Article
Physics, Multidisciplinary
Felix Schindler, Sven Eckert, Till Zuerner, Joerg Schumacher, Tobias Vogt
Summary: In highly turbulent liquid metal convection experiments, the large-scale flow structure and the turbulent transfer of heat and momentum were directly measured. It was found that the aspect ratio has a significant impact on the scaling laws for heat and momentum transfer.
PHYSICAL REVIEW LETTERS
(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
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
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
Mechanics
Anna Hertlein, Ronald du Puits
Summary: This study presents measurements of the thermal dissipation rate in turbulent Rayleigh-Benard convection using a four-thermistor temperature gradient probe. The thermal dissipation rate decreases monotonically with distance from the plate, with maximum near the wall and at the highest Rayleigh number. The normalized thermal dissipation rate scales with an exponent of about 0.29 with the Rayleigh number and is higher in the boundary layer than in the bulk region.
Article
Mechanics
Shashwat Bhattacharya, Mahendra K. Verma, Ravi Samtaney
Summary: In this paper, the GL model is extended for predicting Reynolds number and Nusselt number in turbulent Rayleigh-Benard convection. Functional forms for dissipation rates prefactors are used, and machine learning is applied to determine revised predictions that show better agreement with past results in a three-dimensional unit box setting.
Article
Physics, Fluids & Plasmas
N. C. Tai, Emily S. C. Ching, Lukas Zwirner, Olga Shishkina
Summary: Using a closed set of boundary layer equations, analytical results for the dependence of heat flux on Reynolds and Prandtl numbers and parameters measuring fluctuations in turbulent Rayleigh-Benard convection are derived. The similarity in scaling dependencies of heat flux in steady forced convection and turbulent Rayleigh-Benard convection has been revealed, solving a puzzle in our understanding of heat transfer in the latter.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Physics, Multidisciplinary
Hechuan Jiang, Dongpu Wang, Shuang Liu, Chao Sun
Summary: This study investigates the final state of turbulence when the driving parameter approaches infinity. By adopting a novel experimental setup, the existence of the ultimate regime is demonstrated with direct evidence. The findings greatly contribute to the understanding of flow dynamics in geophysical and astrophysical flows.
PHYSICAL REVIEW LETTERS
(2022)
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
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
V Srinivasan, U. Madanan, R. J. Goldstein
Summary: Turbulent Rayleigh-Benard convection was experimentally studied to assess the effect of sidewall thermal conductance on Nusselt numbers, and a novel experimental method was proposed. Results showed reasonable agreement with semi-analytical models from literature.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
Huilin Tong, Zhengyu Wang, Zhengdao Wang, Hui Yang, Yuehong Qian, Yikun Wei
Summary: The joint effect of rectangular-type roughness and horizontal vibration on two-dimensional turbulent Rayleigh-Benard convection is studied using the thermal lattice Boltzmann method. The Nusselt number and plume dynamics of the convection are the main focus, within the ranges of dimensionless vibration frequency 0≤ω*≤1000 and dimensionless roughness height 0≤h*≤0.05. Numerical results show that the Nusselt number is mostly proportional to the roughness height and exponentially related to the vibration frequency. Furthermore, heat transfer is enhanced by 3.06 times under the joint effect of horizontal vibration and rectangular roughness on turbulent Rayleigh-Benard convection. This provides important insights into the mechanism of cooperative heat transfer enhancement.
NUMERICAL HEAT TRANSFER PART A-APPLICATIONS
(2023)
Review
Mechanics
Robert E. Ecke, Olga Shishkina
Summary: Rotation with thermally induced buoyancy is an important factor in governing various astrophysical and geophysical processes. The rotating Rayleigh-Benard convection (RRBC) experimental system exhibits the features of rotation and buoyancy, and its dynamics are affected by factors such as Rayleigh and Rossby numbers. The RRBC system provides valuable insights into geophysical and astrophysical phenomena, and this review discusses heat transport scaling approaches and related effects.
ANNUAL REVIEW OF FLUID MECHANICS
(2023)
Article
Mechanics
Xin-Qian Guo, Bo-Fu Wang, Jian-Zhao Wu, Kai Leong Chong, Quan Zhou
Summary: Vertical convection in a square cavity under the influence of vertical vibration has been studied using direct numerical simulation. The results show that vibration can induce a transition from laminar flow to turbulent flow, leading to greatly enhanced heat transfer. The analysis also reveals that vibration thins the thermal boundary layer and enhances the thermal dissipation rate in the bulk region, and the heat transfer and flow velocity can be described by the vibrational Rayleigh number under certain conditions.
Article
Chemistry, Multidisciplinary
Massimo Corcione, Alessandro Quintino
Summary: This study presents a numerical investigation on Rayleigh-Benard convection in a shallow cavity filled with different metal-oxide water-based nanofluids. The dispersion of nanoparticles into the base fluid enhances the stability of the nanofluid layer and determines the conditions for convection onset.
APPLIED SCIENCES-BASEL
(2022)
Article
Mechanics
Philipp Reiter, Xuan Zhang, Olga Shishkina
Summary: This work investigates the effects of different thermal sidewall boundary conditions on flow states and heat transport in Rayleigh-Benard convection. The study finds that different thermal conditions at the sidewall lead to significant differences in heat transport, but these differences become less pronounced for larger Rayleigh numbers.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Multidisciplinary
V. S. Zykov, E. Bodenschatz
Summary: Spiral waves are a well-studied phenomenon in excitable media, and recent research has shown that they exhibit unique properties in mediums with bistability. These properties include rotation around an unexcited core or circular trajectories within an excited region. The study also found that the formation of positive or 'negative' cores in spiral waves may depend on initial conditions, and the influence of gradient flow on spiral wave dynamics was explored.
