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This study proposes a computational fluid dynamics (CFD)-modified potential (CMP) model. This hybrid model uses linear potential theory with a corrected damping ratio obtained from CFD simulations to analyze the seakeeping performance of a small vessel. According to the analysis procedure of the proposed model, a motion analysis, including the prediction of the roll and pitch damping ratio of a small barge, was conducted; to verify reliability; the results were compared to those of an experiment performed in a physical tank. The relative errors in the experiment for peak amplitude in the roll motion response amplitude operators (RAOs) using the CMP model were relatively small, whereas those obtained from only the potential analysis were large errors in all three conventionally used roll-damping ratios. In addition, the computational time consumed by the CMP model was longer than that consumed by the potential theory but faster than the full CFD simulation for all wave conditions. Subsequently, based on the motion analysis results, the seakeeping performance was evaluated in a real sea environment, and the results on the single significant amplitude (SSA) were discussed through comparison with the results of the potential analysis and experiment.

In this study, a computational fluid dynamics (CFD) simulation based on an Eulerian-Eulerian approach was used to evaluate the mixing performance of a mud agitator through the distribution of bulk particles. Firstly, the commercial CFD software Star-CCM+ was verified by performing numerical simulations of single-phase water mixing problems in an agitator with various turbulence models, and the simulation results were compared with an experiment. The standard model was selected as an appropriate turbulence model, and a grid convergence test was performed. Then, a simulation of the liquid-solid multi-phase mixing in an agitator was simulated with different multi-phase interaction models, and lift and drag models were selected. In the case of the lift model, the results were not significantly affected, but Syamlal and O’Brien’s drag model showed more reasonable results with respect to the experiment. Finally, with the properly determined simulation conditions, a multi-phase flow simulation of a mud agitator was performed to predict the mixing time and spatial distribution of solid particles. The applicability of the CFD multi-phase simulation for the practical design of a mud agitator was confirmed.

This study proposes a new wall boundary condition for the grid-stamping on a polygon (G-StoP) model, which enables a simpler and more efficient handling of boundary surfaces of arbitrarily complex-shaped bodies represented using polygons (or meshes). For example, computer-aided design surface data can be used to analyze flow using a particle-based fluid-solver moving particle semi-implicit method. For coupling simulations of fluid–multibody dynamics, the Pusan-National-University-modified MPS method is improved, and the coupling analysis is performed using RecurDyn, a commercial software package for multibody (or flexible multibody) dynamics. To confirm the applicability of the developed G-StoP model, hydrostatic pressure simulations are conducted in a rectangular tank at various corner angles. Then, the hydrostatic pressure results are compared with previously proposed polygonal wall boundary model results and theoretical solutions. That is, in the case with a corner angle of 30°, it was confirmed that the relative error to the experiment of the polygon model was 11.3%, while that of the G-StoP model was 1.3%. This demonstrates that the proposed G-StoP model is exceptional for numerical stability and robustness even when it is difficult to secure information on neighboring particles as the corner angle of the object becomes small. In addition, the G-StoP model was applied to dam breaking, subaerial landslide tsunami, and wine sloshing problems, and its accuracy and applicability were tested through comparison with experimental and other simulation results. As a result, it was shown that the present simulation results were much closer to the experiments than other simulations.

The demand for eco-friendly energy is expected to increase due to the recently strengthened environmental regulations. In particular, the flow inside the pipe used in a cargo handling system (CHS) or fuel gas supply system (FGSS) of hydrogen transport ships and hydrogen-powered ships exhibits a very complex pattern of multiphase-thermal flow, including the boiling phenomenon and high accuracy analysis is required concerning safety. In this study, a feasibility study applying the boiling model was conducted to analyze the multiphase-thermal flow in the pipe considering the phase change. Two types of boiling models were employed and compared to implement the subcooled boiling phenomenon in nucleate boiling numerically. One was the "Rohsenow boiling model", which is the most commonly used one among the VOF (Volume-of-Fluid) boiling models under the Eulerian-Eulerian framework. The other was the "wall boiling model", which is suitable for nucleate boiling among the Eulerian multiphase models. Moreover, a comparative study was conducted by combining the nucleate site density and bubble departure diameter model that could influence the accuracy of the wall boiling model. A comparison of the Rohsenow boiling and the wall boiling models showed that the wall boiling model relatively well represented the process of bubble formation and development, even though more computation time was consumed. Among the combination of models used in the wall boiling model, the simulation results were affected significantly by the bubble departure diameter model, which had a very close relationship with the grid size. The present results are expected to provide useful information for identifying the characteristics of various parameters of the boiling model used in CFD simulations of multiphase-thermalflow, including phase change and selecting the appropriate parameters.

