Theoretical study of the photoacoustic signal produced in a relaxing gas

1986 ◽  
Vol 64 (9) ◽  
pp. 1098-1106 ◽  
Author(s):  
M. Rebelo Da Silva
Keyword(s):  
Theoretical Study ◽  
Sound Propagation ◽  
Photoacoustic Signal ◽  
Rigid Wall ◽  
Gas Cell ◽  
Collisional Relaxation ◽  
Coupled Equations ◽  
Flow Through ◽  
Relaxing Gas ◽  
Lateral Walls

The photoacoustic signal generated in a photoacoustic gas cell with rigid wall boundaries is calculated by solving the coupled equations for sound propagation and thermal diffusion in a viscous and relaxing gas. For a cylindrical geometry, monochromatic radiation, and sinusoidal modulation, when a condition of zero heat flow through the lateral walls of the cell is verified, a general expression is found that can be applied whatever the deactivation scheme is for collisional relaxation in the gas. Both resonant and nonresonant modes of operation are considered.

scholarly journals Mathematical study on two-fluid model for flow of K–L fluid in a stenosed artery with porous wall

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
R. Ponalagusamy ◽  
Ramakrishna Manchi
Keyword(s):  
Theoretical Study ◽  
Fluid Model ◽  
Porous Wall ◽  
Governing Equations ◽  
Rate Of Increase ◽  
Special Cases ◽  
Stenosed Artery ◽  
Flow Through ◽  
Two Fluid Model ◽  
Two Fluid

AbstractThe present communication presents a theoretical study of blood flow through a stenotic artery with a porous wall comprising Brinkman and Darcy layers. The governing equations describing the flow subjected to the boundary conditions have been solved analytically under the low Reynolds number and mild stenosis assumptions. Some special cases of the problem are also presented mathematically. The significant effects of the rheology of blood and porous wall of the artery on physiological flow quantities have been investigated. The results reveal that the wall shear stress at the stenotic throat increases dramatically for the thinner porous wall (i.e. smaller values of the Brinkman and Darcy regions) and the rate of increase is found to be 18.46% while it decreases for the thicker porous wall (i.e. higher values of the Brinkman and Darcy regions) and the rate of decrease is found to be 10.21%. Further, the streamline pattern in the stenotic region has been plotted and discussed.

Upwinding Meshfree Point Collocation Method for Unsteady Magnetohydrodynamic Flow at High Hartmann Numbers

2011 ◽  
Vol 130-134 ◽  
pp. 1668-1671
Author(s):  
Xing Hui Cai ◽  
Cheng Ying Shi ◽  
Guo Liang Wang
Keyword(s):  
Collocation Method ◽  
Numerical Solutions ◽  
Hartmann Number ◽  
Mhd Flow ◽  
Rectangular Section ◽  
Point Collocation ◽  
Coupled Equations ◽  
Meshless Collocation ◽  
Support Domain ◽  
Flow Through

In this paper, a meshfree point collocation method, with an upwinding scheme, is presented to obtain the numerical solutions of the coupled equations in the velocity field for the unsteady magnetohydrodynamic (MHD) flow through a straight duct of rectangular section with insulated walls. Computations have been carried out for the unsteady MHD flow, which is under the external applied magnetic field of arbitrary orientation, of different Hartmann number from 5 to 106 and at various time levels. As the adaptive upwinding local support domain is introduced in the meshless collocation method, numerical results show that the method can compute MHD problems with Hartmann numbers up to 106 with good accuracy. The results also show that as Hartmann number increases, the time needed to reach the steady state decreases.

