Pulsatile Flow and Mass Transport Over an Array of Cylinders: Gas Transfer in a Cardiac-Driven Artificial Lung

2005 ◽  
Vol 128 (1) ◽  
pp. 85-96 ◽  
Author(s):  
Kit Yan Chan ◽  
Hideki Fujioka ◽  
Robert H. Bartlett ◽  
Ronald B. Hirschl ◽  
James B. Grotberg
Keyword(s):  
Pressure Drop ◽  
Steady Flow ◽  
Void Fraction ◽  
Pulsatile Flow ◽  
Fiber Bundle ◽  
Gas Transfer ◽  
Right Heart ◽  
Flow Through ◽  
The Right ◽  
Array Geometry

The pulsatile flow and gas transport of a Newtonian passive fluid across an array of cylindrical microfibers are numerically investigated. It is related to an implantable, artificial lung where the blood flow is driven by the right heart. The fibers are modeled as either squared or staggered arrays. The pulsatile flow inputs considered in this study are a steady flow with a sinusoidal perturbation and a cardiac flow. The aims of this study are twofold: identifying favorable array geometry/spacing and system conditions that enhance gas transport; and providing pressure drop data that indicate the degree of flow resistance or the demand on the right heart in driving the flow through the fiber bundle. The results show that pulsatile flow improves the gas transfer to the fluid compared to steady flow. The degree of enhancement is found to be significant when the oscillation frequency is large, when the void fraction of the fiber bundle is decreased, and when the Reynolds number is increased; the use of a cardiac flow input can also improve gas transfer. In terms of array geometry, the staggered array gives both a better gas transfer per fiber (for relatively large void fraction) and a smaller pressure drop (for all cases). For most cases shown, an increase in gas transfer is accompanied by a higher pressure drop required to power the flow through the device.

scholarly journals Pressure drop and average void fraction measurements for two-phase flow through highly permeable porous media

2016 ◽  
Vol 94 ◽  
pp. 422-432 ◽  
Author(s):  
N. Chikhi ◽  
R. Clavier ◽  
J.-P. Laurent ◽  
F. Fichot ◽  
M. Quintard
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through

scholarly journals The study of systemic hemodynamic disorders of patients with varicose and post-thrombotic diseases

2020 ◽  
Vol 19 (2) ◽  
pp. 32-37
Author(s):  
I. N. Shanaev
Keyword(s):  
Blood Flow ◽  
Right Ventricle ◽  
Right Atrium ◽  
Ultrasound Examination ◽  
Anterior Wall ◽  
Right Heart ◽  
Normal Limits ◽  
Flow Through ◽  
The Right ◽  
Restrictive Type

Aim. Study of heart function in the patients with CVD. Materials and methods. 46 patients with varicosity (VD) and 34 patients with post-thrombotic disease (PTD) were examined; the control group was represented by 15 healthy volunteers. The diagnosis was established using the CEAP basic classification. The study did not include patients with a diagnosed arterial hypertension, diabetes mellitus, chronic lung disease, significant hemodynamic heart defects, coronary heart disease. Ultrasound examination of the heart and veins of the lower extremities was performed on a Saote My Lab Alpha, Acuson Sequoia 512 apparatus. In addition to the standard protocol of heart ultrasound examination, the parameters of the right heart were calculated: sizes of the right ventricle (RV), right atrium, thickness of the anterior wall of the pancreas; to assess the ejection fraction (EF) of the pancreas the mobility of the lateral edge of the tricuspid ring was calculated, and the pressure on the tricuspid valve (TV) was measured. Diastolic ventricular function was studied by spectrograms of tricuspid and mitral blood flow. Results. Most of the indicators of cardiac activity in patients with VD were within normal limits, but a tendency to increase increasing of the right heart size was noted. In addition, the thickness of the interventricular septum and the right ventricle (RV) anterior wall was found to increase from 0.8 to 1.1 cm and from 0.3 to 0.5 cm, respectively, according clinical classes from C2 to C6 (CEAP). Eject fraction (EF) of both the RV and the left ventricle (LV) were also within normal limits, but with a tendency to decrease (67.8 % – C2, to 62 % – C6). The growth of the clinical class is followed by the increasing of percentage of non-restrictive blood flow through the tricuspid valve (TV). The restrictive type of blood flow in patients with VD had not been identified. Patients with PTD also showed a tendency to increase the right heart. However, whereas the size of the RV, as a rule, did not exceed 3.0 cm, the size of the right atrium was slightly higher than normal one in the clinical class C4 and C5.6. All the patients had EF of LV within normal limits, but it slightly decreased by the growth of class. Only patient classes C3 and C4 had EF of RV within the normal range. The 18 % of patient class C5.6 had EF lower than normal with value 48%. Diastolic dysfunction (DD) of the RV was detected in 73.3% of patients with class C3 and 100% with classes C4 and C5.6. Moreover, a restrictive type of blood flow through TV appeared from class C4 and the percentage increased up to 27.2% (class C5,6). Conclusions. DD of the RV was the main hemodynamic disorder.

