• Proceedings of KOSOMES biannual meeting
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• 2007.05a
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• pp.161-168
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• 2007

In this paper, the floating body with double barriers is introduced with a study on the flow patterns and characteristics in around the floating body by using 2 frame p article tracking method. This paper introduce an analisys method to predict the characteristics of flow around the neighbording fields of Floating Body with double barriers in order to investigate a high performance model. Flow visualization has conducted in a circulating water channel by a high speed camera and etc. Flow phenomena according to velocity distribution and flow separation around the floating body with double barriers were obtained by two-dimensional PIV system.

• Wind and Structures
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• v.13 no.6
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• pp.557-580
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• 2010

A new inflow turbulence generation method and a combined dynamic SGS model recently developed by the authors were applied to evaluate the wind effects on 508 m high Taipei 101 Tower. Unlike the majority of the past studies on large eddy simulation (LES) of wind effects on tall buildings, the present numerical simulations were conducted for the full-scale tall building with Reynolds number greater than $10^8$. The inflow turbulent flow field was generated based on the new method called discretizing and synthesizing of random flow generation technique (DSRFG) with a prominent feature that the generated wind velocity fluctuations satisfy any target spectrum and target profiles of turbulence intensity and turbulence integral length scale. The new dynamic SGS model takes both advantages of one-equation SGS model and a dynamic production term without test-filtering operation, which is particular suitable to relative coarse grid situations and high Reynolds number flows. The results of comparative investigations with and without generation of inflow turbulence show that: (1) proper simulation of an inflow turbulent field is essential in accurate evaluation of dynamic wind loads on a tall building and the prescribed inflow turbulence characteristics can be adequately imposed on the inflow boundary by the DSRFG method; (2) the DSRFG can generate a large number of random vortex-like patterns in oncoming flow, leading to good agreements of both mean and dynamic forces with wind tunnel test results; (3) The dynamic mechanism of the adopted SGS model behaves adequately in the present LES and its integration with the DSRFG technique can provide satisfactory predictions of the wind effects on the super-tall building.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.55-63
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• 1995

This paper describes the procedure to analyze the performance of the end-plated propeller(EPP) by a boundary integral method. The screw blade(SB) and end-plate(EP) are represented by a set of quadrilateral panels, where the source and normal dipole of uniform strength are distributed. The perturbation velocity potential, being the only unknown via the potential-based formulation, is determined by satisfying the flow tangency condition on the blade and the end-plate at the same time. The Kutta condition is satisfied through an iterative process by requiring the null pressure jump across the upper and lower sides of the trailing edges of both the SH and the EP. Sample calculations indicate that the EP increases the loading near the tip of the SB while spreading the trailing vortices along the trailing edge of the EP, thus avoiding the strong tip-vortex formation. Predicted performance of the EPP shows good correlations with the experimental results. The method is therefore considered applicable in designing and analyzing the EPP which may be an alternative for energy-saving propulsive devices.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.75-81
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• 2009

A study was performed to investigate the characteristics of two-phase jet injected into subsonic cross-flow using the external mixed gas blast two-phase nozzle. The shadowgraph method was adopted for the cross-flow jet visualization and PDPA system was used to measure droplet size, velocity, and volume flux. The atomization of two-phase jet is initially determined according to gas to liquid mass flow-rate ratio and the Reynolds number of cross-flows. The highest penetration trajectories of two-phase jet injected into cross-flow are governed by the momentum ratio at subsonic cross-flow. As GLR of two-phase jet injected into cross-flow increases, the droplet size decreases and the distribution area of volume flux increases. The distribution of volume flux that influenced by the counter vortex pair at the downstream of cross-flow is symmetric in shape of horseshoe.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2546-2551
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• 2007

Weather Strip(W/S) is a rubber part to proof water, sound and dust for opening and shutting devices including vehicle doors. And it requires high dimension precision and durability to proof water, noise, vibration and etc. But ironically it itself makes some wind noise because of some protuberance with glasses. The air flow analysis of door part of vehicle makes it possible to calculate and find out the cause of wind noise. In previous analysis, we focus on the numerical air flow analysis of the automobile side part. We do 2D-C.F.D first and 3D second. Through simulations, we can calculate the amount of sound pressure level at the glass run and find out the effects of glass run to make wind noise. Finally we can improve shape of glass run to reduce wind noise although it is small amounts of sound pressure reduction compared with total vehicle noise level.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.557-572
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• 2018

