• Journal of Energy Engineering
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• v.13 no.2
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• pp.152-160
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• 2004

The present study investigates on the experimental and numerical results of heat transfer in the acoustic fields induced by ultrasonic waves. The strong upwards flow which moves from the bottom surface in a cavity to the free surface called as "acoustic streaming" was visualized by a particle image velocimetry (PIV). In addition, the augmentation ratio of heat transfer was experimentally investigated in the presence of acoustic streaming and was compared with the profiles of acoustic pressure calculated by the numerical analysis. A coupled finite element-boundary element method (FE-BEM) was applied for a numerical analysis. The results of experimental and numerical studies clearly show that acoustic pressure variations caused by ultrasonic waves in a medium are closely related to the augmentation of heat transfer.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.77-83
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• 2007

This paper presents numerical and experimental works for simultaneous pumping and mixing small liquid using asymmetric microelectrode arrays, based on AC electroosmotic flows. To this end, four arrangements of electrode pairs were considered with diagonal/herringbone shapes. Numerical simulations were made of three-dimensional geometries by using the linear theory. The results indicated that the helical flow motions induced by the electrode arrays play a significant role in the mixing enhancement. The pumping performance was influenced by the slip velocity at the center region of the channel compared to that near the side walls. To validate the numerical predictions, the microfluidic devices were made through MEMS. The flow rate was obtained by using micro PIV, increasing the applied frequency. The electrolyte was potassium chloride solution. The flow patterns above electrodes were visualized to see lateral flow for mixing. The experimental results showed good agreements with the numerical predictions.

• Smart Structures and Systems
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• v.32 no.6
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• pp.349-358
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• 2023

Real-Time Hybrid Testing (RTHT) requires the numerical substructure calculations to be completed within the defined integration time interval due to its real-time loading demands. For solving the problem, A Real-Time Hybrid Testing based on Restart-Loading Technology (RTHT-RLT) is proposed in this paper. In the proposed method, in case of the numerical substructure calculations cannot be completed within the defined integration time interval, the experimental substructure was returned back to the initial state statically. When the newest loading commands were calculated by the numerical substructure, the experimental substructure was restarted loading from the initial state to the newest loading commands so as to precisely disclosing the dynamic performance of the experimental substructure. Firstly, the methodology of the RTHT-RLT is proposed. Furthermore, the numerical simulations and experimental tests on one frame structure with a viscous damper are conducted for evaluating the feasibility and effectiveness of the proposed RTHT-RLT. It is shown that the proposed RTHT-RLT innovatively renders the nonreal-time refined calculation of the numerical substructure feasible for the RTHT. The numerical and experimental results show that the proposed RTHT-RLT exhibits excellent performance in terms of stability and accuracy. The proposed RTHT-RLT may have broad application prospects for precisely investigating the dynamic behavior of large and complex engineering structures with specific experimental substructure where a restarting procedure does not affect the relevant hysteretic response.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1284-1291
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• 2006

Single phase pressure drops in micro tubes were investigated through an experimental measurement and a numerical simulation. Experimental Po was obtained in circular micro tubes with 87 and $118{\mu}m$ diameter with distilled water. Experiments were carried out in laminar flow region with varying the Re 15-450 for the $87{\mu}m$ diameter tubes and 60-1300 for the $118{\mu}m$ diameter tube. No early transition from laminar to turbulent flow was detected for the experimental range. The computational estimation of pressure drop in the $87{\mu}m$ diameter tube was performed with the aid of CFD software. Boundary conditions from experiments were used for the numerical simulation. The results of experimental and numerical studies showed a good agreement with the conventional macro theory.

• Journal of Coastal Disaster Prevention
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• v.1 no.1
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• pp.1-9
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• 2014

In order to examine the characteristics of tsunami run-up heights on impermeable/permeable slope, a numerical wave tank by upgrading LES-WASS-3D was used in this study. Then, the model were compared with existing hydraulic model test for its verification. The numerical results well reproduced experimental results of solitary wave deformation, propagation and run-up height under various conditions. Also, the numerical simulation with a slope boundary condition has been carried out to understand solitary wave run-up on impermeable/permeable slope. It is shown that the run-up heights on permeable slope is 52.64-63.2% smaller than those on the impermeable slope because of wave energy dissipation inside the porous media. In addition, it is revealed that the numerical results with slope boundary condition agreed well with experimental results in comparison with the results by using stair type boundary condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.1014-1021
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• 2002