CFD Analysis Comparing Steady Flow and Pulsatile Flow Through the Aorta and its Main Branches

2016 ◽  
Author(s):  
John D. Martin
Keyword(s):  
Blood Flow ◽  
Steady Flow ◽  
Pulsatile Flow ◽  
Close Association ◽  
Beating Heart ◽  
Pressure Data ◽  
Heart Model ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Very High

A computational fluid dynamics (CFD) study has been done comparing pulsatile and non-pulsatile blood flow through the aortic arch and its main branches. The pulsatile flow was to mimic the blood flow due to a beating heart and the non-pulsatile or steady flow was to mimic cardiopulmonary bypass (CPB). The purpose of the study was too narrow in on possible reasons CPB may contribute to the development of atherosclerosis. The main focus of the study was to look at the wall shear stress (WSS) values due to their close association with the development of atherosclerosis. In addition velocity and pressure data were also analyzed. The results of this study showed a stark contrast between the WSS values between the CPB model and the beating heart model. The CPB model did not have any points of oscillating WSS combined with the fact that there were regions of very high and very low constant WSS values in comparison with the beating heart analysis suggests that there may be potential for atherosclerotic development or plaque buildup within the artery. The beating heart model showed a range of WSS values within the aorta that were much lower overall compared with the CPB model.

Pulsatile Flow and Oxygen Transport Past Cylindrical Fiber Arrays for an Artificial Lung: Computational and Experimental Studies

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Jennifer R. Zierenberg ◽  
Hideki Fujioka ◽  
Keith E. Cook ◽  
James B. Grotberg
Keyword(s):  
Right Ventricular ◽  
Steady Flow ◽  
Oxygen Transport ◽  
Pulsatile Flow ◽  
Experimental Studies ◽  
Artificial Lung ◽  
Transport Efficiency ◽  
Fiber Arrays ◽  
Cylindrical Fiber ◽  
The Right

The influence of time-dependent flows on oxygen transport from hollow fibers was computationally and experimentally investigated. The fluid average pressure drop, a measure of resistance, and the work required by the heart to drive fluid past the hollow fibers were also computationally explored. This study has particular relevance to the development of an artificial lung, which is perfused by blood leaving the right ventricle and in some cases passing through a compliance chamber before entering the device. Computational studies modeled the fiber bundle using cylindrical fiber arrays arranged in in-line and staggered rectangular configurations. The flow leaving the compliance chamber was modeled as dampened pulsatile and consisted of a sinusoidal perturbation superimposed on a steady flow. The right ventricular flow was modeled to depict the period of rapid flow acceleration and then deceleration during systole followed by zero flow during diastole. Experimental studies examined oxygen transfer across a fiber bundle with either steady, dampened pulsatile, or right ventricular flow. It was observed that the dampened pulsatile flow yielded similar oxygen transport efficiency to the steady flow, while the right ventricular flow resulted in smaller oxygen transport efficiency, with the decrease increasing with Re. Both computations and experiments yielded qualitatively similar results. In the computational modeling, the average pressure drop was similar for steady and dampened pulsatile flows and larger for right ventricular flow while the pump work required of the heart was greatest for right ventricular flow followed by dampened pulsatile flow and then steady flow. In conclusion, dampening the artificial lung inlet flow would be expected to maximize oxygen transport, minimize work, and thus improve performance.

Vortex Generation in Pulsatile Flow Through Arterial Bifurcation Models Including the Human Carotid Artery

1988 ◽  
Vol 110 (3) ◽  
pp. 166-171 ◽  
Author(s):  
Takayoshi Fukushima ◽  
Tatsuji Homma ◽  
Kiyohito Harakawa ◽  
Noriyuki Sakata ◽  
Takehiko Azuma
Keyword(s):  
Steady Flow ◽  
Pulsatile Flow ◽  
Separation Bubble ◽  
Vortex Formation ◽  
Flow Distribution ◽  
Horseshoe Vortex ◽  
Helical Flow ◽  
Elastic Tube ◽  
Recirculating Flow ◽  
Flow Through