The academic research works about liquid storage tanks are reviewed for the purpose of providing valuable reference to the engineering practice on their aseismic design. A summary of the performance of tanks during past earthquakes is described in this paper. Next, the seismic response of tanks under unidirectional earthquake is reported, supplemented with the dynamic response under multidirectional motions. Then, researches on the influence of soil-structure interaction are brought out to help modify the seismic design approach of tanks in different areas with variable properties of soils. Afterwards, base isolation systems are reported to demonstrate their effectiveness for the earthquake-resistant design of liquid storage tanks. Further, researches about the liquid-structure interaction are reviewed with description of simplified models and numerical analytical methods, some of which consider the elastic effect of tank walls. Moreover, the liquid sloshing phenomenon on the hydrodynamic behaviors of tanks is presented by various algorithms including grid-based and meshfree method. And then the impact of baffles in changing the dynamic characteristics of the liquid-structure system is raised, which shows the energy dissipation by the vortex motion of liquid. In addition, uplifting effect is given to enhance the understanding on the capacity of unanchored tanks and some assessment of their development. At last, the concluding remarks and the aspects of extended research in the field of liquid storage tanks under seismic loads are provided, emphasizing the thermal stress analysis, the replaceable system for base isolation, the liquid-solid interaction and dynamic responses with stochastic excitations.

• Wind and Structures
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• v.21 no.1
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• pp.25-40
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• 2015

Oscillating motions of flexible cylinders are associated to some extent with the aerodynamic response of plants. Tandem motions of reeds with flexible stems in a colony are experimentally investigated using an array of flexible cylinders made of polydimethylsiloxane (PDMS). Consecutive images of flexible cylinders subjected to oncoming wind are recorded with a high-speed camera. To quantify oscillating motions, the average bending angle and displacement of flexible cylinders are evaluated using point-tracking method and spectral analysis. The tandem motions of flexible cylinders are closely related to the flow characteristics around the cylinders. Thus, the dynamic motions of a tandem arrangement of flexible cylinders are investigated with varying numbers of cylinders arranged in-line, numbers of cylinders in a group (behaving like a single body), and Reynolds numbers (Re). When the number of cylinders in a group increases, the damping effect caused by the support of downstream cylinders is pronounced. These results would be provide useful information on the tandem-arranged design of complex structures and energy harvesting devices.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.8
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• pp.2561-2571
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• 1996

The flow in the turbomachinery is very unsteady due to the stator-rotor interaction. It has been indicated that the stator-rotor interaction has three distinct causes of unsteadiness: that is, the viscous vortex shedding, wake rotor interaction and potential stator-rotor interaction. In this paper, the mechanism of unsteady potential interaction and wake interaction in the stator-rotor stage flow is numerically investigated in two-dimensional view point. The numerical technique used is the upwind scheme of Van Leer's Flux Vector Splitting(FVS) and cubic spline interpolation is applied on zonal interface. Then, the flow field of a compressor stage composed of NACA 65410 is analyzed. Flow fields are found to be simulated reasonably by this method and the sensitivity due to back-pressure variation is more stronger than rotor-velocity variation.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.3 s.147
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• pp.285-293
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• 2006

Three-dimensional and time-dependent solution for the fluid flow and heat transfer past a circular cylinder with fins is obtained using accurate and efficient spectral methods. A Fourier expansion with a corresponding uniform grid is used along the circumferential direction. A spectral multi-domain method with a corresponding Chebyshev collocation is used along r-z plane to handle fins attached to the surface of a circular cylinder. At the Reynolds number of 300 based on a cylinder diameter, results with fins are compared with those without fins in order to see the effects of the presence of fins on three-dimensional and unsteady fluid flow and heat transfer past a bluff body. The detail structures of fluid flow and temperature field are obtained as a function of time to investigate how the presence of fins changes heat transfer mechanism related to the vortical structure in the wake region.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.68-77
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• 2005

A transient liquid crystal technique has become one of the most effective ways in measuring the local heat transfer coefficients on the entire surface. The key Point of this technique is to convert the inlet flow temperature into an exponential temperature profile using a mesh heater. In order to verify the validity of this technique. the heat transfer characteristics on the wall surface by a pair of longitudinal vortices is investigated experimently and numerically. A standard ${\kappa}-{\varepsilon}$ is used for the numerical analysis of turbulent flow field. It is found from experiment and numerical analysis that two peak values exist over the whole domain. as the longitudinal vortices move to the farther downstream. these peak values decrease and the dimensionless averaged Nusselt number with the lapse of time is maintained nearly at constant values. The experiment results obtained from the present experiment in terms of the transient liquid crystal technique are in good agreement with the numerical results. Therefore, the transient liquid crystal technique developed for the measurement of heat transfer coefficient is proved to be a valid method.