Journal of Non-Newtonian Fluid Mechanics最新文献

{"title":"The effects of suspending fluid viscoelasticity on the mechanical properties of capsules and red blood cells in flow","authors":"Boon Siong Neo ,&nbsp;Eric S.G. Shaqfeh","doi":"10.1016/j.jnnfm.2024.105215","DOIUrl":"https://doi.org/10.1016/j.jnnfm.2024.105215","url":null,"abstract":"<div><p>The mechanical behavior of spherical capsules and red blood cells in shear and confined pressure-driven flow of polymeric fluids was studied computationally. In particular, we study the effect of suspending fluid elasticity on the steady mechanical behavior of spherical capsules and red blood cells suspended in an Oldroyd-B fluid, in dilute shear and confined pressure-driven flow, as a model system for dilute suspensions of capsules in polymeric fluids. We investigate the effects of suspending fluid elasticity at fixed capillary number on the capsule deformation, membrane tensions, and effective viscosity for a range of capsule capillary numbers. For both spherical capsules and red blood cells, capsule deformation was found to decrease with increasing fluid elasticity in shear flow, and increase in confined pressure-driven flow. The average membrane tension for spherical capsules was found to follow the same trends: decreasing in shear and increasing in pressure-driven flow; however, the average membrane tension for red blood cells had a less pronounced trend with fluid elasticity, which we attribute to the reduced volume of the red blood cell. On the other hand, the effective viscosity of the suspension was found to be non-monotonic with an increase in suspending fluid elasticity for both flows and particle types. The underlying mechanisms for these trends were investigated by comparing these capsule simulations to results from rigid spherical particles. These results indicate that the mechanical behavior of these dilute capsule suspensions can be qualitatively understood by examining the disturbance flow created by the introduction of rigid spherical particles, and the subsequent stress induced in the polymeric fluid to these disturbances.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"326 ","pages":"Article 105215"},"PeriodicalIF":3.1,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139992931","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 polymer diffusive instability in highly concentrated polymeric fluids","authors":"Theo Lewy,&nbsp;Rich Kerswell","doi":"10.1016/j.jnnfm.2024.105212","DOIUrl":"https://doi.org/10.1016/j.jnnfm.2024.105212","url":null,"abstract":"<div><p>The extrusion of polymer melts is known to be susceptible to ‘melt fracture’ instabilities, which can deform the extrudate, or cause it to break entirely. Motivated by this, we consider the impact that the recently discovered polymer diffusive instability (PDI) can have on polymer melts and other concentrated polymeric fluids using the Oldroyd-B model with the effects of polymer stress diffusion included. Analytic progress can be made in the concentrated limit (when the solvent-to-total-viscosity ratio <span><math><mrow><mi>β</mi><mo>→</mo><mn>0</mn></mrow></math></span>), illustrating the boundary layer structure of PDI, and allowing the prediction of its eigenvalues for both plane Couette and channel flow. We draw connections between PDI and the polymer melt ‘sharkskin’ instability, both of which are short wavelength instabilities localised to the extrudate surface. Inertia is shown to have a destabilising effect, reducing the smallest Weissenberg number (<span><math><mi>W</mi></math></span>) where PDI exists in a concentrated fluid from <span><math><mrow><mi>W</mi><mo>∼</mo><mn>8</mn></mrow></math></span> in inertialess flows, to <span><math><mrow><mi>W</mi><mo>∼</mo><mn>2</mn></mrow></math></span> when inertia is significant.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"326 ","pages":"Article 105212"},"PeriodicalIF":3.1,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377025724000284/pdfft?md5=d5f2290074c51216f4a96d454f79203b&pid=1-s2.0-S0377025724000284-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139985581","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":"Numerical simulations of the Oldroyd-B fluid flow around triangular cylinders with different orientations","authors":"Fanji Sun ,&nbsp;Xiaoyu Wen ,&nbsp;Xinhui Si ,&nbsp;Chiyu Xie ,&nbsp;Botong Li ,&nbsp;Limei Cao ,&nbsp;Jing Zhu","doi":"10.1016/j.jnnfm.2024.105204","DOIUrl":"10.1016/j.jnnfm.2024.105204","url":null,"abstract":"&lt;div&gt;&lt;p&gt;This study numerically simulates the two-dimensional flow of Oldroyd-B fluid around an isosceles right-angled triangular cylinder with five orientations. The log-conformation reformulation is employed to stabilize the numerical simulations. By adjusting the triangular orientation angle (&lt;span&gt;&lt;math&gt;&lt;mi&gt;θ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;), three types of fluids development process can be observed: from steady to vortex shedding at &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;θ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mi&gt;π&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, keeping