Experiment of Chaotic Vibration of Loosely Supported Tube Rows in Cross-Flow

1995 ◽  
Vol 117 (3) ◽  
pp. 204-212 ◽  
Author(s):  
S. S. Chen ◽  
S. Zhu ◽  
Y. Cai
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Unsteady Flow ◽  
Cross Flow ◽  
Mean Square ◽  
Support Plate ◽  
Chaotic Vibration ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Inactive Mode

A tube array supported by baffle plates in cross-flow may be subjected to fluidelastic instability in the tube-support-plate-inactive mode. An experimental study is presented to characterize the tube motion. Three series of tests were performed to measure tube displacements as a function of flow velocity for differing clearances. The motion was examined by root-mean-square values of tube displacements, power spectral densities, phase planes, Poincare´ maps, and Lyapunov exponents. The experimental data agree reasonably well with an analytical model based on the unsteady flow theory.

Flow-Induced Vibration of Cross-Shaped Tube Bundle: The Effect of Tube Bundle Arrangement

2003 ◽  
Author(s):  
Fumio Inada ◽  
Takashi Nishihara ◽  
Akira Yasuo ◽  
Ryo Morita ◽  
Akihiro Sakashita ◽  
...  
Keyword(s):  
Correlation Length ◽  
Random Vibration ◽  
Tube Bundle ◽  
Cross Flow ◽  
Flow Induced Vibration ◽  
Power Spectral ◽  
Shaped Tube ◽  
Excited Vibration ◽  
Power Spectral Densities ◽  
Staggered Arrangement

A cross-shaped tube bundle is proposed for the lower plenum structure in the next-generation LWR. The effect of tube bundle arrangement on the flow-induced vibration characteristics of the cross-shaped tube bundle in cross flow was considered experimentally. Regarding random vibration, the power spectral density of the fluid force of the staggered arrangement as well as the correlation length was measured and those of the normal arrangement were compared with those of the staggered arrangement. Regarding self-excited vibration, vibration response was compared. The trend of the power spectral densities, correlation length, and the critical velocity of the normal arrangement were similar to those of the staggered arrangement.

scholarly journals A minimal time-scale for the spectral states of GX 339−4

2020 ◽  
Vol 499 (2) ◽  
pp. 2513-2522
Author(s):  
E Sonbas ◽  
K Mohamed ◽  
K S Dhuga ◽  
A Tuncer ◽  
E Göğüş
Keyword(s):  
Black Hole ◽  
Root Mean Square ◽  
Time Scale ◽  
Power Spectra ◽  
Mean Square ◽  
X Ray ◽  
Minimal Time ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Spectral States

ABSTRACT Black hole transients are known to undergo spectral transitions that form q-shaped tracks on a hardness intensity diagram. In this work, we use the archival Rossi X-ray Timing Explorer data to extract a characteristic minimal time-scale for the spectral states in GX 339−4 for the 2002–2003 and 2010 outbursts. We use the extracted time-scale to construct an intensity variability diagram for each outburst. This new diagram is comparable to the traditional hardness intensity diagram and offers the potential for probing the underlying dynamics associated with the evolution of the relevant emission regions in black hole transients. We confirm this possibility by connecting the minimal time-scale with the inner disc radius, Rin (estimated from spectral fits), and demonstrate a positive correlation between these variables as the system evolves through its spectral transitions. Furthermore, we probe the relation between the minimal time-scale and the break frequencies extracted from the power spectral densities. Lastly, we examine a possible link between the extracted time-scale and a traditional measure of variability, i.e. the root mean square, determined directly from the power spectra.

scholarly journals A Theory for Fluidelastic Instability of Tube-Support-Plate-Inactive Modes

1992 ◽  
Vol 114 (2) ◽  
pp. 139-148 ◽  
Author(s):  
Y. Cai ◽  
S. S. Chen ◽  
S. Chandra
Keyword(s):  
Heat Exchangers ◽  
Linear Models ◽  
Cross Flow ◽  
Bilinear Model ◽  
Steam Generators ◽  
Unstable Region ◽  
Fluid Forces ◽  
Support Plate ◽  
Fluidelastic Instability ◽  
Inactive Mode

Fluidelastic instability of loosely supported tubes, vibrating in a tube support plate (TSP)-inactive mode, is suspected to be one of the main causes of tube failure in some operating steam generators and heat exchangers. This paper presents a mathematical model for fluidelastic instability of loosely supported tubes exposed to nonuniform cross flow. The model incorporates all motion-dependent fluid forces based on the unsteady-flow theory. In the unstable region associated with a TSP-inactive mode, tube motion can be described by two linear models: TSP-inactive mode when tubes do not strike the TSP, and TSP-active mode when tubes do strike the TSP. The bilinear model (consisting of these linear models) presented here simulates the characteristics of fluidelastic instability of loosely supported tubes in stable and unstable regions associated with TSP-inactive modes. Analytical results obtained with the model are compared with published experimental data; they agree reasonably well. The prediction procedure presented for the fluidelastic instability response of loosely supported tubes is applicable to the stable and unstable regions of the TSP-inactive mode.

