Aerodynamic Forces of Stay Cables Incorporating in Flutier Analysis

2013 ◽  
Vol 438-439 ◽  
pp. 894-900
Author(s):  
Ke Jian Ouyang ◽  
Yi Long ◽  
Bi Cao Peng
Keyword(s):  
Aerodynamic Force ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Test Results ◽  
Stay Cable ◽  
Aerodynamic Forces ◽  
Stay Cables ◽  
Stiffness Matrices ◽  
Flutter Analysis ◽  
Sutong Bridge

With the length of stay cables close to 580m, only inclusion in aerodynamic forces of main deck cannot reflect the actual situation during wind-resistant design. The aerodynamic forces of stay cables should be considered in the three-dimensional flutter analysis of cable-stayed bridges. In this paper, mathematic expressions of unsteady aerodynamic force of stay cable were then derived in terms of aerodynamic damping and stiffness matrices. The above procedure is implemented into NACS by an independent module. As an example, the multimode flutter analysis of Sutong Bridge was conducted by using NACS. Fair agreement is achieved between the present numerical simulation and wind tunnel test results.

Experimental Study of Fatigue Performance of Stay Cable Damper

2014 ◽  
Vol 487 ◽  
pp. 404-407
Author(s):  
Dong Liang ◽  
Zi Shuo Li
Keyword(s):  
Experimental Study ◽  
Good Condition ◽  
Experimental Results ◽  
Test Results ◽  
Stay Cable ◽  
Damping Force ◽  
Durability Test ◽  
Equivalent Damping ◽  
Stay Cables ◽  
Performance Deterioration

Oil dampers are widely used as a popular countermeasure to mitigate the stay cables vibration. In this study, one actual oil damper designed for some long cable-stayed was experimentally investigated to evaluate the durability. 4 million cycles loading, with frequency of 4 Hz and amplitude of 1 mm, was imposed on the damper. The excitation displacement and damping force were measured and the equivalent damping was calculated from the experimental results. The stiffness effects of dampers behaved during durability tests were also analyzed quantitatively. The test results showed that the dampers were still in good condition after 4 million cycles loading and the dampers temperatures were stable at 50 degree centigrade during the test. According to the durability test results, a model for performance deterioration of damper was proposed to predict the lifetime of oil dampers.

Experimental Study on Multi-Mode Vibration Control of a Stay Cable with a Passive Magnetorheological Damper

2013 ◽  
Vol 361-363 ◽  
pp. 1402-1405
Author(s):  
Zhi Hao Wang
Keyword(s):  
Vibration Control ◽  
Mr Damper ◽  
Magnetorheological Damper ◽  
Test Results ◽  
Stay Cable ◽  
Mr Dampers ◽  
Stay Cables ◽  
Modal Damping ◽  
Mode Vibration ◽  
Multi Mode

Effective vibration control technology for stay cables is extremely critical to safe operations of cable-stayed bridges. For super-long cables, passive linear damper cannot provide sufficient damping since it can be only optimum for a given mode of cable, while a long cable may vibrate with several modes. This paper focuses on multi-mode vibration control of stay cables with passive magnetorheological (MR) dampers. Firstly, a 21.6m-long model cable was designed and established in the laboratory.Then, control performance of the cable with a passive MR damper was tested. The test results show that modal damping ratios of the cable in the first four modes can be improved significantly with the MR damper. It is further demonstrated that optimal tuned passively operated MR damper can outperform the passive viscous damper.

Large Eddy Simulation of Aerodynamic Forces on a Bridge Pylon

2011 ◽  
Vol 243-249 ◽  
pp. 1578-1582
Author(s):  
Xu Yong Ying ◽  
Fu You Xu ◽  
Zhe Zhang ◽  
Yong Gang Tan
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Navier Stokes ◽  
Aerodynamic Forces ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Les Model

In this study, aerodynamic forces on a bridge pylon are investigated by three-dimensional computational fluid dynamics using Large eddy simulation (LES) technology. The main objective is to identify the wind load parameters of the pylon and examine the accuracy of LES model applied to the bluff-body flows. The numerical results were compared with the available wind tunnel test results. Also, a comparison between using LES and Reynolds averaged Navier-Stokes equations with the RNG model have been made. It is found that the LES model competes the RNG model in accuracy for predictions of aerodynamic forces on the pylon.