Acute pulmonary embolism (APE) is one of the leading causes of cardiovascular (CV) morbidity and mortality. To select appropriate therapeutic strategy and/or to minimize the mortality and morbidity, rapid and correct identification of life-threatening APE is very important. Also, right ventricular (RV) failure usually precedes acute hemodynamic compromise or death, and thus the identification of RV failure is another important step in risk stratification or treatment of APE. With advances in diagnosis and treatment, the prognosis of APE has been dramatically improving in most cases, but inadequate therapy or recurrent episodes of pulmonary embolism (PE) may result in negative outcomes or, so called, chronic thromboembolic pulmonary hypertension (CTEPH). CTEPH is a condition characterized by remaining chronic thromboembolic material in the pulmonary vasculature and subsequent chronic pulmonary hypertension. Various imaging modalities include chest computed tomography pulmonary angiography (CTPA), echocardiography, magnetic resonance imaging, and nuclear imaging and each are used for the assessment of varying status of PE. Assessment of thromboembolic burden by chest CTPA is the first step in the diagnosis of PE. Hemodynamic assessment can be achieved by echocardiography and also by chest CTPA. Nuclear imaging is useful in discriminating CTEPH from APE. Better perspectives on diagnosis, risk stratification and decision making in PE can be provided by combining multimodality CV imaging. Here, the advantages or pitfalls of each imaging modality in diagnosis, risk stratification, or management of PE will be discussed.

In the present study, the model-scale Propeller Open Water (POW) tests for the propeller of 176K bulk carrier and 8600TEU container ship were conducted through Computational Fluid Dynamics (CFD) simulation. In order to solve the incompressible viscous flow field, the Reynolds-averaged Navier-Stokes (RaNS) equations were employed as the governing equations. The γ-Reθ(gamma-Re-theta) transition model combined with the SST k-ωturbulence model was introduced to describe the laminar-turbulence transition considering the low Reynolds number of model-scale. Firstly, the flow simulation developing over a flat plate was performed to verify the transition modeling, in which the wall shear stresses were compared with experiments and other numerical results. Then, to investigate the effect of the model, the CFD simulation for the POW test was performed and the simulated propeller performance was validated through comparison with the experiment conducted at Korea Research Institute of Ships & Ocean Engineering (KRISO).

This study entailed the estimation of wind loads performed using computational fluid dynamics (CFD) simulations for four typical offshore vessels and for a Floating Production, Storage, and Offloading (FPSO) and shuttle tanker in a side-by-side configuration on offloading. For all vessels, under the wind heading condition, four meshes were used to carry out the verification and validation (V&V) study to check the numerical uncertainty. The CFD simulation results for the aerodynamic coefficients were compared with wind tunnel tests from the Offloading Operability 2 JIP. All CFD simulation results show generally good agreement with the experimental data, and the overall trend of the coefficients are well captured. In addition, the effect on the gap sizes between the FPSO and shuttle tanker in the range of 4–30 m was examined. On this basis, the shielding effect was analyzed according to the size of the gap between the two ships.

A rogue wave is a huge wave that is generated by wave energy focusing. Rogue waves can cause critical damage to ships and offshore platforms due to their great wave energy and unpredictability. In this paper, to generate a rogue wave, a bull’s-eye wave, which is a focusing of multi-directional waves, was simulated in a numerical wave tank. A multi-directional wave generating boundary was developed using OpenFOAM, which is an open-source computational fluid dynamics (CFD) library. The wave height and profile of the generated rogue wave were compared to those of the regular wave. In addition, the pressure and velocity contours of water particles and velocity vectors at the free surface of the rogue wave were studied, along with the kinematic and dynamic effects of the rogue wave on a floating body.

