Damping Effect on Mechanical Waves in an Elastic Solid Expanded Tubular

2006 ◽  
Vol 129 (4) ◽  
pp. 698-712
Author(s):  
A. Karrech ◽  
A. Seibi ◽  
T. Pervez
Keyword(s):  
Mathematical Model ◽  
Wave Propagation ◽  
Pressure Wave ◽  
Elastic Solid ◽  
Tube System ◽  
Structure Interaction ◽  
Damping Effect ◽  
Elastic Tubes ◽  
Mechanical Waves ◽  
Critical Regions

The present paper studies the dynamics of submerged expanded elastic tubes due to postexpansion sudden mandrel release known as pop-out phenomenon. A mathematical model describing the dynamics of the borehole-fluid-tube system is presented. Coupling of the fluid-structure interaction and damping effects were taken into consideration. An analytical solution for the displacement, stress, and pressure wave propagation in the fluid-tube system was obtained. The developed model predicted localized critical regions where the structure might experience failure.

The Pathogenesis of Syringomyelia: A Re-Evaluation of the Elastic-Jump Hypothesis

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
N. S. J. Elliott ◽  
D. A. Lockerby ◽  
A. R. Brodbelt
Keyword(s):  
Spinal Cord ◽  
Wave Propagation ◽  
Subarachnoid Space ◽  
Pressure Wave ◽  
Fluid Accumulation ◽  
Elastic Tubes ◽  
Spinal Subarachnoid Space ◽  
Poor Treatment ◽  
Relative Rarity ◽  
Set Up

Syringomyelia is a disease in which fluid-filled cavities, called syrinxes, form in the spinal cord causing progressive loss of sensory and motor functions. Invasive monitoring of pressure waves in the spinal subarachnoid space implicates a hydrodynamic origin. Poor treatment outcomes have led to myriad hypotheses for its pathogenesis, which unfortunately are often based on small numbers of patients due to the relative rarity of the disease. However, only recently have models begun to appear based on the principles of mechanics. One such model is the mathematically rigorous work of Carpenter and colleagues (2003, “Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 1: Basic Theory,” ASME J. Biomech. Eng., 125(6), pp. 852–856; 2003, “Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 2: Mechanisms for the Pathogenesis of Syringomyelia,” ASME J. Biomech. Eng., 125(6), pp. 857–863). They suggested that a pressure wave due to a cough or sneeze could form a shocklike elastic jump, which when incident at a stenosis, such as a hindbrain tonsil, would generate a transient region of high pressure within the spinal cord and lead to fluid accumulation. The salient physiological parameters of this model were reviewed from the literature and the assumptions and predictions re-evaluated from a mechanical standpoint. It was found that, while the spinal geometry does allow for elastic jumps to occur, their effects are likely to be weak and subsumed by the small amount of viscous damping present in the subarachnoid space. Furthermore, the polarity of the pressure differential set up by cough-type impulses opposes the tenets of the elastic-jump hypothesis. The analysis presented here does not support the elastic-jump hypothesis or any theory reliant on cough-based pressure impulses as a mechanism for the pathogenesis of syringomyelia.

A Study for Theoretical Modeling of Cavitation Inducement From the Solid-Fluid Interface With Fluid-Structure Interaction

2018 ◽  
Author(s):  
Tomohisa Kojima ◽  
Kazuaki Inaba ◽  
Yuto Takada
Keyword(s):  
Wave Propagation ◽  
Fracture Mechanics ◽  
Pressure Wave ◽  
Fluid Structure Interaction ◽  
Initial Crack ◽  
Elastic Tube ◽  
Fluid Interface ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Cavitation Intensity

A theoretical model was explored for predicting cavitation generation from a solid-fluid interface with fluid-structure interaction. Predicting cavitation generation is crucial to evaluate the lifetime of fluid machines. Cavitation has been generated from a solid-fluid interface with tensile stress (pressure) wave propagation across the interface. It was revealed that cavitation generation was suppressed when the surface wettability of the solid in a solid-fluid interface was improved (hydrophilized). It means that a condition exists in which cavitation is not generated despite the existence of bubble nuclei in water. This phenomenon cannot be explained by the conventional theory of fluid mechanics. In this study, an analogy between the theory of crack propagation in fracture mechanics and cavitation generation and propagation from a solid-fluid interface with fluid-structure interactions is developed and applied. An impact experiment was conducted with a free-falling projectile that hit a cylindrical solid buffer placed on top of a water surface within an elastic tube standing on the ground. The projectile impact created a stress wave propagating through the buffer and across the interface of the buffer and water. During the experiments, cavitation bubbles were generated from the interface of the buffer and water due to tensile wave propagation across the interface. Cavitation intensity was controlled by adding a surfactant to water. A bubble was set on the solid-fluid interface beforehand, then its growth with stress (or pressure) wave propagation was observed. The formularization of cavitation occurrence was tested by using initial crack length and stress in fracture mechanics as an analogy for the diameter of pre-set bubble and pressure wave amplitude.

Wave Propagation Across the Interface of Fluid-Structure Interaction With Various Surface Conditions of Solid Medium

2016 ◽  
Author(s):  
Tomohisa Kojima ◽  
Kazuaki Inaba ◽  
Kosuke Takahashi
Keyword(s):  
Contact Angle ◽  
Wave Propagation ◽  
Pressure Wave ◽  
Solid Medium ◽  
Surface Condition ◽  
Fluid Structure Interaction ◽  
Fluid Interface ◽  
Fluid Structure ◽  
Surface Conditions ◽  
Structure Interaction

This study aims to clarify the effect of surface conditions of solid on wave propagation at solid-fluid interface with fluid-structure interaction. Although many studies have been done to develop the theoretical models of fluid-structure interaction caused by wave propagation, they do not take into account the surface conditions of the solid medium on the solid-fluid interface where interaction occurs. In this study, we experimentally investigated the wave propagation across the solid-fluid interface with several value of surface wettabilities and roughnesses of solid. We conducted an impact experiment with a free-falling projectile which hit the cylindrical solid buffer placed on top of the water surface within the elastic tube standing on the ground. During the experiments, cavitation bubbles were generated from the interface of the buffer and water. That generation was inhibited according to the decrease of the value of the contact angle (improve of the wettability) of the buffer surface. The amplitude of transmitted pressure wave from the buffer to water become smaller than the theoretical value according to the decrease of the value of the contact angle on the buffer surface (the smallest value was 55% of the theoretical value). Concerning the surface roughness, the amplitude of transmitted pressure wave becomes smaller than the theoretical value according to the shape of the buffer surface become more different from flat surface (the smallest value was 75% of the theoretical value). These experimental results indicate that by taking into account the surface condition of the solid on the interface, more accurate model of fluid-structure interaction or ways to reduce the damage of structures by fluid-structure interaction would be proposed.

Mathematical Model of Wave Propagation in Thermo-Magneto-Piezoelectric Elastic Solid Bar Immersed in an Inviscid Fluid

2017 ◽  
Vol 14 (8) ◽  
pp. 3764-3771
Author(s):  
S. R Mahmoud ◽  
E. O Alzahrani ◽  
A. K Alzahrani ◽  
E Ghandourah ◽  
Shafeek A Ghaleb
Keyword(s):  
Mathematical Model ◽  
Wave Propagation ◽  
Elastic Solid ◽  
Inviscid Fluid
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