• Wind and Structures
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• v.25 no.2
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• pp.177-193
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• 2017

The accelerated development of new materials, technologies and construction processes, in parallel with advances in computational algorithms and ever growing computational power, is leading to more daring and innovative architectural and structural designs. The search for non-regular building shapes and slender structures, as alternative to the traditional architectural forms that have been prevailing in the building sector, poses important engineering challenges in the assessment of the strength and mechanical stability of non-conventional structures and systems, namely against highly variable actions as wind and seismic forces. In case of complex structures, laboratory experiments are a widely used methodology for strength assessment and loading characterization. Nevertheless, powerful numerical tools providing reliable results are also available today and able to compete with the experimental approach. In this paper the wind action on a free-form complex thin shell is investigated through 3D-CFD simulation in terms of the pressure coefficients and global forces generated. All the modelling aspects and calibrating process are described. The results obtained showed that the CFD technique is effective in the study of the wind effects on complex-shaped structures.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.315-323
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• 2009

Pressure oscillations triggered by the unstable interaction of dynamic flow features of the hydraulic turbine with the hydraulic plant system - including the electrical design - can at times reach significant levels and could lead to damage of plant components or could reduce component lifetime significantly. Such a problem can arise for overload as well as for part load operation of the turbine. This paper discusses an approach to analyze the overload high pressure oscillation problem using computational fluid dynamic (CFD) modeling of the hydraulic machine combined with a network modeling technique of the hydraulic system. The key factor in this analysis is the determination of the overload vortex rope volume occurring within the turbine under the runner which is acting as an active element in the system. Two different modeling techniques to compute the flow field downstream of the runner will be presented in this paper. As a first approach, single phase flow simulations are used to evaluate the vortex rope volume before moving to more sophisticated modeling which incorporates two phase flow calculations employing cavitation modeling. The influence of these different modeling strategies on the simulated plant behavior will be discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2575-2580
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• 2013

An intake port for Range Extender engine has been developed using CFD technique. Three dimensional intake port model has been built and computational analysis has been performed. Computed non-dimensional flow coefficient, swirl ratio and swirl number have been compared with the experimental result. Convex and concave curvature of the intake port have been optimized to reduce recirculation flow and flow resistance. Finally, the mean flow coefficient is 0.383 and the mean swirl number is 1.544. The intake port shows relatively excellent performance compared with those of general 2 valve engine system intake ports.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.1
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• pp.52-60
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• 2005

The CFD coupled aeroelastic analyses have significant advantages over linear panel methods in their accuracy and usefulness for the simulation of actual aeroelastic motion after specific initial disturbance. However, in spite of their advantages, a heavy computation time is required. In this paper, a method is discussed to save a computational cost in the time domain aeroelastic analysis based on the system identification technique. The coefficients of system identification model are fit to the computed time response obtained from a previously developed aeroelastic analysis code. Because the non-dimensionalized data is only used to construct the model structure, the resulting model of the unsteady CFD solution is independent of dynamic pressure and this independency makes it possible to find the flutter dynamic pressure without the unsteady aerodynamic computation. To confirm the accuracy of the system identification methodology, the system model responses are compared with those of the CFD coupled aeroelastic analysis at the same dynamic pressure.

• The KSFM Journal of Fluid Machinery
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• v.15 no.5
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• pp.37-41
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• 2012

High-efficiency and low-noise axial flow fan is developed by combining the FanDAS, a computerized axial fan design/performance analysis system, and CFD software(CFX). Based on fan design requirements, FanDAS conducts 3-D blade geometry design, quasi-3D flow/ performance analyses and noise evaluation by using through-flow analysis method and noise models for discrete frequency and broadband noise sources. Through the parametric studies of fan design variables using FandDAS, preliminary and baseline design is achieved for high efficiency and low noise fan, and then can be coupled with a CFD technique such as the CFX code for constructing final and optimized fan design. The FanDAS-CFX coupled system and its design procedure are applied to actual fan development practice. The FanDAS provides an optimized 3-D fan blade geometry, and its predictions on the performance and the noise level of designed fan are well agreed with actual test results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.263-270
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• 2014