Despite recent breakthroughs in the fabrication of spin-coated small-area devices (≤0.1 cm2) with power conversion efficiencies (PCEs) of more than 17%, printed large-area organic solar cells (OSCs) are significantly less efficient because of the intrinsic differences between the coating dynamics of the two types of OSCs. The PCEs of printed large-area (∼100 cm2) OSCs have typically been decreased compared with those of small-area spin-coated devices. In this work, an efficient low-temperature printing method to fabricate high-efficiency large-area nonfullerene-based OSC modules is successfully demonstrated. A systematic study of the relationship between the concentration of the photoactive solution and the resulting film properties reveals that the large-area modules (85 cm2) produced in this work deliver excellent performance, yielding PCEs of up to 8.18% with a geometric fill factor of 85%. These novel OSC modules are ∼87% as efficient as small-area printed single cells (cell PCE ∼9.43% with 1 cm2).

Kommerell diverticulum is a rare congenital anomaly of the aortic arch characterized by dilation at the proximal descending aorta, which gives rise to an aberrant subclavian artery. Kommerell diverticulum is usually asymptomatic, but can also be associated with symptoms due to compression of the esophagus or trachea, and can rarely be fatal due to dissection or rupture of the diverticulum. Here, we report a rare case of dysphagia caused by compression of the esophagus by Kommerell diverticulum originating from the right-sided aortic arch.

Aims Intensive and repetitive athletic training may result in cardiac geometric changes, but the determinants of left atrial (LA) enlargement (LAE) has been poorly studied. We investigated incidence and determinants of LAE and its association with LA strains in highly trained university athletes. Methods and results A total of 1073 athletes (451 females, 22.4 ± 2.4 years old) who were able to measure LA size, volume, and strains during 2015 Gwangju Summer Universiade were enrolled. LAE was defined as the increased LA volume index > 42 mL/m2. LA strains, reservoir, conduit, and contractile were measured by 2D speckle tracking method, and LA reservoir strain Conclusion LAE was common in university athletes (19.1%) and associated with heart rate, sports type with CV demand, LVGLS, and LVSV. Although LAE was significantly associated with the lower LA reservoir strain, the incidence of abnormal value was very low (5.2%) and indifferent between LAE and no LAE group.

In recent years, oil prices have continued to be low owing to the development of unconventional resources such as shale gas, coalbed methane gas, and tight gas. However, shipping companies are still experiencing difficulties because of recession in the shipping market. Hence, they devote considerable effort toward reducing operating costs. One of the important parameters for reducing operating costs is the frictional resistance of vessels. Generally, a vessel is covered with paint for smoothing its surface. However, frictional resistance increases with time owing to surface roughness, such as that caused by fouling. To prevent this, shipping companies periodically clean or repaint the surfaces of vessels using analyzed operating data. In addition, studies using various methods have been continuously carried out to identify this phenomenon such as fouling for managing ships more efficiently. In this study, numerical simulation was used to analyze the change in the resistance performance of a ship owing to an increase in surface roughness using commercial software, i.e., Star-CCM+, which solves the continuity and Navier–Stokes equations for incompressible and viscous flow. The conditions for numerical simulation were verified through comparison with experiments, and these conditions were applied to three ships to evaluate resistance performance according to surface roughness.

A computational fluid dynamic (CFD) simulation is performed to evaluate the resistance performance of a self-propelled amphibious vessel with caterpillars to be operated as a marine debris collection vessel at hard-to-reach areas. This study focuses on the influence of the addition of caterpillars on the vessel to the resistance performance. To capture the free surface model, the volume of fluid (VOF) method was adopted, and to express the sinkage and trim acting on the ship the Dynamic Fluid-body Interaction (DFBI) model was applied. A series of numerical simulations for resistance performance were carried out in the range of Froude number (Fn) of 0.12–0.32 for the vessels with and without caterpillars. A model test was carried out independently to verify the numerical simulation of resistance, and it indicated that the present simulation is valid with relative errors of less than 2% over the entire speed range. In subsequence, the resistance performance of the ship due to the addition of the caterpillars was evaluated, and an increase of nearly 40% at the design speed of Fn = 0.27 could be observed. In addition, in the present amphibious vessel, it was found that the ratio of the pressure resistance occupied in the total resistance was dominant, reaching around 81~92% for both cases.

