• Journal of Ship and Ocean Technology
• /
• v.10 no.3
• /
• pp.27-35
• /
• 2006

The static stability of a high-speed hovercraft is estimated by model tests, simplified restoring moment equations and CFD. Well-known methods to increase the stability of hovercrafts are introduced. Roll and pitch moments of a scaled model with a skirt system are measured over inclination angles. The tests are performed on cushion at zero speed both on-land and over-water. To predict the static stability performance, simple restoring moment equations and CFD approach are introduced. Both shows a quantitative difference from the model test results, however, could be used as a design tool for relative comparison prior to model tests.

• Architectural research
• /
• v.10 no.2
• /
• pp.21-26
• /
• 2008

The number of measured degrees of freedom for detecting the damage of any structures is usually less than the number of model degrees of freedom. It is necessary to expand the measured data to full set of model degrees of freedom for updating modal data. This study presents the expansion methods to estimate all static displacements and dynamic modal data of finite element model from the measured data. The static and dynamic methods are derived by minimizing the variation of the potential energy and the Gauss's function, respectively. The applications illustrate the validity of the proposed methods. It is observed that the numerical results obtained by the static approach correspond with the Guyan condensation method and the derived static and dynamic approaches provide the fundamental idea for damage detection.

• Journal of ILASS-Korea
• /
• v.11 no.3
• /
• pp.168-175
• /
• 2006

The static pressure distribution and flow characteristics inside the high-pressure swirl spray were investigated by measuring the static pressure inside the spray and applying the computational fluid dynamics (CFD). The static pressure difference between inner and outer part of spray was measured at different axial locations and operating conditions using a piezo-resislive pressure transducer. To obtain the qualitative value of swirl motion at different operating conditions, the spray impact-pressure at the nozzle exit was measured using a piezo-electric pressure transducer, and the flow angle was measured using a microscopic imaging system. The flow characteristics inside the high pressure swirl spray was simulated by the 1-phase 3-dimensional CFD model. The effect of pressure alternations on spray development was discussed with macroscopic spray images and a mathematical liquid film model. The results showed that the static pressure drop is observed inside the swirl spray as a result of the dragged air motion and the centrifugal force of the air. The recirculation vortex inside the spray was also observed inside the swirl spray as a result of the adverse pressure gradient along the axial locations. The results of analytical liquid film model and macroscopic spray images showed that the static pressure structure is one of the main parameters affecting the swirl spray development.

• Journal of Environmental Science International
• /
• v.20 no.1
• /
• pp.25-34
• /
• 2011

The new empirical static model was constructed on the basis of dimension analysis to predict the pressure drop according to the operating conditions. The empirical static model consists of the initial pressure drop term (${\Delta}P_{initial}$) and the dust mass number term($N_{dust}=\frac{{\omega}_0{\nu}_f}{P_{pulse}t}$), and two parameters (dust deposit resistance and exponent of dust mass number) have been estimated from experimental data. The optimum injection distance was identified in the 64 experimental data at the fixed filtration velocity and pulse pressure. The dust deposit resistance ($K_d$), one of the empirical static model parameters got the minimum value at d=0.11m, at which the total pressure drop was minimized. The exponent of dust mass number was interpreted as the elasticity of pressure drop to the dust mass number. The elasticity of the unimodal behavior had also a maximum value at d=0.11m, at which the pressure drop increased most rapidly with the dust mass number. Additionally, the correlation coefficient for the new empirical static model was 0.914.

• Journal of Mechanical Science and Technology
• /
• v.17 no.11
• /
• pp.1608-1615
• /
• 2003

This paper studies on the linearization of a looper system in hot strip mills, that plays an important role in regulating a strip tension or a strip width. Nonlinear dynamic equations of the looper system are analytically linearized by a static feedback linearization algorithm with a compensator. The proposed linear model of the looper is validated by a comparison with a linear model using Taylor's series. It is shown that the linear model by static feedback well describes nonlinearities of the looper system than one using Taylor's series. Furthermore, it is shown from the design of an ILQ controller that the linear model by static feedback is very useful in designing a linear controller of the looper system.

• Structural Engineering and Mechanics
• /
• v.45 no.2
• /
• pp.145-157
• /
• 2013

Based on link-model, we conducted a static analysis and computation of a three-span suspended cable structure in the present paper, and obtained the static configuration and tension distribution of the cable. Using the link and beam model based on finite element method, we analyzed the vibration modal of three-span suspended cable structure, and compared with the results obtained from ANSYS using link and beam element. The vibration modals of shallow sagging inclined cables calculated from proposed method agrees well with ANSYS results, which validates the proposed method. As a result, the influence of bend stiffness on in-plane natural frequencies is much greater than that on out-of-plane natural frequencies of inclined cables.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.4
• /
• pp.47-56
• /
• 2005

In GPS/INS/barometer navigation system for UAV, vertical channel damping loop was introduced to suppress divergence of the vertical axis error of INS, which could be reduced to the level of accuracy of pressure altitude measured by a pitot-static tube. Because static pressure measured by the pitot-static tube depends on the speed and attitude of the vehicle, static pressure error models, based on aerodynamic data from wind tunnel test, CFD analysis, and flight test, were applied to reduce the error of pressure altitude. Through flight tests and sensitivity analyses, the error model using the ratio of differential pressure and static pressure turned out to be superior to the model using only differential pressure, especially in case of high altitude flight. Both models were proposed to compensate the effect of vehicle speed change and used differential and static pressure which could be obtained directly from the output of pressure transducer.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.6
• /
• pp.472-481
• /
• 2003

Low-frequency hi-static reverberation model (LHYREV-B, Low-frequency Hanyang univ. Reverberation model-Bistatic) based on the parabolic approximation for shallow water environment is presented. In this paper bistatic reverberation level is computed using the angle-independent scattering strength function and the wave-based acoustic model. The signal simulated by the LHYREV-B model is compared with the observed signals and it is shown that the LHYREV-B model provides a closer fit to the observed signals.

• Proceedings of the KIEE Conference
• /
• 1991.07a
• /
• pp.370-374
• /
• 1991

This paper presents a static circuit model for static ant dynamic simulation of induction motors and identification of motor parameters. Instead of usual T-circuits, equivalent ${\pi}$-circuit has been proposed so that power Inputs into motor terminals can very easily calculated with very well known load flow method. It has been shown that, with wide range variation of applied voltage and frequency, successful static simulations can be performed and further the proposed static model can be used to simulate dynamic characteristics. Finally it is shown also that motor parameters can easily be identified based on the proposed static circuit.

• Structural Engineering and Mechanics
• /
• v.63 no.2
• /
• pp.251-257
• /
• 2017

A local damage identification method using measured structural static displacement is proposed in this study. Based on the residual force vector deduced from the static equilibrium equation, residual strain energy (RSE) is introduced, which can localize the damage in the element level. In the case of all the nodal displacements are used, the RSE can localize the true location of damage, while incomplete displacement measurements are used, some suspicious damaged elements can be found. A model updating method based on static displacement response sensitivity analysis is further utilized for accurate identification of damage location and extent. The proposed method is verified by two numerical examples. The results indicate that the proposed method is efficient for damage identification. The advantage of the proposed method is that only limited static displacement measurements are needed in the identification, thus it is easy for engineering application.