scholarly journals Extended Rayleigh Damping Model

2016 ◽  
Vol 2 ◽  
Author(s):  
Naohiro Nakamura
Keyword(s):  
Rayleigh Damping ◽  
Damping Model

Modeling the damped dynamic behavior of a flexible pendulum

2019 ◽  
Vol 54 (2) ◽  
pp. 116-129 ◽  
Author(s):  
Roberto Ortega ◽  
Geraldine Farías ◽  
Marcela Cruchaga ◽  
Matías Rivero ◽  
Mariano Vázquez ◽  
...  
Keyword(s):  
High Speed ◽  
Time Integration ◽  
Integration Scheme ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Rayleigh Damping ◽  
Integration Schemes ◽  
Time Integration Schemes ◽  
Damping Model

The focus of this work is on the computational modeling of a pendulum made of a hyperelastic material and the corresponding experimental validation with the aim of contributing to the study of a material commonly used in seismic absorber devices. From the proposed dynamics experiment, the motion of the pendulum is recorded using a high-speed camera. The evolution of the pendulum’s positions is recovered using a capturing motion technique by tracking markers. The simulation of the problem is developed in the framework of a parallel multi-physics code. Particular emphasis is placed on the analysis of the Newmark integration scheme and the use of Rayleigh damping model. In particular, the time step size effect is analyzed. A strong time step size dependency is obtained for dissipative time integration schemes, while the Rayleigh damping formulation without time integration dissipation shows time step–independent results when convergence is achieved.

scholarly journals Aerodynamic Damping Prediction for Turbomachinery Based on Fluid-Structure Interaction with Modal Excitation

2019 ◽  
Vol 9 (20) ◽  
pp. 4411
Author(s):  
Jianxiong Li ◽  
Xiaodong Yang ◽  
Anping Hou ◽  
Yingxiu Chen ◽  
Manlu Li
Keyword(s):  
Wave Mode ◽  
Aeroelastic Stability ◽  
Fluid Structure ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
Rayleigh Damping ◽  
Flutter Boundary ◽  
Novel Method ◽  
Bending Modes ◽  
Damping Model

Aerodynamic damping predictions are critical when analyzing aeroelastic stability. A novel method has been developed to predict aerodynamic damping by employing two single time-domain simulations, specifically, one with the blade impulsed naturally in a vacuum and one with the blade impulsed in flow. The focus is on the aerodynamic damping prediction using modal excitation and the logarithmic decrement theory. The method is demonstrated by considering the first two bending modes with an inter-blade phase angle (IBPA) of 0° on a transonic compressor. The results show that the flutter boundary prediction is basically consistent with the experiment. The aerodynamic damping prediction with an IBPA of 180° is also performed, demonstrating that the method is suitable for different traveling wave mode representations. Furthermore, the influence of the amplitude of modal excitation and mechanical damping using the Rayleigh damping model for aerodynamic damping was also investigated by employing fluid-structure coupled simulations.

Multi-objective optimisation of a small aircraft turbine engine rotor system with self-updating Rayleigh damping model and frequency-dependent bearing-pedestal model

2019 ◽  
Vol 233 (16) ◽  
pp. 5710-5723 ◽  
Author(s):  
Joseph Shibu K ◽  
K Shankar ◽  
Ch Kanna Babu ◽  
Girish K Degaonkar
Keyword(s):  
Power Unit ◽  
Rotor System ◽  
Frequency Dependent ◽  
Turbine Engine ◽  
Multi Objective ◽  
Auxiliary Power Unit ◽  
Rayleigh Damping ◽  
Auxiliary Power ◽  
Damping Model ◽  
Engine Rotor

