Investigation of the Influence of Aerodynamic Coupling on Response Levels of Mistuned Bladed Discs With Weak Structural Coupling

2005 ◽  
Author(s):  
I. Sladojevic´ ◽  
E. P. Petrov ◽  
A. I. Sayma ◽  
M. Imregun ◽  
J. S. Green
Keyword(s):  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Response Distribution ◽  
Aerodynamic Forces ◽  
Torsional Mode ◽  
Structural Coupling ◽  
Unsteady Aerodynamic ◽  
The Difference ◽  
Statistical Results

The paper summarises the results of a study investigating the correlation between the aerodynamic blade-to-blade coupling in mistuned bladed disc assemblies and the level of forced response. The focus was placed on the torsional mode of vibration, where blades’ coupling through the disc is weak, exposing the effects of aerodynamic coupling. The forced response of a large number of mistuned discs was computed, using whole-annulus finite element (FE) models. The unsteady aerodynamic forces that act upon the disc were calculated using a three-dimensional Reynolds-averaged Navier-Stokes CFD code. The results show the difference in response with and without aerodynamic coupling, exposing higher blade-to-blade interaction in the latter case. The statistical results show the change of the forced response distribution curves with the introduction of aero-coupling and their deviation from Gaussian distribution.

Forced Response Variation of Aerodynamically and Structurally Mistuned Turbo-Machinery Rotors

2006 ◽  
Author(s):  
I. Sladojevic´ ◽  
E. P. Petrov ◽  
M. Imregun ◽  
A. I. Sayma
Keyword(s):  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Fe Model ◽  
Frequency Shifts ◽  
Aero Engine ◽  
Different Types ◽  
Aerodynamic Parameters ◽  
Reynolds Averaged Navier Stokes ◽  
Response Variation

The paper presents the results of a study looking into changes in the forced response levels of bladed disc assemblies subject to both structural and aerodynamic mistuning. A whole annulus FE model, representative of a civil aero-engine fan with 26 blades was used in the calculations. The forced response of all blades of 1000 random mistuned patterns was calculated. The aerodynamic parameters, frequency shifts and damping, were calculated using a three-dimensional Reynolds-averaged Navier-Stokes aero-elasticity code. They were randomly varied for each mistuning pattern, with the assumption that the system would remain stable, i.e. flutter would not occur due to aerodynamic mistuning. The results show the variation of the forced response with different types of mistuning, with structural mistuning only, with aerodynamic mistuning only and with both structural and aerodynamic mistuning.

scholarly journals Numerical Investigation on Flapping Aerodynamic Performance of Dragonfly Wings in Crosswind

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Chao Wang ◽  
Rui Zhang ◽  
Chaoying Zhou ◽  
Zhenzhong Sun
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Lateral Force ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Aerodynamic Forces ◽  
Sideslip Angle ◽  
Flight Direction ◽  
Time Average ◽  
Dragonfly Wings

Numerical simulations are performed to investigate the influence of crosswind on the aerodynamic characteristics of rigid dragonfly-like flapping wings through the solution of the three-dimensional unsteady Navier-Stokes equations. The aerodynamic forces, the moments, and the flow structures of four dragonfly wings are examined when the sideslip angle ϑ between the crosswind and the flight direction varied from 0o to 90o. The stability of the dragonfly model in crosswind is analyzed. The results show that the sideslip angle ϑ has a little effect on the total time-average lift force but significant influence on the total time-average thrust force, lateral force, and three-direction torques. An increase in the sideslip angle gives rise to a larger total time-average lateral force and yaw moment. These may accelerate the lateral skewing of the dragonfly, and the increased rolling and pitching moments will further aggravate the instability of the dragonfly model. The vorticities and reattached flow on the wings move laterally to one side due to the crosswind, and the pressure on wing surfaces is no longer symmetrical and hence, the balance between the aerodynamic forces of the wings on two sides is broken. The effects of the sideslip angle ϑ on each dragonfly wing are different, e.g., ϑ has a greater effect on the aerodynamic forces of the hind wings than those of the fore wings. When sensing a crosswind, it is optimal to control the two hind wings of the bionic dragonfly-like micro aerial vehicles.

scholarly journals Calculation and Correlation of the Unsteady Flowfield in a High Pressure Turbine

2002 ◽  
Author(s):  
Milind A. Bakhle ◽  
Jong S. Liu ◽  
Josef Panovsky ◽  
Theo G. Keith ◽  
Oral Mehmed
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Forced Vibrations ◽  
Forced Response ◽  
Operating Conditions ◽  
Test Facility ◽  
Navier Stokes ◽  
Turbine Stage ◽  
High Pressure Turbine

Forced vibrations in turbomachinery components can cause blades to crack or fail due to high-cycle fatigue. Such forced response problems will become more pronounced in newer engines with higher pressure ratios and smaller axial gap between blade rows. An accurate numerical prediction of the unsteady aerodynamics phenomena that cause resonant forced vibrations is increasingly important to designers. Validation of the computational fluid dynamics (CFD) codes used to model the unsteady aerodynamic excitations is necessary before these codes can be used with confidence. Recently published benchmark data, including unsteady pressures and vibratory strains, for a high-pressure turbine stage makes such code validation possible. In the present work, a three dimensional, unsteady, multi blade-row, Reynolds-Averaged Navier Stokes code is applied to a turbine stage that was recently tested in a short duration test facility. Two configurations with three operating conditions corresponding to modes 2, 3, and 4 crossings on the Campbell diagram are analyzed. Unsteady pressures on the rotor surface are compared with data.

