scholarly journals Experimental Investigation on the Nonlinear Coupled Flutter Motion of a Typical Flat Closed-Box Bridge Deck

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 568 ◽  
Author(s):  
Guangzhong Gao ◽  
Ledong Zhu ◽  
Feng Wang ◽  
Hua Bai ◽  
Jianming Hao
Keyword(s):  
Bridge Deck ◽  
Aerodynamic Force ◽  
Hysteresis Loops ◽  
Limit Cycle Oscillation ◽  
Displacement Sensors ◽  
Tunnel Technique ◽  
Flutter Boundary ◽  
Sectional Model ◽  
Measured Force ◽  
Order Components

The nonlinear post-flutter instabilities were experimentally investigated through two-degree-of-freedom sectional model tests on a typical flat closed-box bridge deck (width-to-depth ratio 9.14). Laser displacement sensors and piezoelectric force balances were used in the synchronous measurement of dynamic displacement and aerodynamic force. Beyond linear flutter boundary, the sectional model exhibited heave-torsion coupled limit cycle oscillation (LCOs) with an unrestricted increase of stable amplitudes with reduced velocity. The post-critical LCOs vibrated in a complex mode with amplitude-dependent mode modulus and phase angle. Obvious heaving static deformation was found to be coupled with the large-amplitude post-critical LCOs, for which classical quasi-steady theory was not applicable. The aerodynamic torsional moment and lift during post-critical LCOs were measured through a novel wind-tunnel technique by 4 piezoelectric force balances. The measured force signals were found to contain significantly higher-order components. The energy evolution mechanism during post-critical LCOs was revealed via the hysteresis loops of the measured force signals.

Ground Flutter Simulation Test Based on Reduced Order Modeling of Aerodynamics by CFD/CSD Coupling Method

2019 ◽  
Vol 11 (01) ◽  
pp. 1950008
Author(s):  
Binwen Wang ◽  
Xueling Fan
Keyword(s):  
Aerodynamic Force ◽  
Test System ◽  
Simulation Test ◽  
Robust Controller ◽  
Test Technique ◽  
Reduced Order ◽  
Aerodynamic Model ◽  
Flutter Boundary ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Flutter is an aeroelastic phenomenon that may cause severe damage to aircraft. Traditional flutter evaluation methods have many disadvantages (e.g., complex, costly and time-consuming) which could be overcome by ground flutter test technique. In this study, an unsteady aerodynamic model is obtained using computational fluid dynamics (CFD) code according to the procedure of frequency domain aerodynamic calculation. Then, the genetic algorithm (GA) method is adopted to optimize interpolation points for both excitation and response. Furthermore, the minimum-state method is utilized for rational fitting so as to establish an aerodynamic model in time domain. The aerodynamic force is simulated through exciters and the precision of simulation is guaranteed by multi-input and multi-output robust controller. Finally, ground flutter simulation test system is employed to acquire the flutter boundary through response under a range of air speeds. A good agreement is observed for both velocity and frequency of flutter between the test and modeling results.

scholarly journals Structural Audit of Sadhu Vaswani Pul using Institutionally Developed Displacement Sensors.

2020 ◽  
Vol 9 (9) ◽  
pp. 387-394
Keyword(s):  
Real Time ◽  
Bridge Deck ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Rebound Hammer ◽  
Reliable Test ◽  
Displacement Sensors ◽  
Rolling Load ◽  
Critical Sections

