Analysis of Flow Induced Vibration Using the Vorticity Transport Equation

1993 ◽  
Vol 115 (3) ◽  
pp. 485-492 ◽  
Author(s):  
Jure Marn ◽  
Ivan Catton
Keyword(s):  
Parametric Analysis ◽  
Dynamic Instability ◽  
Equations Of Motion ◽  
Fluid Motion ◽  
Governing Equations ◽  
Flow Induced Vibration ◽  
The Subject ◽  
An Array Of Cylinders ◽  
Vorticity Transport ◽  
Square Array

Crossflow induced vibrations are the subject of this work. The analysis is two dimensional. The governing equations for fluid motion are solved using linearized perturbation theory and coupled with the equations of motion for cylinders to yield the threshold of dynamic instability for an array of cylinders. Parametric analysis is performed to determine the lowest instability threshold for a rotated square array and correlations are developed relating the dominant parameters. The results are compared with theoretical and experimental data for similar arrays and the discrepancies are discussed.

Stability of asymmetric rotors with asymmetric flexible disks

2021 ◽  
pp. 107754632110004
Author(s):  
Naim Khader
Keyword(s):  
Equations Of Motion ◽  
Ritz Method ◽  
Lagrangian Approach ◽  
Governing Equations ◽  
Stability Boundaries ◽  
System Solution ◽  
Asymmetric Rotor ◽  
Constant Coefficients ◽  
The Subject ◽  
Flexible Disk

The presented work examines the dynamic behavior of an asymmetric rotor with asymmetric flexible disk, contrary to previous works on the subject, where researchers examined the effect of either rigid disk asymmetry or disk flexibility at a time. Account for the asymmetry of flexible disk in rotors constitutes the new contribution in this work. The suggested mathematical model combines Lagrangian approach with Rayleigh–Ritz method to derive the governing equations of motion of the rotor. Account for asymmetry of the flexible disk results in complicated and lengthy expressions for the potential and kinetic energies of the rotor, required in the adopted Lagrangian approach. Using symbolic computation simplified the derivation of the governing equations of motion with constant coefficients in terms of rotating coordinate system. Solution of the resulting eigenvalue problem provided numerical results for rotors with symmetric and asymmetric flexible disks, required to assess the effect of disk flexibility and asymmetry on the resulting frequencies and stability boundaries of the examined rotor system.

scholarly journals Flow and heat transfer in MHD visco-elastic fluid with ohmic heating

2016 ◽  
Vol 12 (1) ◽  
Author(s):  
Bandita Das ◽  
Rita Choudhury
Keyword(s):  
Ohmic Heating ◽  
Perturbation Technique ◽  
Equations Of Motion ◽  
Fluid Motion ◽  
Concentration Field ◽  
Governing Equations ◽  
Free Convective Flow ◽  
Flow And Heat Transfer ◽  
Graphical Illustration ◽  
Infinite Vertical Plate

An investigation is made of the motion of a visco-elastic, MHD free convective flow and mass transfer past an infinite vertical plate. The effects of ohmic heating and viscous dissipation are taken into account. For solving the non-dimensional governing equations of motion perturbation technique has been into used and the important properties of the overall structure of the fluid motion are studied. The effect of various parameters of the velocity field, concentration field and temperature distribution are discussed with the help of graphical illustration.

The Skateboard Speed Wobble

2015 ◽  
Author(s):  
Marco Rosatello ◽  
Jean-Luc Dion ◽  
Franck Renaud ◽  
Luigi Garibaldi
Keyword(s):  
Vehicle Dynamics ◽  
Dynamic Instability ◽  
Equations Of Motion ◽  
Stability Study ◽  
Loss Of Control ◽  
Parametric Stability ◽  
Human Control ◽  
Multipliers Method ◽  
The Subject ◽  
Lagrange Formalism

The speed wobble is a phenomenon in nonlinear dynamics that can occur in many vehicles such as bicycles, motorbikes, skateboards and airplanes nose landing gear. The dynamic instability affects the steerable wheels of a vehicle and can lead to the loss of control. While for bikes, motorbikes and airplanes the dynamics and causes of the wobble are well known and the literature fully describes the subject, for the skateboard the literature is very poor and there is no paper which investigates this type of instability. In order to do that, the skateboard equations of motion were obtained through Lagrange formalism and Lagrange multipliers method was used to solve the non-holonomic constraints. A parametric stability study was carried out on the linearized equations of motion and the influence of different skateboard parameters was investigated. The main discovery is that the wobble doesn’t strictly depend on skateboard configuration, but the human control characteristics are predominant in the vehicle dynamics.