Vascular peripheral resistance and compliance in the lobster Homarus americanus

1997 ◽  
Vol 200 (3) ◽  
pp. 477-485 ◽  
Author(s):  
J Wilkens ◽  
G Davidson ◽  
M Cavey
Keyword(s):  
Striated Muscle ◽  
Peripheral Resistance ◽  
Systolic Pressure ◽  
Body Part ◽  
Homarus Americanus ◽  
Arterial System ◽  
Flow Rates ◽  
Flow Through ◽  
Lateral Walls

The peripheral resistance to flow through each arterial bed (in actuality, the entire pathway from the heart back to the pericardial sinus) and the mechanical properties of the seven arteries leaving the lobster heart are measured and compared. Resistance is inversely proportional to artery radius and, for each pathway, the resistance falls non-linearly as flow rate increases. The resistance of the hepatic arterial system is lower than that predicted on the basis of its radius. Body-part posture and movement may affect the resistance to perfusion of that region. The total vascular resistance placed on the heart when each artery is perfused at a rate typical of in vivo flow rates is approximately 1.93 kPa s ml-1. All vessels exhibit adluminal layers of fibrils and are relatively compliant at pressures at or below heart systolic pressure. Arteries become stiffer at pressures greater than peak systolic pressure and at radii greater than twice the unpressurized radius. The dorsal abdominal artery possesses striated muscle in the lateral walls. This artery remains compliant over the entire range of hemolymph pressures expected in lobsters. These trends are illustrated when the incremental modulus of elasticity is compared among arteries. All arteries should function as Windkessels to damp the pulsatile pressures and flows generated by the heart. The dorsal abdominal artery may also actively regulate its flow.

Plastic Flow in Confined Porous Media of Complex Contours

1999 ◽  
Author(s):  
Mario F. Letelier ◽  
César E. Rosas
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Fluid Flow ◽  
Theoretical Study ◽  
Perturbation Parameter ◽  
Resistance Coefficient ◽  
Boundary Perturbation ◽  
Bingham Plastic ◽  
Flow Through ◽  
Central Plug

Abstract A theoretical study of the fully developed fluid flow through a confined porous medium is presented. The fluid is described by the Bingham plastic model for small values of the yield number. The analysis allows for many admissible shapes of the wall contour. The velocity field is computed for several combination of relevant parameters, i.e., the yield number, Darcy resistance coefficient and the boundary perturbation parameter. The wall effect is especially highlighted and the characteristics of the central plug region as well. Plots of isovel curves and velocity profiles are included for a variety of flow and geometry parameters.

scholarly journals Effect of Lateral Walls on Peristaltic Flow through an Asymmetric Rectangular Duct

2011 ◽  
Vol 8 (3-4) ◽  
pp. 295-308 ◽  
Author(s):  
Kh. S. Mekheimer ◽  
S. Z.-A. Husseny ◽  
A. I. Abd el Lateef
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Viscous Fluid ◽  
Wave Train ◽  
Peristaltic Flow ◽  
Frame Of Reference ◽  
Rectangular Duct ◽  
Long Wavelength ◽  
Flow Through ◽  
Lateral Walls

Peristaltic transport of an incompressible viscous fluid due to an asymmetric waves propagating on the horizontal sidewalls of a rectangular duct is studied under long-wavelength and low-Reynolds number assumptions. The peristaltic wave train on the walls have different amplitudes and phase. The flow is investigated in a wave frame of reference moving with velocity of the wave. The effect of aspect ratio, phase difference, varying channel width and wave amplitudes on the pumping characteristics and trapping phenomena are discussed in detail. The results are compared to with those corresponding to Poiseuille flow.

A Theoretical Study of the Performance of an Axial Flow Turbine for a Microhydro Installation

1996 ◽  
Vol 210 (2) ◽  
pp. 121-129 ◽  
Author(s):  
G J Parker
Keyword(s):  
Theoretical Study ◽  
Draft Tube ◽  
Guide Vane ◽  
Turbine Blades ◽  
Axial Flow ◽  
Prototype System ◽  
Blade Angle ◽  
Flow Through ◽  
Loss Coefficients ◽  
Vane Angle

The Bernoulli-with-loss equation, with the losses represented by a constant times the velocity head, has been applied to each section of the flow through a small turbine system consisting of inlet guide vanes, axial flow turbine and draft tube. Using experimental data and the sets of equations, the flow angles around the turbine blades and the loss coefficients in the turbine and in the draft tube were determined. These were used to predict the effect of varying the guide vane angle and the turbine blade angle on performance. They were also used to predict the effects on the performance of a geometrically similar prototype system.

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