Article
Mathematics, Applied
T. M. Pu, Y. Zhang, C. H. Zhou
Summary: In this work, a non-equilibrium analytical wall model is implemented in an immersed boundary (IB) method, named the local domain-free discretization method (DFD), for large eddy simulation (LES) of turbulent flows. The unknown coefficients of the assumed velocity profile in the non-equilibrium wall model are determined from the constraints provided by the vertically integrated turbulent-boundary-layer equations and appropriate matching conditions. The proposed LES-DFD method shows good agreement with experimental data or numerical results and demonstrates improvements compared to the equilibrium model.
COMPUTERS & MATHEMATICS WITH APPLICATIONS
(2023)
Article
Mechanics
Alexander J. Smits, Marcus Hultmark, Myoungkyu Lee, Sergio Pirozzoli, Xiaohua Wu
Summary: The new scaling shows a Reynolds-number-independent profile for all components of the Reynolds stress in the near-wall region of wall-bounded flows, highlighting the significance of wall shear stress fluctuations and the role of large eddies in determining the Reynolds number dependence of near-wall turbulence behavior.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Eron T. V. Dauricio, Joao Luiz F. Azevedo
Summary: Wall-Modeled Large Eddy Simulation (WMLES) is an important technique for obtaining high-fidelity solutions of turbulent, high Reynolds number flows with acceptable computational costs. However, the thin laminar boundary layer near the body leading edge poses restrictive mesh resolution requirements for external flows, resulting in high costs. To address this issue, we propose a wall-modeling approach based on local self-similar solutions of the boundary layer in the context of the WMLES approach. The proposed wall model demonstrates good agreement with the reference solution and is suitable for external laminar flows.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Computer Science, Interdisciplinary Applications
Francesco De Vanna, Giacomo Baldan, Francesco Picano, Ernesto Benini
Summary: The study examines how numerical schemes and discretization approaches impact the outcomes of wall-resolved and wall-modeled LES. Utilizing a turbulent boundary layer setup over a flat plate in super- and hypersonic conditions, the effect of different numerical discretization strategies are demonstrated. The analysis reveals that the injected numerical viscosity significantly alters the wall dynamics, especially in wall-modeled arrangements, and suggests criteria for selecting a suitable numerical setup in wall-modeled LES.
COMPUTERS & FLUIDS
(2023)
Article
Mechanics
Alexander J. Smits
Summary: Our understanding of turbulent boundary layer scaling and structure has greatly advanced in the past few decades, thanks to the progress in numerical simulations and experimental methods.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
F. Ghanadi, L. Djenidi
Summary: The study investigates the combined effect of Reynolds number and localized wall suction on a fully rough wall turbulent boundary layer using hot-wire anemometry. The response of the boundary layer to suction is modulated by the ratio of suction and friction velocities. Suction decreases the impact on mean velocity and turbulence intensity profiles, reduces energy at all scales of motion, and induces a structural change in the boundary layer.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Multidisciplinary
Waqas Ali Faridi, Muhammad Abu Bakar, Ali Akgul, Magda Abd El-Rahman, Sayed M. El Din
Summary: The main objective of this paper is to mathematically explore the partial differential equation of thin-film ferroelectric materials, which are being studied for their applications in various electrical systems. The article employs the fractional travelling wave transformation and a combination of mathematical methods to analyze the considered fractional model and obtain different types of soliton solutions. The obtained solutions are visually represented through generated graphics, showcasing the impact of the fractional parameter on soliton propagation.
ALEXANDRIA ENGINEERING JOURNAL
(2023)
Article
Meteorology & Atmospheric Sciences
Aaron Wang, Ying Pan, George H. Bryan, Paul M. Markowski
Summary: Large-eddy simulations (LES) frequently assume statistically steady and horizontally homogeneous conditions, which may lead to unrealistic results in simulating tornadoes. This study compares three different approaches to model near-surface turbulence in LES runs of tornado simulations and finds that the nonequilibrium approaches improve the accuracy of the results and better capture the characteristics of tornadoes.
