In this study, Large Eddy Simulations (LES) are employed to investigate the fundamental interplay between magnetic fields and thermal convection in a vertical, turbulent, liquid metal channel flow. The primary focus is on understanding the modifications to mean flow characteristics and higher-order statistical properties. This interaction leads to significant modifications to the turbulent flow structures, resulting in directional dependencies in the flow properties. The calculations are conducted at a friction Reynolds number of Re_τ≈395, Hartmann number (Ha) in the range of 0≤Ha≤15, and Richardson number (Ri) varying between 0 and 0.05. We reveal that the presence of a wall-normal magnetic field in this particular setup suppresses turbulent kinetic energy, while buoyancy forces counteract this effect, promoting turbulence and introducing asymmetry into the statistical properties of the flow. Moreover, the magnetic field induces a preferential alignment of both vortical structures and near-wall streaks. The correlation analysis discovers a stretch of the longitudinal scales, while the spectral analysis indicates that both the magnetic field and buoyancy forces affect the distribution of turbulent kinetic energy at different scales. Notably, at Ha=15, the two-dimensional (2D) energy spectrum function has a slope similar to that predicted by the κ⁻³ law in the inertial range. This deviation of mechanism from “classical” turbulence scaling suggests that the applied magnetic field alters the energy cascade, primarily due to enhanced Joule dissipation.

Recently, reconfigurable intelligent surface (RIS) has been widely used to enhance the performance of millimeter wave (mmWave) communication systems, making beam alignment more challenging. To ensure efficient communication, this paper proposes a novel intelligent angle map-based beam alignment scheme for both general user equipments (UEs) and RIS-aided UEs simultaneously in a fast and effective way. Specifically, we construct a beam alignment architecture that utilizes only angular information. To obtain the angle information, the currently hottest seq2seq model-the Transformer-is introduced to offline learn the relationship between UE geographic location and the corresponding optimal beam direction. Based on the powerful machine learning model, the location-angle mapping function, i.e., the angle map, can be built. As long as the location information of UEs is available, the angle map can make the acquisition of beam alignment angles effortless. In the simulation, we utilize a ray-tracing-based dataset to verify the performance of the proposed scheme. It is demonstrated that the proposed scheme can achieve high-precision beam alignment and remarkable system performance without any beam scanning.

Mixed convection of an electrically conductive fluid in a square duct with imposed transverse magnetic field is studied using Large Eddy Simulation (LES) paradigms. The duct walls are electrically conductive, with the wall conductivity parameter c_w ranging from 0 to 0.5. The Reynolds number is Re=5602 and the Prandtl number is Pr=0.0238. The focus of the study is on flows at Hartmann numbers Ha⩽125, Richardson numbers Ri⩽10 and two different thermal boundary conditions are considered: four wall uniform heat fluxes and one-sided heating (fixed wall temperature). The results show that the transition from laminar to turbulent flow depends not only on the ratio Ri/Ha, but also on c_w and on the local thermal boundary conditions. In the turbulent regime with one-sided heating, the turbulent heat fluxes play an important role in the total heat transfer, in contrast with the typical behaviours of liquid metals. Moreover, the turbulent and thermal structures are highly dependent on the thermal boundary conditions, which completely alter the flow structure. It is also found that at c_w≥0.01 the turbulent heat fluxes decrease.

Turbulent structures in a concentric annular pipe within a uniform transverse magnetic field are examined for a liquid metal flow. Large-eddy simulations are performed to study the effect of magnetic field on turbulence suppression and heat transfer within this geometry. At the characteristic Prandtl number of liquid metals, the smallest scales based on temperature fluctuations are much larger than those of the velocity, which allows to resolve all the temperature scales with sufficient accuracy. The calculations are run at Reynolds number 8900 for three different Hartmann numbers, H a = 40, 60, 120. The comparison with available direct numerical simulation data shows encouraging agreement. The main findings of this work show a circumferential dependency of the flow characteristics on the local orientation of the magnetic field, with increased anisotropy observed at all Hartmann numbers studied. Anisotropic effects of the magnetic field are predominant for Ha = 60 and Ha = 120 causing turbulence to deviate from its conventional state. At these Hartmann numbers, a partial redistribution of the turbulent kinetic energy from the axial and radial components to the azimuthal component is observed. This effect, observed here for the first time, appears to be related to the appearance of coexisting quasi two-dimensional (2D) and three-dimensional (3D) turbulence states. Moreover, large skin friction increments are also observed at Ha = 60 and Ha = 120, while coherent structures stretching and streak suppression are found for all three Hartmann numbers.