Viscous flow in collapsible tubes of slowly varying elliptical cross-section

1977 ◽  
Vol 81 (2) ◽  
pp. 273-294 ◽  
Author(s):  
Rosemary Wild ◽  
T. J. Pedley ◽  
D. S. Riley
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Transverse Velocity ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Collapsible Tube ◽  
Experimental Conditions ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Collapsible Tubes

This paper is concerned with steady flow in collapsible tubes, such as veins, at fairly low Reynolds number. Lubrication theory is used to calculate the velocity and pressure distribution in an elliptical tube whose cross-sectional area and eccentricity vary slowly and in a given way with longitudinal distance x. The transverse velocity field and the effect of inertia on the primary velocity and pressure distributions are calculated to first order in the relevant small parameter. The results of these calculations are combined with a relationship between transmural pressure and the cross-sectional area at any x which is close to that measured in (large) veins, and are used to predict the pressure and flow in a collapsible tube when a given distribution of external pressure is applied. Different relationships between the tube perimeter and cross-sectional area are examined. The theory is applied to an experiment in which a segment of collapsible tube is supported between two rigid segments, and squeezed; predictions of the relationship between the pressure drop and flow rate are made for various experimental conditions. In particular, when the resistance of the downstream rigid segment is held constant, a range of flow rates is found in which the pressure drop falls as the flow rate is raised; this agrees with experiment.

scholarly journals Steady analysis of transcritical flows in collapsible tubes with discontinuous mechanical properties: implications for arteries and veins

2013 ◽  
Vol 736 ◽  
pp. 195-215 ◽  
Author(s):  
A. Siviglia ◽  
M. Toffolon
Keyword(s):  
Mechanical Properties ◽  
Free Surface Flows ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Collapsible Tube ◽  
Cross Sectional ◽  
Collapsible Tubes ◽  
The Cross ◽  
Transcritical Flows ◽  
Arteries And Veins

AbstractWe study the conditions under which discontinuous mechanical properties of a collapsible tube can induce transcritical flows, i.e. the transition through the critical state where the speed index (analogous to the Mach or the Froude numbers for compressible and free surface flows, respectively) is one. Such a critical transition may strongly modify the flow properties, cause a significant reduction in the cross-sectional area of the tube, and limit the flow. General relationships are obtained for a short segment using a one-dimensional model under steady flow conditions. Marginal curves delimiting the transcritical regions are identified in terms of the speed index and the cross-sectional area ratio. Since there are many examples of such flows in physiology and medicine, we also analyse the specific case of prosthesis (graft or stent) implantation in blood vessels. We then compute transcritical conditions for the case of stiffness and reference area variations, considering a collapsible tube characterized by physiological parameters representative of both arteries and veins. The results suggest that variations in mechanical properties may induce transcritical flow in veins but is unrealistic in arteries.

Accuracy and precision of MR velocity mapping in measurement of stenotic cross-sectional area, flow rate, and pressure gradient

1993 ◽  
Vol 3 (2) ◽  
pp. 433-437 ◽  
Author(s):  
Lars Søndergaard ◽  
Freddy Ståhlberg ◽  
Carsten Thomsen ◽  
Anders Stensgaard ◽  
Knud Lindvig ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Flow Rate ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Velocity Mapping ◽  
Cross Sectional ◽  
Accuracy And Precision

192 Verification of Scale Effect on Pressure Drop Characteristics in Curved Rectangular Ducts with Change of Cross Sectional Area

2016 ◽  
Vol 2016.51 (0) ◽  
pp. 181-182
Author(s):  
Kota KOBAYASHI ◽  
Yosuke HATA ◽  
Takashi FUKUE ◽  
Koichi HIROSE ◽  
Fumiaki KUSAKABE ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Scale Effect ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional

scholarly journals EFFECT OF OPERATING PARAMETERS UPON PERFORMANCE OF FUNCTIONAL SPECIMENS OF HIGH EXPANSION FOAM GENERATORS

2020 ◽  
Vol 1 (2) ◽  
pp. 14-21
Author(s):  
V Chuian ◽  
O Тymoshenko ◽  
A Hrachov
Keyword(s):  
Flow Rate ◽  
Cross Sectional Area ◽  
Solution Flow Rate ◽  
Operating Parameters ◽  
Spray Nozzle ◽  
Sectional Area ◽  
Solution Flow ◽  
Cross Sectional ◽  
Foam Expansion ◽  
Expansion Foam

The issues related to application of high expansion foam as flooding fire extinguishing agent as well as necessity of the development of high expansion foam generators in Ukraine are considered. Patent search concerning appropriate devices for generation of high expansion foam from foam solutions was conducted and it showed specific features of the components when generating high expansion foam. The results of the research of operating parameters of prototypes of high expansion foam generators of fan and ejection types are presented. For high expansion foam generators of fan type dependence of foam expansion, foam solution flow rate and amount of spent foam solution on the performance of the spray nozzle at different pressures and ratio of fan performance to the spray nozzle performance was established; the ratio of the cross-sectional area of the fan to the total area of the perforated holes in the foaming grid was studied, too. For high-expansion foam generators of the ejection type dependence of foam expansion, foam solution flow rate and amount of spent foam solution on the capacity of the spray nozzle unit at different pressures, foam solution flow rate to the total area of the holes in the foaming grid, and ratio of the cross-sectional area of the generator to the total area of the perforated holes of the foaming grid were studied. Functional models of the mentioned types of generators (both ejection (aspiration) one and generator equipped with fan (air blowing unit)) were developed, created and tested for the purpose of derivation of appropriate relations between their conditions of use and performance. At the same time, high expansion foam generators of fan type by their weight and size parameters are intended for use in the divisions of the Operative and Rescue Service of Civil Protection of the State Emergency Service of Ukraine as portable firefighting units. Such firefighting units are intended to be installed first of all on any state-of-the-art municipal fire engines equipped with autonomous AC generators. High expansion foam generators of ejection type are intended for use as firefighting units in foam firefighting systems of various facilities with fire hazard.