Theoretical and Experimental Investigation on Tip Forces and Temperature Distributions of the Brush Seal Coupled Aerodynamic Force

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Shouqing Huang ◽  
Shuangfu Suo ◽  
Yongjian Li ◽  
Yuming Wang
Keyword(s):  
Aerodynamic Force ◽  
Three Dimensional ◽  
Frictional Coefficient ◽  
Infrared Camera ◽  
Beam Theory ◽  
Aerodynamic Forces ◽  
Balance Principle ◽  
Temperature Distributions ◽  
Brush Seal ◽  
Frictional Coefficients

Based on a type of three-dimensional slice model of a brush seal combined with the commercial CFD software FLUENT, the study calculated the leakage flow of the brush seal. The aerodynamic forces applied on upstream and downstream bristles are analyzed and reduced to a smaller amount of point forces for analysis convenience. The frictional coefficient between the bristle material Haynes 25 and rotor material 1Cr14Mn14Ni are tested. Tip forces including normal reaction and frictional forces caused by aerodynamic forces are quantitatively investigated under conditions with and without frictions using the torque balance principle and nonlinear beam theory (by ANSYS simulations), respectively. Torques, frictional heats, and the temperature distributions of the rotor and bristle pack are studied further. Details and characteristics of the flow and temperature distributions inside the bristle pack are presented. In the experiments, besides traditional tests, such as leakage and torque tests, an infrared camera is employed to capture temperature distributions at the interface of the rotor, bristle pack and nearby zones under various pressure differentials and rotation speeds. The three-dimensional slice model is firstly verified by calculating the leakages, torques and temperature distributions of the brush seal and confirmed via experimentation. The influence of various frictional coefficients and pressure differentials on tip forces, torque and temperature distributions are also examined.

scholarly journals Direct Numerical Simulations on the three-dimensional wake transition of flows over NACA0012 airfoil at Re = 1000

2021 ◽  
Vol 13 ◽  
pp. 175682932110556
Author(s):  
Taiba Kouser ◽  
Yongliang Xiong ◽  
Dan Yang ◽  
Sai Peng
Keyword(s):  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
Micro Air Vehicles ◽  
Reynold Number ◽  
Angle Of Incidence ◽  
Aerodynamic Forces ◽  
Vortex Pattern ◽  
Naca0012 Airfoil ◽  
Wake Modes

For micro air vehicles (MAV), the precise prediction of aerodynamic force plays an important role. The aerodynamic force of a comparative low Reynold number (Re) vehicle tends to be affected by the different flow modes. In this paper, the aerodynamic performance of a three-dimensional NACA0012 airfoil is studied numerically. A range of angles of attack ( α) 0°−25° and Reynolds number 1000 is considered. Mean and fluctuating coefficients of aerodynamic forces around NACA0012 airfoil are analyzed for different wake modes. The difference of aerodynamic forces between two and three-dimensional simulations are compared. The results show that the wake remains steady two-dimensional for lower angles of attack. At α = 9°, Von Karman vortex pattern is noticed. Flow transition to three-dimensional as the angle of attack increases from α = 13°. 3D wake is found to be stable with parallel shedding mode for 14°-17°. However, these modes become finer with the gradual increase in angle of incidence. While, wake loses its three-dimensional stability to chaotic with gradual increment in angle of attack afterwards.

