Article
Mechanics
Alexandru Fikl, Daniel J. Bodony
Summary: A continuous adjoint formulation was developed to control droplet deformation in Stokes flow driven by surface tension. Shape optimization results were applied to derive optimal conditions for various interfacial problems, with boundary integral methods used for numerical discretization. The methodology was tested on tracking-type cost functions in static cases, showing consistency with finite difference gradients and accurate minimization of cost functionals. Finally, the methodology was demonstrated on controlling unsteady droplet deformation through external forcing.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Sammar Bashir, Muhammad Sajid
Summary: The article investigates the flow of two immiscible uniformly rotating micropolar and viscous fluid layers at the interface. It analyzes co-rotating and counter-rotating cases for different angular velocities ratios. The study utilizes a numerical technique called the Keller-box approach to obtain solutions for the ordinary differential equation.
ZAMM-ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK
(2023)
Article
Automation & Control Systems
K. D. Do
Summary: This paper considers the problem of boundary feedback stabilization of an elastic body surrounding a viscous incompressible fluid. It gives a proof of global existence of a weak solution of the closed-loop system and handles the issue of unbounded forces induced by the fluid on the elastic body due to less regular initial values of the fluid velocity.
Article
Mechanics
Mohit P. Dalwadi, Radu Cimpeanu, Hilary Ockendon, John Ockendon, Tom Mullin
Summary: Experiments have shown that a horizontal cylinder placed on a vertically moving belt coated with viscous fluid can levitate at a fixed height and rotate around its own axis at a specific belt velocity. By developing a model and utilizing a combination of asymptotic analysis and direct numerical simulation, researchers have successfully established a relationship between the belt speed and cylinder rotation rate, which has been validated against experimental results.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Kersten Schmidt, Anastasia Thoens-Zueva
Summary: This paper presents impedance boundary conditions for the viscoacoustic equations, with approximative models that can be discretized by finite element methods without resolving boundary layers. The conditions are stable and asymptotically exact, and the results of numerical experiments illustrate the theoretical foundations.
MATHEMATICAL METHODS IN THE APPLIED SCIENCES
(2022)
Article
Mechanics
Tao Chen, Tianshu Liu
Summary: Lie derivative is evaluated and interpreted in relation to fundamental surface physical quantities in near-wall incompressible viscous flows, providing insights into boundary vorticity dynamics and near-wall flow physics. The Lie derivatives are found to be directly associated with boundary enstrophy flux and orthogonal pairs of skin friction, surface vorticity, surface enstrophy gradient, and its conjugate vector.
Article
Physics, Multidisciplinary
Sammar Bashir, Muhammad Sajid, Muhammad Noveel Sadiq
Summary: This study investigates the flow characteristics of two immiscible rotating layers of fluids and explores their behaviors under co-rotation and counter-rotation. The findings have significant implications for scientific and industrial applications.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Engineering, Multidisciplinary
P. H. Wen, Y. D. Tang, J. Sladek, V Sladek
Summary: The study utilizes boundary integral equations and displacement discontinuity methods to solve smooth curved crack problems, numerically determining stress intensity factors and showing equivalence between direct and indirect boundary element methods. Convergence is demonstrated by increasing collocation points, and comparison is made with analytical solutions. High accuracy of numerical solutions allows for benchmarking and evaluating accuracy of numerical algorithms.
ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS
(2021)
Article
Instruments & Instrumentation
M. Ghassabi, R. Talebitooti
Summary: This paper focuses on using graphene-platelet reinforced composites and magneto-electro-elastic (MEE) materials to improve noise reduction in structures and human living environments. The study analyzes the sound transmission loss (STL) through a three-layer sandwich doubly-curved shell and finds that electromagnetic boundary conditions parameters have the greatest impact on STL. The results show that even a slight change in electric potential can result in significant changes in STL.
SMART MATERIALS AND STRUCTURES
(2023)
Article
Engineering, Multidisciplinary
Yuki Noguchi, Takayuki Yamada
Summary: This study proposes a level set-based topology optimization method for designing acoustic structures with viscous and thermal boundary layers. By introducing a sequential linearized Navier-Stokes model, the viscothermal effects can be estimated, and the design sensitivity is obtained using the adjoint variable method and the concept of the topological derivative. The results of the study demonstrate the effectiveness of the proposed method.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
Article
Polymer Science
Junxiu Liu, Wenqiang Song, Gan Ma, Kai Li
Summary: This article introduces the use of an elastic polymer film covering the surface to regulate Faraday instability phenomenon and studies its influencing factors. The results show that factors such as bending stiffness, surface tension, and viscosity have important effects on the critical parameters of Faraday instability.