NEW JOURNAL OF PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
Robert E. Ecke, Xuan Zhang, Olga Shishkina
Summary: Using direct numerical simulations, this study investigates rotating Rayleigh-Benard convection and connects linear wall-mode states with the boundary zonal flow in the geostrophic regime. The data from various sources are quantitatively collapsed, providing insights into the heat transport contributions of the wall modes and boundary zonal flow.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Mechanics
Marcel Wedi, Viswa M. Moturi, Denis Funfschilling, Stephan Weiss
Summary: This study reports the presence of the boundary zonal flow in rotating Rayleigh-Benard convection using two-dimensional particle image velocimetry. The results confirm the findings of previous numerical simulations and provide an analysis of the thickness and maximum velocity of the boundary zonal flow.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Multidisciplinary
Guenter Ahlers, Eberhard Bodenschatz, Robert Hartmann, Xiaozhou He, Detlef Lohse, Philipp Reiter, Richard J. A. M. Stevens, Roberto Verzicco, Marcel Wedi, Stephan Weiss, Xuan Zhang, Lukas Zwirner, Olga Shishkina
Summary: The study demonstrates that small-Gamma cells significantly stabilize flow and impact heat transfer, with the critical Rayleigh number for onset of convection following a specific relationship at given Gamma. Additionally, rescaling within a wide aspect ratio range collapses heat transport data, predicting the dependence of the onset of ultimate regime in a particular case.
PHYSICAL REVIEW LETTERS
(2022)
Article
Mechanics
Guru Sreevanshu Yerragolam, Richard J. A. M. Stevens, Roberto Verzicco, Detlef Lohse, Olga Shishkina
Summary: A scaling theory is proposed for passive scalar transport in Couette flow and is validated through numerical simulations and theoretical calculations.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Chemistry, Multidisciplinary
Isabella Guido, Andrej Vilfan, Kenta Ishibashi, Hitoshi Sakakibara, Misaki Shiraga, Eberhard Bodenschatz, Ramin Golestanian, Kazuhiro Oiwa
Summary: This study reports the bottom-up engineering of a sustained beating nanoscale machine capable of mimicking ciliary beating and achieving fluid transport, using a pair of microtubules connected by axonemal dynein.
Review
Mechanics
Robert E. Ecke, Olga Shishkina
Summary: Rotation with thermally induced buoyancy is an important factor in governing various astrophysical and geophysical processes. The rotating Rayleigh-Benard convection (RRBC) experimental system exhibits the features of rotation and buoyancy, and its dynamics are affected by factors such as Rayleigh and Rossby numbers. The RRBC system provides valuable insights into geophysical and astrophysical phenomena, and this review discusses heat transport scaling approaches and related effects.
ANNUAL REVIEW OF FLUID MECHANICS
(2023)
Review
Construction & Building Technology
Robert S. McLeod, Christina J. Hopfe, Eberhard Bodenschatz, Heinz-Joern Moriske, Ulrich Poeschl, Tunga Salthammer, Joachim Curtius, Frank Helleis, Jennifer Niessner, Caroline Herr, Thomas Klimach, Martin Seipp, Thomas Steffens, Christian Witt, Stefan N. Willich
Summary: Evidence shows that implementing layered prevention strategies and appropriate measures can greatly reduce the risk of COVID-19 transmission in classroom teaching. Wearing high-quality masks and regular testing are among the most important measures, and effective ventilation systems can significantly reduce infection risks in classrooms.
Article
Physics, Multidisciplinary
Bardia Hejazi, Christian Kuechler, Gholamhossein Bagheri, Eberhard Bodenschatz
Summary: Flying bees are able to maneuver well in turbulent conditions, exhibiting flight-crash behavior similar to turbulence itself.
NEW JOURNAL OF PHYSICS
(2022)
Article
Physics, Multidisciplinary
Bardia Hejazi, Hugo Antigny, Sophia Huellstrunk, Eberhard Bodenschatz
Summary: This study reports on the flight behavior of honeybees under varying wind speeds and finds that their velocities, accelerations, and angular velocities increase with increasing wind speeds. The researchers also observe that the separation between honeybees remains consistent regardless of wind speeds, which may have implications for coordinated flight of unmanned aerial vehicles.
NEW JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
Christian Kuechler, Gregory P. Bewley, Eberhard Bodenschatz
Summary: In turbulent flows, kinetic energy is converted to heat by viscosity as it is transferred from large scales to small scales. Kolmogorov conjectured in 1941 that this transfer is dominated by inertial forces at intermediate scales in strong turbulence. Experimental results in a wind tunnel flow suggest universal behavior of decaying turbulence, but do not show power laws even at high Reynolds numbers.
PHYSICAL REVIEW LETTERS
(2023)
Article
Chemistry, Physical
Raheel Ahmad, Albert J. Bae, Yu-Jung Su, Samira Goli Pozveh, Eberhard Bodenschatz, Alain Pumir, Azam Gholami
Summary: The researchers built efficient micro-swimmers driven by flagella that consume ATP to propel micron-sized beads. The motion of the beads changes depending on the calcium concentration. This study has important implications for the design of synthetic micro-swimmers and bio-actuated medical micro-robots for targeted drug delivery.
