Article
Mechanics
Jian-Chao He, Yun Bao, Xi Chen
Summary: Direct numerical simulation (DNS) is conducted for non-slip two dimensional (2D) Rayleigh-Benard convection (RBC) with a wide range of Rayleigh number (Ra up to 10^13), Prandtl number Pr 1/4 0.7, and aspect ratio gamma= 1. The thermal dissipation rate shows an evident scaling transition at Ra asymptotic to 10^9. The mean temperature gradient in the thermal boundary layer is the dominant contribution to the transition. The Nusselt number also exhibits the transition at Ra asymptotic to 10^9. Rating: 7/10.
Article
Chemistry, Physical
Declan Finn Keogh, Mark Baldry, Victoria Timchenko, John Reizes, Chris Menictas
Summary: Liquid metal batteries (LMBs) are influenced by the interaction of thermal, compositional, and electromagnetic forces, and a three-layer numerical model was developed to investigate this behavior. The results showed that thermal convection was suppressed by electro-vortex flow and swirl flow induced by a background magnetic field. Compositional gradients in the cathode had a significant impact on the flow, highlighting the challenge of mixing in large-scale LMBs.
JOURNAL OF POWER SOURCES
(2023)
Article
Chemistry, Physical
Declan Finn Keogh, Victoria Timchenko, John Reizes, Chris Menictas
Summary: Liquid Metal Batteries offer promising grid-scale energy storage with low costs, high energy and current densities, and low fade rates. This study investigates the interaction of Rayleigh-Be & acute;nard convection and Electro-vortex flow, finding that current strength can affect the stability of convection cells and lead to dominance of Electro-vortex flow in the central region of the electrode. The results provide insight into the interaction between these flow phenomena in the anodes of discharging Liquid Metal Batteries.
JOURNAL OF POWER SOURCES
(2021)
Article
Mechanics
Alessandro De Rosis, Giovanni Giustini
Summary: This paper analyzes the flow and heat transfer regimes in Rayleigh-Benard convection with a melting boundary using numerical simulations. The results provide insight into the complex behavior of thermal convection, melting, and fluid dynamics.
Article
Thermodynamics
Paolo Personnettaz, Tanja Sophia Klopper, Norbert Weber, Tom Weier
Summary: Liquid metal batteries (LMBs) are developed for economic stationary energy storage, and the coupling of flow phenomena between the three liquid layers is crucial for their economic operation. Solutal convection appears first, followed by thermal convection, and their occurrence is influenced by the operation mode and geometry. Solutal convection can drive flow in the positive electrode and electrolyte.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Sebastian Moller, Theo Kaeufer, Ambrish Pandey, Joerg Schumacher, Christian Cierpka
Summary: Turbulent superstructures in horizontally extended three-dimensional Rayleigh-Benard convection flows are investigated in controlled laboratory experiments in water at Prandtl number Pr = 7. The experimental results confirm that the superstructure patterns are an important backbone of the heat transfer.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Multidisciplinary Sciences
Umar Nazir, Muhammad Sohail, Poom Kumam, Yasser Elmasry, Kanokwan Sitthithakerngkiet, Mohamed R. Ali, Muhammad Jahangir Khan, Ahmed M. Galal
Summary: The research investigates the enhancement of thermal performance by including nanoparticles and studies heat mass transport in synovial material. The study utilizes mathematical modeling and numerical analysis to analyze the problem and obtain theoretical and numerical results.
SCIENTIFIC REPORTS
(2022)
Article
Mechanics
Alessio Boaro, Marcello Lappa
Summary: This study investigates the non-linear behavior of Marangoni convection by considering a differentially heated rectangular layer of liquid. The results show that with increasing values of the Marangoni number and/or elasticity parameter, there is a non-trivial interplay between transverse and longitudinal disturbances, leading to different outcomes. The characteristic marks of elastic turbulence are highlighted through analysis of the velocity spectrum scaling laws and their sensitivity to the driving force and elasticity level.
Article
Thermodynamics
R. H. Hernandez, M. Vial
Summary: This study reports experimental results on inclined Rayleigh–Benard convection in a convection cell with moderate aspect ratio using a high Prandtl aqueous solution of glycerol. The aim is to measure the transition from convective to conductive regime by varying the tilt angle of the cell. Flow transitions between different flow patterns are observed by measuring changes in the heat transfer curve and visualizing the flow.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Thermodynamics
Justine Noel, Christel Metivier, Simon Becker, Sebastien Leclerc
Summary: Natural convection in melting material was experimentally studied using Magnetic Resonance Imaging. The experiments revealed enhanced transient evolution of liquid height under convection, as well as a 4-fold increase in steady averaged liquid height in the convective regime. The convection patterns observed were in the form of hexagons/polygons, with scaling laws converging to beta = 1/4 showing an increase in convective intensity.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
Xiaoran Ma, Yourong Li, Sen Yao, Yong Chen
Summary: This study investigated the effects of aspect ratio and density inversion parameters on the critical conditions for convection in vertical cylindrical containers. The results showed that increased aspect ratio led to a reduction in the critical Rayleigh number and an increase in the number of convective rolls. The density inversion parameter had a significant influence on the critical Rayleigh number and flow structure, with higher values resulting in higher critical Rayleigh numbers and a more localized flow near the bottom wall.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Mechanics
Shashwat Bhattacharya, Mahendra K. Verma, Arnab Bhattacharya
Summary: A multivariate regression model and a neural network model were developed in this paper to predict the Reynolds number and Nusselt number in turbulent thermal convection. By comparing with earlier models, it was found that the machine-learning models in this work provided the best match with the experimental and numerical results.