Article
Physics, Fluids & Plasmas
Jonas Helboe Joergensen, Henrik Bruus
Summary: A theoretical and numerical model is proposed in this study to investigate the thermal boundary layers and acoustic heating in microscale acoustofluidic devices. The model allows for simulation of nonlinear thermoviscous effects and three-dimensional flow using effective boundary conditions. The results demonstrate the local heating caused by friction in the boundary layers and the dominant thermoacoustic bulk streaming at high acoustic energy densities. This model is valuable for the design and fabrication of high-throughput acoustofluidic devices.
Article
Chemistry, Multidisciplinary
Frederik Philippi, Daniel Rauber, Kira Lieberkind Eliasen, Nathalie Bouscharain, Kristine Niss, Christopher W. M. Kay, Tom Welton
Summary: The optimization of viscosity in room temperature ionic liquids must consider both coulombic compaction and charge network interactions, as revealed by comparing the viscosity of charged and uncharged molecular mimics.
Article
Physics, Multidisciplinary
Wei Qiu, Jonas Helboe Joergensen, Enrico Corato, Henrik Bruus, Per Augustsson
Summary: The study reveals that using a non-dissipative acoustic body force created by light-induced temperature gradients significantly increases the velocity of acoustic streaming in liquids, outperforming traditional Rayleigh streaming and Rayleigh-Benard convection. This thermoacoustic streaming has the potential to enhance heat transfer efficiency at the microscale.
PHYSICAL REVIEW LETTERS
(2021)
Article
Engineering, Chemical
Hanguang Xie, Yuan Zong, Lian Shen, Gance Dai
Summary: Research shows that mass transfer efficiency decreases with increasing viscosity, posing challenges for industrial processes. By using twin-liquid films with open windows, the velocity and mass transfer rate of highly viscous films are significantly increased. This method enhances mass transfer without additional cost, providing a more efficient solution for highly viscous mixtures.
CHEMICAL ENGINEERING SCIENCE
(2021)
Article
Physics, Multidisciplinary
Jacob S. Bach, Henrik Bruus
PHYSICAL REVIEW LETTERS
(2020)
Article
Acoustics
Bjorn Hammarstrom, Nils R. Skov, Karl Olofsson, Henrik Bruus, Martin Wiklund
Summary: This study introduces a novel concept for acoustic trapping of particles and cells, enabling dynamic trapping patterns in a simple and inexpensive setup by using a modified piezoelectric transducer in direct contact with the liquid sample. The system allows for dynamic arraying of levitated trapping sites at low power with potential applications in cell-based sample preparation and cell culture.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2021)
Article
Acoustics
William Naundrup Bode, Henrik Bruus
Summary: By numerical simulation, the impact of the coupling layer between the transducer and microfluidic chip on acoustic resonances in ultrasound acoustofluidic devices was studied. It was found that by controlling the thickness and material of the coupling layer, optimal and robust acoustofluidic resonances can be achieved. The study also established a simple criterion based on the phase of the acoustic wave to determine whether a given resonance is sustained or attenuated by the addition of the coupling layer.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2021)
Article
Acoustics
Fabian Lickert, Mathias Ohlin, Henrik Bruus, Pelle Ohlsson
Summary: The study introduces a finite-element model for simulating acoustic focusing of microparticles in a microchannel embedded in a polymer chip and driven by a piezoelectric transducer. The optimal resonance mode identified is related to an acoustic resonance of the combined system, rather than the conventional pressure half-wave resonance of the microchannel. Experimental results validate the numerical predictions, demonstrating comparable quality and strength to traditional silicon-glass or pure glass devices.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2021)
Article
Acoustics
Andre G. Steckel, Henrik Bruus
Summary: This study demonstrates that integrated PZE thin-film transducers, constituting less than 0.1% of the bulk acoustofluidic device, can work equally well in exciting acoustic resonance modes for fluid and microparticle handling. The ability of thin-film transducers to create the desired acoustofluidic effects in bulk acoustofluidic devices relies on the in-plane expansion of the thin-film transducer under the applied electric field, the resonance of the system, and the high Q-factor of the elastic solid.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2021)
Article
Acoustics
Bjorn G. Winckelmann, Henrik Bruus
Summary: This study successfully demonstrates the suppression of acoustic streaming by combining ultrasound acoustics and ac electroosmosis, validated experimentally through simulation results in an acoustofluidic device.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2021)
Article
Physics, Multidisciplinary
Wei Qiu, Jonas Helboe Joergensen, Enrico Corato, Henrik Bruus, Per Augustsson
Summary: The study reveals that using a non-dissipative acoustic body force created by light-induced temperature gradients significantly increases the velocity of acoustic streaming in liquids, outperforming traditional Rayleigh streaming and Rayleigh-Benard convection. This thermoacoustic streaming has the potential to enhance heat transfer efficiency at the microscale.