Visualization experiments were performed to elucidate the complicated flow pattern in pulsatile flow through arterial bifurcations. Human common carotid arteries, which were made transparent, and glass-models simulating Y- and T-shaped bifurcations were used. Pulsatile flow with wave forms similar to those of arterial flow was generated with a piston pump, elastic tube, airchamber, and valves controlling the outflow resistance. Helically recirculating flow with a pattern similar to that of the horseshoe vortex produced around wall-based protuberances in circular tubes was observed in pulsatile flow through all the bifurcations used in the present study. This flow type, which we shall refer to as the horseshoe vortex, has also been demonstrated to occur at the human common carotid bifurcation in steady flow with Reynolds numbers above 100. Time-varying flows also produced the horseshoe vortex mostly during the decelerating phase. Fluid particles of dye solution approaching the bifurcation apex diverged, divided into two directions perpendicularly, and then showed helical motion representing the horseshoe vortex formation. While this helical flow was produced, the stagnation points appeared on the wall upstream of the apex. Their position was dependent upon the flow distribution ratio between the branches in the individual arteries. The region affected by the horseshoe vortex was smaller during pulsatile flow than during steady flow. Lowering the Reynolds number together with the Womersley number weakened the intensity of helical flow. A separation bubble, resulting from the divergence or wall roughness, was observed at the outer or inner wall of the branch vessels and made the flow more complicated.

Interfacial Drag for Two-Phase Flow Through High Permeability Porous Beds

1984 ◽  
Vol 106 (4) ◽  
pp. 865-870 ◽  
Author(s):  
N. K. Tutu ◽  
T. Ginsberg ◽  
J. C. Chen
Keyword(s):  
Particle Size ◽  
Pressure Drop ◽  
Void Fraction ◽  
Phase Flow ◽  
High Permeability ◽  
Two Phase ◽  
Liquid Flux ◽  
Flow Through ◽  
Interfacial Drag ◽  
Drag Term

Pressure drop and void fraction measurements in two-phase (air–water) flow through porous beds of randomly packed spheres have been used to determine the interfacial gas–liquid drag and the gas–solid drag for the case of zero net liquid flux through the bed. The results, presented for beds of 3.18-, 6.35-, and 12.7-mm spheres, show that the interfacial gas–liquid drag term is of the same order as the gas-solid drag term when the particle size is greater than 6 mm.

Pressure drop due to viscous flow through cylinders

1959 ◽  
Vol 6 (4) ◽  
pp. 542-546 ◽  
Author(s):  
Howard Brenner
Keyword(s):  
Pressure Drop ◽  
Circular Cylinder ◽  
Viscous Fluid ◽  
Viscous Flow ◽  
Steady Flow ◽  
Equations Of Motion ◽  
Point Force ◽  
Flow Through ◽  
Bounding Surfaces ◽  
Simple Fashion

A general formula is developed which permits a calculation of the pressure drop arising from the slow steady flow of a viscous fluid through a circular cylinder for arbitrarily assigned conditions of velocity on the bounding surfaces of the cylinder. In particular, the diminution in pressure can be calculated directly from the prescribed boundary velocities without requiring a detailed solution of the equations of motion. Hence it is possible to compute, in comparatively simple fashion, the magnitude of this macroscopic parameter for a large variety of complex motions which would normally present great analytical difficulties.By way of illustration the additional pressure drop arising from the presence of a point force situated along the axis of a cylinder is calculated. The additional force required to maintain the motion in the presence of the obstacle is exactly twice the magnitude of the point force itself.

Study the Geometrical Effects on the Unsteady Pulsatile Flow Through a Microchannel With a Sudden Step Shape

2013 ◽  
Author(s):  
Amir Nejat ◽  
Farshad Kowsary ◽  
Saman Ebrahimi ◽  
Amin Hasanzadeh
Keyword(s):  
Flow Field ◽  
Pulsatile Flow ◽  
Axisymmetric Flow ◽  
Expansion Ratio ◽  
Field Configuration ◽  
Primary Objective ◽  
Geometrical Parameters ◽  
Actuation Mechanism ◽  
Flow Through ◽  
The Right

In this paper, pulsatile flow through a microchannel with step expansion shape and working as valveless microvalve is investigated. The design of the microchannel is such that it causes the production of different vortex structures in the flow field and near corners. Our primary objective is to investigate how geometrical parameters affect the performance of the microvalve under different flow conditions. Unsteady, two-dimensional axisymmetric flow of an incompressible Newtonian fluid with laminar regime was simulated numerically using finite element approach. In order to imitate the actuation mechanism of a micropump, a time-varying sinusoidal pressure was set at the inlet region of the microchannel. Two basic dimensions were found to have crucial effect on the flow field configuration and vortex generation: the expansion ratio of the channel and the distance of the obstacle from the expansion region. The frequency of the actuation mechanism was varied from 1Hz to 1000Hz to cover the working range for many micropump applications. As the pressure is a key factor and should be manipulated in the right way, the pressure contours were studied. Vortex growth was captured through a single cycle and their size and existence time was compared for different geometrical inputs. At last, Strouhal number which is a measure of unsteadiness of the flow was calculated. This way we can investigate the sensitivity of the flow to changes in block obstacle distance from the expansion section and the expansion ratio. The obtained results lead to better understanding of the physics of pulsatile flows through microchannels and help in improving the efficiency of the existing configuration in designing more efficient micropump systems.

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