Direct Use of Unsteady Aerodynamic Pressures in the Flutter Analysis of Mistuned Blades

1995 ◽  
Vol 5 (10) ◽  
pp. 1587-1597 ◽  
Author(s):  
A. V. Srinivasan ◽  
G. G. Tavares
Keyword(s):  
Unsteady Aerodynamic ◽  
Flutter Analysis ◽  
Direct Use

scholarly journals Direct Use of Unsteady Aerodynamic Pressures in the Flutter Analysis of Mistuned Blades

1994 ◽  
Author(s):  
A. V. Srinivasan ◽  
G. G. Tavares
Keyword(s):  
Stability Analysis ◽  
Aspect Ratio ◽  
Unique Feature ◽  
Mode Shapes ◽  
Complex Eigenvalue ◽  
Aeroelastic Stability ◽  
Low Aspect Ratio ◽  
Unsteady Aerodynamic ◽  
Flutter Analysis ◽  
Direct Use

An aeroelastic stability analysis of a cascade of engine blades coupled only through aerodynamica is developed. The unique feature of the analysis is the direct use of unsteady aerodynamic pressures, rather than lifts and moments, in calculating the susceptibility of a cascade to flutter. The approach developed here is realistic and relevant for analysis of low aspect ratio blades. However, in the calculations presented in this paper, the surface is assumed to be divided into equal elemental areas. The formulation leads to a complex eigenvalue problem, the solution of which determines the susceptibility of the cascade to flutter. The eigenvalues of an assembly of alternately mistuned blades, operating at high reduced frequencies, appear to be very sensitive to the level of mistuned frequencies. The locus of eigenvalues shows a strong tendency to split even for very small percentage differences between the frequencies of the two sets of blades. Further, blades with identical frequencies, but alternately mistuned mode shapes, operating at high reduced frequencies show a tendency towards instability.

Nonlinear flutter analysis of composite panels

2018 ◽  
Vol 32 (12n13) ◽  
pp. 1840043
Author(s):  
Xiaomin An ◽  
Yan Wang
Keyword(s):  
Dynamic Pressure ◽  
Composite Panel ◽  
Composite Panels ◽  
Nonlinear Finite Element Method ◽  
Nonlinear Flutter ◽  
Unsteady Aerodynamic ◽  
Flutter Analysis ◽  
Time Marching ◽  
Coupled Solution ◽  
Nonlinear Panel Flutter

Nonlinear panel flutter is an interesting subject of fluid–structure interaction. In this paper, nonlinear flutter characteristics of curved composite panels are studied in very low supersonic flow. The composite panel with geometric nonlinearity is modeled by a nonlinear finite element method; and the responses are computed by the nonlinear Newmark algorithm. An unsteady aerodynamic solver, which contains a flux splitting scheme and dual time marching technology, is employed in calculating the unsteady pressure of the motion of the panel. Based on a half-step staggered coupled solution, the aeroelastic responses of two composite panels with different radius of R = 5 and R = 2.5 are computed and compared with each other at different dynamic pressure for Ma = 1.05. The nonlinear flutter characteristics comprising limited cycle oscillations and chaos are analyzed and discussed.

Unsteady Aerodynamic Analysis of an Oscillating Cascade at Large Incidence

1999 ◽  
Author(s):  
Jong-Shang Liu ◽  
Durbha V. Murthy
Keyword(s):  
Mach Number ◽  
Fluid Dynamic ◽  
Leading Edge ◽  
Two Dimensional ◽  
Edge Region ◽  
Unsteady Aerodynamic ◽  
High Incidence ◽  
Flutter Analysis ◽  
High Mach ◽  
Good Agreement

The flutter analysis capability of the quasi-3D aeroelastic computational fluid dynamic (CFD) code UNSFLO is evaluated by comparing to unsteady pressure results in an oscillating cascade. The geometry is two-dimensional and the oscillation is well-controlled. Time unsteady UNSFLO results are compared with data at inlet Mach number from 0.2 to 0.8 with incidence 0° and 10°. Three reduced frequencies, 0.4, 0.8, and 1.2 with inter-blade phase angle of 180 degrees were tested. The calculated steady state loadings show good agreement with data at zero incidence. The correlations become worse for high incidence angles because of the separation. The calculated aerodynamic work capture the chordwise distribution except in the near leading edge region. The correlations become also worse for high incidence from the leading edge to midchord especially at high Mach number.

scholarly journals On Aerodynamic Models for Flutter Analysis: A Systematic Overview and Comparative Assessment

2021 ◽  
Vol 2 (3) ◽  
pp. 516-541
Author(s):  
Marco Berci
Keyword(s):  
Stability Boundary ◽  
Control Point ◽  
Unsteady Aerodynamics ◽  
Aerodynamic Load ◽  
Test Cases ◽  
Unified Approach ◽  
Flexible Wing ◽  
Unsteady Aerodynamic ◽  
Circulatory Effects ◽  
Flutter Analysis

This work reviews different analytical formulations for the time-dependent aerodynamic load of a thin aerofoil and clarifies numerical flutter results available in the literature for the typical section of a flexible wing; inviscid, two-dimensional, incompressible, potential flow is considered in all test cases. The latter are investigated using the exact theory for small airflow perturbations, which involves both circulatory and non-circulatory effects of different nature, complemented by the p-k flutter analysis. Starting from unsteady aerodynamics and ending with steady aerodynamics, quasi-unsteady and quasi-steady aerodynamic models are systematically derived by successive simplifications within a unified approach. The influence of the aerodynamic approximations on the aeroelastic stability boundary is then rigorously assessed from both physical and mathematical perspectives. All aerodynamic models are critically discussed and compared in the light of the numerical results as well, within a comprehensive theoretical framework in practice. In all cases, results accuracy depends on the aero-structural arrangement of the flexible wing; however, simplified unsteady and simplified quasi-unsteady aerodynamic approximations are suggested for robust flutter analysis whenever the wing’s elastic axis lies ahead of the aerofoil’s control point.

Flutter of Swept Fan Blades

1985 ◽  
Vol 107 (2) ◽  
pp. 394-398
Author(s):  
R. E. Kielb ◽  
K. R. V. Kaza
Keyword(s):  
Detrimental Effect ◽  
Structural Model ◽  
Aerodynamic Loads ◽  
Unsteady Aerodynamic ◽  
Aeroelastic Analysis ◽  
Flutter Analysis ◽  
Blade Flutter ◽  
Fan Blade ◽  
Element Technique ◽  
Nonuniform Beam

The purpose of the research presented in this paper is to study the effect of sweep on fan blade flutter by applying the analytical methods developed for aeroelastic analysis of advanced turboprops. Two methods are used. The first method utilizes an approximate structural model in which the blade is represented by a swept, nonuniform beam. The second method utilizes a finite element technique to conduct modal flutter analysis. For both methods, the unsteady aerodynamic loads are calculated using two-dimensional cascade theories that are modified to account for sweep. An advanced fan stage is analyzed with 0, 15, and 30 deg of sweep. It is shown that sweep has a beneficial effect on predominantly torsional flutter and a detrimental effect on predominantly bending flutter. This detrimental effect is shown to be significantly destabilizing for 30 deg of sweep.

Flutter Analysis of a Tapered Viscoelastic Wing Subjected to a Follower Thrust Force

2019 ◽  
Vol 12 (1) ◽  
pp. 46
Author(s):  
Youssef S. Matter ◽  
Tariq Taha Darabseh ◽  
Abdel-Hamid I. Mourad
Keyword(s):  
Thrust Force ◽  
Flutter Analysis
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