Aerodynamic Characteristics Analysis of Ultra-High-Speed Elevator with Different Hoistway Structures

2021 ◽  
Author(s):  
Hao Jing ◽  
Qing Zhang ◽  
Ruijun Zhang ◽  
Qin He
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Sudden Increase ◽  
Aerodynamic Forces ◽  
Cross Sectional ◽  
Ultra High Speed ◽  
Characteristics Analysis ◽  
Ventilation Hole

The high-speed airflow generated by ultra-high-speed elevators causes significant aerodynamic force, which seriously reduces the comfort and safety of passengers. First, a multi-parameter general model of ultra-high-speed elevator was established, and the three-dimensional numerical simulation of incompressible flow in the ultra-high-speed elevator was simulated. The correctness of the model and method was verified by experiments and grid-independence analyses. On this basis, the variation in the aerodynamic forces and the pressure in the hoistway was analyzed. Finally, the influence of different hoistway structures and parameters of ventilation holes on the aerodynamic forces and hoistway pressure were analyzed. The results showed that the opening of ventilation holes significantly reduced the aerodynamic forces and hoistway pressure for most of the period of the car’s operation period, but both the aerodynamic forces and hoistway pressure showed a sudden increase–decrease process. The aerodynamic forces and hoistway pressure were highly sensitive to changes in the hoistway blockage ratio, the cross-sectional area of the ventilation hole, and the position of the ventilation hole. When a pair of ventilation holes were opened, those in the middle of the hoistway reduced aerodynamic problems in the hoistway to the greatest extent. The increase in the connection angle between the ventilation hole and the hoistway eliminated the low-speed recirculation zone at the ventilation hole and increased the total volume of exhaust air at the ventilation hole.

scholarly journals Assessing aerodynamic force estimation with experiments and simulations of flapping-airfoil flows on the verge of three-dimensionality

2019 ◽  
Vol 234 (2) ◽  
pp. 428-444 ◽  
Author(s):  
M Moriche ◽  
M Raiola ◽  
S Discetti ◽  
A Ianiro ◽  
O Flores ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Numerical Study ◽  
Three Dimensional ◽  
Leading Edge ◽  
Minor Effect ◽  
Two Dimensional ◽  
Force Estimation ◽  
Aerodynamic Forces ◽  
Pitching Airfoil ◽  
Moderate Reynolds Number

This paper reports a combined experimental and numerical study of the flow over a rigid airfoil in flapping motion. The setup consists of a heaving and pitching airfoil at a moderate Reynolds number ([Formula: see text]), at a Strouhal number St = 0.1. The aim is to assess the accuracy of two-dimensional direct numerical simulations in predicting aerodynamic forces in a flow configuration, which is nominally two-dimensional but is at the verge of three-dimensionality. The assessment is carried out with experiments, including flow field and aerodynamic force measurements with particle image velocimetry and a load cell. The comparative study shows a good qualitative agreement between the experiments and the simulations at comparable Reynolds numbers both in terms of forces and flow fields, but with some quantitative differences. The quantitative discrepancies between experiments and simulation are analyzed and reduced to inherent differences between experimental and computational setups. It is observed that the significant differences are apparent almost exclusively in the wake evolution. Nonetheless, this is shown to have a minor effect on the aerodynamic force estimation. Overall, the trends observed when varying the mean pitch angle and the pitching amplitude are the same in both experiments and simulations. This suggests that two-dimensional/three-dimensional effects do not alter significantly the relationship between the unsteady flow mechanisms (i.e. leading edge vortex) and the aerodynamic forces in the parametric range considered here.

Interval Analysis-Based Flutter Analysis of Airplane Wings

2012 ◽  
Author(s):  
Singiresu S. Rao ◽  
Luna Majumder
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Reduction Process ◽  
Probabilistic Information ◽  
Natural Modes ◽  
Stiffness Matrices ◽  
Flutter Analysis ◽  
Improved Performance ◽  
Equivalent Reduction ◽  
Structural Mode

