The Effect of a Surrounding Fluid on Pressure Waves in a Fluid-Filled Elastic Tube

1955 ◽  
Vol 22 (2) ◽  
pp. 227-231
Author(s):  
M. C. Junger
Keyword(s):  
Sound Velocity ◽  
Surrounding Medium ◽  
Elastic Tube ◽  
Pressure Waves ◽  
End Effects ◽  
Fluid Medium ◽  
Phase Velocities ◽  
Radiation Losses ◽  
Surrounding Fluid ◽  
Theory Of Shells

Abstract The analysis of the transmission of pressure waves in a fluid-filled elastic tube has been extended to the case where the tube is surrounded by a fluid medium. The sound pressure inside the tube is the resultant of a number of modes, some of which are nonpropagating, while others propagate at their own characteristic phase velocities. Neglecting end effects, and for continuously generated waves, it is found that only the modes whose velocity is larger than the sound velocity of the surrounding medium radiate sound energy radially outward. These modes will be damped out by radiation losses, while modes having a phase velocity smaller than this sound velocity are propagated without attenuation (if viscous and heat-transfer losses are neglected). Consequently, if the fluid is the same in the surrounding medium and in the tube only the lowest mode, which resembles a plane wave, propagates unattenuated. In any case, the mass-loading of the surrounding fluid lowers the phase velocities of the propagating modes, particularly at intermediate frequencies. It is shown that in this application the membrane theory of shells will lead to incorrect results, even in thin-walled tubes. This is illustrated by comparison with experimental data.

Net flow generation in closed-loop valveless pumping

2020 ◽  
Vol 234 (11) ◽  
pp. 2126-2142 ◽  
Author(s):  
Christos Manopoulos ◽  
Sokrates Tsangaris ◽  
Dimitrios Mathioulakis
Keyword(s):  
Flow Rate ◽  
Closed Loop ◽  
Simultaneous Recording ◽  
Elastic Tube ◽  
Fluid Medium ◽  
Flexible Tube ◽  
Flow Generation ◽  
Valveless Pumping ◽  
Valveless Pump ◽  
Flexible Walls

Net flow generation in valveless pumping, met in many physiological applications and recently in micropumping devices, constitutes an open fluid dynamics issue due to the complex interaction between the fluid medium and the flexible walls of the pump. In the context of the present experimental work, the conditions of the net flow generation are examined in a closed-loop horizontal valveless pump, which consists of a rigid and an elastic tube of equal diameters and lengths, and a pincher that forces the liquid within the tube to oscillate at Reynolds and Womersley numbers up to 7800 and 48, respectively. Pinching off as well as at the mid-length of the pump flexible tube, net flow is generated at certain pinching frequencies for which details are presented based on simultaneous recording of the pressure at the two tube junctions, the flow rate and the displacement of the pincher. Pinching off the mid-length of the pump at low pinching frequencies, net flow rate is practically null due to the almost identical pressure waveforms at the tube junctions, which vary in phase with the pincher motion. However, close to the first natural frequency of the hydraulic loop, the reflection of the pressure waves at the tube junctions combined with their increased phase difference cause high axial pressure gradients, which when they increase simultaneously with the squeezing of the tube, net flow rate maximization occurs. Pinching at the flexible tube mid-length area, nonzero net flow rates can also be generated, the sign of which changes when the pincher mid-point crosses the tube mid-length without being nullified.

The Fine Structure of the Cockroach Subgenual Organ

1970 ◽  
Vol 28 ◽  
pp. 80-81
Author(s):  
David T. Moran
Keyword(s):  
Fine Structure ◽  
Circulatory System ◽  
Epidermal Cells ◽  
Mechanical Stimuli ◽  
Sense Organs ◽  
Fluid Medium ◽  
Blaberus Discoidalis ◽  
Highly Sensitive ◽  
Surrounding Fluid ◽  
Subgenual Organ

Insects are abundantly endowed with mechanoreceptors, sense organs that transduce mechanical stimuli into nerve impulses. Like most cockroaches, Blaberus discoidalis is highly sensitive to vibrations of the substrate on which it walks. This sensitivity is thought to be due in large part to the subgenual organ — an intricately constructed mechanoreceptor located near the proximal end of the tibia. The exoskeleton of the cockroach is secreted by a layer of epidermal cells which enclose the haemocoele of animal's open circulatory system. The subgenual organ is a thin, fan-shaped flap of tissue which is suspended from the epidermis and occludes much of the dorsal blood space in the hollow leg. It is therefore surrounded by blood on all sides; its position renders it susceptible to minor displacements of the surrounding fluid medium. Highly modified epidermal cells which are packed with hundreds of parallel microtubules support the subgenual organ as a ligament. The cells which compose the bulk of the organ are populated with a few mitochondria and many microtubules.

