• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.5
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• pp.490-498
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• 2004

This paper measures the forced convective heat transfer from heated cylinder to air flow in a rectangular duct at Re$_{D}$ =2,337, 4,589, 6,621 and 7,944 through experiments. And the heat transfer is computed by 3-D numerical computation in which various turbulent models are applied. It is shown through the comparison of experimental and computed data that numerical computation with standard k-$\varepsilon$ model predicts the experimental data most accurately. Furthermore, the correlation from the computed heat transfer is almost similar to that from the experiment when Re$_{D}$ is greater than 4,589. In addition, the correlation of McAdams is the closest to that from experimental data among various correlations from literature in the range of Reynolds number.ber.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.1
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• pp.101-113
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• 1994

This research has presented and experimental investigation on the characteristics of turbulent wake past a rectanular cylinder, according to various width/height ratio such as B/H=2.0, 2.79, 3.0, and 4.0 in a uniform shear flow. In order to perform this study, a special shear flow generator which produces the uniform shear flow has been designed and manufactured. It is found that the characteristics of the wake in a uniform shear flow are quite different from those of a uniform flow and vary with shear rate. And also, the formation of regular vortex structure is concerned with shear rate.

• Proceeding of EDISON Challenge
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• 2012.04a
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• pp.29-32
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• 2012

변장비의 변화가 사각실린더에 작용하는 유체력에 미치는 영향을 알기 위해 EDISON_열유체를 사용하여 수치해석을 하였다. 낮은 레이놀즈수 영역($100{\leq}Re{\leq}200$)에서 사각실린더의 변장비(W/H)를 0.5, 0.75, 1, 2로 변화시키며 해석을 수행하였고, 레이놀즈수와 변장비에 따른 스트로할수(St), 항력계수($C_D$), 양력계수($C_L$)를 비교하였다. 본 논문에서는 레이놀즈수와 실린더의 변장비가 스트로할수, 항력계수, 양력계수에 미치는 영향을 알아보는 데 중점을 두었다. 해석결과 레이놀즈수가 증가하고 변장비가 감소할수록 스트로할수, 항력계수, 양력계수가 증가하는 것을 확인하였다. 본 논문을 통해서 레이놀즈수와 사각실린더의 변장비가 사각실린더에 작용하는 유체력에 영향을 미친다는 것을 알 수 있었다.

• Wind and Structures
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• v.34 no.1
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• pp.1-14
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• 2022

In this work the flow through a hollow porous 5:1 rectangular cylinder made of perforated plates is numerically investigated by means of 2D URANS based simulations. Two approaches are adopted to account for the porous surfaces: in the first one the pores are explicitly modeled, so providing a detailed representation of the flow. In the second one, the porous surfaces are modeled by means of pressure jumps, which allow to take into account the presence of pores without reproducing the flow details. Results obtained by using the two aforementioned techniques are compared aiming at evaluating differences and similarities, as well as identifying the main flow features which might cause discrepancies. Results show that, even in the case of pores remarkably smaller than the immersed body, their arrangement can lead to local mechanisms able to affect the global flow arrangement, so limiting the accuracy of pressure jumps based simulations. Despite that, time-averaged fields often show a reasonable agreement between the two approaches.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.6 s.150
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• pp.667-674
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• 2006

Accurate prediction of ship dynamics, particularly roll motion, is very important in ship safety. In the past, empirical or vortex based methods were commonly used for the hydrodynamic roll damping predictions but they could not be applied to practical ship roll motion cause of limitations about geometries ad design conditions. Recently RANS-based techniques are developed for the practical ship motion analysis. In this study, RANS based roil analysis about a rectangular cylinder with WAVIS developed by MOERI/KORDI are performed and compared with the experimental data and other RANS results.

• Wind and Structures
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• v.34 no.1
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• pp.29-42
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• 2022

Following the BARC initiative, wind tunnel measurements have been performed on a 5:1 rectangular cylinder. Pressure distribution has been measured in several sections, checking the two-dimensionality of the flow around the model. Mean values compare well with previous data. These measurements have been processed using the standard Proper Orthogonal Decomposition (POD) and the snapshot POD to obtain phase-resolved cycles. This decomposition has been used to analyze the characteristics of the flow around the cylinder, in particular, the behavior of the recirculation bubble in the upper/lower surfaces. The effect of the angle of attack, the turbulence intensity and the Reynolds number has been studied. First and second modes extracted from POD have been found to be related to the reattachment of the flow in the upper surface. Increasing the angle of attack is related to a delay in the reattachment position, while an increase in turbulence intensity makes the reattachment point to move towards the windward face.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.2
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• pp.69-78
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• 2013

