Gas Dispersion in a Model Pulmonary Bifurcation During Oscillatory Flow

1997 ◽  
Vol 119 (3) ◽  
pp. 309-316 ◽  
Author(s):  
M. Nishida ◽  
Y. Inaba ◽  
K. Tanishita
Keyword(s):  
Velocity Profile ◽  
Axial Velocity ◽  
Oscillatory Flow ◽  
Gas Transport ◽  
Main Bronchus ◽  
High Frequency Oscillation ◽  
Laser Doppler Velocimeter ◽  
Straight Tube ◽  
Gas Dispersion ◽  
Axial Velocity Profile

In order to clarify the gas transport process in high-frequency oscillation, we measured the axial velocity profile and the axial effective diffusivity in a single asymmetric bifurcating tube, based on the Horsfield airway model, with sinusoidally oscillatory flow. The axial velocity profiles were measured using a laser-Doppler velocimeter, and the effective diffusivities were evaluated using a simple bolus injection method. The axial velocity profile was found to be nonuniform, promoting axial gas dispersion by the spread of the concentration profile and lateral mixing. The geometric asymmetry of the bifurcation was responsible for the difference in gas transport between the main bronchi. The axial gas transport in the left main bronchus was 2.3 times as large as that of the straight tube, whereas the gas transport in the right main bronchus was slightly larger than that of the straight tube. Thus localized variation in gas transport characterized the heterogeneous respiratory function of the lung.

scholarly journals A Study of Oscillatory Flow in Curved Pipes : 2nd Report, Axial Velocity Profile

1985 ◽  
Vol 28 (245) ◽  
pp. 2644-2651
Author(s):  
Kouzou SUDOU ◽  
Masaru SUMIDA ◽  
Toshihiro TAKAMI ◽  
Ryuichiro YAMANE
Keyword(s):  
Velocity Profile ◽  
Axial Velocity ◽  
Oscillatory Flow ◽  
Curved Pipes ◽  
Axial Velocity Profile

Augmentation of Axial Dispersion by Intermittent Oscillatory Flow

1998 ◽  
Vol 120 (3) ◽  
pp. 405-415 ◽  
Author(s):  
G. Tanaka ◽  
Y. Ueda ◽  
K. Tanishita
Keyword(s):  
Stationary Phase ◽  
High Frequency ◽  
Oscillatory Flow ◽  
Effective Diffusivity ◽  
Axial Dispersion ◽  
High Frequency Oscillation ◽  
Gas Transfer ◽  
Straight Tube ◽  
Gas Dispersion ◽  
Molecular Diffusivity

The efficiency of axial gas dispersion during ventilation with high-frequency oscillation (HFO) is improved by manipulating the oscillatory flow waveform such that intermittent oscillatory flow occurs. We therefore measured the velocity profiles and effective axial gas diffusivity during intermittent oscillatory flow in a straight tube to verify the intermittency augmentation effect on axial gas transfer. The effective diffusivity was dependent on the flow patterns and significantly increased with an increase in the duration of the stationary phase. It was also found that the ratio of effective diffusivity to molecular diffusivity is two times greater than that in sinusoidal oscillatory flow. Moreover, turbulence during deceleration or at the beginning of the stationary phase further augments axial dispersion, with the effective diffusivity being over three times as large, thereby proving that the use of intermittent oscillatory flow effectively augments axial dispersion for ventilation with HFO.

scholarly journals A study of oscillatory flow in curved pipes (2nd report, Axial velocity profile)

1985 ◽  
Vol 51 (463) ◽  
pp. 811-819 ◽  
Author(s):  
Kouzou SUDOU ◽  
Masaru SUMIDA ◽  
Toshihiro TAKAMI ◽  
Ryuichiro YAMANE
Keyword(s):  
Velocity Profile ◽  
Axial Velocity ◽  
Oscillatory Flow ◽  
Curved Pipes ◽  
Axial Velocity Profile

Spatial and Temporal Variation of Secondary Flow During Oscillatory Flow in Model Human Central Airways

1999 ◽  
Vol 121 (6) ◽  
pp. 565-573 ◽  
Author(s):  
G. Tanaka ◽  
T. Ogata ◽  
K. Oka ◽  
K. Tanishita
Keyword(s):  
Secondary Flow ◽  
Oscillatory Flow ◽  
Main Bronchus ◽  
Spatial And Temporal Variation ◽  
High Frequency Oscillation ◽  
Laser Doppler Velocimeter ◽  
Left Bronchus ◽  
Secondary Velocity ◽  
Human Airways ◽  
The Right

Axial and secondary velocity profiles were measured in a model human central airway to clarify the oscillatory flow structure during high-frequency oscillation. We used a rigid model of human airways consisting of asymmetrical bifurcations up to third generation. Velocities in each branch of the bifurcations were measured by two-color laser-Doppler velocimeter. The secondary velocity magnitudes and the deflection of axial velocity were dependent not only on the branching angle and curvature ratio of each bifurcation, but also strongly depended on the shape of the path generated by the cascade of branches. Secondary flow velocities were higher in the left bronchus than in the right bronchus. This spatial variation of secondary flow was well correlated with differing gas transport rates between the left and right main bronchus.