MONTHLY WEATHER REVIEW
(2023)
Article
Mechanics
Sean P. Carney, Robert D. Moser
Summary: For wall-bounded turbulent shear flows with strong pressure gradients, an asymptotic model is developed to explain the effect of mean flow growth on small-scale near-wall turbulence, by performing asymptotic analysis of the Navier-Stokes equations.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Geosciences, Multidisciplinary
Xin Li, Zhaoxia Pu
Summary: The study found a linear relationship between the maximum intensity of large eddies and the square of mean horizontal divergence, and using this relationship in the PBL parameterization scheme can improve the accuracy of hurricane forecasts.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Mechanics
Yongxiang Wu, Gabriel Axtmann, Ulrich Rist
Summary: Rotating cylinder stubs can exert significant control on their wake, creating a 'dominating inner vortex' which intensifies lift-up effects and generates high-amplitude streaks. These effects can effectively stabilize Tollmien-Schlichting modes. However, roughness elements also introduce irregularities in the boundary layer flow, leading to increased fluid instability.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
M. Gul, B. Ganapathisubramani
Summary: This study investigates the flow characteristics of a turbulent boundary layer over different sand-grain roughness created by different sandpapers. The results show self-similarity in flow properties within a certain range, regardless of transitional or fully rough conditions. Despite differences in turbulence profiles, large-scale structures across all locations remain independent of roughness parameters.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
F. Ghanadi, L. Djenidi
Summary: The behavior of a fully rough-wall turbulent boundary layer under different pressure gradients is studied. It is found that the boundary layer remains in a self-preserving state regardless of the pressure gradient, but different pressure gradients lead to different self-preservation states. The study also reveals that the roughness effect is more significant than the pressure gradient, especially near the wall.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
G. G. Rooney
Summary: Dynamical constraints on the wall layer in turbulent pipe flow result in a narrow peak in the streamwise component of the turbulent Lamb vector near the wall, and a scaling relationship between the wall layer depth and the depth of the viscous sublayer. An approximation of the Lamb vector distribution, which is equivalent to the gradient of Reynolds stress, is proposed. Integration of the equation for streamwise mean flow allows for an expression of the velocity profile in the wall layer.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Tie Wei, Zhaorui Li, Tobias Knopp, Ricardo Vinuesa
Summary: Researchers derived an analytical formulation for the mean wall-normal velocity in turbulent boundary layers and validated its accuracy and robustness through comparisons with numerical simulation data. They also investigated the physical significance of the formulation and its connection to predicting the behavior of turbulent boundary layers.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
Yudai Nishiyama, Yusuke Kuwata, Kazuhiko Suga
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2020)
Article
Mechanics
Kazuhiko Suga, Yuki Okazaki, Yusuke Kuwata
JOURNAL OF FLUID MECHANICS
(2020)
Article
Materials Science, Multidisciplinary
Masayuki Kaneda, Hiroaki Fujiwara, Kengo Wada, Kazuhiko Suga
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2020)
Article
Mechanics
Y. Kuwata, K. Tsuda, K. Suga
JOURNAL OF FLUID MECHANICS
(2020)
Article
Materials Science, Textiles
Suguru Ando, Masayuki Kaneda, Kazuhiko Suga
Summary: The D3Q27 lattice Boltzmann method combined with the fsBR and IPBB schemes is used to predict the permeability of nonwoven fibrous porous media. The results show that this method is highly accurate and can be applied to different types of permeability prediction.
