An evaluation of different RANS turbulence models for simulating breaking waves past a vertical cylinder

The purpose of the present study is to evaluate the performance of different turbulence models for predicting the interaction between breaking waves and a vertical cylinder based on the volume of fluid (VOF) method. Six different models are investigated in the present study, i.e., no turbulence model, the k − ω SST turbulence model, the buoyancymodified k − ω SST turbulence model, the stabilized k − ω SST turbulence model, the modified stabilized k − ωSST turbulence model and the realizable k − ε turbulence model. The vertical cylinder is installed at the edge of a 1:10 slope on the bottom of the numerical wave tank. The numerical simulations are conducted by solving the unsteady ReynoldsAveraged Navier-Stokes (RANS) equations using waves2Foam (a solver based on the open-source Computational Fluid Dynamic (CFD) software OpenFOAM). The present numerical results of the surface elevations and the breaking wave forces are compared with published experimental data. The kinetic characteristics beneath the free surface including averaged velocity, turbulent kinetic energy and turbulent kinematic viscosity are also investigated. It is observed that the stabilized k − ω SST turbulence (λ2 = 0.05, αβs = 1.36) and the buoyancy-modified k − ωSST turbulence model (αβs = 1.176) effectively reduce the turbulent kinetic energy before wave breaking, but the predicted breaking wave forces on the cylinder are smaller than that of the experimental data. The k − ω SST turbulence model shows good agreement with the experimental data in terms of the free surface elevation and the breaking wave force, but it overpredicts the turbulent kinetic energy. The realizable k − ε turbulence model does not give good predictions of both the free surface elevation and the breaking wave force as compared to the published experimental data.publishedVersio

Numerical investigation of breaking wave loads on the downstream inclined cylinder under shelter effect from the upstream vertical cylinder

Breaking waves interaction with two tandem cylinders are numerically studied using Computational Fluid Dynamic (CFD) software OpenFOAM. The effects of transverse inclined angles of the downstream cylinder and separation distances between two cylinders on breaking wave loads and free surface elevations are investigated. The interface between air and water phases is captured by the Volume of Fluid (VOF) method. The Shear Stress Transport k − v(SST k − v) turbulence model is employed to solve the incompressible Reynolds-Averaged Navier-Stokes (RANS) equations. The present numerical model is validated against published experimental data by examining the horizontal breaking wave loads and free surface elevations of breaking waves past a vertical cylinder and an inclined cylinder. In the present incident wave conditions, the breaking wave force on the downstream cylinder decreases first and then increases with the transverse inclined angle varying from 0o to 30o, while it shows an opposite trend versus the distance between cylinders. The maximum breaking wave load on the downstream cylinder occurs when the it is installed vertically with a separation distance of four times diameter.publishedVersio

Processing outcomes of the AFM probe-based machining approach with different feed directions

We present experimental and theoretical results to describe and explain processing outcomes when producing nanochannels that are a few times wider than the atomic force microscope (AFM) probe using an AFM. This is achieved when AFM tip-based machining is performed with reciprocating motion of the tip of the AFM probe. In this case, different feed directions with respect to the orientation of the AFM probe can be used. The machining outputs of interest are the chip formation process, obtained machined quality, and variation in the achieved channel depth. A three-sided pyramidal diamond probe was used under load-controlled conditions. Three feed directions were first investigated in detail. The direction parallel to and towards the probe cantilever, which is defined as “edge forward”, was then chosen for further investigation because it resulted in the best chip formation, machining quality, and material removal efficiency. To accurately reveal the machining mechanisms, several feed directions with different included angles for the pure edge-forward direction were investigated. Upon analysis of the chips and the machined nanochannels, it was found that processing with included angles in the range 0–30° led to high-quality channels and high material-removal efficiency. In this case, the cutting angles, such as the rake angle, clearance angle, and shear angle, have an important influence on the obtained results. In addition, a machining model was developed to explain the observed machined depth variation when scratching in different feed directions

Association of cardiovascular health and periodontitis: a population-based study

Abstract Background There is a strong association between cardiovascular disease (CVD) and periodontitis. This study utilized the Life Essentials 8 (LE8) score, a composite measure of cardiovascular health (CVH), to elucidate the relationship between CVH and periodontitis. Methods Data from 8,649 nationally representative participants in the National Health and Nutrition Examination Survey (NHANES) were analyzed. The independent variable in our study was the CVH score (a higher CVH score indicates better cardiovascular health), and the dependent variable was the presence or absence of periodontitis. The association between CVH and periodontitis was investigated using weighted multivariable logistic regression models and restricted cubic spline (RCS). We controlled for potential confounders such as age, sex, race, education, and socioeconomic status to minimize bias. Results There was a negative association between the total CVH score and the odds of periodontitis. After adjusting for all covariates, a 10-point increase in total CVH score was associated with a 10% lower in the odds of periodontitis [0.90 (0.87, 0.93)]. Participants with a higher CVH had 40% lower odds of periodontitis compared with those with a lower CVH. Socioeconomic status (education and income) modified this association (P for interaction < 0.05). Conclusion Our study suggests that better cardiovascular health, as indicated by higher CVH scores, is associated with a reduced likelihood of periodontitis among US adults. The relationship between CVH and periodontitis appears to be influenced by socioeconomic status, emphasizing the need for targeted interventions in populations with lower socioeconomic status

Additional file 1 of Association of cardiovascular health and periodontitis: a population-based study