the vortex shedding at &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;θ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;mi&gt;π&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mi&gt;π&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;/math&gt;&lt;/span&gt;, and from vortex shedding to steady state at &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;θ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;mi&gt;π&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. When the triangular cylinder faces the incoming stream with the inclined plane, the elastic effect acting on the cylinder is strong, otherwise it is weak. For &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;θ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mfrac&gt;&lt;mrow&gt;&lt;mi&gt;π&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/mfrac&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, the effects of the viscosity ratio (&lt;span&gt;&lt;math&gt;&lt;mi&gt;β&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;), the Reynolds number (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;), and the Weissenberg number (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) are further investigated. When the elasticity is reduced by changing the viscosity ratio (&lt;span&gt;&lt;math&gt;&lt;mi&gt;β&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) that ranged from 0 to 0.9, the final flow state will transition from stable to vortex shedding state, which indicates the restraining effect of elasticity on wake instability. In the high elastic Oldroyd-B fluid, the critical Reynolds number for vortex shedding is about 110 for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Besides, the Weissenberg numbers (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) ranged from 0.25 to 8 are discussed at &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;100&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. With the increase of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, four different flow states of the wake are observed: periodic vortex shedding at low Weissenberg number &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;25&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, stabilizing for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; ranged from 0.5 to 1, semi-periodic strong vortex shedding for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; is about 2, and chaos when &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The results indicate that excessively strong elastic effects may also lead to unstable flows. Finally, the flow states corresponding to each Reynolds number and Weissenberg number in a certain range (&lt;span&gt;&lt;math","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"326 ","pages":"Article 105204"},"PeriodicalIF":3.1,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139955365","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":"Semi-analytical solutions of Newtonian fluid-FENE-P fluid core annular flow","authors":"Yuying Guo ,&nbsp;Jiaqiang Jing ,&nbsp;Jie Sun","doi":"10.1016/j.jnnfm.2024.105205","DOIUrl":"10.1016/j.jnnfm.2024.105205","url":null,"abstract":"<div><p>Water-lubricated transportation of viscous oil is an important application of core annular flow (CAF), which significantly reduces friction pressure drop and saves pump power. However, the core oil floats up due to the density difference of oil and water, causing instability and even destruction of CAF, which restricts the application and development of the drag reduction technology. The viscoelastic fluid in the annular can inhibit the tendency of the core oil to float up and enhance the stability of the CAF. Nevertheless, theoretical studies related to the viscoelastic fluid CAF are currently missing. To make up for the lack of theoretical research, the solutions of laminar concentric viscous oil-viscoelastic fluid CAF in horizontal and inclined pipes are obtained in this work, and the annular fluid is regarded as viscoelastic fluid conforming to the FENE-P model. Based on the Navier–Stokes equation and FENE-P model, a non-dimensional CAF model is established, and the Newton–Raphson method is used to solve the model. The rheological behavior of annular fluid and the effects of viscoelastic fluid rheology and viscosity ratio on various CAF flow characteristics, including holdup, pressure gradient, slip ratio, and Ledinegg instability, are investigated. The results indicate that the shear-thinning effect of viscoelastic fluid has a significant effect on water holdup and expands the multi-solution region. Different from Newtonian fluid, when the annulus fluid is viscoelastic, the slip ratio can be less than 2. The most significant property is that the shear-thinning effect can transform the hydraulic characteristic curve in the multi-valued region into a single-valued curve, which helps to eliminate Ledinegg instability.