Article
Mechanics
Alexander Blass, Roberto Verzicco, Detlef Lohse, Richard J. A. M. Stevens, Dominik Krug
Summary: In this study, large-scale circulation of turbulent Rayleigh-Benard convection was investigated in a large container with high Rayleigh number conditions. The results showed that the properties of LSC remain consistent even with varying boundaries, and the transition to the ultimate regime is predicted to occur in unconstrained geometries. Additionally, observations were in line with experimental data from Gottingen.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Thermodynamics
Hao Liu, Zhong Zeng, Zhouhua Qiu, Linmao Yin
Summary: This study investigates the onset of Rayleigh-Benard convection of cold water near its density maximum in a vertical cylindrical container and the stability of the steady axisymmetric flow through linear stability analysis. It is found that the critical Rayleigh number for the onset of convection increases with the density inversion parameter Tm, leading to new flow patterns. Different initial conditions result in distinct basic flows, and top-bottom symmetry breaking causes axisymmetry-breaking instability.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Physics, Multidisciplinary
P. Urban, T. Kralik, M. Macek, P. Hanzelka, T. Veznik, L. Skrbek
Summary: This experimental study focused on the role of boundary conditions in turbulent thermal convection of cryogenic helium gas at high Rayleigh numbers. Switching between constant heat flux and constant temperature boundary conditions resulted in significant changes in temperature fluctuations at the bottom plate, while top plate dynamics and bulk convective flow remained unaffected. There were no observable changes in Reynolds number scaling, Nusselt number scaling, or rate of direction reversals of large scale circulation within the experimental accuracy.
Article
Mechanics
Y. Tasaka, T. Yanagisawa, K. Fujita, T. Miyagoshi, A. Sakuraba
Summary: The study investigates the 2-D oscillation of quasi-2-D convection rolls in a liquid metal layer under a horizontal magnetic field. The oscillations are caused by the oscillations of recirculation vortex pairs between the main rolls, and instability is induced at sufficiently large Reynolds numbers. As Q/Ra ratio increases, the Reynolds number decreases and the variations in the oscillations can be approximated by the effective Ra number, approaching a scaling law of velocity reduction.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
D. Noto, Y. Tasaka, T. Yanagisawa, T. Miyagoshi
Summary: Transient behaviours during spin-up in rotating Rayleigh-Benard convection were quantitatively investigated in laboratory experiments with water as the test fluid. The formation of toroidal and spiral rolls, as well as azimuthally aligned vortices induced by Kelvin-Helmholtz instability, were observed during the development of spin-up. The system eventually reached an equilibrium state dominated by columnar vortices in rotating RBC.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Mechanical
D. Noto, Y. Tasaka
Summary: A novel dual-plane SP-PIV method was introduced to determine both in-plane and out-of-plane velocity fields with single-pixel resolution. The method was validated by comparing its results with conventional PIV, showing good agreement in terms of magnitude and spatial distribution of out-of-plane velocities, providing a new approach for measuring 3C velocity fields with high spatial resolution.
EXPERIMENTS IN FLUIDS
(2021)
Article
Engineering, Mechanical
Kohei Ohie, Taiki Yoshida, Yuji Tasaka, Yuichi Murai
Summary: In this study, a practical map representation called rheology mapping was proposed to comprehensively evaluate the dependence of viscoelasticity on applied shear deformation and shear timescale. The results showed that the viscoelasticity of polymer solutions varied widely depending on the applied shear rate, strain, and oscillation frequency. The mapping also revealed the clear dependence of viscosity on shear rate and shear strain for different solutions.
EXPERIMENTS IN FLUIDS
(2022)
Review
Mechanics
Chao Tan, Yuichi Murai, Weiling Liu, Yuji Tasaka, Feng Dong, Yasushi Takeda
Summary: Ultrasound Doppler is crucial for measuring instantaneous velocity of multiphase flow, providing insights into fluid dynamics investigations, industrial safety assurance, production estimation, and process control. This technique offers non-intrusive spatial temporal distribution of velocity and has advantages in monitoring flow structures and gas-liquid interface positions.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2021)
Article
Food Science & Technology
Kohei Ohie, Haruko Chiba, Satomi Kumagai, Taiki Yoshida, Yuji Tasaka
Summary: We have developed an effective method using ultrasonic spinning rheometry (USR) to evaluate the time-resolved rheological functionalities of swallowed foods. This method allows for measurement of the rheological properties of foods in nonequilibrium conditions and assesses the time variations of shear-thinning property. Demonstrations with various thickener solutions confirmed the quantitative characterization of the thickeners' time variations in the K-n space. This method provides a practical tool to evaluate the time-resolved rheological properties of swallowed foods.