Article

1998 ◽  
Vol 76 (9) ◽  
pp. 739-746
Author(s):  
H A Attia
Keyword(s):  
Energy Equation ◽  
Constant Pressure ◽  
Viscous Incompressible Fluid ◽  
Equations Of Motion ◽  
Fluid Motion ◽  
Governing Equations ◽  
Electrically Conducting ◽  
Flow And Heat Transfer ◽  
Temperature Distributions ◽  
External Uniform Magnetic Field

The unsteady flow and heat transfer of an electrically conducting, viscous, incompressible fluid bounded by two parallel nonconducting porous plates are studied taking the Hall effect into consideration. An external uniform magnetic field is applied normal to the plates, and the fluid motion is subjected to a constant pressure gradient and a uniform suction and injection. An analytical solution for the governing equations of motion is obtained and a numerical solution for the energy equation including the Joule and the viscous dissipation terms is developed. The effect of the Hall term on both the velocity and temperature distributions is examined.PACS No.: 47.70

Model of vortex flow of charge in a vessel with turbine impeller

1987 ◽  
Vol 52 (8) ◽  
pp. 1888-1904
Author(s):  
Miloslav Hošťálek ◽  
Ivan Fořt
Keyword(s):  
Boundary Conditions ◽  
Equations Of Motion ◽  
Theoretical Data ◽  
Eddy Diffusion ◽  
Quantitative Agreement ◽  
Creeping Flow ◽  
Model Parameters ◽  
Mean Flow ◽  
Two Dimensional Flow ◽  
Vorticity Transport

A theoretical model is described of the mean two-dimensional flow of homogeneous charge in a flat-bottomed cylindrical tank with radial baffles and six-blade turbine disc impeller. The model starts from the concept of vorticity transport in the bulk of vortex liquid flow through the mechanism of eddy diffusion characterized by a constant value of turbulent (eddy) viscosity. The result of solution of the equation which is analogous to the Stokes simplification of equations of motion for creeping flow is the description of field of the stream function and of the axial and radial velocity components of mean flow in the whole charge. The results of modelling are compared with the experimental and theoretical data published by different authors, a good qualitative and quantitative agreement being stated. Advantage of the model proposed is a very simple schematization of the system volume necessary to introduce the boundary conditions (only the parts above the impeller plane of symmetry and below it are distinguished), the explicit character of the model with respect to the model parameters (model lucidity, low demands on the capacity of computer), and, in the end, the possibility to modify the given model by changing boundary conditions even for another agitating set-up with radially-axial character of flow.

Simulation of Engine Vibration on Nonlinear Hydraulic Engine Mounts

2005 ◽  
Author(s):  
A. R. Ohadi ◽  
G. Maghsoodi
Keyword(s):  
Equations Of Motion ◽  
Low Frequency ◽  
Governing Equations ◽  
Engine Mounts ◽  
Engine Vibration ◽  
Engine Mount ◽  
Rotational Motions ◽  
The Time Domain ◽  
Nonlinear Equations Of Motion ◽  
Four Cylinders

In this paper, vibration behavior of engine on nonlinear hydraulic engine mount including inertia track and decoupler is studied. In this regard, after introducing the nonlinear factors of this mount (i.e. inertia and decoupler resistances in turbulent region), the vibration governing equations of engine on one hydraulic engine mount are solved and the effect of nonlinearity is investigated. In order to have a comparison between rubber and hydraulic engine mounts, a 6 degree of freedom four cylinders V-shaped engine under inertia and balancing masses forces and torques is considered. By solving the time domain nonlinear equations of motion of engine on three inclined mounts, translational and rotational motions of engines body are obtained for different engine speeds. Transmitted base forces are also determined for both types of engine mount. Comparison of rubber and hydraulic mounts indicates the efficiency of hydraulic one in low frequency region.