The main aim of this study is to conduct the structural audit of the Sadhu Vaswani Pul which is a Rail Over Bridge, situated in Koregaon Park, Pune and to establish the displacement sensors developed in the institution as a reliable test for structural auditing of the bridge decks. Traditional methods of auditing like the Rebound Hammer test and the Ultrasonic pulse velocity tests have been considered in this study. Very few methods are available for testing the deck displacement and this problem has been tackled here. The novelty of this research is that the institutionally developed displacement sensors are used for determining the deck displacement of the selected bridge. These sensors have not been used before and no on-site techniques are available to obtain the deck deflections under real-time loading. The displacement test on the decks was conducted. The critical decks which were determined during the Visual Inspections were tested by the displacement sensors. A two-axle truck of 18.5 tonnes was passed over the bridge deck and the displacement readings were recorded at the same time. The displacement reading thus obtained indicated the deflection of the deck under a uniform rolling load. The displacements obtained were then validated by the standards given in AASTHO-LFRD. After conducting the above tests, the overall condition of the bridge was determined and the critical sections which should be repaired were mentioned.

Short-Term Response of a Bridge-Winglet Sectional Model under Active Flutter Control

2020 ◽  
Vol 20 (08) ◽  
pp. 2050084
Author(s):  
Bowen Yan ◽  
Ke Li ◽  
Shaopeng Li ◽  
Guowei Qian ◽  
Yi Hui
Keyword(s):  
Closed Loop ◽  
Aerodynamic Force ◽  
Open Loop ◽  
Closed Loop Control ◽  
Control Effect ◽  
Short Term ◽  
Loop Control ◽  
Control Interval ◽  
Sectional Model ◽  
Term Response

Active winglets, with a manually controlled attitude angle, can take advantage of the self-excited force to suppress the flutter tendency of a bridge girder. Previous studies mostly focused on the effectiveness and robustness under long-term closed-loop control. However, the deck-winglet system’s short-term response, due to the memory effect of the aerodynamic force, is of concern. A bridge sectional model with active winglets was developed to investigate this problem. Experiments with different phase shifts between the members of the winglet pair were carried out in a wind tunnel. We found that the influence residue of an instantaneous change of the control pattern lasted about three pitching cycles, indicating that a large control interval was acceptable for practical applications. A theoretical relationship between the control effect and control phase was derived to explain the results of the open-loop control. The system responses under different control intervals were analyzed by the closed-loop control, demonstrating that a large control interval was acceptable if some time-consuming algorithms are used in a practical bridge’s flutter control operation.

MEASUREMENTS OF FLUTTER DERIVATIVES OF A BRIDGE DECK SECTIONAL MODEL

2015 ◽  
Vol 20 (4) ◽  
pp. 107-116
Author(s):  
Leonardo Gunawan ◽  
Hadyan Hafizh ◽  
Hari Muhammad
Keyword(s):  
Bridge Deck ◽  
Sectional Model ◽  
Derivatives Of ◽  
Flutter Derivatives

Statistical Sensitivity Study of Frequency Mistuning on the Prediction of the Flutter Boundary in a Transonic Fan

2016 ◽  
Author(s):  
Atsushi Tateishi ◽  
Toshinori Watanabe ◽  
Takehiro Himeno ◽  
Mizuho Aotsuka ◽  
Takeshi Murooka
Keyword(s):  
Aerodynamic Force ◽  
Sensitivity Study ◽  
Dominant Mode ◽  
Operating Conditions ◽  
Modal Properties ◽  
Numerical Predictions ◽  
Wide Range ◽  
Damping Rate ◽  
Flutter Boundary ◽  
Transonic Fan

This paper aims at quantifying the stabilization effect of mistuning in transonic fan flutter. The results are used to support the evaluation of flutter boundary and to clarify the reason for the mismatch observed in the numerical predictions reported in our previous study. Mistuning is modeled by the deviation of blade-mode frequency, and the stability analysis of vibrating blades is formulated as an eigenproblem of the equation of motion including self-excited aerodynamic force obtained by fluid-structure interaction simulations. Statistics about the modal properties are obtained by Monte Carlo simulation. The change in the averaged damping rate and flutter boundary is evaluated in a wide range of mistuning levels and operating conditions. Nominal levels of mistuning due to manufacturing tolerance have little effect to the flutter boundary because the decline in aerodynamic damping is very steep. Therefore, the accuracy associated with the computational fluid dynamics is likely to have caused the mismatch in the flutter boundary. Histograms of modal properties show that the inter-blade phase angle and blade amplitudes in flutter mode can be highly scattered, even if the level of mistuning is nominal. For largely mistuned cases, new crests which do not exist in nominal cases appear in the eigenvalue histogram. They were found to be highly-localized, single-blade dominant mode.

