Article
Mechanics
Subham Pal, Arghya Samanta
Summary: This study conducted a linear stability analysis of a surfactant-laden viscoelastic liquid flowing down a slippery inclined plane. The results showed that the viscoelastic coefficient has a destabilizing effect on the primary instability induced by the surface mode in the long-wave regime, but has a stabilizing effect when the Reynolds number is far from the onset of instability. Additionally, a shear mode was identified at high Reynolds numbers and low inclination angles, which significantly accelerated the transition from stable to unstable flow configurations for the viscoelastic liquid.
Article
Physics, Multidisciplinary
M. Kamran Alam, K. N. Memon, A. M. Siddiqui, S. F. Shah, Muhammad Farooq, Muhammad Ayaz, Taher A. Nofal, Hijaz Ahmad
Summary: This paper investigates the steady state thin layer flow of viscoelastic Ellis fluid in contact with a vertical cylinder, focusing on drainage and lift problems. Solutions are obtained using binomial series technique, exploring special cases for high shear viscoelastic Ellis liquid film. Analysis includes investigation of vorticity vector, thickness of the fluid film, flow rate, average velocity, as well as calculations of thickness of the Ellis fluid film on cylindrical surfaces. Velocity profiles are graphically sketched, showing the model's behavior at high shear rates and low shear stress. Results suggest that velocity increases with alpha and R for drainage, while it decreases for lift case. Velocity profiles for Newtonian and Bingham plastic fluids are calculated, indicating different effects on drainage and lift cases. The variation of n for power law model in drainage and lift is also investigated, showing growth in fluid layer velocity.
Article
Mechanics
Yunxing Su, Alfonso Castillo, On Shun Pak, Lailai Zhu, Roberto Zenit
Summary: In this study, it is found that due to the asymmetric shear-induced elastic stresses, a dense sphere rotating near a wall can levitate at a fixed distance away from the wall by generating a net elastic vertical force.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Computer Science, Interdisciplinary Applications
Joe Alexandersen
Summary: This paper presents a topography optimisation model for fluid flow with varying channel height. It introduces an augmentation of the mass conservation equation to allow for continuously varying channel heights and provides a planar model that describes fully developed flow between two plates of varying channel height. The proposed model bridges the gap between topography and topology optimisation of fluid flow, ensuring a high accuracy for low-to-moderate Reynolds numbers in the laminar regime.
STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION
(2022)
Article
Materials Science, Characterization & Testing
Bingfan Li, Gang Liu, Shiyuan Liu, Lei Chen
Summary: This study developed a viscoelastic fluid transient flow model and verified its reliability through numerical calculations, analyzing the effects of geometric dimensions and material viscoelastic characteristics on transient testing in unsteady shear flow. The results showed that the elastic modulus, viscosity, and system inertia have significant impacts on the behavior of the flow, highlighting the coupling between the test system inertia and the viscoelastic fluid as the essential cause of creep oscillation.
Article
Thermodynamics
Muhammad Waris Saeed Khan, Zeeshan Asghar, Khalil Ur Rehman, Wasfi Shatanawi
Summary: This study solves the heat conduction equation problem with non-homogeneous boundary conditions using the superposition principle and separation of variable approach. The MATLAB algorithm is used to calculate eigenvalues and related eigenfunctions. The simplified Phan-Thien-Tanner (SPTT) fluid and finite extendable non-linear elastic peterline (FENE-P) fluid models are also discussed.
CASE STUDIES IN THERMAL ENGINEERING
(2023)
Article
Mechanics
Jin-Xiang Zhou, Hong-Wei Xiao, Ya-Ping Wang, Adnan Khan, Xiao-Dong Niu, Ming-Fu Wen, Mu-Feng Chen, De-Cai Li, Hiroshi Yamaguchi
Summary: This article investigates the active control of post-impact dynamics of ferrofluid droplets using an external magnetic field. By simulating the flow field, the effects of magnetic field on different phenomena are explored, and it is found that a vertical non-uniform magnetic field and optimal starting moment of magnetic field introduction can effectively improve control.
Article
Mechanics
Souradip Chattopadhyay, Akshay S. Desai, Amar K. Gaonkar, Amlan K. Barua, Anandamoy Mukhopadhyay
Summary: The study focuses on the stability of weakly viscoelastic film flowing down a slippery inclined plane, examining the interaction of bottom slip with viscoelastic parameters and other flow parameters. Two different methods were used to analyze the critical Reynolds numbers of the system, with the result indicating that in some cases, for small slip lengths, the first-order weighted residual method is more accurate in predicting instability thresholds than the first-order Benney equation model.