JOURNAL OF TEXTURE STUDIES
(2022)
Article
Engineering, Marine
Taiji Tanaka, Yoshihiko Oishi, Hyun Jin Park, Yuji Tasaka, Yuichi Murai, Chiharu Kawakita
Summary: Experimental investigation demonstrated that bubble injection can effectively reduce frictional drag and increase the drag reduction ratio in a turbulent boundary layer beneath a flat-bottom model ship. The reduction of drag followed an exponential relationship with the air flow rate, and a maximum reduction of 28% was achieved. The measured local wall shear stress showed a significant decrease in the local friction coefficient immediately downstream of the bubble injector and at the stern, with a nonlinear decay observed in the downstream region, indicating the dependence of local drag reduction characteristics on bubble dispersion.
Article
Mechanics
Dongik Yoon, Hyun Jin Park, Yuji Tasaka, Yuichi Murai
Summary: This study experimentally investigates the behavior of bubbles traveling near a tilted wall in order to understand the fundamental sliding motion of bubbles inside turbulent boundary layers along an inclined wall. The experimental results confirm that bubble buoyancy contributes to the sliding motion, which differs under negative and positive slope conditions. A combined measurement technique is used to explore the sliding motion, including obtaining liquid velocity profiles and the distance between the bubble and wall. The modeling equations for the lift coefficient expressed in terms of the Reynolds, Weber, and Bond numbers are proposed to further understand the characteristics of bubble sliding motion.
Article
Engineering, Chemical
Taiki Yoshida, Kohei Ohie, Yuji Tasaka
Summary: This paper presents a novel method for in situ measurement in a reserve tank to evaluate an instantaneous viscosity curve. It aims to meet the practical demand of monitoring real-time rheological properties in industrial production processes without the need for sampling. By changing the fluid temperature, this method enables the evaluation of shear thinning viscosity characteristics and is expected to have further applications in measuring viscosity during chemical reaction processes.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2022)
Article
Engineering, Mechanical
Kohei Ohie, Taiki Yoshida, Yuji Tasaka, Masako Sugihara-Seki, Yuichi Murai
Summary: A method for reconstructing velocity fields of non-Newtonian fluids is proposed, which ensures consistency with experimentally evaluated rheological properties. The method is based on a convergence calculation scheme and does not require a separate rheological model for each complex fluid.
EXPERIMENTS IN FLUIDS
(2022)
Article
Engineering, Chemical
Kohei Ohie, Taiki Yoshida, Yuji Tasaka, Yuichi Murai
Summary: Flow prediction of complex fluids in a circular pipe was successfully conducted using a velocity-profiling-assisted rheometer. The obtained results demonstrated the high industrial practicality of this method for complex fluids that are outside the application scope of a standard rheometer.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2022)
Article
Engineering, Mechanical
Daisuke Noto, Yuji Tasaka, Yuichi Murai
Summary: The statistical performance of a 3D color particle tracking velocimetry method based on digital slit calibration is evaluated. This low-cost method utilizing only a color camera and a consumer-grade liquid crystal display projector shows promise as an alternative to tomographic measurements. Artificial neural networks eliminate human decisions in constructing a color-to-depth conversion function, making it quick and less expensive. The reconstructed flow fields captured the same statistics of velocity components in both laminar and turbulent states.
EXPERIMENTS IN FLUIDS
(2023)
Article
Computer Science, Interdisciplinary Applications
T. Terada, D. Noto, Y. Tasaka, T. Miyagoshi, T. Yanagisawa
Summary: Flow structures in a rectangular fluid layer driven by a horizontal temperature gradient along the top boundary were investigated using flow visualization techniques. The influence of the heating plate arrangement on the determination of the flow structure was examined. In developing cases with initial stable temperature stratification, the flow structures consisted of shallow circulation beneath the top boundary, while in the equilibrium state, the flow structures were more complex due to the influence of the unstable temperature stratification modified by circulation.
JOURNAL OF VISUALIZATION
(2023)
Article
Engineering, Marine
Taiji Tanaka, Yoshihiko Oishi, Hyun Jin Park, Yuji Tasaka, Yuichi Murai, Chiharu Kawakita
Summary: Frictional drag reduction using repetitive bubble injection in a turbulent boundary layer beneath a towing model ship was studied. The drag reduction ratio reached 24%, which was a 5% improvement compared to continuous bubble injection. The transition of bubble dispersion status was found to cause the streamwise decay of local drag reduction. Repetitive bubble injection improved the downstream persistence of the drag-reduction effect by a factor of 15. The estimation of full-scale performance indicated that repetitive bubble injection provided approximately 7 times the drag reduction of continuous bubble injection for long ship hulls exceeding 130m.
Article
Engineering, Electrical & Electronic
Hyun Jin Park, Shintaro Akasaka, Yuji Tasaka, Yuichi Murai
Summary: This article proposed a method of instantaneously measuring void fraction and bubble size in narrow-channel bubbly-flow using ultrasonic pulse, which provided reasonable results utilizing attenuation and phase velocity of ultrasonic pulse.
IEEE SENSORS JOURNAL
(2021)