Advanced Pipeline Vibroacoustic Monitoring

2013 ◽  
Author(s):  
Giancarlo Bernasconi ◽  
Silvio Del Giudice ◽  
Giuseppe Giunta ◽  
Francesco Dionigi
Keyword(s):  
Environmental Sustainability ◽  
Oil And Gas ◽  
Surrounding Medium ◽  
Third Party ◽  
Pressure Waves ◽  
Elastic Parameters ◽  
Gas Industry ◽  
Acoustic Data ◽  
Key Factor ◽  
Fluid Properties

Remote real-time monitoring of pipelines reliability is becoming a key factor for the environmental sustainability of oil&gas industry. Multipoint Acoustic Sensing (MAS) technology makes use of multi sensors placed at discrete distances to detect Third Party Interference (TPI) and fluid leaks along the pipeline. In fact, any interaction with the pipe generates pressure waves that are guided within the fluid (gas or oil) for long distances, carrying information on the source event. Pressure propagation is mainly governed by the absorption coefficient and the sound speed. These parameters are in turn complicated functions of the frequency, the geometrical and elastic parameters of the pipe shell, the elastic parameters of the surrounding medium, and the acoustic and thermodynamic properties of the transported fluid. We have analyzed these aspects while processing acoustic data collected on crude oil and gas transportation pipelines, in different operational and flow conditions. This study describes the acquisition campaigns and the data analysis steps used for the experimental derivation of fluid properties and pipe anomalies. The results are also used for the validation of mathematical models of pressure waves propagation in fluid filled pipes.

Transient Response of Viscoplastic and Viscoelastic Shells Submerged in Fluid Media

1976 ◽  
Vol 43 (1) ◽  
pp. 137-143 ◽  
Author(s):  
T. A. Duffey
Keyword(s):  
Surrounding Medium ◽  
Viscoelastic Behavior ◽  
Rate Sensitivity ◽  
Viscoelastic Materials ◽  
Elementary Functions ◽  
Fluid Medium ◽  
Fluid Media ◽  
Viscoelastic Shells ◽  
Interaction Problem ◽  
Linearly Elastic Materials

The transient fluid-shell interaction problem is investigated for thin shells constructed of other than linearly elastic materials. Specifically, solutions are developed in terms of elementary functions for the transient responses of impulsively loaded, fluid-surrounded spherical shells constructed of either viscoplastic or viscoelastic materials. In all cases the fluid medium surrounding the shell is taken as inviscid and compressible and only spherically symmetric shell motions and radiation of sound into the surrounding medium are considered. It is found that the influence of material strain hardening and strain-rate sensitivity can be significant in reducing fluid-shell displacement responses. Further, limited investigations for viscoelastic materials indicate that for higher loss materials, displacement response of the shell is significantly altered by the inclusion of the viscoelastic behavior.

scholarly journals Buckling of a Short Cylindrical Shell Surrounded by an Elastic Medium

1999 ◽  
Vol 67 (1) ◽  
pp. 212-214 ◽  
Author(s):  
S. Naili ◽  
C. Oddou
Keyword(s):  
Tube Wall ◽  
Surrounding Medium ◽  
External Pressure ◽  
Elastic Tube ◽  
Geometrical Parameters ◽  
Buckling Mode ◽  
Uniform External Pressure ◽  
Cylindrical Structure ◽  
Thin Tube ◽  
Theoretical Results

The lateral surface of a cylindrical structure, which is composed of a thin tube embedded in a large outer medium, is submitted to a uniform external pressure. The buckling pressure of such a structure, corresponding to a low flexural state of the inner tube wall, is theoretically analyzed on the basis of the asymptotic method. The theoretical results are compared with experimental ones obtained from a compression test realized on an elastic tube inserted in a foam. It is found that the Euler pressure and the associated buckling mode index strongly depend upon the rheological and geometrical parameters of both the tube and the surrounding medium. [S0021-8936(00)00201-4]

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