Measurements of wave speed and compliance in a collapsible tube during self-excited oscillations: a test of the choking hypothesis

1991 ◽  
Vol 29 (5) ◽  
pp. 493-500 ◽  
Author(s):  
C. D. Bertram ◽  
C. J. Raymond
Keyword(s):  
Wave Speed ◽  
Collapsible Tube

Measurement of Wall Deformation and Flow Limitation In a Mechanical Trachea

1995 ◽  
Vol 117 (1) ◽  
pp. 146-152 ◽  
Author(s):  
C. Walsh ◽  
P. A. Sullivan ◽  
J. S. Hansen ◽  
L.-W. Chen
Keyword(s):  
Mechanical Model ◽  
Wave Speed ◽  
Nonlinear Material ◽  
Collapsible Tube ◽  
Wall Model ◽  
Rigid Tube ◽  
Long Wave ◽  
Wall Deformation ◽  
Human Trachea ◽  
Material Constitutive Equation

A mechanical model of the human trachea is investigated experimentally. A modified version of an earlier model, it consists of a square sectioned rigid tube in which part of one wall is removed, and replaced by a prestretched flat latex membrane. Air is drawn from atmosphere through an inlet into the rigid upstream tube; it then flows through the flexible section and finally through a rigid section Into a plenum chamber where suction is applied. As the membrane collapses in response to flow, the transmural pressure and deflection are measured at the mid-point. These values are used in conjunction with a finite deformation membrane wall theory to determine the elastic constant in a nonlinear material constitutive equation. This equation is used to predict the tube law. Results show that the flow limits at the long wave speed predicted by this law. Thus it behaves as a conventional collapsible tube while having the advantage of a rational wall model.

Flow Regulation Characteristics of Thin-Walled Compliant Tubes: Part I—Theoretical Analysis

1990 ◽  
Vol 112 (3) ◽  
pp. 319-329
Author(s):  
Ifiyenia Kececioglu
Keyword(s):  
Reynolds Number ◽  
Wave Speed ◽  
Active Element ◽  
Flow Regulation ◽  
Collapsible Tube ◽  
Speed Flow ◽  
Thin Walled ◽  
Flow Regulator ◽  
High Reynolds ◽  
Set Up

The objective of this investigation is the study of the flow limitation behavior of thin-walled compliant tubes for the design of a flow regulator employing a collapsible tube as its active element. In this paper, the theoretical basis is set up for the high-Reynolds-number wave-speed flow regulation and the low-Reynolds-number frictional flow regulation behaviors of thin-walled compliant tubes. In Part II of this paper [1], experimental results and design criteria are provided in support of the analytically derived characteristic flow regulation curve for the wave-speed flow regulator.

scholarly journals Sufficient conditions for hyperbolicity and consistency of the dynamic equations for fluid-saturated solids

2021 ◽  
Author(s):  
Vladimir A. Osinov
Keyword(s):  
Boundary Value Problem ◽  
Wave Speed ◽  
Boundary Value ◽  
Sufficient Conditions ◽  
Positive Definiteness ◽  
Dynamic Equations ◽  
Necessary Condition ◽  
Systems Of Equations ◽  
Acoustic Tensor ◽  
Ill Posed

AbstractPrevious studies showed that the dynamic equations for a porous fluid-saturated solid may lose hyperbolicity and thus render the boundary-value problem ill-posed while the equations for the same but dry solid remain hyperbolic. This paper presents sufficient conditions for hyperbolicity in both dry and saturated states. Fluid-saturated solids are described by two different systems of equations depending on whether the permeability is zero or nonzero (locally undrained and drained conditions, respectively). The paper also introduces a notion of wave speed consistency between the two systems as a necessary condition which must be satisfied in order for the solution in the locally drained case to tend to the undrained solution as the permeability tends to zero. It is shown that the symmetry and positive definiteness of the acoustic tensor of the skeleton guarantee both hyperbolicity and the wave speed consistency of the equations.