A self-updating Rayleigh damping model and frequency-dependent bearing-pedestal model for multi-objective optimisation is presented through this paper and is applied for a small turbine engine rotor system for aircraft application. This engine is used as an auxiliary power unit on aircraft. The Rayleigh damping model and frequency-dependent bearing pedestal model are verified by carrying out experiments on this auxiliary power unit rotor system. The novel self-updating feature calculates the Rayleigh damping coefficients and frequency-dependent bearing-pedestal stiffness for each chromosome and modifies rotor system equation of motion for computing the objectives during multi-objective optimisation for each chromosome. This novel model is used for multi-objective optimisation of auxiliary power unit rotor system. The unbalance response and weight are minimised subjected to critical speed constraint. Controlled elitist genetic algorithm is used for the optimisation resulting in Pareto optimal solutions and the acceptable solution is identified as the solution close to Utopia point. The results are compared with the constant Rayleigh damping model. The new model has produced an accurate optimum solution superior to constant Rayleigh damping model.

scholarly journals A 3D Shear Material Damping Model for Man-Made Vibrations of the Ground

2016 ◽  
Author(s):  
Darius Macijauskas ◽  
Stefan Van Baars
Keyword(s):  
Soil Surface ◽  
Pulse Load ◽  
The Finite Element Method ◽  
Circular Area ◽  
3 Dimensional ◽  
Rayleigh Damping ◽  
Soil Model ◽  
Shear Damping ◽  
Damping Model ◽  
Good Agreement

In this article, a 3 dimensional shear damping constitutive soil model is presented. This model has been implemented as a user defined soil model for the Finite Element Method software of Plaxis 2D. Verification tests demonstrate a good agreement with the theoretical model. A pulse load on a circular area on a soil surface has been numerically modelled with this shear damping soil model and compared to the results obtained by using the Rayleigh damping. The shear damping model demonstrates a different physical behaviour of the soil, in comparison to the Rayleigh damping.

scholarly journals Model Updating for Systems with General Proportional Damping Using Complex FRFs

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xinhai Wu ◽  
Huan He ◽  
Yang Liu ◽  
Guoping Chen
Keyword(s):  
Model Updating ◽  
Damping Ratio ◽  
Viscous Damping ◽  
Rayleigh Damping ◽  
Damping Matrix ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Resonance Frequencies ◽  
Updating Procedure ◽  
Damping Model

In this paper, we propose a model updating method for systems with nonviscous proportional damping. In comparison to the traditional viscous damping model, the introduction of nonviscous damping will not only reduce the vibration of the system but also change the resonance frequencies. Therefore, most of the existing updating methods cannot be directly applied to systems with nonviscous damping. In many works, for simplicity, the Rayleigh damping model has been applied in the model updating procedure. However, the assumption of Rayleigh damping may result in large errors of damping for higher modes. To capture the variation of modal damping ratio with frequency in a more general way, the diagonal elements of the modal damping matrix and relaxation parameter are updated to characterize the damping energy dissipation of the structure by the proposed method. Spatial and modal incompleteness are both discussed for the updating procedure. Numerical simulations and experimental examples are adopted to validate the effectiveness of the proposed method. The results show that the systems with general proportional damping can be predicted more accurately by the proposed updating method.

A Comparison of Different Models for Beam Vibrations From the Standpoint of Control Design

1990 ◽  
Vol 112 (3) ◽  
pp. 349-356 ◽  
Author(s):  
K. A. Morris ◽  
M. Vidyasagar
Keyword(s):  
Distributed System ◽  
Closed Loop ◽  
Control Design ◽  
Viscous Damping ◽  
Closed Loop System ◽  
Rayleigh Damping ◽  
Negative Results ◽  
Finite Dimensional ◽  
Constant Coefficients ◽  
Damping Model

In this paper we analyze different models for beam vibrations from the standpoint of designing finite-dimensional controllers to stabilize the beam vibrations. We show that a distributed system described by an undamped Euler-Bernoulli equation cannot be stabilized by any finite-dimensional controller, i.e., any controller which can be described an ordinary differential equation with constant coefficients. If viscous damping is included, a similar problem occurs in that all the poles can’t be moved to the left of a given vertical line. These negative results should be interpreted as a commentary on the limitations of these models, rather than on the control of real beams. We then show that if a Rayleigh damping model is used, a finite-dimensional controller may be designed to move the closed loop system poles essentially as far to the left in the complex plane as desired. This result will also hold for certain hysteresis damping models. This has implications for the settling time of the vibrations.

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