• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.9-17
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• 2002

For turbulent spray combustion flows a coupled numerical procedure was developed, This method was discretized by using generalized curvilinear coordinates to handle complex geometries. The preconditioning and eigenvalue rescaling techniques were employed to provide efficient convergences over a wide range of subsonic Mach numbers. The accuracy was validated by simulating the laminar cavity flow. The film cooling effect of a liquid rocket engine (KSR-III) were investigated by a spray combustion analysis. The film cooling showed a negative effect on the combustion efficiency. In the combustion chamber wall, the film cooling effect was revealed to be promoted by the production of fuel rich zone.

• IE interfaces
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• v.11 no.2
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• pp.177-190
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• 1998

The work-order performs an important role in make-to-order production. The development of work-order system in this production is more complex than work-order system in planing production. To construct work-order system, load of directors for work-order must be decreased, and production management between scheduling of master plan and current workshop conditions must be considered. In this study, we grasped troubles in present work-order system and flows of information for work order. Using these results are made database schemas and data flow diagrams for effective development of work-order system. And then, for successful establishment of work-order system and actual use of directors, we considered systematic and easy user-interface. For a case study, development procedures of work-order system are presented for plant factory.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.468-480
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• 1998

A flow measurement system which is able to measure the instantaneous three-dimensional velocity components and the pressure distribution of fluid flows is developed using a digital image processing system and the stereoscopic photogrammetry. This system consists of two TV cameras a digital image processor and a 32-bit microcomputer. The capability of the developed system is verified by a preliminary test in which three-dimensional displancements of moving particles arranged on a rotating plate are tracked automatically. The constructed system is through the measurement and spatial pressure distribution is also obtained. The measurement uncertainty of this system is evaluated quantitatively. The present technique is applicable to the measurement of an unsteady fluid phenomenon especially to the measurement of three-dimensional velocity field of a complex flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.3 s.246
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• pp.230-237
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• 2006

Flows in the cavity with pump out vane are calculated using the CFX-Tascflow CFD code. flow calculations are performed for different values of vane height, numbers, leakage flow rate, and rotational speed. The flow is very complex and three dimensional with strong vortex and leakage flow over the vane. The variations of pressure coefficient and K-factor with these parameters and resulting effects on the thrust and torque are studied. The present study contributes to showing the capability of flow simulation of back cavity with pump-out vane. The calculated results are good enough to be used back cavity design.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.311-319
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• 2008

We present an innovative method of multi physics application involving energetic materials. Energetic materials are related to reacting flows in extreme environments such as fires and explosions. They typically involve high pressure, high temperature, strong shock waves and high strain rate deformation of metals. We use an Eulerian methodology to address these problems. Our approach is naturally free from large deformation of materials that make it suitable for high strain rate multi-material interacting problems. Furthermore we eliminate the possible interface smearing by using the level sets. We heave devised a new level set based tracking framework that can elegantly handle large gradients typically found in reacting gases and metals. We show several work-in-progress application of our integrated framework.

• Coupled systems mechanics
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• v.11 no.1
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• pp.43-54
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• 2022

In order to analyse the thermal performance of battery systems in electric vehicles complex simulation models with high computational cost are necessary. Using reduced order methods, real-time applicable model can be developed and used for on-board monitoring. In this work a data driven model of the cooling plate as part of the battery system is built and derived from a computational fluid dynamics (CFD) model. The aim of this paper is to create a meta model of the cooling plate that estimates the temperature at the boundary for different heat flow rates, mass flows and inlet temperatures of the cooling fluid. In order to do so, the cooling plate is simulated in a CFD software (ANSYS Fluent ®). A data driven model is built using the design of experiment (DOE) and various approximation methods in Optimus ®. The model can later be combined with a reduced model of the thermal battery system. The assumption and simplification introduced in this paper enable an accurate representation of the cooling plate with a real-time applicable model.

• International Journal of Computer Science & Network Security
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• v.24 no.5
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• pp.205-211
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• 2024

The increasing number of botnet attacks incorporating new evasion techniques making it infeasible to completely secure complex computer network system. The botnet infections are likely to be happen, the timely detection and response to these infections helps to stop attackers before any damage is done. The current practice in traditional IP networks require manual intervention to response to any detected malicious infection. This manual response process is more probable to delay and increase the risk of damage. To automate this manual process, this paper proposes to automatically select relevant countermeasures for detected botnet infection. The propose approach uses the concept of flow trace to detect botnet behavior patterns from current and historical network activity. The approach uses the multiclass machine learning based approach to detect and classify the botnet activity into IRC, HTTP, and P2P botnet. This classification helps to calculate the risk score of the detected botnet infection. The relevant countermeasures selected from available pool based on risk score of detected infection.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1017-1026
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• 2016

The present paper describes the two off-surface visualization techniques and their application examples to vortex flows. One of the two visualization techniques is the classical smoke-wire technique, and the other is the visualization technique using the micro water-droplets generated by the home-style ultrasonic humidifier. The smoke-wire technique has the limit of air flow speed (about 5 m/sec for 0.07 mm-diameter wire) and the pollution problem, but it produces very fine and clear streak line sheet. It is applied to visualize the wing-tip vortices of a 3-dimensional wing. The micro water-droplet technique has the larger limit of air flow speed (above 10 m/sec) and is free from pollution and toxic problems compared to the smoke-wire technique. It is successfully applied to visualize the complex vortex system of a double-delta wing with an apex strake.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.6
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• pp.850-858
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• 2002

The present study investigates in detail the combined effects of the Coriolis force and centrifugal force on the development of turbulent flows in a square-sectioned U-bend rotating about an axis parallel to the center of bend curvature. When a viscous fluid flows through a curved region of U-bend, two types of secondary flow occur. One is caused by the Coriolis force due to the rotation of U-bend and the other by the centrifugal force due to the curvature of U-bend. For positive rotation, where the rotation is in the same direction as that of the main flow, both the Coriolis force and the centrifugal force act radially outwards. Therefore, the flow structure is qualitatively similar to that observed in a stationary curved duct. On the other hand, under negative rotation, where these two forces act in opposite direction, more complex flow fields can be observed depending on the relative magnitudes of the forces. Under the condition that the value of Rossby number and curvature ratio is large, the flow field in a rotating U-bend can be represented by two dimensionless parameters : $K_{TC}$ =Re $\sfrac{1}{4}$√λand a body force ratio F=λ/Ro. Here, $K_{TC}$ has the same dynamical meaning as $K_{TC}$ =Re√λ for laminar flow.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.495-504
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• 2012

In recent years, urbanization has been a hot issues in watershed management due to increased pollutant loads from impervious urban areas. The Soil and Water Assessment Tool (SWAT) model has been widely used in hydrology and water quality studies at watershed scale. However, the SWAT has limitations in simulating water flows between HRUs and hydrological effects of LID practices. The Storm Water Management Model (SWMM) has LID capabilities, but it does not simulate non-urban areas, especially agricultural areas. In this study, a SWAT-SWMM coupled model was developed to evaluate effects of LID practices on hydrology and water quality at mixed-landuse watersheds. This coupled SWAT-SWMM was evaluated by comparing calibrated flow with and without coupled SWAT-SWMM. As a result of this study, the $R^2$ and NSE values with SWAT are 0.951 and 0.937 for calibration period, and 0.882 and 0.875 for validation period, respectively. the $R^2$ and NSE values with SWAT-SWMM are 0.877 and 0.880 for validation period. Out of four LID scenarios simulated by SWAT-SWMM model, the green roof scenario was found to be most effective which reduces about 25% of rainfall-runoff flows.