Experimental study on liquid metal free surface flow under magnetic and electric field for nuclear fusion

In the future application of nuclear fusion, the liquid metal flows are considered to be an attractive option of the first wall of the Tokamak which can effectively remove impurities and improve the confinement of plasma. Moreover, the flowing liquid metal can solve the problem of the corrosion of the solid first wall due to high thermal load and particle discharge. In the magnetic confinement fusion reactor, the liquid metal flow experiences strong magnetic and electric, fields from plasma. In the present paper, an experiment has been conducted to explore the influence of electric and magnetic fields on liquid metal flow. The direction of electric current is perpendicular to that of the magnetic field direction, and thus the Lorentz force is upward or downward. A laser profilometer (LP) based on the laser triangulation technique is used to measure the thickness of the liquid film of Galinstan. The phenomenon of the liquid column from the free surface is observed by the high-speed camera under various flow rates, intensities of magnetic field and electric field. Under a constant external magnetic field, the liquid column appears at the position of the incident current once the external current exceeds a critical value, which is inversely proportional to the magnetic field. The thickness of the flowing liquid film increases with the intensities of magnetic field, electric field, and Reynolds number. The thickness of the liquid film at the incident current position reaches a maximum value when the force is upward. The distribution of liquid metal in the channel presents a parabolic shape with high central and low marginal. Additionally, the splashing, i.e., the detachment of liquid metal is not observed in the present experiment, which suggests a higher critical current for splashing to occur.

CFD Research on the Hydrodynamic Performance of Submarine Sailing near the Free Surface with Long-Crested Waves

The simulations of submarine sailing near the free surface with long-crested waves have been conducted in this study using an in-house viscous URANS solver with an overset grid approach. First, the verification and validation procedures were performed to evaluate the reliability, with the results showing that the generation of irregular waves is adequately accurate and the results of total resistance are in good agreement with EFD. Next, three different submerged depths ranging from 1.1D to 3.3D were selected and the corresponding conditions of submarine sailing near calm water were simulated, the results of which were then compared with each other to investigate the influence of irregular waves and submerged depths. The simulations of the model near calm water at different submerged depths demonstrated that the free surface will cause increasing resistance, lift, and bow-up moments of the model, and this influence decreases dramatically with greater submerged depths. The results of the irregular wave simulations showed that irregular waves cause considerable fluctuations of hydrodynamic force and moments, and that this influence remains even at a deeper submerged depth, which can complicate the control strategies of the submarine. The response spectrum of hydrodynamic forces and moments showed slight amplitudes in the high-frequency region, and the model showed less sensitivity to high-frequency excitations.

An affine generalized optimal scheme with improved free-surface expression using adaptive strategy for frequency-domain elastic wave equation

Effective frequency-domain numerical schemes were central for forward modeling and inversion of the elastic wave equation. The rotated optimal nine-point scheme was a highly used finite-difference numerical scheme. This scheme made a weighted average of the derivative terms of the elastic wave equations in the original and the rotated coordinate systems. In comparison with the classical nine-point scheme, it could simulate S-waves better and had higher accuracy at nearly the same computational cost. Nevertheless, this scheme limited the rotation angle to 45°; thus, the grid sampling intervals in the x- and z-directions needed to be equal. Otherwise, the grid points would not lie on the axes, which dramatically complicates the scheme. Affine coordinate systems did not constrain axes to be perpendicular to each other, providing enhanced flexibility. Based on the affine coordinate transformations, we developed a new affine generalized optimal nine-point scheme. At the free surface, we applied the improved free-surface expression with an adaptive parameter-modified strategy. The new optimal scheme had no restriction that the rotation angle must be 45°. Dispersion analysis found that our scheme could effectively reduce the required number of grid points per shear wavelength for equal and unequal sampling intervals compared to the classical nine-point scheme. Moreover, this reduction improved with the increase of Poisson’s ratio. Three numerical examples demonstrated that our scheme could provide more accurate results than the classical nine-point scheme in terms of the internal and the free-surface grid points.

Mucosal Bridge Reconstruction: A Novel Approach for the Vocal Fold Mucosal Bridge

Introduction: Mucosal Bridges (MBs) are defined as benign connective tissue abnormalities of unclear etiology that extend over the free surface of the vocal fold, are attached to the front and back of the vocal fold but are not attached to its free surface, and are histologically covered by stratified squamous epithelium. In order to overcome these drawbacks, we aimed to retrospectively evaluate and present the preoperative and postoperative results of patients with MB, who were applied the method we call “Mucosal Bridge Reconstruction” (MBR), which we apply as suturing rather than resection of the MB. Methods: Between January 2016 and February 2020, 5 patients who applied to the voice clinic due to dysphonia and were diagnosed with MB via laryngostroboscopic examination and direct laryngoscopy under general anesthesia were included in the study. Dr Speech software was used for acoustic analysis; mean fundamental frequency (fo), jitter %, shimmer %, and noise to harmonic ratio (NHR) were objectively measured and recorded. Voice Handicap Index-10 (VHI-10) was used for positive self-reporting of the severity of vocal symptoms. GRBAS scale (G: Grade, R: Roughness, B: Breathiness, A: Asthenia, and S: Strain) was also used (by the same clinician) for clinic subjective evaluation. Results: Patient age ranged from 33 to 55 years and mean patient age was 42 years. Mean duration of symptoms was 22 months (range 16-30). Mean postoperative follow-up time was 14 months (range 6-24). Unilateral MB was observed in all patients (2 left, 3 right). There was a significant improvement in objective and subjective assessment methods in all our patients after surgery. Conclusions: According to the results of our few patients, MBR offers a physiological and anatomical approach to the treatment of patients with MB. The outcomes of delicate microlaryngeal surgery are promising.