Background/Aims The aim of this study was to investigate useful cardiac biomarkers in the differential diagnosis of acute pulmonary embolism (APE) with troponin elevation from acute non-ST elevation myocardial infarction (NSTEMI). Methods A total of 771 consecutive NSTEMI patients with D-dimer measurements and 90 patients with troponin-I (TnI) elevation out of 233 APE patients were enrolled, and cardiac biomarkers were compared. Results D-dimer elevation was noted in 382 patients with NSTEMI (49.5%), and TnI elevation was noted 90 out of 233 APE patients (38.6%). Unnecessary coronary angiography was performed in 10 patients (11.1%) among 90 APE patients with TnI elevation. D-dimer was significantly elevated in APE than in NSTEMI (9.9 ± 11.6 mg/L vs. 1.8 ± 4.3 mg/L, p < 0.001), whereas TnI was significantly elevated in NSTEMI (22.4 ± 41.5 ng/mL vs. 0.7 ± 1.4 ng/mL, p < 0.001). D-dimer/TnI ratio was significantly higher in APE than in NSTEMI (50.6 ± 85.3 vs. 1.6 ± 5.7, p < 0.001). On receiver operation characteristic curve analysis, the optimal cut-off value for differentiating APE from NSTEMI was 1.12 mg/L for D-dimer (sensitivity 81.1%, specificity 70.2%), 0.72 ng/mL for TnI (sensitivity 80.6%, specificity 78.9%), and 1.82 for D-dimer/TnI ratio (sensitivity 93.3%, specificity 86.6%). Conclusions D-dimer/TnI ratio would be a simple and useful parameter for differentiating APE with cardiac troponin elevation from NSTEMI. Optimal cardiovascular imaging to identify APE should be considered in patients with D-dimer/ TnI ratio > 1.82 before performing coronary angiography to avoid unnecessary invasive procedure.

Background Primary thrombosis of the pulmonary vasculatures without extra-pulmonary sources of embolism are uncommon. Here, we report 2 cases of thrombosis of the stump of the remnant pulmonary vasculatures after lung resection complicated by embolic events with review of the literature. Case presentation A 75-year-old female was consulted to evaluate cardiac source of embolism for acute cerebral infarction. The patient underwent left upper lobectomy because of lung cancer 2 years ago. Cardiovascular imaging revealed about 1.6 cm × 1.4 cm sized thrombus within the remnant stump of the left superior pulmonary vein. The patient was treated by anticoagulation with warfarin, because the patients refused surgical removal of thrombus. A 57-year-old female who had a history of right pneumonectomy 10 years ago presented with dyspnea. Cardiovascular imaging revealed 1.7 × 1.5 cm sized thrombus in the right pulmonary artery stump and small pulmonary embolism in the left lower segmental pulmonary artery. The patient was treated by long-term anticoagulation with warfarin, and the thrombus and pulmonary embolism were resolved. Conclusion The present cases demonstrated that very late thrombosis of the remnant pulmonary vascular structures and subsequent fatal embolic complications can develope even several years later after lung resection. Therefore, the dead space of the remnant vascular structures should be minimized during lung resection surgery, and the developement of delayed thromboembolic complications associated with vascular stump thrombosis should be carefully monitored.

