A Study on the Natural Frequencies of Coupled In-Line Towers

1991 ◽  
Vol 113 (1) ◽  
pp. 81-85
Author(s):  
N. Qingde ◽  
C. Jiaqi ◽  
Z. Mingxian ◽  
H. Zenyan
Keyword(s):  
Experimental Data ◽  
Dynamic Analysis ◽  
Analytical Method ◽  
Natural Frequencies ◽  
Wind Loads ◽  
Seismic Loads ◽  
Wind Induced Vibration ◽  
Theoretical Results ◽  
Good Agreement

The natural frequencies of the coupled in-line towers are the most important parameters for dynamic analysis when the designer takes steps to assure that damages due to wind loads, seismic loads, or wind-induced vibration would not occur. In this paper the authors present an analytical method for determining these parameters. The theoretical results are compared with the experimental data obtained from the industrial towers in the field, and are in good agreement.

Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Lift Coefficient ◽  
Cavity Surface ◽  
Air Bubbles ◽  
Incoming Flow ◽  
Fluid Density ◽  
Air Content ◽  
Theoretical Results ◽  
Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

Vibration Characteristics of Straight Blades of Asymmetrical Aerofoil Cross-Section

1969 ◽  
Vol 20 (2) ◽  
pp. 178-190 ◽  
Author(s):  
W. Carnegie ◽  
B. Dawson
Keyword(s):  
Analytical Solution ◽  
Cross Section ◽  
Natural Frequencies ◽  
Equations Of Motion ◽  
Limited Range ◽  
First Order ◽  
Special Cases ◽  
Theoretical Results ◽  
Theoretical Procedure ◽  
Good Agreement

SummaryTheoretical and experimental natural frequencies and modal shapes up to the fifth mode of vibration are given for a straight blade of asymmetrical aerofoil cross-section. The theoretical procedure consists essentially of transforming the differential equations of motion into a set of simultaneous first-order equations and solving them by a step-by-step finite difference procedure. The natural frequency values are compared with results obtained by an analytical solution and with standard solutions for certain special cases. Good agreement is shown to exist between the theoretical results for the various methods presented. The equations of motion are dependent upon the coordinates of the axis of the centre of flexure of the beam relative to the centroidal axis. The effect of variations of the centre of flexure coordinates upon the frequencies and modal shapes is shown for a limited range of coordinate values. Comparison is made between the theoretical natural frequencies and modal shapes and corresponding results obtained by experiment.

Vibration of a Rotating Asymmetric Shaft Supported in Asymmetric Bearings

1968 ◽  
Vol 10 (3) ◽  
pp. 252-261 ◽  
Author(s):  
H. F. Black ◽  
A. J. McTernan
Keyword(s):  
Natural Frequencies ◽  
Equations Of Motion ◽  
Forced Vibrations ◽  
Variation Method ◽  
Approximate Theory ◽  
Cross Sectional ◽  
Mass Unbalance ◽  
The Mean ◽  
Theoretical Results ◽  
Good Agreement

The parametrically excited vibrations of this system with assumed small asymmetry of the shaft cross-section are discussed in terms of the motion of a symmetric shaft having the mean cross-sectional flexibility, and the equations of motion are solved by the approximate perturbation-variation method of Hsu. Both features yield a more lucid appreciation of the motions expected than previous treatments: in particular, simpler explicit expressions for unstable bounds are given and forced vibrations due to mass unbalance are discussed with greater facility. The practically important case of nearly coincident natural frequencies is examined. The theoretical results are compared with analogue computation: good agreement with the approximate theory is found even for quite large shaft asymmetry.

Dynamic Analysis of an Elevator Traveling Cable Using a Singularity-Free Beam Formulation

2017 ◽  
Vol 84 (4) ◽  
Author(s):  
W. Fan ◽  
W. D. Zhu
Keyword(s):  
Dynamic Analysis ◽  
Multibody Dynamics ◽  
Natural Frequencies ◽  
Vertical Motion ◽  
Dynamic Responses ◽  
Mode Shapes ◽  
Out Of Plane ◽  
Forced Responses ◽  
Free Beam ◽  
Good Agreement

A round elevator traveling cable is modeled using a singularity-free beam formulation. Equilibria of the traveling cable with different elevator car positions are studied. Natural frequencies and the corresponding mode shapes of the traveling cable are calculated and they are in excellent agreement with those calculated by abaqus. In-plane natural frequencies of the traveling cable do not change much with the car position compared with its out-of-plane ones. Dynamic responses of the traveling cable are calculated and they are in good agreement with those from commercial multibody dynamics software recurdyn. Effects of vertical motion of the car on free responses of the traveling cable and those of in-plane and out-of-plane building sways on forced responses are investigated.

In-Plane Vibrations of Thick Circular Rings With T or I Cross Sections

1979 ◽  
Vol 46 (2) ◽  
pp. 470-472
Author(s):  
H. Lecoanet ◽  
J. Piranda
Keyword(s):  
Experimental Data ◽  
Eigenvalue Problem ◽  
Cross Section ◽  
Cross Sections ◽  
Rectangular Cross Section ◽  
Circular Rings ◽  
Theoretical Results ◽  
Good Agreement

This paper deals with the problem of eigenfrequencies and eigenvectors for rings whose cross section may be decomposed in basic rectangular cross sections. The solution is derived from a solution of the in-plane eigenvalue problem for rectangular cross-section thick rings. A good agreement between theoretical results and experimental data is obtained.

