• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.609-614
• /
• 2000

This numerical study investigate resonance frequency of natural convection for steady state, periodic flow and chaotic flow in two-dimensional direct numerical simulations, differentially heated, vertical cavities having aspect ratios near unity. The enclosure cavity has isothermal and time dependent temperature side walls and adiabatic top/bottom walls. The aspect ratio is 1/3, 1/2, 1, 2, and 3 for the varying Rayleigh number. Resonance frequency for AR=1 has decrease as the aspect ratio and the Rayleigh number are increasing.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.12
• /
• pp.1014-1021
• /
• 2009

A new eddy viscosity equation was formulated from assumption of turbulence length scale equation and specific dissipation ratio equation. Then, a set of turbulence model equations for the turbulent kinetic energy ${\kappa}$, the viscosity ${\nu}_t$, and the intermittency factor ${\gamma}$ is proposed by considering the entrainment effect. Closure coefficients are determined by experimental data and resorting to numerical optimization. Present model has been applied to compute four representative cases of free shear flows and successfully compared with experimental data. In particular, the spreading rate, the centreline mean velocity and the profiles of intermittency are calculated with improved accuracy. Also, the proposed ${\nu}_t-{\kappa}-{\gamma}$ model was applied to channel flow by considering the wall effect and the results show good agreements with the Direct Numerical Simulation data.

• Journal of computational fluids engineering
• /
• v.14 no.1
• /
• pp.35-44
• /
• 2009

To adequately analyze flows in pipe or duct network system, traditional node-based junction coupling methods require the junction loss which is specified by empirical or analytic correlations. In this paper, a new finite volume junction coupling method using a ghost junction cell is developed by considering the interchange of linear momentum as well as the important wall-effect at junction without requiring any correlation on the junction loss. Also, boundary treatment is modified to preserve the stagnation enthalpy across boundaries, such as pipe-end and the interface between junction and branch. Also, the computational accuracy and efficiency of the Godunov-type finite volume schemes are investigated by tracing the total mechanical energy of rapid transients due to sudden closure of valve at downstream end.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.6
• /
• pp.1541-1546
• /
• 1993

To extend the widely used Gibson and Launder's second order closure model to the low-Reynolds-number region near a wall, modifications have been made for velocity pressure-gradient interaction and dissipation terms in the stress equations, and also for the dissipation rate equation. From the computation of fully developed plane channel flow, it is found that the results with present model agree well with the data of direct numerical simulation in the predictions of stress components. And, the computed mean velocity profile coincides with the universal velocity law.

• Journal of Chest Surgery
• /
• v.24 no.4
• /
• pp.390-396
• /
• 1991

From July 1984 to September 1990, 316 patients of congenital heart diseases were operated and 15 patients died. Hospital mortality was 4.75%. Five patients of 73 PDA had residual shunt after operation: 4 were ligated under support of Dacron patch, 1 was closed through the pulmonary arteriotomy under CPB. 3 patients were reoperated. No patient had residual shunt or reopening among the patients of simple ligation or division and suture. During the ligation of PDA, Dacron patch for protection from tearing may disturb the complete interruption of shunt. If the tissue around the ductus arteriosus looks weak or fragile, division and suture may be more reliable other than ligation with supporting patch. If the septal leaflet of tricuspid valve is adherent around the VSD, remained opening of VSD may be closed with simple suture directly. In these cases, the incidence of postoperative residual shunt is as high as the incidence of more large VSD closed with patch [10.9%: 9.6%]. During the direct closure of remained opening of VSD, another leaking route should be looked for carefully beneath the septal leaflet of tricuspid valve.

• Journal of Chest Surgery
• /
• v.32 no.10
• /
• pp.939-942
• /
• 1999

Partial anomalous pulmonary venous connection is frequently found in any ASD(atrial septal defect) patients. These patients are usually symptomatic, therefore, easily diagnosed as just simple ASD. We experienced a case of a 37-year-old female patient with ASD in which the left upper pulmonary vein was connected to SVC by the left inominate vein. The patient was diagnosed as simple ASD previously. During cardiac catheterization, we found a meaningful oxygen saturation step up between the SVC and its upper portion. Angiogram confirmed PAPVC. The surgical correction of anastomosis of PAPVC with left atrial appendage and direct closure of ASD were done. The patient was discharged 15 days later.