PHYSICAL REVIEW LETTERS
(2021)
Review
Physics, Applied
Andre G. Steckel, Henrik Bruus, Paul Muralt, Ramin Matloub
Summary: This study presents a fabrication method for millimeter-sized soda-lime-silicate float-glass blocks with a thin-film piezoelectric transducer and characterizes their electromechanical properties through impedance measurements. Experimental and simulation results show that optimizing the simulation parameters can reduce the relative deviation between simulated and experimental resonance frequencies for these devices.
PHYSICAL REVIEW APPLIED
(2021)
Article
Biology
M. Rode, A. Bioue, F. Miano, H. Bruus, T. Kiorboe, A. Andersen
Summary: This study demonstrates the construction and application of an acoustic tethering setup for behavioral observations of individual microorganisms using simple laboratory equipment and a standard light microscope. The setup allows tethering of cells in focus in the mid-plane of the sample chamber, enabling high magnification observations without affecting flagellar beat frequencies. The method has the potential to explore appendage motion and swimming kinematics of various flagellates and ciliates.
JOURNAL OF EXPERIMENTAL BIOLOGY
(2022)
Article
Chemistry, Analytical
Fabian Lickert, Henrik Bruus, Massimiliano Rossi
Summary: This study examines the effects of supplying a piezoelectric transducer with constant voltage or constant power during a frequency sweep on acoustofluidic resonance frequencies. It is shown that providing constant average power dissipation in the transducer is the most reliable approach for characterizing the intrinsic properties of acoustofluidic devices.
Article
Physics, Multidisciplinary
Jonas Helboe Joergensen, Wei Qiu, Henrik Bruus
Summary: This study investigates acoustic streaming at high acoustic energy densities in a microfluidic channel. The results obtained from theoretical, numerical, and experimental methods demonstrate that frictional heating can significantly alter the streaming pattern at energy densities above 400 J/m3. The study shows that with increasing energy density at a fixed frequency, the traditional boundary-driven four streaming rolls transition into two larger streaming rolls.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Applied
William N. Bode, Fabian Lickert, Per Augustsson, Henrik Bruus
Summary: A method for determining the complex-valued compression and shear elastic moduli of polymers for ultrasound applications is presented. The method is low cost, easy to execute, and not limited to specific geometries and crystal symmetries. The resulting values have high accuracy and can provide important references for related research in the field.
PHYSICAL REVIEW APPLIED
(2022)
Article
Physics, Fluids & Plasmas
Bjorn G. Winckelmann, Henrik Bruus
Summary: General analytical expressions for the time-averaged acoustic radiation force on a small spherical particle suspended in a fluid and located in an axisymmetric incident acoustic wave are derived in this study. The cases of elastic solid and fluid particles are considered, and the effects of particle vibrations, acoustic scattering, acoustic microstreaming, heat conduction, and temperature-dependent fluid viscosity are all taken into account. Acoustic streaming inside the particle is also considered for the case of a fluid particle. No restrictions are placed on the widths of the viscous and thermal boundary layers relative to the particle radius. The resulting acoustic radiation force is compared with previous theories in the literature, and limits of agreement as well as deviations in specific cases of particle and fluid materials are identified.
Article
Physics, Fluids & Plasmas
Jonas Helboe Joergensen, Henrik Bruus
Summary: A theoretical and numerical model is proposed in this study to investigate the thermal boundary layers and acoustic heating in microscale acoustofluidic devices. The model allows for simulation of nonlinear thermoviscous effects and three-dimensional flow using effective boundary conditions. The results demonstrate the local heating caused by friction in the boundary layers and the dominant thermoacoustic bulk streaming at high acoustic energy densities. This model is valuable for the design and fabrication of high-throughput acoustofluidic devices.
Article
Acoustics
Jonas Helboe Joergensen, Henrik Bruus
Summary: This study presents an effective thermoviscous theory of acoustofluidics, including pressure acoustics, thermoviscous boundary layers, and streaming phenomena in fluids embedded in elastic cavities. By incorporating thermal fields, the effective model extends previous viscous theories and allows for numerical simulations of acoustofluidic systems. The research shows how acoustic streaming is influenced by thermal fields and material parameters, affecting both boundary conditions and body forces in the bulk.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2021)
