Steady pressure-flow relationship of a model of the canine bronchial tree

1981 ◽  
Vol 51 (5) ◽  
pp. 1072-1079 ◽  
Author(s):  
D. B. Reynolds ◽  
J. S. Lee
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Kinetic Energy ◽  
Total Pressure ◽  
Gas Flow ◽  
Static Pressure ◽  
Bronchial Tree ◽  
Flow Pressure ◽  
Expiratory Flow ◽  
Relationship Of

Static pressure differences (deltaP) across the entire length and portions of a latex reproduction of a canine bronchial tree were measured during steady inspiratory or expiratory flow (V). The reproduction consists of a 10-cm length of trachea through bronchi of about 2 mm in diameter. The airflow was simulated by a water flow with tracheal Renolds number (Re0) in the range from 1,500 to 10,000. Loss in total pressure (deltaPt) was computed by summing deltaPt and V were well described (r greater than 0.98) by a dimensionless Rohrer equation deltaPt/deltaPd0 = A + B Re0 applicable to gas flow, in which deltaPd0 is a Poiseuille pressure drop. For expiratory deltaPt, A was about twice that for inspiration, while the values for B were nearly equal. Differences in kinetic energy between sites of static pressure measurement are important in determining loss in total pressure. Rohrer's equation is a good approximation to the phenomenological laws of steady inspiratory and expiratory flow-pressure relations in the canine bronchial tree for the range of Reynolds number investigated.

Research on Relationship of Pressure Distribution and Particles Separation in Cyclone

2013 ◽  
Vol 394 ◽  
pp. 65-68
Author(s):  
Ying Zhang ◽  
Xiao Qian Ma ◽  
Zhen Wei Zhang ◽  
Cheng Ming Kang
Keyword(s):  
Pressure Drop ◽  
Pressure Distribution ◽  
Theoretical Basis ◽  
Total Pressure ◽  
Static Pressure ◽  
Structure Optimization ◽  
Exhaust Pipe ◽  
Relationship Of

This paper mainly deals with pressure situation in cyclone aiming to obtain the pressure distribution and pressure drop in cyclone separation by taking advantage of the model of RSM of software Fluent, and put forward that the total pressure of import part is the highest and the minimum total pressure locates inside exhaust pipe in cyclone. Static pressure of outside swirl is relatively higher than the inner swirl, and the minimum static pressure occurs in the axis of the separator extending into the dust hopper. Relationship of pressure distribution and particles separation can be obtained according to the analysis, which can provide the theoretical basis for further enhancement of performance and structure optimization.

Steady Expiratory Flow-Pressure Relationship in a Model of the Human Bronchial Tree

1982 ◽  
Vol 104 (2) ◽  
pp. 153-158 ◽  
Author(s):  
D. B. Reynolds
Keyword(s):  
Turbulent Flows ◽  
Total Pressure ◽  
Static Pressure ◽  
Bronchial Tree ◽  
Tree Model ◽  
Simplifying Assumptions ◽  
Flow Velocity Profile ◽  
Entire Flow ◽  
Average Loss ◽  
Expiratory Flow

Static pressure differences across a human bronchial tree model were obtained for steady expiratory flows of several gases producing Reynolds numbers (Re1) in the bronchus carrying the entire flow (first bronchus) between 150 and 50,000. The model was constructed from an air-dried lung and was complete to bronchi about 2 mm in diameter. Dimensionless static pressure plotted against Re1 consolidated the data on a single curve, phenomenologically described by an equation of the form: ΔPs/ΔPd1 = A + B Re1 where ΔPd1 is a pressure drop for Poiseuille flow. Velocity profile measurements at two sites along the first bronchus for laminar and turbulent flows indicate a dependence on the latter and distance from the first junction. Loss in total pressure was computed and may result from both frictional dissipation and changes in momentum flux associated with development of velocity profiles near the junctions. An average loss in total pressure within a single bronchus was calculated after making several simplifying assumptions, and this result may be useful in modeling both the resistance of the entire bronchial tree and the more complex phenomenon of maximal expiratory flow.