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"326 ","pages":"Article 105205"},"PeriodicalIF":3.1,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139955360","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":"Viscoplastic flows in superhydrophobic channels with oriented grooves: From anisotropic slip to secondary flow","authors":"H. Rahmani,&nbsp;S.M. Taghavi","doi":"10.1016/j.jnnfm.2024.105203","DOIUrl":"10.1016/j.jnnfm.2024.105203","url":null,"abstract":"<div><p>In this work, Poiseuille flows of viscoplastic fluids in typically thin channels equipped with a superhydrophobic groovy wall are numerically studied. The orientation of the groove relative to the applied pressure gradient can vary, and this orientation is measured via the groove orientation angle (<span><math><mi>θ</mi></math></span>). In particular, longitudinal (<span><math><mrow><mi>θ</mi><mo>=</mo><mn>0</mn></mrow></math></span>), oblique (<span><math><mrow><mn>0</mn><mo>&lt;</mo><mi>θ</mi><mo>&lt;</mo><mn>9</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span>), and transverse (<span><math><mrow><mi>θ</mi><mo>=</mo><mn>9</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>∘</mo></mrow></msup></mrow></math></span>) flow configurations are considered. The Bingham constitutive equation is employed to model the viscoplastic rheology, within the framework of the Papanastasiou regularization method. Assuming that air (gas) fills the groove completely and that the formed liquid/air interface remains flat while pinned at the groove edges, the viscoplastic fluid slippage is modeled on the liquid/air interface using the Navier slip law. Due to the anisotropic slip dynamics for the oblique flow configuration, a secondary flow is generated normal to the direction of the pressure gradient, offering unique flow features. Our work systematically analyzes the effects of the flow parameters, <em>i.e.</em>, the groove orientation angle (<span><math><mi>θ</mi></math></span>), the Bingham (<span><math><mi>B</mi></math></span>) and slip (<span><math><mi>b</mi></math></span>) numbers, the groove periodicity length (<span><math><mi>ℓ</mi></math></span>), and the slip area fraction (<span><math><mi>φ</mi></math></span>) on the flow variables of interest, <em>i.e.</em>, the main and secondary velocity fields, the unyielded center plug zone, the effective slip length tensor (<span><math><mi>χ</mi></math></span>), the secondary flow index (<span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>S</mi></mrow></msub></math></span>), the slip angle difference (<span><math><mrow><mi>θ</mi><mo>−</mo><mi>s</mi></mrow></math></span>), and the pressure drop (<span><math><mrow><mi>Δ</mi><mi>P</mi></mrow></math></span>). It is demonstrated that <span><math><mi>χ</mi></math></span>’s shear component, <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>S</mi></mrow></msub></math></span>, and <span><math><mrow><mi>θ</mi><mo>−</mo><mi>s</mi></mrow></math></span> are maximum at intermediate <span><math><mi>θ</mi></math></span>, the value of which generally decreases with <span><math><mi>B</mi></math></span>. In addition, the center plug is unbroken for the longitudinal flow while it breaks with an increase in <span><math><mi>θ</mi></math></span> for sufficiently large <span><math><mi>b</mi></math></span>.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"326 ","pages":"Article 105203"},"PeriodicalIF":3.1,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377025724000193/pdfft?md5=888609c0fb3b426c000961c153d89929&pid=1-s2.0-S0377025724000193-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139876818","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":"A finite-volume framework to solve the Fokker–Planck equation for fiber orientation kinetics","authors":"Dogukan T. Karahan,&nbsp;Devesh Ranjan,&nbsp;Cyrus K. Aidun","doi":"10.1016/j.jnnfm.2024.105199","DOIUrl":"https://doi.org/10.1016/j.jnnfm.2024.105199","url":null,"abstract":"<div><p>In this work, a new solver, FPSolve, is developed to study fiber orientation kinetics using the Fokker–Planck (FP) equation. The solver employs the finite-volume method. The FP equation is discretized on unstructured cubed-sphere grids using the centered differencing scheme (CDS) or a blend of the CDS and the upwind differencing scheme. Time integration is performed using a second-order two-stage explicit Runge–Kutta scheme. Different shape factors and rotational diffusion coefficients are implemented to study suspensions in dilute to semiconcentrated regimes. The verification of the solver is performed for the fiber orientation in simple shear flow up to a Peclet number of <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>. Grid independence analysis is presented to show the second-order accuracy of FPSolve. It is demonstrated that the solver does not need stabilization by upwinding. Simulations for semiconcentrated suspensions are performed using the model of Ferec et al. (2014). Time-accurate solutions of the FP equation with explicit time stepping for this model are presented for the first time.