A fluid transport technique is a key issue for the development of microfluidic systems. In this paper, a new concept for transporting a droplet without external power sources is proposed and verified numerically. The proposed device is a heterogeneous surface which has both hydrophilic and hydrophobic horizontal surfaces. The numerical simulation to demonstrate the new concept is conducted by an in-house solution code (PowerCFD) which employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method (CICSAM) in a volume of fluid (VOF) scheme for phase interface capturing. It is found that the proposed concept for droplet transport shows superior performance for droplet transport in microfluidic systems.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.3
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• pp.181-189
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• 2008

GaAs film growth process from trimethylgallium(TMGa) and tertiary-butylarsine(TBAs) using a horizontal MOCVD reactor was numerically studied to explain the experimental result that the decreasing surface reaction rate as the increasing partial pressure of group III species. Using the non-linear model based on the Langmuir isotherm which considers the adsorption and desorption of molecules, film deposition over the entire reactor scale was predicted by computational fluid dynamics (CFD) with the aid of the parameters obtained from the selective area growth (SAG) technique. CFD Results using the non-linear surface reaction model with the parameters determined from the SAG experiments predicted too high film growth rate compared to the measured values at the downstream region where the temperature was decreased abruptly. The pairs of ($k_s^n$, K) from the numerical simulations was $(2.52{\times}10K^{-6}mol/m^2/s,\;1.6{\times}10^5m^3/mol)$, whereas the experimentally determined was $(3.58{\times}10^{-5}mol/m^2/s,\;6.9{\times}10^5m^3/mol)$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.737-740
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• 2004

The interior noise reduction of construction equipment is concerned for improving the driver comfort in this study. From the baseline test, the exhaust noise gives a big contribution to the interior noise of construction equipment. And the detail noise contribution analysis of the exhaust system, the tail pipe, which is for ventilation an engine room hot air to outside, amplify the exhaust noise around operating engine RPM associated with tail pipe structural and cavity resonances. To remove the noise amplifying effects, the tail pipe has to be shorted its length. Even the noise can be attenuated the ventilation flux when using the redesigned tail pipe is reduced than the original one. Thus, a shape change of the tail pipe is additionally needed for increasing the ventilation flux and attenuating the exhaust noise using CFD technique. The CFD results of the tail pipe give a meaning full information what obstructs the ventilation flex in the current design and how changes the tail pipe.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.48-59
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• 2020

A traditional propeller can easily become entangled with floating objects while operating. In this paper, we present a newly developed Electromagnetic-valve-control-based Water-jet Propulsion System (ECWPS) for an unmanned surface cleaning vessel that can be flexibly controlled via a Micro Control Unit (MCU). The double-structure was adapted to the unmanned surface cleaning vessel for floating-collection missions. Computational Fluid Dynamics (CFD) software for operating effect simulation was also used to reveal the working principle of the ECWPS under different conditions. Neglecting the assembly technique, the design level, controlling strategy, and maneuvering performance of the ECWPS reached unprecedented levels. The ECWPS mainly consists of an Electromagnetic-valve Array (EA), pipeline network, control system, and water-jet source. Both CFD analyses and experimental results show that the hydraulic characteristic of the ECWPS was predicted reasonably, which has enormous practical value and development prospects.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.5
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• pp.861-868
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• 2022

The purpose of this study is to design an effective atmospheric environment system through the design of the dust collection in the air shot room being operated in a domestic shipyard. The ventilation system in the current air shot room mostly uses a dust collecting filter to filter internal particles and releases them in the atmosphere. A conventional design was made too much. In order to prevent an error and draw an optimal design, Computational fluid dynamics (CFD) tried to be applied only to air shot room. In the advanced design technique, computer simulation was conducted to secure basic design data. In order to find the basic design of the ventilation system and the flow field in the air shot room at propeller mold workplace of a shipyard, the CFD was conducted. In the case of Model-1 as a conventional workplace, where air flows in the inlet due to the subatmospheric pressure generated by inhalation of an air blower and flows out to the outlet, a discharge flow rate was somewhat low, and there was the holdup zone in the room. In the case of Model-2 as an improved model, the ventilation system was improved in the Push-Pull type, and the holdup of the internal flow field was improved.