Modern aircrafts require improved performance and maneuverability while they conduct the missions. The flutter, an aeroelastic phenomenon is one of the important situations that limit the aircraft speed. Furthermore, for aircraft operated at high speed, many uncertainties may exist in its structural and aerodynamics characteristics. Especially, a slight change in the wing structural mode may induce a variation in its aerodynamic force distribution. In this work, an interval-based approach is used to handle the uncertainties associated with the flutter analysis. The set-theoretic representation of uncertainty is motivated by a possible lack of detailed probabilistic information on the distributions of the parameters. The analysis procedure is performed on an aircraft wing structure using finite element idealization and the results have shown the effectiveness and feasibility of the interval method. The order of the aerodynamic, mass and stiffness matrices of the assembled structures is reduced by introducing the first few natural modes of the structure as generalized coordinates. System equivalent reduction expansion process is used for model reduction which uses the generalized inverse and carries information pertaining to the selected modes at the selected set of degrees of freedoms. The system equivalent reduction formulation allows the reduction process to preserve the dynamics of the full system in a reduced set of matrices. Thus the order of the eigenvalue problem in the flutter analysis is reduced to one-third of the corresponding statics problem.

scholarly journals State-space aerodynamic model reveals high force control authority and predictability in flapping flight

2021 ◽  
Vol 18 (181) ◽  
pp. 20210222
Author(s):  
Yagiz E. Bayiz ◽  
Bo Cheng
Keyword(s):  
State Space ◽  
Force Control ◽  
Aerodynamic Force ◽  
State Space Model ◽  
Three Dimensional ◽  
Large Degree ◽  
Flapping Wing ◽  
Flapping Flight ◽  
Aerodynamic Forces ◽  
Control Authority

Flying animals resort to fast, large-degree-of-freedom motion of flapping wings, a key feature that distinguishes them from rotary or fixed-winged robotic fliers with limited motion of aerodynamic surfaces. However, flapping-wing aerodynamics are characterized by highly unsteady and three-dimensional flows difficult to model or control, and accurate aerodynamic force predictions often rely on expensive computational or experimental methods. Here, we developed a computationally efficient and data-driven state-space model to dynamically map wing kinematics to aerodynamic forces/moments. This model was trained and tested with a total of 548 different flapping-wing motions and surpassed the accuracy and generality of the existing quasi-steady models. This model used 12 states to capture the unsteady and nonlinear fluid effects pertinent to force generation without explicit information of fluid flows. We also provided a comprehensive assessment of the control authority of key wing kinematic variables and found that instantaneous aerodynamic forces/moments were largely predictable by the wing motion history within a half-stroke cycle. Furthermore, the angle of attack, normal acceleration and pitching motion had the strongest effects on the aerodynamic force/moment generation. Our results show that flapping flight inherently offers high force control authority and predictability, which can be key to developing agile and stable aerial fliers.

scholarly journals A three-dimensional model for rain-wind induced vibration of stay cables in cable-stayed bridges

2019 ◽  
Vol 14 (1) ◽  
pp. 89-102
Author(s):  
Truong Viet Hung ◽  
Vu Quang Viet ◽  
Vu Quoc Anh
Keyword(s):  
Wind Velocity ◽  
Three Dimensional ◽  
Stay Cable ◽  
Three Dimensional Model ◽  
Central Difference ◽  
Theoretical Formulation ◽  
Wind Speed Profile ◽  
Stay Cables ◽  
Wind Induced Vibration ◽  
Cable Stayed Bridges

In this paper, the effects of wind velocity according to height above the ground on the rain-wind induced vibration (RWIV) of stay cables are investigated. RWIV of the cable is modeled using the linear theory of cable vibration and the central difference algorithm. The wind speed profile according to height above the ground, which affects both aerodynamic forces acting on the cable and the oscillation of the rivulet on the cable surface, is taken into account in the theoretical formulation. The fourth-order method Runge-Kutta is used for solving the system of differential equation of the cable oscillation. The proposed 3D model of the stay cable is then used to assess the effects of wind velocity distribution on cable RWIV. The results obtained in this study showed that in most current cable-stayed bridges, in which the height of pylons is lower than 200 m, the change of wind velocity according to the height above the ground should be included in RWIV analyses. Keywords: stay cable; rain - wind induced vibration; rivulet; analytical model; vibration.

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