Analysis of two-dimensional secondary flows given by an oscillatory motion of a liquid with a free surface in a rectangular container subject to a linear reciprocating force is performed by numerical and experimental methods. FVM is used for the numerical computation of the two-dimensional flows. We considered the effects of the free-surface properties such as the surface tension and the dilatational viscosity. The boundary-layer analysis as well as an experiment is used in establishing the free surface properties. The secondary flow patterns are visualized by a laser sheet. It is shown that the secondary flow patterns predicted by the numerical methods are in good agreement with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.2
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• pp.213-221
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• 1985

Two dimensional laminar natural convection in a rectangular enclousure composed of a hot bottom wall, a partially cold side wall and insulated walls except the above walls was studied by numerical analysis and also by esperiments. In the experiments, the temperature distributions in the enclosure and Nusselt number distribution along the hot and cold walls were obtained by the use of Mach-Zehnder interferometer. At first, numerical analysis with the boundary conditions of the experimental apparatus was performed and the comparison of the results of the numerical and the experimental results validated the numerical model good ennough. Heat transfer characteristics were investigated by applying the verified numerical model with the parameters, i.e. Grashof number, aspect ratio, position of cold plate and insulation condition. The results showed the optimal conditions of temperature distribution and the position of cold wall, and the characteristics of insulation materials.

• Earthquakes and Structures
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• v.14 no.6
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• pp.551-565
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• 2018

Experimental testing is considered the most realistic approach to obtain a detailed representation of the nonlinear behaviour of masonry-infilled reinforced concrete (RC) structures. Among other applications, these tests can be used to calibrate the properties of numerical models such as simplified macro-models (e.g., strut-type models) representing the masonry infill behaviour. Since the significant cost of experimental tests limits their widespread use, alternative approaches need to be established to obtain adequate data to validate the referred simplified models. The proposed paper introduces a detailed finite element modelling strategy that can be used as an alternative to experimental tests to represent the behaviour of masonry-infilled RC frames under earthquake loading. Several examples of RC infilled frames with different infill configurations and properties subjected to cyclic loading are analysed using the proposed modelling approach. The comparison between numerical and experimental results shows that the numerical models capture the overall nonlinear behaviour of the physical specimens with adequate accuracy, predicting their monotonic stiffness, strength and several failure mechanisms.

• Journal of Korea Water Resources Association
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• v.48 no.4
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• pp.281-290
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• 2015

Numerical simulations of free surface flow over a broad-crested rectangular weir are conducted by using the volume of fraction (VOF) method and three different turbulence models, the k-${\varepsilon}$, RNG k-${\omega}$ and k-${\omega}$ SST models. The governing equations are solved by a second-order accurate finite volume method and the grid sensitivity study of solutions is carried out. The numerical results are evaluated by comparing the solutions with experimental and numerical results of Kirkgoz et al. (2008) and some non-dimensionalized experimental results obtained by Moss (1972) and Zachoval et al. (2012). The results show that the present numerical model can reasonably reproduce the experimental results, while three turbulent models yield different numerical predictions of two distinct zones of flow separation, the first zone is in front of the upstream edge of the weir and the second is created immediately behind the upstream edge of the weir where the flow is separated to form the separation bubble. The standard k-${\varepsilon}$ model appears to significantly underestimate the size of both separation zones and the k-${\omega}$ SST model slightly over-estimates the first separation zone in front of the weir. The RNG k-${\varepsilon}$ model predicts both separation zones in overall good agreement with the experimental measurement, while the k-${\omega}$ SST model yields the best numerical prediction of separation bubble at the upstream edge of the weir.

• Structural Engineering and Mechanics
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• v.43 no.6
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• pp.725-737
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• 2012

The temperature on steel structures is larger than the ambient air temperature under solar radiation and the temperature distribution on the affected structure is non-uniform and complicated. The steel tube, as a main structural member, has been investigated through experiment and numerical analysis. In this study, the temperature distribution on a properly designed steel tube under solar radiation is measured. A finite element transient thermal analysis method is presented and verified by the experimental results and a series of parametric studies are carried out to investigate the influence of various geometric properties and orientation on the temperature distribution. Furthermore, a simplified approach is proposed to predict the temperature distribution of steel tube. Based on both the experimental and the numerical results, it is concluded that the solar radiation has a significant effect on the temperature distribution of steel tubes. Under the solar radiation, the temperature of steel tubes is about $20.6^{\circ}C$ higher than the ambient air temperature. The temperature distribution of steel tubes is sensitive to the steel solar radiation absorption, steel tube diameter and orientation, but insensitive to the solar radiation reflectance and thickness of steel tube.