scholarly journals Unsteady Aerodynamic Characteristics Simulations of Rotor Airfoil under Oscillating Freestream Velocity

2020 ◽  
Vol 10 (5) ◽  
pp. 1822
Author(s):  
Qing Wang ◽  
Qijun Zhao
Keyword(s):  
Three Dimensional ◽  
Grid Method ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Critical Value ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Freestream Velocity ◽  
Unsteady Aerodynamic ◽  
Edge Vortex

The dynamic stall characteristics of rotor airfoil are researched by employing unsteady Reynolds-Averaged Navier-Stokes (RANS) method under oscillating freestream velocity conditions. In order to simulate the oscillating freestream velocity of airfoil under dynamic stall conditions, the moving-embedded grid method is employed to simulate the oscillating velocity. By comparing the simulated dynamic stall characteristics of two-dimensional airfoil and three-dimensional rotor, it is indicated that the dynamic stall characteristics of airfoil under oscillating freestream velocity reflect the actual dynamic stall characteristics of rotor airfoil in forward flight more accurately. By comparing the simulated results of OA209 airfoil under coupled freestream velocity/pitching oscillation conditions, it is indicated that the dynamic stall characteristics of airfoil associate with the critical value of Cp peaks (i.e., the dynamic stall characteristics of OA209 airfoil would be enhanced when the maximum negative pressure is larger than −1.08, and suppressed when this value is smaller than −1.08). By comparing the characteristics of vortices under different oscillating velocities, it indicates that the dissipation rate of leading edge vortex presents as exponent characteristics, and it is not sensitive to different oscillating velocities.

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.

Blade Aerodynamic Damping Variation With Rotor-Stator Gap: A Computational Study Using Single-Passage Approach

2003 ◽  
Vol 127 (3) ◽  
pp. 573-579 ◽  
Author(s):  
H. D Li ◽  
L. He
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
Single Passage ◽  
Finite Volume Discretization ◽  
Shape Correction ◽  
Gap Spacing

One of the outstanding issues in turbomachinery aeromechanic analysis is the intrarow interaction effects. The present work is aimed at a systematic examination of rotor-stator gap effects on blade aerodynamic damping by using a three-dimensional (3D) time-domain single-passage Navier-Stokes solver. The method is based on the upwind finite volume discretization and the single-passage shape-correction approach with enhanced accuracy and efficiency for unsteady transonic flows prediction. A significant speedup (by a factor of 20) over to a conventional whole annulus solution has been achieved. A parametric study with different rotor-stator gaps (56%–216% rotor tip chord) for a 3D transonic compressor stage illustrates that the reflection from an adjacent stator row can change rotor aerodynamic damping by up to 100% depending on the intrarow gap spacing. Furthermore, this rotor aerodamping dependency on the intrarow gap seems also to be affected by the number of stator blades. The predicted nonmonotonic relationship between the rotor blade aerodynamic damping and the gap spacing suggests the existence of an optimum gap regarding rotor flutter stability and/or forced response stress levels.

The Effects of Aerodynamic Asymmetric Perturbations on Forced Response of Bladed Disks

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Tomokazu Miyakozawa ◽  
Robert E. Kielb ◽  
Kenneth C. Hall
Keyword(s):  
Coefficient Matrix ◽  
Forced Response ◽  
Influence Coefficient ◽  
Single Family ◽  
Aerodynamic Forces ◽  
Unsteady Aerodynamic ◽  
The Matrix ◽  
Blade Frequency ◽  
Wave Coordinates ◽  
Aerodynamic Asymmetry

Most of the existing mistuning research assumes that the aerodynamic forces on each of the blades are identical except for an interblade phase angle shift. In reality, blades also undergo asymmetric steady and unsteady aerodynamic forces due to manufacturing variations, blending, mis-staggered, or in-service wear or damage, which cause aerodynamically asymmetric systems. This paper presents the results of sensitivity studies on forced response due to aerodynamic asymmetry perturbations. The focus is only on the asymmetries due to blade motions. Hence, no asymmetric forcing functions are considered. Aerodynamic coupling due to blade motions in the equation of motion is represented using the single family of modes approach. The unsteady aerodynamic forces are computed using computational fluid dynamics (CFD) methods assuming aerodynamic symmetry. Then, the aerodynamic asymmetry is applied by perturbing the influence coefficient matrix in the physical coordinates such that the matrix is no longer circulant. Therefore, the resulting aerodynamic modal forces in the traveling wave coordinates become a full matrix. These aerodynamic perturbations influence both stiffness and damping while traditional frequency mistuning analysis only perturbs the stiffness. It was found that maximum blade amplitudes are significantly influenced by the perturbation of the imaginary part (damping) of unsteady aerodynamic modal forces. This is contrary to blade frequency mistuning where the stiffness perturbation dominates.

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