scholarly journals Effects of Varying Inhalation Duration and Respiratory Rate on Human Airway Flow

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 221
Author(s):  
Manikantam G. Gaddam ◽  
Arvind Santhanakrishnan
Keyword(s):  
Respiratory Rate ◽  
Cross Sections ◽  
Particle Deposition ◽  
Oscillatory Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Stroke Length ◽  
Human Airway ◽  
Flow Through

Studies of flow through the human airway have shown that inhalation time (IT) and secondary flow structures can play important roles in particle deposition. However, the effects of varying IT in conjunction with the respiratory rate (RR) on airway flow remain unknown. Using three-dimensional numerical simulations of oscillatory flow through an idealized airway model (consisting of a mouth, glottis, trachea, and symmetric double bifurcation) at a trachea Reynolds number (Re) of 4200, we investigated how varying the ratio of IT to breathing time (BT) from 25% to 50% and RR from 10 breaths per minute (bpm) corresponding to a Womersley number (Wo) of 2.41 to 1000 bpm (Wo = 24.1) impacts airway flow characteristics. Irrespective of IT/BT, axial flow during inhalation at tracheal cross-sections was non-uniform for Wo = 2.41, as compared to centrally concentrated distribution for Wo = 24.1. For a given Wo and IT/BT, both axial and secondary (lateral) flow components unevenly split between left and right branches of a bifurcation. Irrespective of Wo, IT/BT and airway generation, lateral dispersion was a stronger transport mechanism than axial flow streaming. Discrepancy in the oscillatory flow relation Re/Wo2 = 2L/D (L = stroke length; D = trachea diameter) was observed for IT/BT ≠ 50%, as L changed with IT/BT. We developed a modified dimensionless stroke length term including IT/BT. While viscous forces and convective acceleration were dominant for lower Wo, unsteady acceleration was dominant for higher Wo.

Tip Leakage Flow Characteristics Downstream of an Axial Flow Fan

1996 ◽  
Author(s):  
P. Puddu
Keyword(s):  
Vortex Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Tip Leakage Flow ◽  
Single Wire ◽  
Vortex System ◽  
Tip Leakage ◽  
Stress Components ◽  
Computer Controlled

The three-dimensional viscous flow characteristics and the complex vortex system downstream of the rotor of an industrial exial fan have been determined by an experimental investigation using hot-wire anemometer. Single-wire slanted and straight type probes have been rotated about the probe axis using a computer controlled stepper motor. Measurements have been taken at four planes behind the blade trailing edge. The results show the characteristics of the relative flow as velocity components, secondary flow and kinetic energy defect. Turbulence intensity and Reynolds stress components in the leakage vortex area are also presented. The evolution of the leakage vortex flow during the decay process has also been evaluated in terms of dimension, position and intensity.

Viscous Flow in an Annulus With a Sector Cavity

1982 ◽  
Vol 104 (4) ◽  
pp. 500-504 ◽  
Author(s):  
V. O’Brien
Keyword(s):  
Biharmonic Equation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Cavity Flow ◽  
Three Dimensional Flow ◽  
Circular Annulus ◽  
Dimensional Interaction ◽  
Laminar Mixing ◽  
Flow Through ◽  
Finite Difference Solution

The two-dimensional interaction of a circular shear flow and a sector cavity flow is predicted by finite-difference solution of the governing biharmonic equation for steady Stokes planar flow. The location of the dividing streamline is a function of geometry, lying perhaps wholly within the cavity or bulging up into the circular annulus. Also pressure-driven axial flow through the annular configuration is predicted by numerical solution of the governing Poisson equation. The results can be combined with the planar solution to describe a steady three-dimensional flow field which will enhance laminar mixing.

Visualization Study of Flow in Axial Flow Inducer

1972 ◽  
Vol 94 (4) ◽  
pp. 777-787 ◽  
Author(s):  
B. Lakshminarayana
Keyword(s):  
Radial Velocity ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Theory ◽  
Secondary Flows ◽  
Flow Coefficient ◽  
Flow Through

A visualization study of the flow through a three ft dia model of a four bladed inducer, which is operated in air at a flow coefficient of 0.065, is reported in this paper. The flow near the blade surfaces, inside the rotating passages, downstream and upstream of the inducer is visualized by means of smoke, tufts, ammonia filament, and lampblack techniques. Flow is found to be highly three dimensional, with appreciable radial velocity throughout the entire passage. The secondary flows observed near the hub and annulus walls agree with qualitative predictions obtained from the inviscid secondary flow theory. Based on these investigations, methods of modeling the flow are discussed.

Effect of Pitch Chord Ratio and Side Wall Expansion Angle on Flow Through Vane Swirlers

2006 ◽  
Author(s):  
R. Thundil Karuppa Raj ◽  
V. Ganesan
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Side Wall ◽  
Reynolds Stress Model ◽  
Swirl Flow ◽  
Expansion Angle ◽  
Turbulence Effects ◽  
Flow Field Characteristics ◽  
Flow Through

This paper is concerned with the computational study of steady flow through the vane swirlers. Swirl flow field characteristics for various pitch chord ratio (s/c) at swirler mean radius are studied for a 45° vane swirler under both sudden and gradual expansions with side-wall expansion angles of 90° and 45° respectively. In the computational study the geometry and meshing is done using pre-processor GAMBIT. Three-dimensional flow within the geometry and through the swirler has been simulated by solving the appropriate governing equations viz. conservation of mass and momentum using FLUENT code. Turbulence effects are taken care of by the Reynolds stress model and shear stress transport k-ω model for high swirls and standard k-ε model for low and medium swirls. The effect of pitch to chord ratio (s/c) on flow characteristics have been studied. The predicted results are validated with the experimental data available in the literature for s/c ratio of 1. The numerical results of axial velocity profiles downstream of the swirler at various axial planes are found to be in close agreement with the experimental results. It is found that the s/c ratio of 1 provides good turning efficiency.