This study is constructed to investigate the sloshing effect on the motions of a two-dimensional rectangular cylinder experimentally and numerically. The modes of motion under consideration are sway and roll, and also experimental cases are divided by two categories; 1-DoF roll motion and 2-DoF motion (Coupling sway and roll). It is found that the sway response is considerably affected by the motion of the fluid, particularly near the sloshing natural frequency, while the roll response changes comparatively small. The dominant mode of motion is analyzed for 2-DoF experiments as well. The measured data for 1-DoF motions is compared with numerical results obtained by the Multi-modal approach. The numerical schemes vary in detail with the number of dominant sloshing modes; i.e. there is a single dominant mode for the Single-dominant method, while the Model 2 method assumes that the first two modes are superior. For the roll motion, numerical results obtained by the two different methods are relatively in good agreement with the experiments, and these two results are similar in most wave frequency range. However, the discrepancies are apparent where the fluid motion is not governed by a single mode. But both of numerical methods over-predict the motion at the vicinity of the sloshing natural frequency. In order to correct the discrepancy, the modal damping needs to be investigated more precisely. Furthermore, another multi-modal approach, such as the Boussinesq-type method, seems to be required in the region of the intermediate liquid.

• Wind and Structures
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• v.34 no.1
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• pp.81-90
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• 2022

To better understand the vortex-induced vibration (VIV) characteristics of a 5:1 rectangular cylinder, the distribution of aerodynamic force and the non-dimensional power spectral density (PSD) of fluctuating pressure on the side surface were studied in different VIV development stages, and their differences in the stationary state and vibration stages were analyzed. The spanwise and streamwise correlations of surface pressures were studied, and the flow field structure partitions on the side surface were defined based on the streamwise correlation analysis. The results show that the variation tendencies of mean and root mean square (RMS) pressure coefficients are similar in different VIV development stages. The RMS values during amplitude growth are larger than those at peak amplitude, and the smallest RMS values are observed in the stationary state. The spanwise correlation coefficients of aerodynamic lifts increase with increase of the peak amplitude. However, for the lock-in region, the maximum spanwise correlation coefficient for aerodynamic lifts occurs in the VIV rising stage rather than in the peak amplitude stage, probably due to the interaction of vortex shedding force (VSF) and self-excited force (SEF). The streamwise correlation results show that the demarcation point positions between the recirculation region and the main vortex region remain almost constant in different VIV development stages, and the reattachment points gradually move to the tailing edge with increasing amplitude. This study provides a reference to estimate the demarcation point and reattachment point positions through streamwise correlation and phase angle analysis from wind tunnel tests.

• Bulletin of the Society of Naval Architects of Korea
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• v.14 no.3
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• pp.13-22
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• 1977

The hydrodynamic forces acting on a forced oscillating 2-dimensional cylinder on a free surface of a fluid of a finite depth are calculated by distributing singularities on the immersed body surface. And the Haskind-Newman relation in a fluid of a finite depth is derived. The wave exciting force of the cylinder to an oscillation is also calculated by using the above relation. The method is applied to a circular cylinder swaying in a water of finite depth, and then, to a rectangular cylinder heaving, swaying, and rolling. The results of above cases give a good agreement with those by earlier investigators such as Bai, Keil, and Yeung. Also, this method is applied to a Lewis form cylinder with a half beam-to-draft ratio of 1.0 and a sectional area coefficient of 0.941, and to a bulbous section cylinder which is hard to represent by a mapping function. The results reveal that the hydrodynamic forces in heave increase as the depth of a water decrease, but in sway or roll, the tendency of the hydrodynamic forces is difficult to say in a few words. The exciting force to heave for a bulbous section cylinder becomes zero at two frequencies. The added mass moment of inertia for roll is seemed to mainly depend on the sectional shape than the water depth.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.1967-1974
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• 2005

The subsurface stress field caused by both normal loads and tangential loads has been evaluated using the rectangular patch solution. The effect of tangential loading on the subsurface stress field has been investigated in detail for both the cylinder-on-cylinder contact and a spur gear teeth contact. For the cylinder-on-cylinder contact, the subsurface stress fields are moved more to the direction of tangential loads and the positions where the maximum stress occur are getting closer to the surface with the increasing tangential loads. The subsurface stress fields of the gear teeth contact are expanded more widely to the direction of tangential loads with the increasing tangential loads. The friction coefficient of a gear teeth contact is low because they are operated in a lubricated condition, and therefore surface tractions in the EHL condition hardly affect on the subsurface stress field.