Chaotic Vibration in Fluid-Stiffness-Controlled Instability of a Tube Row in Crossflow

1996 ◽  
Vol 63 (2) ◽  
pp. 487-492 ◽  
Author(s):  
S. H. Chen ◽  
S. S. Chen
Keyword(s):  
Analytical Model ◽  
Heat Exchangers ◽  
Chaotic Motion ◽  
Elastic Instability ◽  
Bifurcation Diagrams ◽  
Spectral Densities ◽  
Chaotic Vibration ◽  
Power Spectral ◽  
Tube Arrays ◽  
Power Spectral Densities

The fluid-elastic instability of tube arrays in heat exchangers may become chaotic, especially when clearances exist between tubes and supports. When chaotic motion appears in tube arrays, significant sliding between the tubes and supports may be induced. An analytical model, consisting of a row of rigid tubes with three tubes supported by springs, is presented. Bifurcation diagrams, Poincare´ maps, power spectral densities, and tube orbits are used to investigate the conditions under which the unpredictable motion can arise. The emphasis is on fluid-stiffness-controlled instability.

scholarly journals Transmission of lateral vibrations to children during car traveling and possibilities for their reduction

2019 ◽  
Vol 287 ◽  
pp. 03007
Author(s):  
Nikolay Pavlov ◽  
Evgeni Sokolov ◽  
Emil Iontchev ◽  
Rossen Miletiev ◽  
Mihail Peychev
Keyword(s):  
Root Mean Square ◽  
Tilt Angle ◽  
Lateral Acceleration ◽  
Mean Square ◽  
Special Design ◽  
Lateral Vibrations ◽  
Road Section ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Technical Solutions

The publication addresses the need for technical solutions to reduce the transmission of lateral vibrations to passengers, especially children traveling by car in a child seat. A special design of a pendulum type tilting child seat has been proposed. Results of road trial conducted on a specific mountain road section are shown. The differences in the values of lateral accelerations acting on a child traveling in a conventional and in a tilting seat are given. The power spectral densities of lateral accelerations for both types of child seats are presented and compared. The root mean square values of lateral acceleration are given. Results for the values of the seat tilt angle are presented.

scholarly journals Dynamic Characteristics of Heat Exchanger Tubes Vibrating in a Tube Support Plate Inactive Mode

1986 ◽  
Vol 108 (3) ◽  
pp. 256-266 ◽  
Author(s):  
J. A. Jendrzejczyk
Keyword(s):  
Experimental Study ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Damping Ratio ◽  
Steam Generators ◽  
Support Plate ◽  
Interaction Dynamics ◽  
Fabrication Tolerances ◽  
Shell And Tube ◽  
Inactive Mode

Tubes in shell-and-tube heat exchangers, including nuclear plant steam generators, derive their support from longitudinally positioned tube support plates (TSPs). Typically, there is a clearance between the tube and TSP hole. Depending on design and fabrication tolerances, the tube may or may not contact all of the TSPs. Non-contact results in an inactive TSP which can lead to detrimental flow-induced tube vibrations under certain conditions dependent on the resulting tube-TSP interaction dynamics and the fluid excitation forces. The purpose of this study is to investigate the tube-TSP interaction dynamics. Results of an experimental study of damping and natural frequency as functions of tube-TSP diametral clearance and TSP thickness are reported. Calculated values of damping ratio and frequency of a tube vibrating within an inactive TSP are also presented together with a comparison of calculated and experimental quantities.

scholarly journals Chaotic Vibrations of Nonlinearly Supported Tubes in Crossflow

1993 ◽  
Vol 115 (2) ◽  
pp. 128-134 ◽  
Author(s):  
Y. Cai ◽  
S. S. Chen
Keyword(s):  
Mathematical Model ◽  
Instability Region ◽  
Phase Portraits ◽  
Bifurcation Diagrams ◽  
Chaotic Motions ◽  
Support Plate ◽  
Chaotic Vibrations ◽  
Power Spectral ◽  
Fluid Damping ◽  
Inactive Mode

Chaotic vibrations associated with the fluidelastic instability of nonlinearly supported tubes in a crossflow is studied theoretically on the basis of the unsteady-flow theory and a bilinear mathematical model. Effective tools, including phase portraits, power spectral density, Poincare maps, Lyapunov exponent, fractal dimension, and bifurcation diagrams, are utilized to distinguish periodic and chaotic motions when the tubes vibrate in the instability region. The results show periodic and chaotic motions in the region corresponding to fluid-damping-controlled instability. Nonlinear supports, with symmetric or asymmetric gaps, significantly affect the distribution of periodic, quasi-periodic, and chaotic motions of a tube exposed to various flow velocities in the instability region of the tube-support-plate-inactive mode.

On the Accuracy of Parametric and Classical Spectra

1988 ◽  
Vol 110 (2) ◽  
pp. 213-219 ◽  
Author(s):  
S. Braun ◽  
A. Sneor
Keyword(s):  
Experimental Data ◽  
Spectral Densities ◽  
Random Inputs ◽  
Fourier Methods ◽  
Spectral Estimates ◽  
Power Spectral ◽  
Power Spectral Densities

This work investigates the accuracy of spectral estimates computed via parametric techniques. Comparisons with results obtained via classical Fourier methods are also presented. The PSD’s (power spectral densities) investigated are of the type encountered in low damped structures excited by random inputs. Qualitative results are shown for simulated as well as experimental data. The results substantiate the claims for the smoothness of parametric spectra, but not the improved resolution capabilities.

EXPERIMENTAL STUDY OF THE KINEMATIC PARAMETERS OF MOVEMENT OF CARS FORCED IDLE MOTION

2018 ◽  
pp. 52-57
Author(s):  
Ivelin Kostov
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Experimental Research ◽  
Kinematic Parameters ◽  
Research Results ◽  
Software Product

In the work brought some experimental data of kinematic parameters of movement of cars forced idle, as the software product was used to diagnose 900 ATS, which recorded kinematic parameters of vehicle. On the basis of the conducted experimental research results are shown tabulated and analysed.

Sign in / Sign up

Export Citation Format

Share Document