Supplementary Material

Numerical Simulation of Breaking Wave Loading on Standing Circular Cylinders with Different Transverse Inclined Angles

The purpose of this paper is to numerically simulate the breaking wave past a standing cylinder with different transverse inclined angles. The numerical simulations are carried out by solving the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with the k−ω SST turbulence model. The air–water interface is captured using the Volume of Fluid (VOF) method. The convergence studies on the grid and time-step are performed by examining the total horizontal breaking wave forces on the vertical cylinder. The present numerical results have been validated with the published experimental data. A good agreement is obtained between the present numerical results and the experimental data in terms of the surface elevation and the horizontal breaking wave force. Moreover, the total horizontal breaking wave force is decomposed into low-order and high-order wave forces through Fast Fourier Transform (FFT). It is observed that the free surface elevations in front of the cylinder and the normalized high-order wave force have a minimum value when the transverse inclined angle of the cylinder is 45°. The secondary load causing the higher-harmonic ringing motion of structures is not observed when the cylinder is placed with the transverse inclined angles of 30° and 45°.publishedVersio

Dynamic buckling response of buried X70 steel pipe with bolted flange connection under two-charge explosion loads

It is of great significance to investigate the dynamic response of pipes under blasting loads for the operation, assessment, and repair of pipes. However, there are few studies available on the dynamic buckling response of pipes under multiple explosion loads. In the present study, pipe-soil coupling 3-D models are established to investigate the dynamic buckling response of X70 steel pipe with bolted flange connection (BFC) under two-charge explosion loads (Charge A lied on the ground surface and Charge B lied in the soil). The main influencing factors are also discussed, including explosion mode, internal pressure, interval time, mass ratio of charges, and diameter-to-thickness ratio (D/t ratio). When Charges A and B were exploded simultaneously, it is found that the non-pressurized X70 pipe produced more significant cross-sectional deformation than in one-point explosion (Charge A or B). Increasing D/t ratio is advantageous for the anti-explosion of the pipe with BFC. Suitable internal pressure can effectively prevent the buckling deformation of the pipe. Compared with the common straight pipe, BFC system can effectively decrease the local buckling deformation and improve the anti-explosion ability of the pipe due to its higher local stiffness and energy absorption

Correction: Characterization of a Novel Phenol Hydroxylase in Indoles Biotransformation from a Strain Arthrobacter sp. W1.

BACKGROUND: Indigoids, as popular dyes, can be produced by microbial strains or enzymes catalysis. However, the new valuable products with their transformation mechanisms, especially inter-conversion among the intermediates and products have not been clearly identified yet. Therefore, it is necessary to investigate novel microbial catalytic processes for indigoids production systematically. FINDINGS: A phenol hydroxylase gene cluster (4,606 bp) from Arthrobacter sp. W1 (PH(w1)) was obtained. This cluster contains six components in the order of KLMNOP, which exhibit relatively low sequence identities (37–72%) with known genes. It was suggested that indole and all the tested indole derivatives except for 3-methylindole were transformed to various substituted indigoid pigments, and the predominant color products derived from indoles were identified by spectrum analysis. One new purple product from indole, 2-(7-oxo-1H-indol-6(7H)-ylidene) indolin-3-one, should be proposed as the dimerization of isatin and 7-hydroxylindole at the C-2 and C-6 positions. Tunnel entrance and docking studies were used to predict the important amino acids for indoles biotransformation, which were further proved by site-directed mutagenesis. CONCLUSIONS/SIGNIFICANCE: We showed that the phenol hydroxylase from genus Arthrobacter could transform indoles to indigoids with new chemical compounds being produced. Our work should show high insights into understanding the mechanism of indigoids bio-production

Numerical Simulation of Pulsed Gravel Packing Completion in Horizontal Wells

The gravel packing completion method for horizontal wells has the advantages of maintaining high oil production for a long time, maintaining wellbore stability, and preventing sand production, so it has become the preferred completion method for horizontal wells. At present, this technology still faces the problems of high sand bed height and poor gravel migration. In order to improve the efficiency of gravel packing in horizontal wells, pulsed gravel packing technology for horizontal wells is proposed for the first time. Based on the mechanism of hydraulic pulse, the Eulerian–Eulerian model, k-ε model based on the renormalization group theory (RNG k-ε model), and Fluent are used to simulate the solid-liquid two-phase flow. By optimizing the parameters such as frequency and amplitude of pulse waveform, the optimal pulse waveform of pulsed gravel packing in horizontal wells is determined. The effects of parameters such as sand-carrying fluid displacement, sand-carrying fluid viscosity, sand-carrying ratio, gravel particle size, and string eccentricity on pulsed gravel packing in horizontal wells are studied, and the distribution law of gravel migration velocity and volume fraction in horizontal wells is obtained. According to the results, it can be seen that with the increase of displacement and viscosity of carrier fluid, the volume fraction of fixed bed and moving bed decreases gradually, while that of suspension bed increases gradually. With the increase of sand-carrying ratio, gravel particle size, and string eccentricity, the volume fraction of fixed bed and moving bed increases gradually, while that of suspended bed decreases gradually. Comparing the effects of conventional gravel packing and pulsed gravel packing in horizontal wells, it can be concluded that the efficiency of pulsed gravel packing in horizontal wells is higher. The volume fraction of fixed bed and moving bed decreased by 30% and 40% respectively, while the volume fraction of suspended bed increased by 20%. The migration velocity of moving bed and suspended bed increased by 40% and 25%, respectively, and the migration ability of gravel improved obviously