Turbulent Flow in Axially Rotating Pipes

1980 ◽  
Vol 102 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Mitsukiyo Murakami ◽  
Kouji Kikuyama
Keyword(s):  
Velocity Profile ◽  
Turbulent Flow ◽  
Flow Pattern ◽  
Axial Velocity ◽  
Hydraulic Loss ◽  
Pressure Distributions ◽  
Axial Velocity Profile ◽  
Fully Developed Turbulent Flow ◽  
Smooth Pipe ◽  
Pipe Rotation

Experimental results concerning the flow pattern and hydraulic resistance in a rotating pipe are described. A fully developed turbulent flow was introduced into a long smooth pipe rotating about its axis, and changes of the flow pattern, together with hydraulic loss within the pipe, were examined by measuring the velocity and pressure distributions across sections at various distance from the pipe entrance. Increase of pipe rotation continuously reduces the hydraulic loss and gradually changes the axial velocity profile from a turbulent type to a laminar one. Governing factors for these changes are discussed.

The Elimination of Wall Effects in Axial-Flow Compressor Stages

1953 ◽  
Vol 57 (508) ◽  
pp. 241-243
Author(s):  
J. M. Stephenson
Keyword(s):  
Velocity Profile ◽  
Axial Velocity ◽  
Radial Profile ◽  
Axial Flow ◽  
Gas Velocity ◽  
Wall Effects ◽  
Axial Velocity Component ◽  
Axial Velocity Profile ◽  
Flow Compressor ◽  
Work Done

Compressor stages are usually designed on the assumption that the gas velocity is nowhere affected by the friction at the walls. The only way in which viscosity is taken into account is in the assumed efficiency, and in a guessed “work-done factor,” which ensures that by aiming high the required work is actually attained.It is known that the radial profile of the axial velocity component becomes more and more peaked through successive stages of a compressor, so that the assumptions just quoted become very inaccurate. It is possible that the efficiency of a stage could be raised considerably if the axial velocity profile were controlled; moreover up to 20 per cent. more work could be done if a “ work-done factor ” did not have to be applied.

A Theoretical Analysis of the Influence of Rotation on Flow in a Tube Rotating about a Parallel Axis with Uniform Angular Velocity

1965 ◽  
Vol 69 (651) ◽  
pp. 201-202 ◽  
Author(s):  
W. D. Morris
Keyword(s):  
Angular Velocity ◽  
Velocity Profile ◽  
Axial Velocity ◽  
Cylindrical Tube ◽  
Fluid Flows ◽  
Leading Edge ◽  
Pressure Fields ◽  
Axial Velocity Profile ◽  
Parallel Axis ◽  
Arbitrary Axis

When fluid flows in a tube which rotates about an arbitrary axis, the presence of centripetal and Coriolis acceleration components modify the velocity and pressure fields which exist in the absence of rotation. Barua considered the case of an incompressible fluid flowing in laminar motion through a cylindrical tube which was rotating about an axis perpendicular to itself with uniform angular velocity. For distances well away from the tube entrance Barua illustrated that secondary flow in the r-θ plane occurred and that the axial velocity profile was distorted towards the leading edge of the tube. Since the pressure gradient along the tube is proportional to the gradient of the axial velocity profile at the tube wall the rotation thus has a consequential influence on the resistance to flow offered by the tube.

Compressor Design

1953 ◽  
Vol 57 (511) ◽  
pp. 463-463
Author(s):  
R. G. Taylor
Keyword(s):  
Velocity Profile ◽  
Axial Velocity ◽  
Axial Flow ◽  
Technical Note ◽  
Basic Design ◽  
Wall Effects ◽  
Axial Flow Compressor ◽  
Axial Velocity Profile ◽  
Compressor Design ◽  
Flow Compressor

In Mr. J. M. Stephenson's Technical Note, “ The Elimination of Wall Effects in Axial-Flow Compressor Stages,” in the April 1953 issue of the Journal, the author suggests that the blade rows of an axial flow compressor are so closely spaced as to ensure that the axial velocity profile is unchanged across the rows. Whether this statement is correct or not such an assumption regarding the axial velocity profile is a basic design condition and when made it will not leave any flexibility in the choice of the function f(r).

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