• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.627-635
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• 2021

The fire damage and structural performance of a steel-concrete composite superstructure under a highway bridge exposed to fire loading was evaluated. To enhance the accuracy and efficiency of the numerical analysis, a proposed fluid-structure interaction fire analysis method was implemented in Ansys Fluent and Ansys Mechanical. The temperature distribution and performance evaluation of the steel-concrete composite superstructure according to the vertical distance from the fire source to the bottom flange were evaluated using the proposed analysis method. From the analysis, the temperature of the concrete slab and the bottom flange of the steel-concrete composite superstructure exceeded the critical temperature. Also, when the vertical distance from the fire source was 13 m or greater, the fire damage of the steel-concrete composite superstructure was found to within a safe limit.

• Wind and Structures
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• v.16 no.5
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• pp.411-431
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• 2013

A computational study of vortex-induced transverse vibrations of a cylinder with low mass-damping is presented. An Arbitrary Lagrangian-Eulerian (ALE) formulation of the Unsteady Reynolds-Averaged Navier-Stokes equations (URANS), along with the Spalart-Allmaras (SA) one-equation turbulence model, are coupled conservatively with rigid body motion equations of the cylinder mounted on elastic supports in order to study the amplitude and frequency response of a freely vibrating cylinder, its flow-induced motion, Vortex Street, near-wake flow structure, and unsteady loading in a moderate range of Reynolds numbers. The time accurate response of the cylinder from rest to its limit cycle is studied to explore the effects of Reynolds number on the start of large displacements, motion amplitude, and frequency. The computational results are compared with published physical experiments and numerical studies. The maximum amplitudes of displacements computed for various Reynolds numbers are smaller than the experimental values; however, the overall agreement of the results is quite satisfactory, and the upper branch of the limit-cycle displacement amplitude vs. reduced velocity response is captured, a feature that was missed by other studies. Vortex shedding modes, lock-in phenomena, frequency response, and phase angles are also in agreement with experiments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.72-78
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• 2008

In this study, advanced (fluid-structure interaction (FSI)) analysis system has been developed in order to predict turbine cascade performance with blade deformation effect due to aerodynamic loads. Intereference effects due to the relative movement of the rotor cascade with respect to the stator cascade are also considered. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation k-ω SST turbulence models are solved to accurately predict fluid dynamic loads considering flow separation effects. A fully implicit time marching scheme based on the (coupled Newmark time-integration method) with high artificial damping is efficiently used to compute the complex fluid-structure interaction problem. Predicted aerodynamic performance considering structural deformation effect of the blade shows somewhat different results compared to the case of rigid blade model. Cascade performance evaluations for different elastic axis positions are importantly presented and its aeroelastic effects are investigated.

• Coupled systems mechanics
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• v.7 no.2
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• pp.233-254
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• 2018

In order to reduce the dependency on fossil fuels, a policy to increase the production capacity of wind turbine is set up. This can be achieved with increasing the dimensions of offshore wind turbine blades. However, this increase in size implies serious problems of stability and durability. Considering the cost of large turbines and financial consequences of their premature failure, it is imperative to carry out numerical simulations over long periods. Here, an energy-conserving time-stepping scheme is proposed in order to ensure the satisfying computation of long-term response. The proposed scheme is implemented for three-dimensional solid based on Biot strain measures, which is used for modeling flexible blades. The simulations are performed at full spatial scale. For reliable design process, the wind loads should be represented as realistically as possible, including the fluid-structure interaction (FSI) dynamic effects on wind turbine blades. However, full-scale 3D FSI simulations for long-term wind loading remain of prohibitive computation cost. Thus, the model to quantify the wind loads proposed here is a simple, but not too simple to be representative for preliminary design studies.

• Earthquakes and Structures
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• v.18 no.4
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• pp.467-480
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• 2020

Concrete rectangular liquid storage tanks are widely used, but there are many cases of damage in previous earthquakes. Nonlinear fluid-structure interaction (FSI) is considered, Mooney-Rivlin material is used for rubber bearing, nonlinear contact is used for sliding bearing, numerical calculation models of no-isolation, rubber isolation, sliding isolation and hybrid isolation concrete rectangular liquid storage tanks are established; dynamic responses of different structures are compared to verify the effectiveness of isolation methods; and influences of earthquake amplitude, bidirectional earthquake and far-field long-period earthquake on dynamic responses are investigated. Results show that for liquid sloshing wave height, rubber isolation cause amplification effect, while sliding isolation and hybrid isolation have reduction effect; displacement of rubber isolation structure is much larger than that of sliding isolation with limiting-devices and hybrid isolation structure; when PGA is larger, wall cracking probability of no-isolation structure becomes larger, and probability of liquid sloshing wave height and structure displacement of rubber isolation structure exceeds the limit is also larger; under bidirectional earthquake, occurrence probabilities that liquid sloshing wave height and structure displacement of rubber isolation structure exceed the limit will be increased; besides, far-field long-period earthquake mainly influences structure displacement and liquid sloshing wave height. On the whole, control effect of sliding isolation is the best, followed by hybrid isolation, and rubber isolation is the worst.

