"10.1016/j.jnnfm.2024.105186","url":null,"abstract":"<div><p><span>This study focuses on the two-dimensional numerical investigation of complex fluid flows through a micro-contraction geometry in the creeping flow<span> regime, specifically examining elastoviscoplastic (EVP) fluids. These fluids exhibit a combination of viscous, elastic, and plastic behaviors. The governing equations, including mass and momentum, are solved using a finite volume method-based discretization technique. Saramito’s constitutive model is utilized to accurately represent the viscous, elastic, and plastic responses of the EVP fluid. The present results demonstrate significant differences in flow dynamics, such as vortex dynamics and transitions between flow regimes (e.g., steady to unsteady), when compared to simple Newtonian and non-Newtonian viscoelastic (VE) or viscoplastic (VP) fluids. This study reveals that when the yield strain </span></span><span><math><mrow><mo>(</mo><msub><mrow><mi>ϵ</mi></mrow><mrow><mi>y</mi></mrow></msub><mo>)</mo></mrow></math></span><span><span> exceeds a critical value, approximately ranging from 0.79 to 0.89, the flow transits from a steady to an unsteady state for the EVP fluids. Importantly, the present study shows that EVP fluids exhibit intensified chaotic flow dynamics and increased instability compared to VE and VP fluids under similar flow conditions. However, the presence of shear-thinning behavior in EVP fluids suppresses this instability. The analysis of local velocity fields<span> and flow deformation in this study highlights the impact on the stretching of fluid microstructure and </span></span>elastic stresses<span>, which ultimately contribute to the origin of this intensified unstable flow condition for EVP fluids. The finding from this study holds significant potential for enhancing heat or mass transfer rates and mixing efficiency in micro-scale systems, where the prevailing steady and laminar flow conditions often hinder these transport processes.</span></span></p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"325 ","pages":"Article 105186"},"PeriodicalIF":3.1,"publicationDate":"2024-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139507598","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}

{"title":"On the use of time-dependent fluids for delaying onset of transition to turbulence in the flat plate boundary-layer flow: A passive control of flow","authors":"Danial Rezaee","doi":"10.1016/j.jnnfm.2023.105184","DOIUrl":"10.1016/j.jnnfm.2023.105184","url":null,"abstract":"<div><p><span>Inelastic time-dependent fluids display continuous and reversible changes in viscosity when subjected to a constant shear-rate. These alterations arise from the gradual modification of the material’s microstructure due to shear-induced effects, known as shear rejuvenation. When this process generates smaller structural units, it is termed thixotropy; conversely, if it produces larger units, it is labeled anti-thixotropy. Aging is another characteristic of such fluids, denoting the capacity of the material to regain its original structure in the absence of shear, thus reversing the initial time-dependent change. This phenomenon often results from thermally activated Brownian motion prompting the reorganization of the material’s microconstituents. Consequently, attractive forces between these components can instigate the reconstruction of a network-like structure within the material. This study centers on investigating how variations in fluid microstructure impact the onset of transition to turbulence in a flat plate boundary-layer flow. Specifically, the focus is on cases where larger structural units emerge during the breakdown process (anti-thixotropy). To represent such fluids, the Quemada model, an inelastic structural-kinetic model, is employed. This model effectively captures thixotropy and anti-thixotropy by appropriately configuring model parameters. The analysis begins with obtaining a local similarity solution for the generalized </span>Blasius equation, representing the base flow. Subsequently, the stability of this flow is assessed using linear temporal stability theory. This involves introducing infinitesimally-small normal-mode perturbations to the base flow, yielding the generalized Orr–Sommerfeld equation. Solving this equation using the spectral method provides insights into stability. Results from this study indicate that for low Deborah numbers, the shear-thickening behavior prevails, causing destabilization. In contrast, higher Deborah numbers lead to stability. This implies that anti-thixotropy effectively delays the onset of transition to turbulence and could hold practical applications for flow control.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"324 ","pages":"Article 105184"},"PeriodicalIF":3.1,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139096192","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}

{"title":"Effect of die exit flow conditions on air-gap film dynamics in two-dimensional film casting processes: Short Communication","authors":"Geunyeop Park, Ho Suk Ji, Joo Sung Lee, Hyun Wook Jung, JaeChun Hyun","doi":"10.1016/j.jnnfm.2023.105182","DOIUrl":"https://doi.org/10.1016/j.jnnfm.2023.105182","url":null,"abstract":"<p>The impact of the inlet velocity profile at the die exit on the film dynamics within the air-gap region was investigated using numerical simulations for both Newtonian and viscoelastic Phan-Thien and Tanner (PTT) fluids in isothermal two-dimensional (2-D) film casting processes. In an industrial context, intentional adjustments were made to reduce the inlet velocities at the edge of the casting die, effectively mitigating the edge-beads characterized by a higher edge thickness than the center thickness of the final films. By varying the inlet velocity conditions with decreasing edge velocities, the steady film dynamics were correlated with the onsets of draw resonance instability and frequency responses to a disturbance, which were determined using the transfer function data obtained under tension-controlled conditions. The results revealed that decreasing the inlet velocity at the edge improved not only the formation of films but also the process stability for both Newtonian and viscoelastic fluids. In addition, the sensitivity or frequency response to a disturbance was effectively reduced by decreasing the inlet velocity at the edge. This observed impact of the inlet velocity was closely related to the increased tension levels at take-up and a greater portion of the neck-like deformation type in the air-gap region.</p>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"49 3 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139030433","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}