scholarly journals Analysis of Liquid Flow and Mixing in an Oscillatory Flow Reactor Provided with 2D Smooth Periodic Constrictions

2018 ◽  
Vol 4 (2) ◽  
pp. 1-15 ◽  
Author(s):  
F. Almeida ◽  
F. Rocha ◽  
A. Ferreira
Keyword(s):  
Flow Rate ◽  
Oscillatory Flow ◽  
Flow Reactor ◽  
Cross Sectional Area ◽  
Axial Dispersion ◽  
Mixing Efficiency ◽  
Sectional Area ◽  
Cross Sectional ◽  
Liquid Dispersion ◽  
Fluid Oscillation

In this research paper the residence time distribution (RTD) was monitored for a range of fluid oscillation, frequency, amplitude and flow rate in two oscillatory flow reactors (OFR) provided with 2D smooth periodic constrictions (2D-SPC) with different designs. It was studied the axial liquid dispersion using axial dispersion model and the mixing efficiency using tank-in-series model for continuous mode. Two cases, with and without fluid oscillation, were studied and determined the optimum conditions to ensure a close plug flow, an efficient mixing and a low axial liquid dispersion. The optimum operation conditions for the two 2D-SPC designs were found. Moreover, the effect of open cross-sectional area (a) on mixing and axial dispersion was also investigated. For low cross-sectional area values the mixing is higher. It was observed that fluid oscillation increases the mixing intensity even at lower flow rates, and the axial dispersion increases as the flow rate increases.

Influence of the Cross Sectional Area of a Separation Column Using Structured Packing

2003 ◽  
Author(s):  
Rosa H. Cha´vez ◽  
Javier de J. Guadarrama ◽  
Osbaldo Pe´rez ◽  
Abel Herna´ndez-Guerrero
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Separation Efficiency ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Structured Packing ◽  
Separation Column ◽  
Transfer Unit ◽  
The Cross

In order to determine the dimension of a separation column, hydrodynamic and mass transfer models are necessary to evaluate the pressure drop and the height of the global mass transfer unit, respectively. Those parameters are a function of the cross sectional area of the column. The present work evaluates the dependency of the pressure drop and height of the global transfer unit with respect to the cross sectional area of the column, using an absorption column with high efficiency structured packing, in order to recover SO2 in the form of NaHSO3, as an example. An optimization was done applying Two Film model which is based on the number of global mass transfer units of both gas and liquid, involving the separation efficiency in terms of the height of a global transfer unit. Structured packing, geometrically heaped in a separation column, has been achieving wider acceptance in the separation processes due to their geometric characteristics that allow them to have greater efficiency in the separation processes. Three different structured packing were evaluated in this work. The results show how ININ packing is one of the packings does the best work having the highest separation efficiency because it has the lowest height of the global mass transfer unit and Mellapak packing has the largest capacity because it manages the largest liquid and gas flows. An analysis is done with respect to the pressure drop through the system for all packings considered, and a discussion is presented for each hydrodynamic and mass transfer parameter studied.

Dynamic Detection and Analysis of Raw Silk’s Flatness

2011 ◽  
Vol 175-176 ◽  
pp. 385-388
Author(s):  
Xin Zhang ◽  
Yi Quan Xu ◽  
Kai Meng ◽  
Qing Guan Chen
Keyword(s):  
Cross Section ◽  
Axial Length ◽  
Minor Axis ◽  
Cross Sectional Area ◽  
Elliptical Cross Section ◽  
Sectional Area ◽  
Cross Sectional ◽  
Elliptical Cross ◽  
Photoelectric Sensor ◽  
Dynamic Detection

The shape of most raw silk’s cross-section can be regarded as ellipse approximately. Axial length of the raw silk’s cross-section was detected and recorded dynamically by photoelectric sensor combined with the software of LabVIEW. Two photoelectric sensors were located orthogonally to measure axial lengths of the ellipse. The major and minor values can be considered as the major and minor axis values of the raw silk’s elliptical cross-section respectively. Thereby, the flatness and the area of raw silk’s cross-section can be calculated according to the values of major and minor axes. In addition, the raw silk’s evenness was characterized based on the variation of the cross-sectional area.

Isometric tension and myofilamental cross-sectional area in striated muscle

1962 ◽  
Vol 202 (5) ◽  
pp. 824-826 ◽  
Author(s):  
Einar Helander ◽  
Carl-Axel Thulin
Keyword(s):  
Striated Muscle ◽  
Protein Composition ◽  
Isometric Tension ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Experimental Conditions ◽  
Cross Sectional ◽  
Total N ◽  
Calf Muscles

Isometric tension in tetanically stimulated calf muscles was examined in vivo in 3 rabbits and 18 cats. In two cats the gastrocnemius and soleus muscles were studied separately. After determination of the isometric tension the muscles were dissected and their water content, total N content, and protein composition were analyzed. On this basis it was possible to calculate that part of the cross-sectional area of the muscle fibers which consisted of myofilaments. The recorded maximum isometric tension was related to the myofilamental cross-sectional area. Under the given experimental conditions, the calf muscles developed a tension of 108 ± 5 g/mm2 cross-sectional area. Higher values resulted from tests of individual calf muscles than from combined muscles.

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