Article
Mechanics
Souradip Chattopadhyay, Anandamoy Mukhopadhyay
Summary: In this study, the nonlinear stability of a thin viscoelastic film under the influence of gravity, Coriolis and centrifugal forces was investigated. Through two-step analysis, the impact of viscoelastic parameter and Taylor number on flow stability was revealed. The findings were validated through direct numerical simulations, showing good agreement between analytical predictions and numerical results.
Article
Metallurgy & Metallurgical Engineering
Khadija Maqbool, Sidra Shaheen, Elena Bobescu, R. Ellahi
Summary: This paper discusses the analysis of two-layer cilia induced flow of Phan-Thien-Tanner fluid, focusing on the velocity, temperature, and concentration profiles in the two layers. The mathematical modeling simplification provides exact solutions, and the impact of physical parameters on pressure rise and profile changes is illustrated through graphs.
JOURNAL OF CENTRAL SOUTH UNIVERSITY
(2021)
Article
Thermodynamics
Rouhollah Moosavi, Reza Moltafet, Cheng-Xian Lin, Po-Ya Abel Chuang
Summary: The study focuses on the unsteady flow and natural convection heat transfer of fractional Maxwell viscoelastic fluid over sudden expansion geometry, showing that the fractional derivative parameters and physical parameters have significant effects on Nusselt number, friction coefficient, velocity, and temperature.
THERMAL SCIENCE AND ENGINEERING PROGRESS
(2021)
Article
Engineering, Multidisciplinary
Pooja Jangir, Anushka Herale, Ratan Mohan, Paresh Chokshi
Summary: This study investigates the effects of incorporating polymer solutions on the viscous fingering patterns in flow displacement. The addition of polymers alters the viscosity contrast between fluids, leading to changes in fingering patterns. Furthermore, the shear-thinning behavior of the polymer promotes the longitudinal growth of fingers, while fluid elasticity inhibits finger growth and improves flow displacement efficiency.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2022)
Article
Thermodynamics
F. Pimenta, M. A. Alves
Summary: This study investigates the conjugate heat transfer of a simplified PTT fluid past an unbounded sphere in the Stokes regime. It analyzes the impact of various parameters such as Deborah, Prandtl, and Brinkman numbers on heat transfer enhancement.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2021)
Article
Multidisciplinary Sciences
Muhammad Naveed Khan, Aamir Abbas Khan, Zhentao Wang, Haifaa F. Alrihieli, Sayed M. Eldin, F. M. Aldosari, Ibrahim E. Elseesy
Summary: This paper theoretically analyzes the stagnation point flow of a 2nd-grade micropolar fluid into a porous material under the magnetic field effect. Non-Newtonian fluids, widely used in various industries, are investigated. The study considers stratification boundary conditions, generalized Fourier and Fick's laws with activation energy for heat and mass transportation. Numerical solutions are obtained using the BVP4C technique on MATLAB for different dimensionless parameters, leading to graphical and numerical results that are discussed. The findings show that accurate predictions of e and M decrease the velocity sketch due to resistance effect, and larger estimation of micropolar parameter improves the fluid's angular velocity.
SCIENTIFIC REPORTS
(2023)
Article
Mechanics
Seng Hoe Hue, Loic Chagot, Panagiota Angeli
Summary: The displacement flow of an organic Newtonian fluid by a pure viscoelastic aqueous solution is experimentally investigated, showing that the viscoelastic fluid produces a thinner displaced phase film compared to a Newtonian fluid. Two modes of instability are observed at the interface during displacement, including a periodic instability induced by elastic stresses. Additionally, microchannel bends downstream of the observation point affect the shape and frequency of the instabilities.
Article
Physics, Fluids & Plasmas
Vlasis Mitsoulas, Stylianos Varchanis, Yannis Dimakopoulos, John Tsamopoulos
Summary: The response of the endothelial glycocalyx (EG) to variations of the hemodynamic environment is crucial for maintaining blood vessel permeability and blood component balance. This study investigates the influence of geometric features and mechanical properties of individual fibers on the apparent permeability of EG, using modeling and experimental predictions.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Physics, Fluids & Plasmas
D. Pettas, G. Karapetsas, Y. Dimakopoulos, J. Tsamopoulos
Summary: We investigated the flow of a Newtonian liquid film over an inclined hydrophobic wall textured with periodical microgrooves. Through numerical simulations and theoretical analysis, we explored the stability of the liquid flow under the influence of inertia, viscous, and capillary forces, as well as substrate wettability and geometric characteristics.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Biophysics
K. Giannokostas, Y. Dimakopoulos, J. Tsamopoulos
Summary: We studied the steady hemodynamics in physiological elastic microvessels using a fluid-structure interaction model. The model takes into account tissue deformation, blood flow, and other factors, and has been validated through calculations and comparisons.
