Analytical model for thermal boundary conductance based on elastic wave theory

2020 ◽  
Vol 159 ◽  
pp. 120117
Author(s):  
Bin Liu ◽  
Vladimir Ivanovich Khvesyuk
Keyword(s):  
Elastic Wave ◽  
Analytical Model ◽  
Wave Theory ◽  
Thermal Boundary Conductance

Modeling of Tuned Liquid Damper With Submerged Nets

1999 ◽  
Vol 121 (3) ◽  
pp. 334-343 ◽  
Author(s):  
S. Kaneko ◽  
M. Ishikawa
Keyword(s):  
Analytical Model ◽  
Wave Theory ◽  
Damping Factor ◽  
Tuned Liquid Damper ◽  
Liquid Motion ◽  
Tuned Mass Dampers ◽  
Dissipation Energy ◽  
Structure Interaction ◽  
Cable Stayed Bridge ◽  
Optimal Damping

An analytical model for describing the effectiveness of tuned liquid damper (TLD) with submerged nets for suppressing horizontal vibration of structures is proposed. Dissipation energy due to the liquid motion under sinusoidal excitation is calculated based on nonlinear shallow water wave theory. In particular, the effects of hydraulic resistance produced by nets installed in a tank on the performance of TLDs are examined. The results of dissipation energy theoretically obtained are confirmed by experiments. To show the effectiveness of the proposed analytical model for TLD-structure interaction problems, the case in which TLD with nets is installed on top of a pylon of a cable-stayed bridge is described and the calculated results are compared with the actual experimental data. In the calculation, it is shown that the optimal damping factor, as is the case for tuned mass dampers (TMD), can be produced by the nets, and the effectiveness of TLD with nets are demonstrated.

The Button Head Bullet Effects on the Incident Pulse of Split Hopkinson Press Bar

2015 ◽  
Vol 782 ◽  
pp. 311-315
Author(s):  
Jia Qu ◽  
Geng Chen ◽  
Guang Ping Zou
Keyword(s):  
Elastic Wave ◽  
Wave Length ◽  
Constant Strain Rate ◽  
Peak Stress ◽  
Wave Theory ◽  
Pulse Shaper ◽  
Lagrange Method ◽  
Stress Increase ◽  
Split Hopkinson ◽  
Peak Value

In order to make the specimen deformed under a constant strain rate and the stress in the specimen kept homogeneous, the wave shaper technology was adopted to modify the incidence waves of the normal Split Hopkinson Press Bar. A method of changing the shape of the bullet was suggested to be applied on the SHPB. Bullets with different length and different curvature have been researched in this paper. And the effection of the button head bullet about incidence pulse was simulated with Lagrange method by ANSYS/LS-DYNA. It is shown in the results that changing the curvature of the bullet impact the rising edge of incidence waves, and the peak stress increase with the speed of the bullet increase, the peak stress and length of incidence waves increased with the length of the button head bullet, when the peak stress reached a certain strength, increasing the bullet length could make the stress peak value lasted longer. Due to the reason that the button head bullet was based on the elastic wave theory, the wave length and the max stress of the shaped wave would be controlled conveniently and avoid the shortcoming that the analogue specimens could not be recycled in the normal pulse shaper technology.

A cracked porous medium elastic wave theory and its application to interpreting acoustic data from tight formations

Geophysics ◽  
2012 ◽  
Vol 77 (6) ◽  
pp. D245-D252 ◽  
Author(s):  
Xiao-Ming Tang ◽  
Xue-lian Chen ◽  
Xiao-kai Xu
Keyword(s):  
Elastic Wave ◽  
Crack Density ◽  
Measurement Data ◽  
Acoustic Property ◽  
Wave Theory ◽  
Velocity Variation ◽  
Porous Rocks ◽  
Tight Sandstone ◽  
Acoustic Data ◽  
Tight Formations

Rocks in the earth’s crust usually contain pores and cracks. Typical examples include tight sandstone and shale rocks that have low porosity but contain abundant microcracks. By extending the classic Biot’s poroelastic wave theory to include the effects of cracks, we obtain an elastic wave theory for porous rocks containing cracks, adding crack density and aspect ratio as two important parameters to the original theory. Because the flat- or narrow-shaped cracks can easily deform under acoustic wave excitation, the acoustic property of a cracked porous rock is quite different for different saturation conditions. The predicted fluid sensitivity is used to interpret acoustic velocity log data from tight sand and shale gas formations. In both scenarios, the new theory correctly predicts the trend of velocity variation with gas saturation. The results confirm that the presence of cracks in tight rocks can give rise to significant hydrocarbon signature in the acoustic measurement data, allowing for identifying hydrocarbons from the data.