{"title":"Effect of die exit flow conditions on air-gap film dynamics in two-dimensional film casting processes","authors":"Geunyeop Park ,&nbsp;Ho Suk Ji ,&nbsp;Joo Sung Lee ,&nbsp;Hyun Wook Jung ,&nbsp;Jae Chun Hyun","doi":"10.1016/j.jnnfm.2023.105182","DOIUrl":"10.1016/j.jnnfm.2023.105182","url":null,"abstract":"<div><p>The impact of the inlet velocity profile at the die exit on the film dynamics within the air-gap region was investigated using numerical simulations for both Newtonian and viscoelastic Phan-Thien and Tanner (PTT) fluids in isothermal two-dimensional (2-D) film casting processes. In an industrial context, intentional adjustments were made to reduce the inlet velocities at the edge of the casting die, effectively mitigating the edge-beads characterized by a higher edge thickness than the center thickness of the final films. By varying the inlet velocity conditions with decreasing edge velocities, the steady film dynamics were correlated with the onsets of draw resonance instability and frequency responses to a disturbance, which were determined using the transfer function data obtained under tension-controlled conditions. The results revealed that decreasing the inlet velocity at the edge improved not only the formation of films but also the process stability for both Newtonian and viscoelastic fluids. In addition, the sensitivity or frequency response to a disturbance was effectively reduced by decreasing the inlet velocity at the edge. This observed impact of the inlet velocity was closely related to the increased tension levels at take-up and a greater portion of the neck-like deformation type in the air-gap region.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"324 ","pages":"Article 105182"},"PeriodicalIF":3.1,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139019107","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}

{"title":"Fish Bone Descending in the Mediastinum.","authors":"Kuniyo Sueyoshi, Kosuke Otsubo, Shinya Hirota, Fumitsugu Kojima, Toru Bando","doi":"10.5761/atcs.cr.22-00042","DOIUrl":"10.5761/atcs.cr.22-00042","url":null,"abstract":"<p><p>Ingested sharp foreign bodies rarely migrate extraluminally into adjacent organs such as the pharynx, lungs, and liver. Herein, we report a case of fish bone ingestion where the foreign body followed a unique migration trajectory. Computed tomography revealed a fish bone extraluminally located in the aortopulmonary space in the left mediastinum and peri-esophageal pneumomediastinum. Endoscopic examination indicated no injury to the esophageal mucosa but showed mucosal lacerations in the left hypopharynx. Accordingly, we reasoned that the fish bone penetrated the laryngopharynx and then descended in the mediastinum.</p>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"86 1","pages":"323-325"},"PeriodicalIF":0.0,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10767657/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78089420","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}

{"title":"Global stability of Oldroyd-B fluids in plane Couette flow","authors":"Joshua Binns,&nbsp;Andrew Wynn","doi":"10.1016/j.jnnfm.2023.105171","DOIUrl":"10.1016/j.jnnfm.2023.105171","url":null,"abstract":"<div><p>We prove conditions for global nonlinear stability of Oldroyd-B viscoelastic fluid flows in the Couette shear flow geometry. Global stability is inferred by analysing a new functional, called a perturbation entropy, to quantify the magnitude of the polymer perturbations from their steady-state values. The conditions for global stability extend, in a physically natural manner, classical results on global stability of Newtonian Couette flow.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"324 ","pages":"Article 105171"},"PeriodicalIF":3.1,"publicationDate":"2023-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139030386","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}

{"title":"Maximum drag enhancement asymptote in turbulent Taylor–Couette flow of dilute polymeric solutions","authors":"Fenghui Lin ,&nbsp;Jiaxing Song ,&nbsp;Nansheng Liu ,&nbsp;Zhenhua Wan ,&nbsp;Xi-Yun Lu ,&nbsp;Bamin Khomami","doi":"10.1016/j.jnnfm.2023.105172","DOIUrl":"10.1016/j.jnnfm.2023.105172","url":null,"abstract":"<div><p><span><span>Direct numerical simulations in a wide-gap turbulent viscoelastic Taylor–Couette flow in the </span>Reynolds number (</span><span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>) range of 1500 to 8000 reveals the existence of a maximum drag enhancement (MDE) asymptote. The statistical properties associated with the turbulent and polymer dynamics demonstrate that the turbulent drag enhances with the increase of the Weissenberg number (<span><math><mrow><mi>W</mi><mi>i</mi></mrow></math></span>) and eventually saturates above a critical <span><math><mrow><mi>W</mi><mi>i</mi></mrow></math></span><span>, namely, the flow reaches the MDE state. The mean velocity profile in MDE state closely follows a logarithmic-like law with an identical slope (</span><span><math><mrow><msub><mrow><mi>κ</mi></mrow><mrow><mi>K</mi></mrow></msub><mo>=</mo><mn>2</mn><mo>.</mo><mn>32</mn></mrow></math></span>) and a <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span><span>-dependent intercept. A detailed analysis of flow structures reveals that the MDE asymptote results from the creation and eventual saturation of small-scale elastic and inertio-elastic Görtler vortices in the inner- and outer-wall regions, respectively. These vortical structures arise due to competing effects of polymer-induced stresses that either suppress or promote turbulent vortices. A close examination of competing forces in the azimuthal direction<span><span> shows that the ratio of polymeric to turbulent stresses reaches a large plateau, underscoring the elastic nature of the MDE state. Moreover, the energy production mechanism in the MDE state further supports: (1) the universal </span>interplay between polymers and turbulent vortices in a broad range of curvilinear and planar turbulent flows, and (2) the fact that the elastically induced asymptotic saturation of drag modification is an inherent property of elasticity-driven and/or elasto-inertial turbulence flow states. Overall, this study provides concrete evidence for our earlier postulate that asymptotic flow states in unidirectional turbulent viscoelastic flows are of elastic nature.</span></span></p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"323 ","pages":"Article 105172"},"PeriodicalIF":3.1,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138680047","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}