Three-Dimensional Hydrostatic Curved Channel Flow Simulations Using Non-Staggered Triangular Grids

Non-staggered triangular grids have many advantages in performing river or ocean modeling with the finite-volume method. However, horizontal divergence errors may occur, especially in large-scale hydrostatic calculations with centrifugal acceleration. This paper proposes an unstructured finite-volume method with a filtered scheme to mitigate the divergence noise and avoid further influencing the velocities and water elevation. In hydrostatic pressure calculations, we apply the proposed method to three-dimensional curved channel flows. Approximations reduce the numerical errors after filtering the horizontal divergence operator, and the approximation is second-order accurate. Numerical results for the channel flow accurately calculate the velocity profile and surface elevation at different Froude numbers. Moreover, secondary flow features such as the vortex pattern and its movement along the channel sections are also well captured.

Regularities of vortex motion in gas-vortex bioreactor

Regularities of the vortex motion in an industrial glass bioreactor with a volume of 12 liters with a reactor vessel diameter D = 190 mm and with a filling of 50% was studied. A 65% water solution of glycerin was used as a model culture medium (density ρ g = 1150 kg/m3 and kinematic viscosity Vg = 15 mm2/s). Methods of particle image velocimetry and adaptive track visualization were used to observe the vortex pattern. The regularities of the vortex motion of the cultural medium were determined. It was found that, similar to the case of two rotating immiscible liquids, a strongly swirling jet was formed near the axis, and the entire flow took on the structure of a miniature gas-liquid tornado. The aerating gas interacted with the liquid only through the free surface, without mixing with it. As a result, the intensification of interphase mass transfer was provided due to the high speed of motion of the aerating gas.

Effects of Electromagnets on Bovine Corneal Endothelial Cells Treated with Dendrimer Functionalized Magnetic Nanoparticles

To improve bovine corneal endothelial cell (BCEC) migration, enhance cell energy, and facilitate symmetric cell distribution in corneal surfaces, an electromagnet device was fabricated. Twenty nanometer superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with fourth-generation dendrimer macromolecules were synthesized, and their size and structure were evaluated using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results confirmed the configuration of the dendrimer on the SPION surfaces. In vitro biocompatibility was assessed using the 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyl tetrazolium bromide assay. No significant toxicity was noted on BCECs within 24 h of incubation. In the cell migration assay, cells treated with dendrimer-coated SPIONs exhibited a relatively high wound healing rate under sample addition (1 μg/mL) under a magnetic field. Real-time PCR on BCECs treated with dendrimer-coated SPIONs revealed upregulation of specific genes, including AT1P1 and NCAM1, for BCECs-dendrimer-coated SPIONs under a magnetic field. The three-dimensional dispersion of BCECs containing dendrimer-coated SPIONs under a magnetic field was evaluated using COMSOL Multiphysics software. The results revealed the BCECs-SPION vortex pattern layers in the corneal surface corresponded to the electromagnet’s displacement from the ocular surface. Magnetic resonance imaging (MRI) indicated that dendrimer-coated SPIONs can be used as a T2 contrast agent.

Numerical investigation into effects of gas concentration and bubble collapse on tip vortex cavitation noise of NACA16-020 wing

In this study, the effects of gas concentration and bubble collapse on tip vortex cavitation noise of NACA16-020 wings are investigated using coupled Eulerian-Lagrangian method based on sequential application of Reynolds averaged Navier-Stokes (RANS) solver, bubble dynamics model and acoustic analogy. The bubble dynamics model used in the preceding study (Ku et al., 2020) is modified by including the gas pressure terms and the bubble collapse model, which depends on the timing and threshold of bubble collapse, the number, initial radius and location of divided bubbles. The validity of the modified bubble dynamics model is confirmed through its application to a benchmark problem where single bubble is triggered by laser. Then, the coupled Eulerian-Lagrangian method based on the modified bubble dynamic model is applied for the prediction of tip-vortex cavitation noise of NACA16-020 wing. The predicted results of the tip vortex pattern and acoustic pressure spectrum are compared with the measured results, which shows closer agreements between two results than those in the previous study.

Occurrence of an Abdominal Leiomyosarcoma in the Cyprinus carpio: Optical and Immunohistochemical Study

A capsulated nodular neoplasm measuring 9 cm in diameter, located between the swim bladder and the kidney sample of Cyprinuscarpio, was in laboratory. The neoplasm had a solid consistency in one sector and very adherent to the capsule. Histopathological examination of the neoplasm revealed a monotonous proliferation of spindle cells, and pleomorphic, sometimes in a vortex pattern and interspersed with collagen fibers. Cells had numerous well-oriented myofibrils giving them a deep red. The cytoplasm is eosinophilic and the nuclei are hyperchromatic located in the center with blunt or "cigar-shaped" ends. In the immunohistochemical examination, the tumor cells were positive for desmin, smooth muscle actin and K-47, the latter antibody showing significant cell proliferation. Due to histopathological and immunohistochemical findings, diagnosis was made with leiomyosarcoma.

Vortex flow aerodynamics behind a symmetric airfoil at low angles of attack and Reynolds numbers

The low Reynolds number aerodynamics is important to investigate for micro air vehicle applications. The current paper covers numerical simulations to present the downstream development of the wake patterns and detailed analysis of the vortices generated at the downstream of NACA 0012 airfoil around the critical angle of attack where the instantaneous vortex patterns are oscillatory and differ from the mean vortex pattern for low Reynolds numbers ranging from 1000 to 4000. The instantaneous and mean aerodynamic forces, pressure and skin friction coefficients, and vorticity values are compared in addition to the path of the vortex centers, their longitudinal and lateral spacings, Kármán spacing ratios, and distortion ratios at the wake of the airfoil in regard to the different Reynolds numbers investigated. The streamwise and crosswise velocities of the vortex cores and relative velocities at different transverse locations are also discussed and presented in detail. The correlations between different non-dimensional numbers (St, Re, Ro) are obtained at these low Reynolds numbers investigated.

Direct Numerical Simulations on the three-dimensional wake transition of flows over NACA0012 airfoil at Re = 1000

For micro air vehicles (MAV), the precise prediction of aerodynamic force plays an important role. The aerodynamic force of a comparative low Reynold number (Re) vehicle tends to be affected by the different flow modes. In this paper, the aerodynamic performance of a three-dimensional NACA0012 airfoil is studied numerically. A range of angles of attack ( α) 0°−25° and Reynolds number 1000 is considered. Mean and fluctuating coefficients of aerodynamic forces around NACA0012 airfoil are analyzed for different wake modes. The difference of aerodynamic forces between two and three-dimensional simulations are compared. The results show that the wake remains steady two-dimensional for lower angles of attack. At α = 9°, Von Karman vortex pattern is noticed. Flow transition to three-dimensional as the angle of attack increases from α = 13°. 3D wake is found to be stable with parallel shedding mode for 14°-17°. However, these modes become finer with the gradual increase in angle of incidence. While, wake loses its three-dimensional stability to chaotic with gradual increment in angle of attack afterwards.