scholarly journals A Semi-Analytical Model for Studying Hydroelastic Behaviour of a Cylindrical Net Cage under Wave Action

2021 ◽  
Vol 9 (12) ◽  
pp. 1445
Author(s):  
Mingyuan Ma ◽  
Hong Zhang ◽  
Dong-Sheng Jeng ◽  
Chien Ming Wang
Keyword(s):  
Analytical Model ◽  
Least Squares Method ◽  
Structural Parameters ◽  
Free Water ◽  
Wave Theory ◽  
Porous Membrane ◽  
Wave Forces ◽  
Different Depths ◽  
Net Cage ◽  
Net Cages

In the present study, a semi-analytical model based on the small-amplitude wave theory is developed to describe the wave fields around a single gravity-type cylindrical open fish net cage. The cage may be submerged to different depths below the free-water surface. The fish cage net is modelled as a flexible porous membrane, and the deflection of the net chamber is expressed by the transverse vibration equation of strings. The velocity potential is expanded in the form of the Fourier–Bessel series and the unknown coefficients in these series are determined from matching the boundary conditions and the least squares method. The number of terms for the series solution to be used is determined from convergence studies. The model results exhibit significant hydroelastic characteristics of the net cages, including the distribution properties of wave surface, pressure drop at the net interface, structural deflection, and wave loading along the cage height. In addition, the relationships between wave forces on the net cage with hydrodynamic and structural parameters are also revealed. The findings presented herein should be useful to engineers who are designing fish cage systems.

Stresses During Impacts on Horizontal Rods

2005 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Elastic Wave ◽  
Maximum Stress ◽  
Wave Theory ◽  
Experimental Results ◽  
Vibration Theory ◽  
Structural Impact ◽  
The Impact ◽  
Insight Into

The impact of an object striking the tip of a horizontally mounted bar provides some insight into the dynamics of structural impact in general. Modeling a cylindrical bar provides significant simplifications to enable comparison between experiment and theory. In particular, experimental results available in the literature are compared herein to both elastic wave theory and vibration theory. Relating these two theories is the focus of this paper. Vibrations can be directly related to the time of impact, the maximum stress at the tip of the bar, and the frequencies of the struck bar. Once these stresses and frequencies are found, elastic wave theory can then be used to describe the stresses throughout the bar.

Inversion of dry and saturated P- and S-wave velocities for the pore-aspect-ratio spectrum using a cracked porous medium elastic wave theory

Geophysics ◽  
2021 ◽  
Vol 86 (6) ◽  
pp. A57-A62
Author(s):  
He-Ming Wang ◽  
Xiao-Ming Tang
Keyword(s):  
Porous Medium ◽  
Aspect Ratio ◽  
Elastic Wave ◽  
Research Work ◽  
Wave Theory ◽  
Wave Dispersion ◽  
Velocity Data ◽  
S Wave ◽  
Ratio Spectrum ◽  
Aspect Ratios

Subsurface rocks contain pores and cracks of various sizes. The cracked porous medium elastic wave theory that describes wave propagation characteristics due to the pore-crack interaction is extended to include cracks of different aspect ratios. The extended theory is applied to model P- and S-wave velocity data of dry and fluid-saturated rock under pressure loading conditions, so as to determine the pore-aspect-ratio spectrum through an inversion procedure. The inversion result is consistent with that from the scanning electron microscope analysis, showing significant improvement versus previous inversion. The inverted pore-aspect-ratio spectrum is input into the wave theory to predict the velocity dispersion of the rock in the full frequency range. The predicted dispersion and its variation trend with pressure agree with the data measured in the (2–200, 106) Hz range at various differential pressures, whereas the modeling using a single-aspect-ratio theory has difficulty matching the data. This research work provides not only a method for analyzing the pore structure characteristics of rocks from the laboratory ultrasonic velocity data, but also a way to predict the seismic wave dispersion from the data.

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