Sang-Mok Han

Relationship between positive end‐expiratory pressure and internal jugular vein cross‐sectional area

Application of positive end‐expiratory pressure (PEEP) has been used to increase the cross‐sectional area (CSA) of the right internal jugular vein (IJV) in order to facilitate catheterisation. We aimed to determine the PEEP level at which the maximum increase of CSA occurred.

Flow of Newtonian and non-Newtonian fluids in a concentric annulus with a rotating inner cylinder

We examine the characteristics of helical flow in a concentric annulus with radii ratios of 0.52 and 0.9, whose outer cylinder is stationary and inner cylinder is rotating. Pressure losses and skin friction coefficients are measured for fully developed flows of water and a 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), when the inner cylinder rotates at the speed of 0∼62.82 rad/s. The transitional flow has been examined by the measurement of pressure losses to reveal the relation between the Reynolds and Rossby numbers and the skin friction coefficients. The effect of rotation on the skin friction coefficient is largely changed in accordance with the axial fluid flow, from laminar to turbulent flow. In all flow regimes, the skin friction coefficient increases due to inner cylinder rotation. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, becomes smaller as the Reynolds number increases for the transitional flow regime, and gradually approaches zero for the turbulent flow regime. The value of skin friction coefficient for a radii ratio of 0.52 is about two times larger than for a radii ratio of 0.9. For 0.4% CMC solution, the value of skin friction coefficient for a radii ratio of 0.52 is about four times larger than for a radii ratio of 0.9.

An Experimental Study of Cuttings Transport in Directional Slim Hole Drilling

During drilling, the precipitation velocity of cuttings within an annulus depends on the density and configuration of the cuttings, and on the density, viscosity, and rheological characteristics of the drilling fluid. In directional drilling in particular, it is difficult to adjust and control the cuttings. In contrast to vertical drilling, it is very important to evaluate the flow characteristics of a drilling flow field. However, research on the transfer features of cuttings is inadequate. In this study, in order to identify transfer features of cuttings, an experiment was performed under wide-ranging conditions by constructing a slim hole annulus (44 mm×30 mm) device. In this experiment, the particle volume fraction were influenced by particle size, particle concentration within the flow, pipe rotation, flow volume, and inclination of the annulus. In addition, a mathematical formula for volumetric concentration was deduced and compared to the test results and behavior of cuttings under the other drilling condition was made to be predicted. Therefore, this study can provide meaningful data for vertical and horizont al drilling, and for directional drilling.

Study on the structural stability evaluation of umbilical winch for ROV LARS

Purpose The purpose of this study is structural stability evaluation of umbilical winch. In accordance with the recent trend for developing natural resources, high-technology equipment on exploration ships is becoming more technologically advanced. One such piece of high-technology equipment is the umbilical winch. In this study, the umbilical winch is divided into two parts (drum and winch), where each is respectively designed with three dimensional models using CATIA, and dynamic simulation and structural analysis are performed using ANSYS. Design/methodology/approach In this paper, the winch is divided into two parts for finite element analysis, the drum and whole winch model, and the parts are designed as three-dimensional models except for some small parts, such as bolt holes. Dynamic simulation and structural analysis are then performed using ANSYS. The analysis results ensure the reliability of the design methods and will be used in the domestic localization of remote operated vehicle (ROV) launch and recovery systems (LARS). Findings The strain is identified from the results, but it is very small. Some stress is concentrated at the lower corner of the drum, but the maximum stress value is lower than the allowable stress; therefore, the structure has no impact on the strain and stress. Thus, it is determined that the designed structure is safe. The results ensure the reliability of the design methods and will be used in the domestic localization of ROV LARS. Originality/value Previous studies focus on the static and mechanic problems of the winch by considering winch and drum breakage in the umbilical winch system. However, ships have a nonlinear motion characteristic with six degrees of freedom according to the constant influence of the external environment. In addition, from a design perspective, the dynamic characteristics (e.g. the ship’s motions) are more important than the static characteristics. Thus, the authors focus on winch stability securement with variable loads, such as ships moving, wave disturbance and other such important environment conditions.

A Study on the Multiphase Flow Characteristics Inside Subsea Separation System

The implementation of subsea separation and liquid boosting is becoming a common development scheme for the exploration of deep water fields. Subsea separation system should be reliable to ensure successful operation in a wide range of 3-phase flow regime, without need for developments. A subsea separator can avoid or simplying costly surface platforms of floating vessels, as well as being an efficient tool to enhance hydrocarbon production. One solution of interest is the separation and re-injection of water at the seabed to avoid bringing the water up to the surface facility. In this study, multiphase flow characteristics inside subsea separation system are investigated for the design of subsea separation system.Copyright

Heat transfer characteristics of non-Newtonian fluid in a rotating annulus

Considerable interest has been shown in the problems of viscous flow between concentric annulus with one or both of the cylinders rotating. And the problem of instability of isothermal viscous flow between rotating concentric annulus is also important problem in a rotating electrical machine, especially in the drilling of oil well. This study concerns the phenomena and variables which control the rate of heat transfer in the gap of a rotating annulus. The objective of this study is to study the non-isothermal case, showing the effect of a radial temperature gradient in the annulus on the instability of this type flow. In this study the effect of axial flow rate, rotational speed of inner cylinder and temperature gradient between the cylinders on the heat transfer were investigated