BIOMECHANICS AND MODELING IN MECHANOBIOLOGY
(2022)
Article
Computer Science, Interdisciplinary Applications
Chris Dritselis, George Karapetsas
Summary: Two new control volume solvers, multiFluidInterFoam and rheoMultiFluidInterFoam, are presented for the simulation of Newtonian and non-Newtonian n-phase flows, fully accounting for interfacial tension and contact-angle effects for each phase. The solvers improve the efficiency and accuracy of surface tension driven flows, and the rheoMultiFluidInterFoam solver is capable of fully considering complex non-Newtonian effects.
COMPUTERS & FLUIDS
(2022)
Article
Mechanics
Konstantina Psaraki, Vlasios Mitsoulas, Stavros Pavlou, Yannis Dimakopoulos
Summary: We investigated the effects of variations in critical shearing parameters on the response of an endothelial cell monolayer. Specifically, we developed a rheometric emulation method that accounts for the interaction between blood plasma and deformable endothelial cells. Our findings provide quantitative predictions for the stresses on different cell compartments and their structural changes. In addition, we highlight the significance of the variation of Wall Shear Stress (WSS) along the cell membrane and its dependence on cell shape.
Article
Computer Science, Interdisciplinary Applications
Alexandros Syrakos, Oliver Oxtoby, Eugene de Villiers, Stylianos Varchanis, Yannis Dimakopoulos, John Tsamopoulos
Summary: This paper proposes a series of gradient reconstruction schemes based on orthogonal or oblique projections to solve over-determined systems. The schemes include weighted least-squares gradients and variations of consistent Green-Gauss gradients. Through testing and comparison on various grids, it is found that there may be numerical instability on high aspect ratio grids, and guidelines are provided for safely using weights within the least squares methods.
MATHEMATICS AND COMPUTERS IN SIMULATION
(2023)
Article
Mechanics
G. Esposito, Y. Dimakopoulos, J. Tsamopoulos
Summary: This study investigates the motion of a viscous drop rising in a viscoelastic liquid with elastic and shear thinning effects. The numerical predictions are validated by comparing them with experimental data, showing agreement in terminal velocities and drop shapes. The interplay of viscous, elastic, and capillary forces is explored through a parametric study. Key findings include the transformation of a spherical drop into one with a cusp and an extended tail due to increasing material elasticity, and the confirmation that viscoelastic materials can encapsulate liquid drops generated by liquid filaments.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2023)
Article
Chemistry, Multidisciplinary
Eleni Kouni, Pantelis Moschopoulos, Yannis Dimakopoulos, John Tsamopoulos
Summary: When a charged particle moves through a solution, the surrounding electric double layer deforms in response to fluid motion, creating an electric force opposite to the particle's direction of motion, which reduces its settling velocity. This phenomenon combines fluid mechanics and electrodynamics, and differs from the classical problem of an uncharged sedimenting particle. Its applications range from mechanical to biomedical fields.
Article
Physics, Fluids & Plasmas
A. Kordalis, D. Pema, S. Androulakis, Y. Dimakopoulos, J. Tsamopoulos
Summary: This study investigates the buoyancy-driven rise and interaction between two coaxial bubbles in an elastoviscoplastic material. The development of a shear stress bridge between the bubbles decreases drag force on the trailing bubble, initiating their approach. The material's solidlike behavior makes it softer for the trailing bubble. Normal stresses primarily extend the bubbles, but the leading bubble eventually adopts a less favorable shape that slows it down. Geometric characteristics and material properties also affect the approach time.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Chemistry, Physical
P. Moschopoulos, E. Kouni, K. Psaraki, Y. Dimakopoulos, J. Tsamopoulos
Summary: This study investigates the stretching dynamics of a yield stress material with both elastic and viscoplastic behavior. The material forms a cylindrical liquid bridge initially and then a neck when subjected to stretching between coaxial disks. Theoretical analysis shows that an elongated thin neck is formed due to elasticity, connecting the upper and lower parts of the bridge. The findings suggest that the consideration of elasticity affects the pinching times and filament length in filament stretching procedures of yield stress materials.
Article
Mechanics
Mateus C. Guimaraes, Fernando T. Pinho, Carlos B. da Silva
Summary: A new theory is proposed to describe the conformation state of polymer chains in free turbulent shear flows of viscoelastic fluids. The theory shows the existence of minimum and maximum solvent dissipation reduction asymptotes and four different polymer deformation regimes, based on self-similarity arguments and new scaling relations for the turbulent flux of conformation tensor. In addition, analytical solutions for the self-similar transverse profiles of the conformation tensor components are obtained. The theory is validated through excellent agreement with direct numerical simulations employing the FENE-P rheological model.
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
(2024)