Search

We study the magnetohydrodynamic flow around a circular cylinder confined in a rectangular duct. In this configuration, both the circular cylinder and the walls of the rectangular duct are electrically insulating, while the magnetic field aligns with the axial direction of the cylinder. The experimental measurements are performed by controlling two parameters Re and N (N is the ratio of electromagnetic forces to inertial forces) in the ranges of (180–722) and (0.8–264), respectively. Utilizing the electrical potential method, we employ both movable and wall probes to obtain the local flow velocities in the wake of the cylinder. By analyzing the space correlation of the signals obtained from the wall probes, a distinct transition in the flow behavior is observed, transitioning from a three-dimensional state to a quasi-two-dimensional (Q2D) state when the external magnetic field reaches a sufficient strength (N > 3). Additionally, the Q2D state allows for a further subdivision based on the scaling relationship R e / H a ∼ (0.41 – 0.42) in the stability map, thereby distinguishing between steady and unsteady flow states, which is consistent with findings from previous studies. [ABSTRACT FROM AUTHOR]

The work aims to study the convection and diffusion of metallic fluid and the tritium in a cavity under the external magnetic field. The solver based on the finite volume method and the consistent and conservative scheme is developed to solve the Navier–Stokes equation considering the Lorentz force, concentration, and thermal buoyancy. The coupling effects of the magnetic field, the internal volumetric heat source, and the concentration difference between the left and right walls of the cavity are investigated. It is found that both the rotation direction and strength of the main circulation flow are controlled by the concentration buoyancy and the thermal buoyancy only regulates the global flow in the cavity. A larger concentration difference or a stronger internal heat source can lead to unstable flow. However, the stronger magnetic field suppresses the main circulation flow and small secondary vortices. The power law scaling of the Sherwood number vs the ratio of the Rayleigh number of the concentration to the Hartman number based on the force balance agrees with the numerical simulation. Four types of flow modes (large-amplitude low-frequency, large-amplitude high-frequency, small-amplitude low-frequency, and stable modes) are observed under the coupled multi-physics fields of the magnetic field, concentration difference, and heat source. The correlation function describing the influence of magnetic field and concentration strength on mass transfer is concluded. [ABSTRACT FROM AUTHOR]

The flow of liquid metal over a backward-facing step (BFS) exhibits unique flow characteristics due to the influence of strong magnetic field. In this study, direct numerical simulation of the BFS flow under a strong magnetic field is conducted based on a quasi-two-dimensional model (with a large interaction number, N ≫ 1 , and a large Hartmann number, H a ≫ 1). The Reynolds number (Re), Hartmann number (Ha), and expansion ratio (ER) are investigated within the ranges of [ 100 − 80 000 ] , [ 100 − 40 000 ] , and [ 1.67 − 5 ] , respectively. Three typical flow regimes are defined based on the evolution of the free shear layer vortices and the separation state of the boundary layer. Furthermore, a comprehensive flow regime map is presented for different ER, revealing a positive correlation between the critical Reynolds number (R e c 1 ) and Ha at the onset of instability. Specifically, R e c 1 is proportional to H a 0.5 , H a 0.54 , and H a 0.56 for ER = 5, 2.5, and 1.67, respectively. Moreover, the maximum relative thickness of the free shear layer at H a c 1 appears in the range of approximately 0.7 – 0.78 L r for ER = 5, while for ER = 2.5, it appears in the range of approximately 0.80 – 0.85 L r , indicating that the instability position of the free shear layer occurs earlier for large ER. Our numerical investigation also demonstrates that an increase in the transverse magnetic field compresses the free shear layer and delays the process of vortex pairing, thereby suppressing the oscillatory behavior of the shear layer. [ABSTRACT FROM AUTHOR]

Considering the existence of a horizontal magnetic field, we experimentally investigate the process of a liquid metal drop with high surface tension impacting a film of the same liquid. High-speed photography is adopted here to capture the dynamics of the interaction between the drop and the liquid film. We observe three typical outcomes after drop impact on the film, namely, symmetric crown, asymmetric crown, and prompt splashing, among which the asymmetric crown is first discovered by the present experiments. Moreover, the experimental variables, such as the drop size, impact velocity, initial film thickness, and intensity of the magnetic field, are included to study the three outcomes in detail. For crown formation, the external horizontal magnetic field changes the shape of the crown from symmetric to asymmetric during the crown expansion process, while for prompt splashing, the external horizontal magnetic field promotes splashing from the liquid layer where the drop and the liquid film meet and reduces the critical Weber number where prompt splashing occurs. Therefore, the present experimental results conclusively prove that the external horizontal magnetic field affects the process of liquid metal drop impact on a liquid metal film. Finally, by selecting a typical case, we carried out the direct numerical simulation to calculate the distribution of the magnetic-field-induced Lorentz force inside the droplet after impact, which helps us fully understand the phenomena observed. [ABSTRACT FROM AUTHOR]