Reduction of Noise Inside a Cavity by Piezoelectric Actuators

2003 ◽  
Vol 125 (1) ◽  
pp. 12-17 ◽  
Author(s):  
I. Hagiwara ◽  
D. W. Wang ◽  
Q. Z. Shi ◽  
R. S. Rao
Keyword(s):  
Sound Pressure ◽  
Control Mechanism ◽  
Equations Of Motion ◽  
Piezoelectric Actuators ◽  
Governing Equations ◽  
Control Laws ◽  
Modal Coupling ◽  
Modal Amplitude ◽  
Global And Local ◽  
Fully Coupled

A new analytical model is developed for the reduction of noise inside a cavity using distributed piezoelectric actuators. A modal coupling method is used to establish the governing equations of motion of the fully coupled acoustics-structure-piezoelectric patch system. Two performance functions relating “global” and “local” optimal control of sound pressure levels (SPL) respectively are applied to obtain the control laws. The discussions on associated control mechanism show that both the mechanisms of modal amplitude suppression and modal rearrangement may sometimes coexist in the implementation of optimal noise control.

Influence of Material Damping on In-Plane Modal Parameters for Rotating Disks

2012 ◽  
Author(s):  
Hamid R. Hamidzadeh ◽  
Ehsan Sarfaraz
Keyword(s):  
Elastic Moduli ◽  
Damping Ratio ◽  
Equations Of Motion ◽  
Elastic Stability ◽  
Rotating Disks ◽  
Governing Equations ◽  
Annular Disk ◽  
Stress Theory ◽  
Hysteretic Damping ◽  
Circumferential Wave

The linear in-plane free vibration of a thin, homogeneous, viscoelastic, rotating annular disk is investigated. In the development of an analytical solution, two dimensional elastodynamic theory is employed and the viscoelastic material for the medium is allowed by assuming complex elastic moduli. The general governing equations of motion are derived by implementing plane stress theory. Natural frequencies are computed for several modes at specific radius ratios with fixed-free boundary conditions and modal loss factors for different damping ratios are determined. The computed results were compared to previously established results. It was observed that the effects of rotational speed and hysteretic damping ratio on natural frequency and elastic stability of the rotating disks were related to the mode of vibration and type of circumferential wave occurring.

scholarly journals Conducting dusty fluid flow through a constriction in a porous medium

2016 ◽  
Vol 5 (1) ◽  
pp. 29
Author(s):  
Madhura K R ◽  
Uma M S
Keyword(s):  
Porous Medium ◽  
Hartmann Number ◽  
Equations Of Motion ◽  
Fluid Phase ◽  
Dust Particles ◽  
Governing Equations ◽  
Electrically Conducting ◽  
Electrically Conducting Fluid ◽  
Flow Through ◽  
Constricted Channel

<p><span lang="EN-IN">The flow of an unsteady incompressible electrically conducting fluid with uniform distribution of dust particles in a constricted channel has been studied. The medium is assumed to be porous in nature. The governing equations of motion are treated analytically and the expressions are obtained by using variable separable and Laplace transform techniques. The influence of the dust particles on the velocity distributions of the fluid are investigated for various cases and the results are illustrated by varying parameters like Hartmann number, deposition thickness on the walls of the cylinder and the permeability of the porous medium on the velocity of dust and fluid phase.</span></p>

scholarly journals Vibration Characteristics of Piezoelectric Microbeams Based on the Modified Couple Stress Theory

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
R. Ansari ◽  
M. A. Ashrafi ◽  
S. Hosseinzadeh
Keyword(s):  
Boundary Conditions ◽  
Couple Stress ◽  
Natural Frequencies ◽  
Couple Stress Theory ◽  
Equations Of Motion ◽  
Modified Couple Stress Theory ◽  
Beam Model ◽  
Governing Equations ◽  
Stress Theory ◽  
Modified Couple Stress

The vibration behavior of piezoelectric microbeams is studied on the basis of the modified couple stress theory. The governing equations of motion and boundary conditions for the Euler-Bernoulli and Timoshenko beam models are derived using Hamilton’s principle. By the exact solution of the governing equations, an expression for natural frequencies of microbeams with simply supported boundary conditions is obtained. Numerical results for both beam models are presented and the effects of piezoelectricity and length scale parameter are illustrated. It is found that the influences of piezoelectricity and size effects are more prominent when the length of microbeams decreases. A comparison between two beam models also reveals that the Euler-Bernoulli beam model tends to overestimate the natural frequencies of microbeams as compared to its Timoshenko counterpart.

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