Analysis of Curved Panel Flutter in Supersonic and Transonic Airflows Using a Fluid–Structure Coupling Algorithm

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Guanhua Mei ◽  
Jiazhong Zhang ◽  
Can Kang
Keyword(s):  
Dynamic Pressure ◽  
Stable State ◽  
Aerodynamic Load ◽  
Panel Flutter ◽  
Governing Equations ◽  
Fluid Structure ◽  
Flutter Suppression ◽  
Flight Vehicles ◽  
Curved Panel ◽  
Coupling Algorithm

In order to accurately study the effect of curvature on panel aeroelastic behaviors, a fluid–structure coupling algorithm is adopted to analyze the curved panel flutter in transonic and supersonic airflows. First, the governing equation for the motion of the curved panel and the structure solver are presented. Then, the fluid governing equations, the fluid solver, and the fluid–structure coupling algorithm are introduced briefly. Finally, rich aeroelastic responses of the curved panel are captured using this algorithm. And the mechanisms of them are explored by various analysis tools. It is found that the curvature produces initial aerodynamic loads above the panel. Thus, the static aeroelastic deformation exists for the curved panel in stable state. At Mach 2, with its stability lost on this static aeroelastic deformation, the curved panel shows asymmetric flutter. At Mach 0.8 and 0.9, the curved panel exhibits only positive static aeroelastic deformation due to this initial aerodynamic load. At Mach 1.0, as the dynamic pressure increases, the curved panel loses its static and dynamic stability in succession, and behaves as static aeroelastic deformations, divergences, and flutter consequentially. At Mach 1.2, with its stability lost, the curved panel flutters more violently toward the negative direction. The results obtained could guide the panel design and panel flutter suppression for flight vehicles with high performances.

Analysis of Supersonic and Transonic Panel Flutter Using a Fluid-Structure Coupling Algorithm

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Guanhua Mei ◽  
Jiazhong Zhang ◽  
Guang Xi ◽  
Xu Sun ◽  
Jiahui Chen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
High Speed ◽  
Stability Boundary ◽  
Harmonic Oscillation ◽  
Limit Cycle Oscillation ◽  
Panel Flutter ◽  
Fluid Structure ◽  
Coupling Algorithm ◽  
Element Method

In order to analyze the supersonic and transonic panel flutter behaviors quantitatively and accurately, a fluid-structure coupling algorithm based on the finite element method (FEM) is proposed to study the two-dimensional panel flutter problem. First, the Von Kármán's large deformation is used to model the panel, and the high speed airflow is approached by the Euler equations. Then, the equation of panel is discretized spatially by the standard Galerkin FEM, and the equations of fluid are discretized by the characteristic-based split finite element method (CBS-FEM) with dual time stepping; thus, the numerical oscillation encountered frequently in the numerical simulation of flow field could be removed efficiently. Further, a staggered algorithm is used to transfer the information on the interface between the fluid and the structure. Finally, the aeroelastic behaviors of the panel in both the supersonic and transonic airflows are studied in details. And the results show that the system can present the flat and stable, simple harmonic oscillation, buckling, and inharmonic oscillation states at Mach 2, considering the effect of the pretightening force; at Mach 1.2, as the panel loses stability, the ensuing limit cycle oscillation is born; at Mach 0.8 and 0.9, positive and negative bucklings are the typical states of the panel as it loses its stability. Further, the transonic stability boundary is obtained and the transonic bucket is precisely captured. More, this algorithm can be applied to the numerical analysis of other complicated problems related to aeroelasticity.

scholarly journals Passive Suppression of Panel Flutter Using a Nonlinear Energy Sink

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Jian Zhou ◽  
Minglong Xu ◽  
Wei Xia
Keyword(s):  
Dynamic Pressure ◽  
Nonlinear Energy Sink ◽  
Aerodynamic Load ◽  
Panel Flutter ◽  
Aeroelastic Model ◽  
Suitable Combination ◽  
Energy Sink ◽  
The Galerkin Method ◽  
Parameter Values ◽  
Nonlinear Energy