Analysis of Thermal Effects in Hydrodynamic Bearings

1986 ◽  
Vol 108 (2) ◽  
pp. 219-224 ◽  
Author(s):  
R. Boncompain ◽  
M. Fillon ◽  
J. Frene
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Effects ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Heat Transfer Equation ◽  
Reversed Flow ◽  
Theoretical Results ◽  
Generalized Reynolds Equation ◽  
Good Agreement

A general THD theory and a comparison between theoretical and experimental results are presented. The generalized Reynolds equation, the energy equation in the film, and the heat transfer equation in the bush and the shaft are solved simultaneously. The cavitation in the film, the lubricant recirculation, and the reversed flow at the inlet are taken into account. In addition, the thermoelastic deformations are also calculated in order to define the film thickness. Good agreement is found between experimental data and theoretical results which include thermoelastic displacements of both the shaft and the bush.

Thermal Behavior and Friction in Journal Bearings

1970 ◽  
Vol 92 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Al. Nica
Keyword(s):  
Experimental Data ◽  
Thermal Behavior ◽  
Heat Dissipation ◽  
Journal Bearings ◽  
Friction Torque ◽  
Operating Characteristics ◽  
Lubricant Flow ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Good Agreement

This paper deals with friction and the field of temperature in the lubricant film of journal bearings. Theoretical results regarding the thermal behavior are checked with experimental data and good agreement is found. Emphasis is put on the variation of temperature and lubricant flow with the operating characteristics of the bearing and it is seen that theoretical predictions for minima of friction torque are backed by temperature measurements. Further on, the friction torque and the mechanism of heat dissipation in bearings are dealt with, in order to verify the assumptions used in the calculation schemes. The means of efficiently cooling the bearing are also discussed, as well as the part played by the divergent zone in this process.

scholarly journals Added Mass and Damping of a Vibrating Rod in Confined Viscous Fluids

1976 ◽  
Vol 43 (2) ◽  
pp. 325-329 ◽  
Author(s):  
S. S. Chen ◽  
M. W. Wambsganss ◽  
J. A. Jendrzejczyk
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Cylindrical Shell ◽  
Closed Form Solution ◽  
Added Mass ◽  
Form Solution ◽  
Viscous Fluids ◽  
Series Of Experiments ◽  
Theoretical Results ◽  
Good Agreement

This paper presents an analytical and experimental study of a cylindrical rod vibrating in a viscous fluid enclosed by a rigid, concentric cylindrical shell. A closed-form solution for the added mass and damping coefficient is obtained and a series of experiments with cantilevered rods vibrating in various viscous fluids is performed. Experimental data and theoretical results are in good agreement.

Natural Frequencies and Mode Shapes of Laminated Composite Plates: Experiments and FEA

1996 ◽  
Vol 2 (4) ◽  
pp. 381-414 ◽  
Author(s):  
T.J. Anderson ◽  
A.H. Nayfeh
Keyword(s):  
Natural Frequencies ◽  
Laminated Composite ◽  
Composite Plates ◽  
Test Methods ◽  
Mode Shapes ◽  
Boundary Condi Tions ◽  
Element Analysis ◽  
Condi Tions ◽  
Theoretical Results ◽  
Good Agreement

The natural frequencies and mode shapes of several graphite-epoxy plates were determined using experimental modal analysis and finite-element analysis. The experimental and theoretical results are com pared. The samples tested included four types of layups: ±15°, ±30°, cross-ply, and quasi-isotropic plates. Each plate was tested in three configurations: free-hanging, cantilever, and fixed-fixed for a total of twelve test configurations. The material properties of the plates and the test methods used to obtain them are in cluded. There is a very good agreement between the experimental and theoretical results for the free-hanging and cantilever configurations. The agreement for the fixed-fixed results is poor. This indicates that the clamps for the fixed-fixed configuralion are not ideal and that they introduce some uncertainty in the boundary condi tions. The free-hanging results provide accurate experimental natural frequencies of several composite plates; they can be used to validate future theoretical developments. The fixed-fixed results are used to provide pos sible explanations for the discrepancies between the measured and calculated natural frequencies previously reported in the literature.

On the Minimum Film Boiling Conditions for Spherical Geometries

1980 ◽  
Vol 102 (2) ◽  
pp. 335-341 ◽  
Author(s):  
F. S. Gunnerson ◽  
A. W. Cronenberg
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Flat Plate ◽  
Analytical Method ◽  
Boiling Point ◽  
Film Boiling ◽  
Heater Surface ◽  
Wide Range ◽  
Minimum Heat ◽  
Good Agreement

An analytical method is presented for predicting the minimum heater temperature and the minimum heat flux at the onset of film boiling for spherical and flat plate heaters in saturated and subcooled liquids. Consideration is given to a variety of factors known to affect the minimum film boiling point, including transient liquid-heater contact, interfacial wettability, heater geometry, and liquid subcooling. The theoretical correlations developed are the first known predictions for spherical geometries. A comparison of theory with experimental data indicates good agreement for the minimum heat flux and the minimum film boiling temperature. Results indicate that the minimum conditions may span a wide range depending upon the thermophysical nature of the heater surface and the boiling liquid.

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