Measurements of the nearly isotropic turbulence behind a uniform jet grid

1974 ◽  
Vol 62 (1) ◽  
pp. 115-143 ◽  
Author(s):  
Mohamed Gad-El-Hak ◽  
Stanley Corrsin
Keyword(s):  
Pressure Drop ◽  
Kinetic Energy ◽  
Static Pressure ◽  
Isotropic Turbulence ◽  
Decay Rates ◽  
Turbulence Energy ◽  
Turbulence Level ◽  
Average Force ◽  
General Behaviour ◽  
Decay Behaviour

Wind-tunnel turbulence behind a parallel-rod grid with jets evenly distributed along each rod is nearly isotropic. Homogeneity improvement over prior related experiments was attained by the use of controllable nozzles. Compared with the ‘passive’ case, the downwind-jet ‘active’ grid has a smaller static pressure drop across it and gives a smaller turbulence level at a prescribed distance from it, while the upwind-jet grid gives a larger static pressure drop and larger turbulence level. ‘Counterflow injection’ generates larger turbulence energy and larger scales, both events being evidently associated with instability of the jet system. This behaviour is much like that commonly observed behind passive grids of higher solidities.If the turbulent kinetic energy is approximated as an inverse power law in distance, the (positive) exponent decreases with increasing (downwind or upwind) jet strength, corresponding to slower absolute decay rates. No peculiar decay behaviour occurs when the jet grid is ‘self-propelled’ (zero net average force), or when the static pressure drop across it is zero.The injection does not change the general behaviour of the energy spectra, although the absolute spectra change inasmuch as the turbulence kinetic energy changes.

Patterns of gas flow in the upper bronchial tree

1959 ◽  
Vol 14 (5) ◽  
pp. 753-759 ◽  
Author(s):  
J. B. West ◽  
P. Hugh-Jones
Keyword(s):  
Gas Flow ◽  
Lower Lobe ◽  
Bronchial Tree ◽  
High Flow ◽  
Human Beings ◽  
Lobe Bronchus ◽  
Flow Rates ◽  
Expiratory Flow ◽  
Different Gases ◽  
Expiratory Flow Rates

Patterns of gas flow in the upper bronchial tree have been studied by observing the flow of dye and different gases through a lung cast, and by measurements made on open-chested dogs and on human beings at bronchoscopy. Flow is completely laminar throughout the bronchial tree at low expiratory flow rates (up to 10 l/min.) and completely turbulent, proximal to the segmental bronchi, at high flow rates (80 l/min.). Both at low and high expiratory flow rates, gas from segmental bronchi was not uniformly mixed in the lobar or main bronchi which they supplied. The composition of a catheter sample in these airways would therefore not be representative of the alveolar gas in the corresponding lobe or lung unless the alveolar gas in all areas distal to the sampling tube was homogeneous. Penetration of the left upper lobe bronchus by gas from the lower lobe was demonstrated in the model and a normal subject at bronchoscopy. Submitted on September 3, 1958

Friction Factor Directly From Roughness Measurements

2001 ◽  
Author(s):  
Elling Sletfjerding ◽  
Jon Steinar Gudmundsson
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Power Spectrum ◽  
Friction Factor ◽  
High Reynolds Number ◽  
Gas Flow ◽  
Relative Roughness ◽  
High Reynolds ◽  
Friction Factor Correlation ◽  
Roughness Measurements

Abstract Pressure drop experiments on natural gas flow in 150 mm pipes at 80 to 120 bar pressure and high Reynolds number were carried out for pipes smooth to rough surfaces. The roughness was measured with an accurate stylus instrument and analyzed using fractal methods. Using a similar approach to that of Nikuradse the measured friction factor was related to the measured roughness values. Taking the value of the relative roughness and dividing it by the slope of the power spectrum of the measured roughness, a greatly improved fit with the measured friction factor was obtained. Indeed, a new friction factor correlation was obtained, but now formulated in terms of direct measurement of roughness.

The Heat Transfer and Pressure-Drop Characteristics of Gas Flow Inside Spirally Corrugated Tubes

1970 ◽  
Vol 92 (3) ◽  
pp. 513-518 ◽  
Author(s):  
G. J. Kidd
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Gas Flow ◽  
Pumping Power ◽  
Friction Factors ◽  
Apparent Correlation ◽  
Smooth Tubes ◽  
Enhancing Heat Transfer

Heat transfer and pressure-drop experiments have been performed for gas flow inside nine, 1/2-in-OD, 0.035-in. wall thickness, A-nickel, spirally corrugated tubes. The corrugations, which varied from 0.003–0.028 in. deep, were formed by pulling the tubes through a rotating head containing four embossing tools; corrugation-spacing-to-corrugation-depth ratios (P/e) ran from 16–41. The data, for heat transfer to nitrogen, at approximately 200 psig, were correlated by an expression of the form NNu,B (NPr,B)−0.4 × (Tw/TB)0.5 = A(NRe,B)m, where all the physical properties were evaluated at bulk gas conditions. The exponent, m, on the Reynolds number was observed to be consistently greater (0.854–0.900) than the value of 0.8 found for smooth tubes; the constant, A, varied from 0.0095–0.0195 with no apparent correlation with P/e. Friction factors, measured with adiabatic airflow, were found to be up to 1.7 times that for smooth tubes. Tubes of this geometry were found to be very effective in enhancing heat transfer. On an equal pumping power basis, for example, a tube with P/e = 22 had a heat transfer coefficient 22 percent greater than a smooth tube.