Background Although many studies showed the predictive factors of stent thrombosis (ST) occurrence, there are few data about clinical outcomes and recurrent ST after percutaneous coronary intervention (PCI) for ST. Furthermore, it is uncertain which factors can cause adverse clinical events including recurrent ST. Methods This study examined the clinical outcomes after treatment for definite ST. Among 18,739 patients between June 2003 and December 2016 who underwent PCI using a drug-eluting stent (DES) or bare-metal stent (BMS), 243 consecutive patients who suffered definite ST were enrolled in this study. The overall incidence of ST was 1.3% (DES 1.4% and BMS 0.8%). The study endpoint was 1-year cardiac death or recurrent definite ST after the initial ST. Results Study endpoint occurred in 57 patients (23.5%) during the 1-year follow-up after the initial ST. In multivariate analysis, the factors predicting 1-year endpoint were early ST [adjusted hazard ratio (HR): 2.23, 95% confidence interval (CI): 1.26–4.08, p = 0.006], BMS ST (HR: 2.42, 95% CI: 1.27–4.81, p = 0.045), serum level of glucose (HR: 1.03, 95% CI: 1.01–1.05, p = 0.048), and ST-segment elevation myocardial infarction (STEMI) at the initial ST (HR: 3.73, 95% CI: 1.82–7.65, p Conclusions Recurrent ST or cardiac death during the first year after the initial ST event occurred in ∼25% of patients treated for definite ST. BMS ST, serum level of glucose, STEMI, and early ST at the initial ST were associated with adverse cardiac events.

Background/aims The impact of the timing of anemia during hospitalization on future clinical outcomes after surviving discharge from an index heart failure (HF) has been poorly studied in patients with acute decompensated heart failure (ADHF). Methods A total of 384 surviving patients with acute ADHF were divided into two groups: an anemia group (n = 270, 199 anemia at admission and 71 pre-discharge anemia) and a no anemia group (n = 114). All-cause mortality and HF re-hospitalization were compared between groups. Results During the follow-up period (median, 528 days), death occurred in 60 patients (15.6%) and HF re-hospitalization occurred in 131 patients (34.1%). Overall anemia was associated with increased mortality (hazard ratio [HR], 1.74; 95% confidence interval [CI], 1.03 to 3.01; p = 0.039), but not HF re-hospitalization (HR, 0.92; 95% CI, 0.59 to 1.42; p = 0.707). Pre-discharge anemia was significantly associated with increased mortality (HR, 1.68; 95% CI, 1.01 to 2.82; p = 0.048), but anemia at admission did not predict increased mortality or re-hospitalization. Conclusion Pre-discharge anemia, rather than anemia at admission, was identified as an independent predictor of mortality in patients with ADHF after surviving discharge. The results of the present study suggest that the identification and optimal management of anemia during hospitalization are important in patients with ADHF.

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare coronary artery anomaly and double right coronary artery (RCA) is a very rare coronary anomaly. Because patients with ALCAPA usually die within 1 year of being born due to myocardial infarction (MI) and heart failure, ALPACA is very rarely seen in adults. Here, we report an extremely rare asymptomatic case of MI, presumably caused by ALCAPA and double RCA, and provide a review of the literature. This is the first reported case of coronary artery anomaly that had both ALCAPA and double RCA. (Korean J Med 2019;94:215-220)

Drilling mud was used once in the step of separating the gas and powder they were transported to a surge tank. At that time, the fine powder, such as dust that is not separated from the gas, is included in the gas that was separated from the mud. The fine particles of the powder are collected to increase the density of the powder and prevent air pollution. To remove particles from air or another gas, a cyclone-type separator generally can be used with the principles of vortex separation without using a filter system. In this study, we conducted numerical simulations of air-particle flow consisting of two components in a cyclone separator in a mud handling system to investigate the characteristics of turbulent vortical flow and to evaluate the collection efficiency using the commercial software, STAR-CCM+. First, the single-phase air flow was simulated and validated through the comparison with experiments (Boysan et al., 1983) and other CFD simulation results (Slack et al., 2000). Then, based on one-way coupling simulation for air and powder particles, the multi-phase flow was simulated, and the collection efficiency for various sizes of particles was compared with the experimental and theoretical results.

The speed trial of a ship is one of the important elements guaranteeing its performance under the contract between the ship owner and shipbuilding company. A speed trial at sea, where the tidal current and waves are suppressed to the maximum, can prevent measurement errors due to external force conditions. On the other hand, it is difficult to maintain a calm sea state in most sea areas determined by the influence of the tidal current, wave, wind, etc. Therefore, this study evaluated a method of simulating a tidal current, which is one of the external force conditions, at the speed test operation of a ship, and applied the simulation result to the plan of a speed trial.