• Wind and Structures
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• v.31 no.4
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• pp.373-380
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• 2020

For large-scale 5MW offshore wind turbines, the discrete equation of fluid domain and the motion equation of structural domain with geometric nonlinearity were built, the three-dimensional modeling of the blade considering fluid-structure interaction (FSI) was achieved by using Unigraphics (UG) and Geometry modules, and the numerical simulation and the analysis of the vibration characteristics for wind turbine structure under rotating effect were carried out based on ANSYS software. The results indicate that the rotating effect has an apparent effect on displacement and Von Mises stress, and the response and the distribution of displacement and Von Mises stress for the blade in direction of wingspan increase nonlinearly with the equal increase of rotational speeds. Compared with the single blade model, the blade vibration period of the whole machine model is much longer. The structural coupling effect reduces the response peak value of the blade displacement and Von Mises stress, and the increase of rotational speed enhances this coupling effect. The maximum displacement difference between two models decreases first and then increases along wingspan direction, the trend is more visible with the equal increase of rotational speed, and the boundary point with zero displacement difference moves towards the blade root. Furthermore, the Von Mises stress difference increases gradually with the increase of rotational speed and decreases nonlinearly from the blade middle to both sides. The results can provide technical reference for the safe operation and optimal design of offshore wind turbines.

• Wind and Structures
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• v.21 no.1
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• pp.105-117
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• 2015

This paper presents a numerical characterization of real railway overhead cables based on computational fluid dynamics (CFD). Complete analysis of the aerodynamic coefficients of this type of cross section yields a more accurate modelling of pressure loads acting on moving cables than provided by current approaches used in design. Thus, the characterization of certain selected commercial cables is carried out in this work for different wind speeds and angles of attack. The aerodynamic lift and drag coefficients are herein determined for two different types of grooved cables, which establish a relevant data set for the railway industry. Finally, the influence of this characterization on the fluid-structure interaction (FSI) is proved, the static behavior of a catenary system is studied by means of the finite element method (FEM) in order to analyze the effect of different wind angles of attack on the stiffness distribution.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.657-662
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• 2011

In this study, aeroelastic performance analyses have been conducted for a 10MW class wind turbine blade model Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate detailed dynamic responsed of wind turbine blade Reynolds-averaged Navier-Stokes (RANS) equations with k-${\omega}$ SST turbulence model are solved for unsteady flow problems of the rotating turbine blade model. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D turbine blade for fluid-structure interaction (FSI) problems.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.1007-1013
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• 2009

The purposes of this study are to evaluate the power performance through CFD analysis and structural integrity through uni-directional FSI analysis in aerodynamic design and structure design of wind turbine blade. The blade was designed to generate the power of 2MW under the rated wind speed of 11 m/s, consisting of NACA 6 series, DU series and FFA series airfoil. The inside section of the blade was designed into D-spar structure and circular stiffener was placed to reinforce the structural strength in the part of hub. CFD analysis with the application of transitional turbulence model was performed to evaluate the power performance of blade according to the change of TSR and 2.024MW resulted under the condition of rated wind speed. TSR of 9 produced the maximum power coefficient and in this case, Cp was 0.494. This study applied uni-directional FSI analysis for more precise evaluation of structural integrity of blade, and the results of fiber failure, inter fiber failure and eigenvalue buckling analysis were evaluated, respectively. For the evaluation, Puck's failure criteria was applied and the result showed that fiber failure and inter fiber failure did not occur under every possible condition of the analysis. As a result, power performance and structural integrity of 2 MW blade designed in this study turned out to satisfy the initial design goals.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.2
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• pp.67-80
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• 2016

The resistance performance of an icebreaking cargo vessel with varied stem angles is investigated numerically and experimentally. Ship-ice interaction loads are numerically calculated based on the fluid structure interaction (FSI) method using the commercial FE package LS-DYNA. Test results obtained from model testing with synthetic ice at the Pusan National University towing tank and with refrigerated ice at the National Research Council's (NRC) ice tank are used to validate and benchmark the numerical simulations. The designed icebreaking cargo vessel with three stem angles ($20^{\circ}$, $25^{\circ}$, and $30^{\circ}$) is used as the target ship for three concentrations (90%, 80%, and 60%) of pack ice conditions. The comparisons between numerical and experimental results are shown and our main conclusions are given.