JOURNAL OF INDUSTRIAL TEXTILES
(2022)
Article
Computer Science, Interdisciplinary Applications
Y. Kuwata, K. Suga
Summary: A novel implementation route of the wall-function method to the lattice Boltzmann method is proposed for extending the LBM applicability in high Reynolds number turbulent heat transfer in complex geometries. The developed method shows capability to handle complex curvilinear walls and yield grid independent solution with satisfactory accuracy. It has great potential in predicting high Prandtl number flows under partially to highly underresolved conditions.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Nanoscience & Nanotechnology
Suguru Ando, Mitsuru Nishikawa, Masayuki Kaneda, Kazuhiko Suga
Summary: This study develops a numerical scheme for simulating three-dimensional two-way fluid-structure interaction problems of flows around flexible fine structures. The scheme employs a partitioned approach to separately calculate fluid flows and structure motions, and utilizes a simple explicit coupling scheme, contact detection algorithm, and fluid-structure interface reconstruction scheme for fluid-structure interactions. Experimental validation confirms the scheme accurately calculates equilibrium states and oscillatory motions of structures in airflows, with errors within 5% for representative rod positions.
Article
Physics, Multidisciplinary
Makoto Sugimoto, Tatsuya Miyazaki, Masayuki Kaneda, Kazuhiko Suga
Summary: This study investigates the flow and wetting characteristics of coolant in the stator coils of automobiles during the cooling process. The study finds that the flow characteristics of the coolant are influenced by the coil structure, flow condition, solid-fluid interaction, and fluid property. Two-phase fluid flow simulations are used to analyze the flow and wetting behavior of single-layered and multi-layered rod arrays.
Article
Engineering, Chemical
Suguru Ando, Mitsuru Nishikawa, Masayuki Kaneda, Kazuhiko Suga
Summary: This study develops a numerical scheme for simulating three-dimensional two-way fluid-structure interaction problems involving multiple simultaneous collisions of flexible fibers. The scheme is successfully validated and applied to investigate the effect of flow-induced deformation on the filtration efficiency of fibrous materials.
CHEMICAL ENGINEERING SCIENCE
(2022)
Article
Engineering, Mechanical
Yuki Okazaki, Yumeto Takase, Yusuke Kuwata, Kazuhiko Suga
Summary: Particle image velocimetry measurements of turbulent channel flows over porous roughness show that turbulence quantities and drag coefficient increase with permeability, but exhibit a reversed trend at a certain threshold.
EXPERIMENTS IN FLUIDS
(2022)
Article
Thermodynamics
Masayuki Kaneda, Shunya Yoshimura, Kazuhiko Suga
Summary: Convection induced by the permanent magnets of the linear Halbach array is studied through numerical simulations and experimental validation. The study uses a paramagnetic fluid as the working fluid, which is weakly attracted to the magnets with temperature dependency. Results show that the Halbach magnet array can induce a stronger thermomagnetic force compared to the conventional alternate magnetic pole array. Additionally, the local Nusselt number is found to be higher and covers a wider area with the Halbach array.
INTERNATIONAL JOURNAL OF THERMAL SCIENCES
(2023)
Article
Physics, Fluids & Plasmas
Ekachai Juntasaro, Kiattisak Ngiamsoongnirn, Phongsakorn Thawornsathit, Kazuhiko Suga
Summary: This study presents an extended analytical wall function capable of predicting the bypass transition from laminar to turbulent flow. Validation with experimental data, Blasius solution, and law of the wall shows good agreement, confirming the accuracy of predicted velocity profiles.
Article
Thermodynamics
Yuki Okazaki, Yumeto Takase, Yusuke Kuwata, Kazuhiko Suga
Summary: The study assessed the effects of different permeable roughness types on turbulent channel flows, revealing a linear relationship between zero-plane displacement and roughness scale, and identifying a linear increase in effective displacement parameter with pore diameter.
JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY
(2021)
Article
Physics, Fluids & Plasmas
Makoto Sugimoto, Yuta Sawada, Masayuki Kaneda, Kazuhiko Suga
Summary: A consistent evaporation model was developed for the conservative Allen-Cahn-based phase-field lattice Boltzmann method, with simulations conducted for Stefan flow and evaporating sessile droplets showing good agreement with analytical solutions or previous model results.
Article
Thermodynamics
Kengo Wada, Hiroaki Fujiwara, Masayuki Kaneda, Kazuhiko Suga
JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY
(2020)