Analysis on Flutter Characteristics of Transonic Compressor Blade Row by a Fluid-Structure Coupled Method

2012 ◽  
Author(s):  
Mingming Zhang ◽  
Anping Hou ◽  
Sheng Zhou ◽  
Xiaodong Yang
Keyword(s):  
Phase Angle ◽  
Information Exchange ◽  
Stokes Equations ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Limit Cycle Oscillation ◽  
Time Step ◽  
Transonic Compressor ◽  
Blade Row

A time domain numerical approach is carried out to enhance the understanding of three dimensional blade row aeroelastic characteristics under the parallel computation. The vibration energy of unsteady aerodynamic force on the entire blade row is investigated using numerical solution of 3-D Navier-Stokes equations, coupled with structure finite element models for the blades to identify modal shapes and the structural deformations simultaneously. Interactions between fluid and structure are dealt with in a coupled manner, based on the interface information exchange until convergence in each time step. With this approach good agreement between the numerical results and the experimental data is observed. The flutter mechanism is analyzed according to deformation of the blades. The effect of inter-blade phase angle (IBPA) is included in the analysis by releasing the hypothesis of constant phase angle between adjacent blades in the traveling wave model. The results illustrate fully three dimensional unsteady nonlinear behaviors, such as limit-cycle oscillation. It is shown that all blades flutter at the same mode and frequency, but not at the same amplitude and IBPA. The analysis of the influence of different tip clearance gaps on the flutter characteristics of the blade row is also performed.

scholarly journals Supersonic Stall Flutter of High-Speed Fans

1982 ◽  
Vol 104 (3) ◽  
pp. 675-682 ◽  
Author(s):  
J. J. Adamczyk ◽  
W. Stevans ◽  
R. Jutras
Keyword(s):  
Dynamic Response ◽  
Rotor Blade ◽  
High Speed ◽  
Aerodynamic Force ◽  
Rotor System ◽  
Flexural Mode ◽  
Disk Model ◽  
Actuator Disk ◽  
Blade Row ◽  
Flutter Boundary

An analytical model is developed for predicting the onset of supersonic stall bending flutter in axial-flow compressors. The analysis is based on a modified two-dimensional, compressible, unsteady actuator disk theory. It is applied to a rotor blade row by considering a cascade of airfoils whose geometry and dynamic response coincide with those of a rotor blade element at 85 percent of the span height (measured from the hub). The rotor blades are assumed to be unshrouded (i.e., free standing) and to vibrate in their first flexural mode. The effects of shock waves and flow separation are included in the model through quasisteady, empirical, rotor total-pressure-loss and deviation-angle correlations. The actuator disk model predicts the unsteady aerodynamic force acting on the cascade blading as a function of the steady flow field entering the cascade and the geometry and dynamic response of the cascade. Calculations show that the present model predicts the existence of a bending flutter mode at supersonic inlet Mach numbers. This flutter mode is suppressed by increasing the reduced frequency of the system or by reducing the steady-state aerodynamic loading on the cascade. The validity of the model for predicting flutter is demonstrated by correlating the measured flutter boundary of a high-speed fan stage with its predicted boundary. This correlation uses a level of damping for the blade row (i.e., the log decrement of the rotor system) that is estimated from the experimental flutter data. The predicted flutter boundary is shown to be in good agreement with the measured boundary. These results show that the model can be used to estimate the relative stability between operating points of a given rotor system. If, in addition, a measure of the mechanical damping of the rotor system is available, the model can also be used to estimate the absolute stability at an operating point.

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