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"325 ","pages":"Article 105199"},"PeriodicalIF":3.1,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139743437","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":"Tricritical state and quasi-periodicity triggered by the non-linear elasticity in an Upper Convected Maxwell fluid confined between two co-oscillating cylinders about zero-mean","authors":"Mohamed Hayani Choujaa ,&nbsp;Mehdi Riahi ,&nbsp;Saïd Aniss","doi":"10.1016/j.jnnfm.2024.105202","DOIUrl":"https://doi.org/10.1016/j.jnnfm.2024.105202","url":null,"abstract":"<div><p>The effects of harmonically co-oscillating the inner and outer cylinders about zero mean rotation in a Taylor–Couette flow are examined numerically using Floquet theory, for the case where the fluid confined between the cylinders obeys the upper convected Maxwell model. Although stability diagrams and mode competition involved in the system were clearly elucidated recently by Hayani Choujaa et al. (2021) in weakly elastic fluids, attention is focused, in this paper, on the dynamic of the system at higher elasticity with emphasis on the nature of the primary bifurcation. In this framework, we are dealing with pure inertio-elastic parametric resonant instabilities where the elastic and inertial mechanisms are considered of the same order of magnitude. It turns out, on the one hand, that the fluid elasticity gives rise, at the onset of instability, to the appearance of a family of new harmonic modes having different axial wavelengths and breaking the spatio-temporal symmetry of the base flow: invariance in the axial direction generating the <span><math><mrow><mi>O</mi><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mrow></math></span> symmetry group and a half-period-reflection symmetry in the azimuthal direction generating a spatio-temporal <span><math><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> symmetry group. On the other hand, new quasi-periodic flow emerging in the high frequency limit and other interesting bifurcation phenomena including bi and tricritical states are also among the features induced by the fluid elasticity. Lastly, and in comparison with the Newtonian configuration of this system, the fluid elasticity leads to a total suppression of the non-reversing flow besides emergence of instabilities with lower wavelengths. Such a comparison provides insights into the dynamics of elastic hoop stresses in altering the flow reversal in modulated Taylor–Couette flow.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"325 ","pages":"Article 105202"},"PeriodicalIF":3.1,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139732936","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":"Mist-control of polyalphaolefin (PAO) lubricants using long pairwise end-associative polymers","authors":"Red C. Lhota ,&nbsp;Robert W. Learsch ,&nbsp;Jacob Temme ,&nbsp;Vincent Coburn ,&nbsp;Julia A. Kornfield","doi":"10.1016/j.jnnfm.2024.105197","DOIUrl":"10.1016/j.jnnfm.2024.105197","url":null,"abstract":"<div><p>Accidental release of pressurized hydrocarbon fuels and lubricants are a major fire hazard due to the formation of small droplet mists that can readily evaporate and ignite. Mist control through increasing droplet size and suppressing droplets has been previously demonstrated with high molecular weight polymer additives, but traditional long polymer additives do not survive the pumping that would usually precede accidental release. This constraint inspired associative polymer additives that can transiently form the high molecular weights needed for mist control, while reversibly breaking during pumping. A prior study demonstrated the efficacy of such a system in fuel: long telechelic polycyclooctadiene (PCOD) with pairwise associating acid and base end-groups. Here, we address an obstacle to applying this same polymeric system in a polyalphaolefin (PAO) solvent—its poorer solvent quality for PCOD than fuel. We measured the effects of the end-associative PCOD compared to a non-associative control on the rheological properties of solutions in both PAO (a common lubricant and heat transfer fluid) and decahydronapthalene (decalin, a solvent with PCOD solubility similar to fuel) in shear and extension, and connect those rheological modifications to observed changes in PAO spray under simulated accidental release conditions. The PCOD additives demonstrated substantial mist control in PAO, both in terms of reduced spray angle and droplet suppression. Despite the worse solubility in PAO and thus smaller effective coil size, these associative PCOD additives are effective at the low concentrations (¡0.1 wt %) necessary for practical use as a safety measure.