Steady expiratory flow in dog lungs: an isovolume preparation

1981 ◽  
Vol 51 (5) ◽  
pp. 1331-1337 ◽  
Author(s):  
S. L. Sneddon ◽  
J. D. Brain
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Flow Region ◽  
Flow Limitation ◽  
Opening Pressure ◽  
Pressure Flow ◽  
Pleural Surface ◽  
Airway Opening ◽  
Expiratory Flow

By supplying air and other gases through discs glued to the pleural surface, we studied steady expiratory flow at constant volume. Dog lungs were studied at constant PA - Ppl (alveolar minus pleural pressure) of 7 to 10 cmH2O, as increasing flow was achieved by increasing driving pressure [Ppl - Pao (airway opening pressure)]. Flow became limited (independent of further increases in Ppl - Pao) at between 3.5 and 5.5 l/s. Isovolume-pressure-flow (IVPF) curves constructed from forced expirations at graded efforts yielded similar maximal flows. When the airways were made rigid by drying, flow limitation was abolished. When various gases were passed through the dried lung Moody plots of normalized pressure drop (CD) vs. Reynolds number (Re) showed that all of the data could be plotted on a single curve. Although variable among animals, all Moody plots showed a laminar flow region at Re below 100 and an inertial region at Re above 10,000, with a distinct transition.

Study on Characteristics of Gas Flow in Catalytic Converter with Different Outlet Diameters

2014 ◽  
Vol 711 ◽  
pp. 16-19
Author(s):  
Zhan Jun Cai ◽  
Wei Min Kang ◽  
Ya Bin Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Catalytic Reaction ◽  
Gas Flow ◽  
Static Pressure ◽  
Catalytic Converter ◽  
Geometric Model ◽  
Flow Pressure ◽  
Different Diameters ◽  
Dynamics Method

. This paper studies the different diameters of tube outlet how to affect the gas flow pressure and velocity distribution in nanofiber catalytic converter by CFD (Computational Fluid Dynamics) method. Geometric model of the catalytic converter has been established and meshed by the pre-processing tool of FLUENT. The distribution of velocity and pressure in the converter which outlet diameter is 70 mm is more evenly than the converter which outlet diameter is 50 mm. It is conducive to reducing airflow static pressure in the catalytic converter that expanding the outlet diameter in the case of other conditions remains unchanged. Therefore, the larger outlet diameter is beneficial to exhaust catalytic reaction.

Numerical Simulation Research of Air-Assisted Atomizer Internal Gas Flow Field Based on Fluent

2014 ◽  
Vol 599-601 ◽  
pp. 377-380
Author(s):  
Qiao Li ◽  
Ya Yu Huang
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Total Pressure ◽  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Mutual Influence ◽  
Simulation Research ◽  
Simulation Calculation ◽  
Gas Flow Field

The numerical simulation calculation of air-assisted atomizer internal gas flow field is done, the distribution and changes of the nozzle inside flow field total pressure, velocity, and dynamic and static pressure are analyzed. The analysis shows that the total pressure loss is less; due to the effect of gas viscous, the high-speed air flow is formed vortex flow near the outlet nozzle and the mutual influence between the dynamic and static pressure. A new way is supported for optimizing the nozzle structure according to these studies.

Effects of Swirling Flows on Pneumatic Transport of Solids in Pipes (Keynote)

2003 ◽  
Author(s):  
Yuji Tomita
Keyword(s):  
Numerical Simulation ◽  
Pressure Drop ◽  
Kinetic Energy ◽  
Total Pressure ◽  
Swirling Flow ◽  
Swirling Flows ◽  
Pneumatic Transport ◽  
Air Velocity ◽  
Low Velocity ◽  
Wall Collision

By applying swirling air flow, particles can be transported with smaller air velocity as compared to the conventional flow without swirl in both horizontal and vertical flows. The total pressure drop along the pipeline is generally larger than that of the flow without swirl, but becomes small and even smaller than that of conventional one when the air velocity decreases. Thus, the swirling flow is effective in low velocity pneumatic transport of suspension mode. By using weak swirl as compared to the previous one, also decreases the particle breakage when the air velocity is low. A numerical simulation shows that the kinetic energy of particles at the wall collision becomes smaller than that in flow without swirl when the breakage is decreased.

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