On the theory of electrohydrodynamically driven capillary jets

1997 ◽  
Vol 335 ◽  
pp. 165-188 ◽  
Author(s):  
ALFONSO M. GAÑÁN-CALVO
Keyword(s):  
Surface Charge ◽  
Electric Fields ◽  
Gas Flow ◽  
Wave Speed ◽  
Propagation Speed ◽  
Field Equations ◽  
Steady Regime ◽  
One Dimensional ◽  
Relaxation Effects ◽  
Capillary Jets

Electrohydrodynamically (EHD) driven capillary jets are analysed in this work in the parametrical limit of negligible charge relaxation effects, i.e. when the electric relaxation time of the liquid is small compared to the hydrodynamic times. This regime can be found in the electrospraying of liquids when Taylor's charged capillary jets are formed in a steady regime. A quasi-one-dimensional EHD model comprising temporal balance equations of mass, momentum, charge, the capillary balance across the surface, and the inner and outer electric fields equations is presented. The steady forms of the temporal equations take into account surface charge convection as well as Ohmic bulk conduction, inner and outer electric field equations, momentum and pressure balances. Other existing models are also compared. The propagation speed of surface disturbances is obtained using classical techniques. It is shown here that, in contrast with previous models, surface charge convection provokes a difference between the upstream and the downstream wave speed values, the upstream wave speed, to some extent, being delayed. Subcritical, supercritical and convectively unstable regions are then identified. The supercritical nature of the microjets emitted from Taylor's cones is highlighted, and the point where the jet switches from a stable to a convectively unstable regime (i.e. where the propagation speed of perturbations become zero) is identified. The electric current carried by those jets is an eigenvalue of the problem, almost independent of the boundary conditions downstream, in an analogous way to the gas flow in convergent–divergent nozzles exiting into very low pressure. The EHD model is applied to an experiment and the relevant physical quantities of the phenomenon are obtained. The EHD hypotheses of the model are then checked and confirmed within the limits of the one-dimensional assumptions.

scholarly journals Lamb-type waves generated by a cylindrical bubble oscillating between two planar elastic walls

2016 ◽  
Vol 472 (2188) ◽  
pp. 20160031 ◽  
Author(s):  
A. A. Doinikov ◽  
F. Mekki-Berrada ◽  
P. Thibault ◽  
P. Marmottant
Keyword(s):  
Resonance Frequency ◽  
Surface Waves ◽  
Wave Speed ◽  
Microfluidic Channel ◽  
Scattered Wave ◽  
Channel Height ◽  
Volume Oscillation ◽  
Scholte Wave ◽  
Rigid Walls ◽  
Elastic Walls

The volume oscillation of a cylindrical bubble in a microfluidic channel with planar elastic walls is studied. Analytical solutions are found for the bulk scattered wave propagating in the fluid gap and the surface waves of Lamb-type propagating at the fluid–solid interfaces. This type of surface wave has not yet been described theoretically. A dispersion equation for the Lamb-type waves is derived, which allows one to evaluate the wave speed for different values of the channel height h . It is shown that for h <λ t , where λ t is the wavelength of the transverse wave in the walls, the speed of the Lamb-type waves decreases with decreasing h , while for h on the order of or greater than λ t , their speed tends to the Scholte wave speed. The solutions for the wave fields in the elastic walls and in the fluid are derived using the Hankel transforms. Numerical simulations are carried out to study the effect of the surface waves on the dynamics of a bubble confined between two elastic walls. It is shown that its resonance frequency can be up to 50% higher than the resonance frequency of a similar bubble confined between two rigid walls.

The Piezoelectric and Piezomagnetic Effects on the Surface Wave Speed

2012 ◽  
Vol 268-270 ◽  
pp. 1619-1622 ◽  
Author(s):  
Li Li ◽  
Yi Wen Wei ◽  
P.J. Wei
Keyword(s):  
Surface Wave ◽  
Half Space ◽  
Wave Speed ◽  
Open Circuit ◽  
Numerical Examples ◽  
Piezomagnetic Effects

the piezoelectric and piezomagnetic effects and the influence of short and open circuit on the surface wave speed are investigated in this paper. First, the elastic, piezoelectric and piezomagnetic coefficients in the considered ordinate system are obtained by Bonde transformation from that in the crystal axes ordinate system. Then, the equation which surface wave speed satisfies is derived from the free traction condition on the surface of piezoelectric and piezomagnetic half space with consideration of short and open circuit case. Some numerical examples are given and the piezoelectric and piezomagnetic effects and the influence of short and open circuit on the surface wave speed are shown graphically.

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