A nonlinear energy sink (NES) is used to suppress panel flutter. A nonlinear aeroelastic model for a two-dimensional flat panel with an NES in supersonic flow is established using the Galerkin method. First-order piston aerodynamic theory is adopted to build the aerodynamic load. The effects of NES parameters on flutter boundaries of the panel are investigated using Lyapunov’s indirect method. The mechanism of the NES suppression of panel flutter is studied through energy analysis. Effects of NES parameters on aeroelastic responses of the panel are obtained, and a design technique is adopted to find a suitable combination of parameter values of the NES that suppresses the panel flutter effectively. Results show that the NES can increase or reduce the onset dynamic pressure of the panel flutter and it can reduce the aeroelastic response amplitude effectively within a certain range of dynamic pressure behind the onset dynamic pressure. The installation position of the NES depends on the direction of the airflow. The robust characteristics should be considered to find the suitable combination of parameter values of the NES.

First-Order Frequency Effects in Supersonic Panel Flutter of Finite Cylindrical Shells

1973 ◽  
Vol 40 (2) ◽  
pp. 464-470
Author(s):  
M. Holt ◽  
T. M. Lee
Keyword(s):  
Mach Number ◽  
Elastic Shell ◽  
Order Effect ◽  
Aerodynamic Load ◽  
Panel Flutter ◽  
Thin Cylindrical Shell ◽  
First Order ◽  
Flutter Boundary ◽  
Shell Equation ◽  
Set Up

An improved calculation of the supersonic panel flutter characteristics of a thin cylindrical shell of finite length is presented. The aerodynamic load is determined with account taken of first-order terms in vibration frequency, and when this is introduced into the elastic shell equation an integro differential equation results. An equivalent eigenvalue problem is set up by applying Galerkin’s method to this equation. The flutter boundary, for given Mach number and circumferential mode n, corresponds to the shell thickness ratio at which the real part of any one of the eigenvalues first becomes non-negative. It is found that the most severe flutter condition, for given Mach number, occurs for a circumferential mode n = 7. The present calculations exclude second-order frequency terms in the elastic part of the flutter equation, even though they may have a first-order effect. A subsequent calculation referred to here shows that these terms indeed have no significant influence on the first-order analysis.

scholarly journals Descriptions of Entropy with Fractal Dynamics and Their Applications to the Flow Pressure of Centrifugal Compressor

Entropy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 266 ◽  
Author(s):  
Yan Liu ◽  
Dongxiao Ding ◽  
Kai Ma ◽  
Kuan Gao
Keyword(s):  
Autocorrelation Function ◽  
Centrifugal Compressor ◽  
Hurst Exponent ◽  
Flow Instability ◽  
Dynamic Pressure ◽  
Stable State ◽  
Nonlinear Dynamic System ◽  
Original Data ◽  
Fractal Spectrum ◽  
Fractal Characteristics

In this study, some important intrinsic dynamics have been captured after analyzing the relationships between the dynamic pressure at an outlet of centrifugal compressor and fractal characteristics, which is one of powerful descriptions in entropy to measure the disorder or complexity in the nonlinear dynamic system. In particular, the fractal dynamics of dynamic pressure of the flow is studied, as the centrifugal compressor is in surge state, resulting in the dynamic pressure of flow and becoming a serious disorder and complex. First, the dynamic pressure at outlet of a centrifugal compressor with 800 kW is tested and then obtained by controlling the opening of the anti-surge valve at the outlet, and both the stable state and surge are initially tested and analyzed. Subsequently, the fractal dynamics is introduced to study the intrinsic dynamics of dynamic pressure under various working conditions, in order to identify surge, which is one typical flow instability in centrifugal compressor. Following fractal dynamics, the Hurst exponent, autocorrelation functions, and variance in measure theories of entropy are studied to obtain the mono-fractal characteristics of the centrifugal compressor. Further, the multi-fractal spectrums are investigated in some detail, and their physical meanings are consequently explained. At last, the statistical reliability of multi-fractal spectrum by modifying the original data has been studied. The results show that a distinct relationship between the dynamic pressure and fractal characteristics exists, including mono-fractal and multi-fractal, and such fractal dynamics are intrinsic. As the centrifugal compressor is working under normal condition, its autocorrelation function curve demonstrates apparent stochastic characteristics, and its Hurst exponent and variance are lower. However, its autocorrelation function curve demonstrates an apparent heavy tail distribution, and its Hurst exponent and variance are higher, as it is working in an unstable condition, namely, surge. In addition, the results show that the multi-fractal spectrum parameters are closely related to the dynamic pressure. With the state of centrifugal compressor being changed from stable to unstable states, some multi-fractal spectrum parameters Δα, Δf(α), αmax, and f(αmin) become larger, but αmin in the multi-fractal spectrum show the opposite trend, and consistent properties are graphically shown for the randomly shuffled data. As a conclusion, the proposed method, as one measure method for entropy, can be used to feasibly identify the incipient surge of a centrifugal compressor and design its surge controller.