scholarly journals Flow Characteristics and Energy Loss within the Static Impeller of Multiphase Pump

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1025
Author(s):  
Zhu Jiang ◽  
Haiying Li ◽  
Guangtai Shi ◽  
Xiaobing Liu
Keyword(s):  
Three Dimensional ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Internal Flow ◽  
Friction Loss ◽  
Turbulent Dissipation ◽  
Multiphase Pump ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
Dissipation Loss

The internal flow is very complex in the multiphase pump, especially in the static impeller, where the flow is more disorganized than that in the impeller wheel, and it will cause greater hydraulic losses. In order to investigate deeply the flow rules within the static impeller, all kinds of the flow losses are analyzed quantificationally in the multiphase pump. Based on the standard SST k-ω turbulence model, selected the helical axial flow multiphase pump as the research object, used the three-dimensional modeling software for the three-dimensional modeling of the flow through parts of the multiphase pump, such as impeller wheel, the static impeller, the suction chamber, and the extrusion chamber. The ANSYS software is used to simulate the three-dimensional flow in static impeller, and the ICEM software was used to divide the mesh of suction chamber, press outlet chamber, moving impeller and static impeller respectively. The results show that the flow within the impeller wheel is more uniform than the static impeller, and larger axial vortexes appear in the static impeller. Compared with the impeller wheel, the effect of the flow rate on the flow within the first static impeller is greater. The friction loss is the largest among all kinds of losses in the static impeller, followed by the turbulence dissipation loss. What’s more, the shock loss and the contraction loss are the smallest, they are all less than 20%, and the main loss within the static impeller are the turbulent dissipation loss and friction loss. The proportion of energy losses in the first and second static impeller is almost the same, which is around 50%, respectively. The results can be used as a reference for the improvement of the hydraulic performance of the multiphase pump.

Three Dimensional Supersonic Flow Through a Cascade of Twisted Flat Plates

1980 ◽  
Vol 102 (3) ◽  
pp. 338-343
Author(s):  
C. F. Grainger
Keyword(s):  
Method Of Characteristics ◽  
Three Dimensional ◽  
Axial Flow ◽  
Finite Difference Approximation ◽  
Difference Approximation ◽  
Flat Plates ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Two Dimensional Flow ◽  
Flow Through

The three-dimensional flow through a cascade of twisted flat-plate blades is calculated using a computer program based on a finite-difference approximation to the method of characteristics. The relative flow is supersonic but the axial flow is subsonic. For two-dimensional flow under similar conditions, the inlet flow field is one of “unique-incidence,” the effect discussed by Starken (5) and others. The main purpose of the present work is to extend the understanding of this effect to three-dimensional flow. Important differences between the two and three-dimensional flow fields are explained in terms of the interaction between neighboring sections of the flow.

An Experimental Arrangement for the Measurement of the Pressure Distribution on High Speed Rotating Blade Rows

1956 ◽  
Author(s):  
K. Leist
Keyword(s):  
Experimental Investigation ◽  
Pressure Distribution ◽  
High Speed ◽  
Three Dimensional ◽  
Axial Flow ◽  
Three Dimensional Flow ◽  
Research Staff ◽  
Rotating Blade ◽  
Flow Through ◽  
Turbine Blading

For several years past, the research staff of the Institute for Turbomachines of the Aachen Technical University has carried out measurements on rotating turbine blading. This program is part of a comprehensive effort directed toward the experimental investigation of the three-dimensional flow through axial-flow turbomachines.

scholarly journals Optimization of Tank Bottom Shape for Improving the Anti-Deposition Performance of a Prefabricated Pumping Station

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 602 ◽  
Author(s):  
Qing Li ◽  
Can Kang ◽  
Shuang Teng ◽  
Mingyi Li
Keyword(s):  
Particle Deposition ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Sand Particle ◽  
Pumping Station ◽  
Tank Bottom ◽  
Underlying Mechanisms ◽  
High Flexibility ◽  
Pump Inlet

High flexibility of prefabricated pumping stations in collecting and transporting storm water has been recognized. Nevertheless, flows inside such a complex system have rarely been reported. The present study aims to reveal water-sand flow characteristics in a prefabricated pumping station and to optimize geometric parameters of the tank to mitigate sand particle deposition. Five tank schemes, varying in the ratio of the diameter to the height of the tank bottom (D/L), were investigated. Flows in the pumping station were simulated using the computational fluid dynamics (CFD) technique. Test data were used to validate the numerical scheme. Three-dimensional water-sand flows in the pumping station were described. Underlying mechanisms of sand particle deposition were explained. The results indicate that the risk of deposition is high at the tank bottom side, close to the tank inlet. Both the tank bottom geometry and the inlet suction of the pump contribute to sand particle deposition. The averaged sand volume fraction at the pump inlet reaches its minimum at D/L = 3. Sand particle velocity at the pump inlet varies inversely with D/L. The highest intensity of the vortex at the pump inlet arises at D/L = 3. The best anti-deposition performance of the pumping station is attained at D/L = 3.

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