• Archives of Reconstructive Microsurgery
• /
• v.25 no.2
• /
• pp.75-78
• /
• 2016

The method of lower limb reconstruction surgery is selected based on a patient's underlying conditions, general conditions, and wound status, and it usually varies from direct closure to skin graft and flap coverage. Herein, we describe a patient with Duchenne muscular dystrophy who developed critical limb ischemia after femoral cannulation for extracorporeal membrane oxygenation was used during knee disarticulation, which was followed by reconstruction of the defect around the knee using a pedicled anterolateral thigh flap and skin graft.

• Journal of Chest Surgery
• /
• v.29 no.12
• /
• pp.1398-1400
• /
• 1996

The cardiac anatomic position immediately beneath the sternum leaves it vulnerable to injury when this bone is fractured. Cardiac rupture, however, is uncommon but survival following this injury is rare. We report the case of one patient who survived right ventricle perforation resulting from sternal fracture. The patient developed signs of pericardial tamponade and was brought to the operating theatre immediately for surgery through the emergency anterolateral thoracotomy Perforation of th right ventricle was repaired by direct closure without cardiopulmonary bypass. We believe that patients with cardiac rupture who reach the hospital alive can often be saved by prompt diagnosis and surgery.

• Advances in aircraft and spacecraft science
• /
• v.10 no.6
• /
• pp.521-543
• /
• 2023

Reynolds-averaged Navier-Stokes (RANS) models are extensively employed in industrial settings for the purpose of simulating intricate fluid flows. However, these models are subject to certain limitations. Notably, disparities persist in the Reynolds stresses when comparing the RANS model with high-fidelity data obtained from Direct Numerical Simulation (DNS) or experimental measurements. In this work we propose an approach to mitigate these discrepancies while retaining the favorable attributes of the Menter Shear Stress Transport (SST) model, such as its significantly lower computational expense compared to DNS simulations. This strategy entails incorporating an explicit algebraic model and employing a neural network to correct the turbulent characteristic time. The imposition of realizability constraints is investigated through the introduction of penalization terms. The assimilated Reynolds stress model demonstrates good predictive performance in both in-sample and out-of-sample flow configurations. This suggests that the model can effectively capture the turbulent characteristics of the flow and produce physically realistic predictions.

• Journal of Korean Neurosurgical Society
• /
• v.58 no.1
• /
• pp.60-64
• /
• 2015

Objective : To present the incidence and management of dural tears and cerebrospinal fluid leakage during corrective osteotomy [Pedicle Subtraction Osteotomy (PSO) or Smith-Petersen Osteotomy (SPO)] for ankylosing spondylitis with kyphotic deformity. Methods : A retrospective study was performed for ankylosing spondylitis patients with fixed sagittal imbalance, who had undergone corrective osteotomy (PSO or SPO) at lumbar level. 87 patients were included in this study. 55 patients underwent PSO, 32 patients underwent SPO. The mean age of the patients at the time of surgery was 41.7 years (21-70 years). Of the 87 patients, 15 patients had intraoperative dural tears. Results : The overall incidence of dural tears was 17.2%. The incidence of dural tears during PSO was 20.0%, SPO was 12.5%. There was significant difference in the incidence of dural tears based on surgical procedures ( PSO vs. SPO) (p<0.05). The dural tears ranged in size from 12 to $221mm^2$. A nine of 15 patients had the relatively small dural tears, underwent direct repair via watertight closure. The remaining 6 patients had the large dural tears, consequently direct repair was impossible. The large dural tears were repaired with an on-lay graft of muscle, fascia or fat harvested from the adjacent operation site. All patients had a successful repair with no patient requiring reoperation for the cerebrospinal fluid leak. Conclusion : The overall incidence of dural tears during PSO or SPO for ankylosing spondylitis with kyphotic deformity was 17.2%. The risk factor of dural tears was complexity of surgery. All dural tears were repaired primarily using direct suture, muscle, fascia or fat graft.