Pressure Distribution in a Simplified Human Ear Model for High Intensity Sound Transmission

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Takumi Hawa ◽  
Rong Z. Gan
Keyword(s):  
Growth Rate ◽  
Middle Ear ◽  
High Intensity ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Linear Growth Rate ◽  
Ear Canal ◽  
Fluid Structure ◽  
Pressure Impulse ◽  
Bench Model

High intensity noise/impulse transmission through a bench model consisting of the simplified ear canal, eardrum, and middle ear cavity was investigated using the CFX/ANSYS software package with fluid-structure interactions. The nondimensional fluid-structure interaction parameter q and the dimensionless impulse were used to describe the interactions between the high intensity pressure impulse and eardrum or tympanic membrane (TM). We found that the pressure impulse was transmitted through the straight ear canal to the TM, and the reflected overpressure at the TM became slightly higher than double the incident pressure due to the dynamic pressure (shocks) effect. Deformation of the TM transmits the incident pressure impulse to the middle ear cavity. The pressure peak in the middle ear cavity is lower than the incident pressure. This pressure reduction through the TM was also observed in our experiments that have dimensions similar to the simulation bench model. We also found that the increase of the pressure ratio as a function of the incident pressure is slightly larger than the linear growth rate. The growth rate of the pressure ratio in this preliminary study suggests that the pressure increase in the middle ear cavity may become sufficiently high to induce auditory damage and injury depending on the intensity of the incident sound noise.

Analysis on location of maximum vibration amplitude in panel flutter

2019 ◽  
Vol 234 (2) ◽  
pp. 457-469 ◽  
Author(s):  
Xianzong Meng ◽  
Zhengyin Ye ◽  
Kun Ye ◽  
Cheng Liu
Keyword(s):  
Theoretical Basis ◽  
Vibration Amplitude ◽  
Dynamic Pressure ◽  
Maximum Amplitude ◽  
Displacement Function ◽  
Limit Cycle Oscillation ◽  
Panel Flutter ◽  
Mathematical Basis ◽  
Critical Dynamic ◽  
Cycle Oscillation

When the panel is under limit cycle oscillation, the location of maximum vibration amplitude always locates at 0.75 of panel length under different dynamic pressure. However, this conclusion is drawn from engineer practice without further investigations on its theoretical basis. Thus, the current study focuses on the theoretical and mathematical basis of this problem. The pattern of the location of maximum amplitude is verified at first by using three numerical methods. Then, based on the law of energy conservation, the displacement function of linear panel oscillation is derived for theoretical investigation. The linear panel consists of two structural modes. Theoretical analysis shows that, under critical dynamic pressure, the generalized displacement responses of two structural modes have opposite phase, the same vibration amplitude and the same vibration frequency. As a result, the superposition of displacement function of two structural modes, which is the displacement function of panel, leads to the occurrence of maximum vibration amplitude at 0.7 of panel length. With more structural modes considered, the location of maximum moves to 0.75 of panel length.

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