• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.18 no.4
• /
• pp.321-328
• /
• 2006

In the present study extensisve numerical experiments are conducted using the CFD code, FLUENT, to investigate the energy dissipation due to perforated walls for various wall-thickness and flow conditions. A new empirical formula for energy loss coefficient considering the effect of the thickness of perforated wall is obtained based on the results of computational experiments. It is found that the energy loss coefficient decreases as the wall-thickness increases and the maximum coefficient reduction reaches upto 40% of the value calculated using the conventional formulas for the sharp-crested orifice. To check the validity of the new formula the reflection coefficient of waves due to perforated wall is evaluated and compared with the results of existing theories and hydraulic experiments. The result shows that the new formula is superior to the conventional ones.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.10 no.4
• /
• pp.100-108
• /
• 2006

Experimental study has been a general way to evaluate inlet and exhaust duct performances, but this is not only costly but also time consuming. Computational simulation is hence replacing experimental study and consequently time and cost saving. This paper therefore aims to investigate typical component performance of the intake and exhaust ducts using 3D representation. In this study a specific inlet and exhaust was modeled and analyzed to estimate its losses and flow field using computational fluid dynamic program with flow visualization capabilities. A process that requires geometry data to be modeled. That allowed for possibility of design trade off in designing phase. Installed performance of a specific turbo shaft engine was finally evaluated with the estimated inlet, exhaust and other accessories losses.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.04a
• /
• pp.144-152
• /
• 2011

In order to investigate the operation performance behaviors of the UAV's propulsion system to be operated long time in high altitude, the engine performance tests, which are simulated in the altitude engine test facility should be needed. If the test is performed in a existing altitude engine test facility, additional test apparatuses are required. Among them a proper design of the inlet and exhaust ducts that may directly affect the engine performance is very important. If the design is not adequate, the engine performance loss due to the flow behavior change and the pressure loss may be not similar to the real engine performance. In this work, firstly the engine inlet and exhaust ducts to be mounted to the existing altitude facility are modelled in 3D and its flow behaviors and pressure losses are analyzed using a commercial CFD tool, ANSYS's CFX, and the engine performance with the duct losses is calculated using the performance analysis program developed by C. Kong et al. Finally, the optimized inlet and exhaust ducts' configurations are proposed through the repeated analyses of various duct configurations.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.11
• /
• pp.1087-1093
• /
• 2008

Regenerative cooling passage to guarantee the thermal survivability in high performance rocket engine combustors could have complex configurations of the branching/merging of channels and flow turning, etc. By applying the classical hydraulic coefficients which can be found in the literature according to the flow conditions, hydraulic characteristics in regenerative cooling passages can be obtained effectively through dividing the pressure loss into friction loss and local resistance loss. Satisfactory agreement has been obtained by comparing the present results with experimental measurement of water flow test. In addition, the present results were in good agreement with CFD results when the actual coolant, kerosene was used. Therefore, the application of the present method is expected to be useful to design regeneratively cooled combustors.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.5
• /
• pp.548-556
• /
• 2013

A tapered production tubing with two different inner diameters has been suggested to increase production rates. In this research, various tapered tubing combinations are taken into account and possible tubing combinations are proposed to satisfy each objective. In previous studies, production enhancement was the main goal. However, this research also considers flow stability by analyzing tubing pressure traverse, liquid holdup, and operating conditions. For a reservoir assumed in this research, a tapered tubing of, 4.5 inch inner diameter(ID) and 2000 ft in length in the lower part and 5.5 inch ID and 8000 ft in the upper part, shows the highest net present value. Compared to a mono tubing, tapered tubings enable various tubing designs because they have smaller differences in frictional pressure loss. It is important to maintain low liquid holdup to prevent liquid loading. Smaller ID of tapered tubing in the lower part enables to achieve the object. In conclusion, it is identified that various tubing designs are achievable from the analyses of overall production operations depending on purposes specified.

• Geotechnical Engineering
• /
• v.11 no.3
• /
• pp.123-138
• /
• 1995

To study the grout flow in jointed rock, various nurser characteristics of grout in a single joint plane and two-dperorbed. The joint plane is described as a channel nets properties of grout are considered. To deal with various prob generator and i oint network generator are used. A loss of head due to friction in laminal flow is adopted to between the grout and joint wall. The grout flow is stopped, setting time. To consider this phenomenon, the idea of maxim From the results of numerical simulation on the single jai etration of grout is confirmed. The basic principles for the ation and the selection of the grout are presented. Correlation ant and grouting pressure is defined by analyzing the effects grout flow. Finally, the grout flow around a tunnel is simulate ins grouting operation for jointed rock mass.

• Applied Chemistry for Engineering
• /
• v.21 no.3
• /
• pp.258-264
• /
• 2010

Most of fluid systems, such as P&ID in ships, power plants, and chemical plants, consist of various components. The components such as bends, tees, sudden-expansions, sudden-contractions, and orifices contribute to overall pressure loss of the system. The local pressure losses across such components are determined using a pressure loss coefficient, k-factor, in lumped parameter models. In many engineering problems Idelchik's k-factor models have been used to estimate them. The present work compares the k-factor based on CFD calculation against Idelchik's model in order to confirm whether a commercial CFD package can be used for pressure loss coefficient estimation of complex geometries. The results show that RSM is the best appropriate for evaluating pressure loss coefficient. Commercial CFD package can be used as a tool evaluating k-factor even though the accuracy is influenced by a turbulence model.

• Fire Science and Engineering
• /
• v.33 no.2
• /
• pp.63-67
• /
• 2019

In this study, the pressure loss of a fire hose reel hydrant was examined and the effects of each factor on the pressure loss were analyzed. First, in the pressure loss experiment according to the length of the reel hose, the pressure loss increased with increasing length of the reel hose; it was approximately 38.86% based on a 25 m hose. Second, the pressure loss of the reel hose per unit length was estimated to be $.13{\sim}.15kgf/cm^2$. Third, in the pressure loss experiment according to the change in the flow rate, the result was similar to the relation, flow rate - pressure loss (${\Delta}P{\sim}Q^2$), in the piping flow. These results provide basic data on the evaluation of fire pump pressure and the performance-based fire-protecting design of fire hose reel hydrants used in buildings.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.16 no.2
• /
• pp.34-41
• /
• 2012

Thrust vector control system is a control device which is mounted on the exit of the nozzle to generate pitch, yaw and roll directional force by deflecting flow direction of the supersonic jet from the nozzle. Thermal and aerodynamic loads are acting on the surface of jet vane when it is exposed to the jet flow. Axial thrust loss and side thrust loss are affected by shock patterns and interactions between jet-vanes which varies with jet-vane geometry and turning angle. In this research, the performance estimation using the numerical simulation analysis of the nozzle is given and the investigation of the flow visualization and aerodynamic performance with the enforced power to the vane is taken.

• Nuclear Engineering and Technology
• /
• v.23 no.3
• /
• pp.340-351
• /
• 1991

Experimental studies were conducted on a l/5.03 scale reactor flow model of the Yong-gwang Nuclear Units 3 and 4. The purpose of the flow model test was to estimate the hydraulic effect in the reactor vessel due to the relative size difference between the ABB-CE's System 80 and the YGN 3&4 reactors. The flow model was designed according to the principle of similarity. Obtained from the test were the core inlet flow distribution, the core exit pressure deviations, and the segmental and overall pressure losses across the flow path from the reactor vessel inlet to outlet nozzle. These data will be used to provide input data for the core thermal margin analysis and to verify the analytical hydraulic design method.