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"326 ","pages":"Article 105197"},"PeriodicalIF":3.1,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377025724000132/pdfft?md5=7ee72566e506e91fc25e1f654f0b3eaf&pid=1-s2.0-S0377025724000132-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139890989","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":"The elastic perfectly plastic constitutive equation for yield stress fluids","authors":"Kamil Fedorowicz,&nbsp;Robert Prosser","doi":"10.1016/j.jnnfm.2024.105201","DOIUrl":"https://doi.org/10.1016/j.jnnfm.2024.105201","url":null,"abstract":"<div><p>We explore the use of an <em>Elastic Perfectly Plastic</em> (EPP) constitutive equation for the modelling of yield stress fluids. Contrary to many other models, stresses in the EPP model arise from elastic deformation rather than as a viscous effect. In this paper, the EPP model is coupled to a standard viscous treatment of the post-yield flow stresses to produce Bingham-like behaviour, and the timescale associated with the yielding mechanism is linked to material parameters. We also show that when the yield stress is much smaller than the elastic modulus, EPP and Bingham models can produce very similar flow fields in channel and contraction geometries. The EPP model is found to be significantly cheaper computationally in both geometries. Additionally, in the case of channel flow where analytical solutions exist, the EPP model is associated with a much smaller error than the regularised Bingham model.</p></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"325 ","pages":"Article 105201"},"PeriodicalIF":3.1,"publicationDate":"2024-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S037702572400017X/pdfft?md5=205eab5204c7171449d25e6304b4ce53&pid=1-s2.0-S037702572400017X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139738184","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":"Mixing in heterogeneous fluids: An examination of fluid property variations","authors":"Mohammad Reza Daneshvar Garmroodi,&nbsp;Ida Karimfazli","doi":"10.1016/j.jnnfm.2024.105196","DOIUrl":"https://doi.org/10.1016/j.jnnfm.2024.105196","url":null,"abstract":"&lt;div&gt;&lt;p&gt;In the context of stirred tanks, “mixing” refers to the purposeful and controlled flow designed to minimize heterogeneity, such as variations in solute or additive concentration. Industries like food and polymer processing often encounter situations where fluid properties are closely tied to additive concentration. However, conventional engineering models of mixing, herein referred to as “homogeneous models”, typically assume that the influence of heterogeneous fluid properties on mixing dynamics is negligible. In these models, flow development is considered independent of mixing, and the fluid’s rheological properties and density are assumed to be uniform. This manuscript’s primary objective is to emphasize the potential for substantial inaccuracies in predicting mixing outcomes when the effects heterogeneous fluid properties are disregarded. We investigate the homogenization of an additive in a fluid-filled cylindrical tank stirred by an axisymmetric disk, where both fluid rheology and density are contingent on the additive concentration. We introduce and compare two models for predicting mixing development. The first model (model problem &lt;span&gt;&lt;math&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) incorporates variations in fluid properties dependent on the additive concentration, while the second model (model problem &lt;span&gt;&lt;math&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) simplifies the fluid properties to their average values. Our approach to modeling mixing centers on a concentration field governed by advection–diffusion. We illustrate that the mapping between the parameter spaces of the two model problems is far from one-to-one. For any given point in the parameter space of model problem &lt;span&gt;&lt;math&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, three distinct parameter groups (buoyancy, Atwood number, and viscosity ratio) exhibit unconstrained variations within the corresponding subset of the parameter space of model problem &lt;span&gt;&lt;math&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;. As a concrete example, we investigate the impact of buoyancy on the evolution of velocity and additive concentration in model problem &lt;span&gt;&lt;math&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;. Our analysis characterizes the influence of buoyancy on the mixing rate by examining the asymptotic behavior of the concentration field. We find that the standard deviation of the concentration asymptotically converges to an exponential decay, with the intercept and decay rate diminishing as a power-law function of buoyancy. This underscores the significant effect that even slight variations in buoyancy can have on the mixing process. Finally, our results conclusively demonstrate that the recirculation zones, areas where fluid velocity is notable, in model problems &lt;em&gt;M&lt;/em&gt; and &lt;em&gt;T&lt;/em&gt; do not align. In model problem &lt;span&gt;&lt;math&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, the well-mixed region and the recirculation zones closely coincide, but this alignment is not observed in model problem &lt;span&gt;&lt;math&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;. Collectively, our study provides a counterexample th","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"325 ","pages":"Article 105196"},"PeriodicalIF":3.1,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139738186","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}