• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.116-116
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• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw and total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.48-56
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• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw abd total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.295-305
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• 2005

To improve the aerodynamic effciency of TR-E2, a new configuration so called TR-E2Sl was introduced. TR-2251 is composed of different wing airfoil section and T-tail shape compared with TR-E2. Wind tunnel test for TR-EBS1 had been performed by changing the incidence angles of wing and deflection angles of control surfaces such as elevator and rudder. Also the on/off effect of ventral fin attached underneath of AFT fuselage was tested. Test result showed that variations of wing incidence angle did not cause any severe differences in aerodynamic characteristics. Longitudinal and directional characteristics of TR-E2S1 show stable for the pitch and yaw motions. However, the lateral stability of TR-E2S1 is not stable for a certain control surface deflection.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.222-227
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• 2001

The time simulation of slow drift motions of moored FPSO in waves is presented. The equation of motion based on Cummin's theory of impulse responses are employed, and are consisted of horizonal plane -surge, sway and yaw. The added mass coefficients, wave damping coefficients, first order wave exciting forces and the second order wave drift forces involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The mooring lines are modeled quasistatically as catenary for chains and touchdown. As for numerical example, time domain analyses are carried out for a box-type FPSO in long crest irregular wave condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.255-265
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• 1996

Up to the present the study on the performance prediction of HAWT was performed mainly by assuming the axial flow. So in this paper we aimed at the fully non-axial flow of HAWT. For this purpose, we defined the wind turbine pitch angle in addition to the yaw angle to specify the arbitrary wind direction. And we adopted the Glauert method as the basic analysis method then modified this method suitably for our goal. By comparing the computational results obtained by this modified new Glauert method with the experimental results, it was proved that our method was a very efficient method. And on the basis of the reliability of this method we considered the effect of all the design parameters and presented the optimum blade geometry and the optimum operating condition to gain the best performance curve.

• International Journal of Railway
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• v.3 no.3
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• pp.95-105
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• 2010

In this paper, a procedure is proposed to optimize bogie suspension parameters in view of minimizing wheel wear produced by curve negotiation, though meeting stability requirements. The problem is dealt with in the form of a constrained minimization problem, in which wheel wear evaluated over a given service scenario is introduced as the cost function to be minimized, and the requirements on vehicle stability are formulated in terms of constraints. The procedure is applied to the case of a non-powered passenger car for high-speed service, and the results obtained are discussed. It is shown that long wheelbase bogie may provide better overall performances than bogies having comparatively short wheelbase. Furthermore, a sensitivity analysis is performed, to define the effect on the optimization results of improving the performances of the yaw dampers in the bogie and of using a different wheel profile.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.536-544
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• 2009

The performance of radars operated near an offshore wind farm region may be degraded due to the distorted signals by wind turbines. This degradation of radar systems includes ghost effects and doppler effects by a tower, nacelle, and turbine blades consisting of the wind turbine. In this paper, electromagnetic wave backscatterings from a offshore wind turbine are numerically simulated in terms of temporal radar cross section and radar cross section spectra, using a quasi-static approach based on physical optics and physical theory of diffraction. The simulations are carried out at 3.05 GHz for the seven yaw angles and four blade pitch angles. From the results, radar cross section values and doppler effect as turbine blades rotate are investigated.

• International Journal of Ocean System Engineering
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• v.4 no.1
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• pp.19-28
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• 2014

The tension leg platform (TLP) is a vertically moored structure with excess buoyancy. The TLP is regarded as moored structure in horizontal plan, while inherit stiffness of fixed platform in vertical plane. In this paper, a numerical study using modified Morison equation was carried out in the time domain to investigate the influence of nonlinearities due to hydrodynamic forces and the coupling effect between surge, sway, heave, roll, pitch and yaw degrees of freedom on the dynamic behavior of TLP's. The stiffness of the TLP was derived from a combination of hydrostatic restoring forces and restoring forces due to cables and the nonlinear equations of motion were solved utilizing Newmark's beta integration scheme. The effect of tethers length and wave characteristics such as wave period and wave height on the response of TLP's was evaluated. Only uni-directional waves in the surge direction was considered in the analysis. It was found that for short wave periods (i.e. 10 sec.), the surge response consisted of small amplitude oscillations about a displaced position that is significantly dependent on tether length, wave height; whereas for longer wave periods, the surge response showed high amplitude oscillations about that is significantly dependent on tether length.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.771-774
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• 2002

Highly sweep leading edge extensions(LEX) applied to delta wings have greatly improved the subsonic maneuverability of contemporary fighters. In this study, systematic approach by PIV experimental method within a circulating water channel was adopted to study the fundamental characteristics of induced vortex generation, development and its breakdown appearing on a delta wing model with or without LEX in terms of four angles of attack($15^{\circ},\;20^{\circ},\;25^{\circ},\;30^{\circ}$) and six measuring sections of chord length($30{\%},\;40{\%},\;50{\%},\;60{\%},\;70{\%},\;80{\%}$). Sideslip effect in case of the LEX was also studied for two sideslip(yaw) angles($5^{\circ},\;10^{\circ}$) at one angle of attack(20). Distribution of time-averaged velocity vectors and vorticity over the delta wing model were compared along the chord length direction. Quantitative comparison of the maximum vorticity featuring the induced pressure distribution were also conducted to clarify the significance of the LEX existence. Animation presentation in velocity distribution was also implemented to reveal the effect of LEX with wing vortex interaction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.5
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• pp.368-375
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• 2018

In the present study, aerodynamic load analysis for a floating off-shore wind turbine was conducted to examine the effect of periodic platform motion in the direction of 6-DOF on rotor aerodynamic performance. Blade-element momentum method(BEM) was used for a numerical simulation, the unsteady airload effects due to the flow separation and the shed wake were considered by adopting a dynamic stall model based on the indicial response method. Rotor induced downwash was estimated using the momentum theory, coupled with empirical corrections for the turbulent wake states. The periodic platform motions including the translational motion in the heave, sway and surge directions and the rotational motion in the roll, pitch and yaw directions were considered, and each platform motion was applied as a sinusoidal function. For the numerical simulation, NREL 5MW reference wind turbine was used as the target wind turbine. The results showed that among the translation modes, the surge motion has the largest influence on changing the rotor airloads, while the effect of pitch motion is predominant for the rotations.