Pressure Drops Through Arterial Stenosis Models in Steady Flow Condition

1992 ◽  
Vol 114 (3) ◽  
pp. 416-418 ◽  
Author(s):  
S. Cavalcanti ◽  
P. Bolelli ◽  
E. Belardinelli
Keyword(s):  
Pressure Drop ◽  
Steady Flow ◽  
Flow Condition ◽  
Momentum Equation ◽  
Arterial Stenosis ◽  
Pressure Drops ◽  
Area Reduction ◽  
Steady Flow Condition ◽  
Equidistant Points ◽  
Arterial Stenoses

Measures of pressure drops were made in two different plexiglass models of axial-symmetric arterial stenoses. The stenosis models had the same are reduction (86 percent) but were of different length so as to have a different tapering degree. Pressures were measured in steady flow condition at three equidistant points of the stenosis: upstream, in the middle, and downstream. Results indicate that: the upstream-middle pressure drop is independent of tapering degree but is highly influenced by area reduction; moreover it is much greater than the middle-downstream drop. The upstream-middle pressure drop can be accurately predicted by means of a relationship deduced by the momentum equation.

Experimental Study of a Radial Turbine Using Floating Nozzle for Wave Energy Conversion

2009 ◽  
Author(s):  
Toshio Konno ◽  
Yoshihiro Nagata ◽  
Manabu Takao ◽  
Toshiaki Setoguchi
Keyword(s):  
Energy Conversion ◽  
Steady Flow ◽  
Wave Energy ◽  
Flow Condition ◽  
Radial Flow ◽  
Guide Vane ◽  
Wave Energy Conversion ◽  
Wells Turbine ◽  
Radial Turbine ◽  
Steady Flow Condition

The objective of this study is to propose a new radial flow turbine for wave energy conversion and to clarify its performance by model testing under steady flow condition. The proposed radial turbine has a rotor blade row for unidirectional airflow and two guide vane rows. The guide vane rows are named ‘floating nozzle’ in the study. The guide vane rows slide in an axial direction and work as nozzle in the turbine alternately for bi-directional airflow, so as to rectify bidirectional airflow and to make uni-directional airflow. The radial flow turbine with a diameter of 500mm has been manufactured and investigated experimentally under steady flow condition generated by a wind tunnel using a piston/cylinder system with a diameter of 1.4m. As a result, it has been found in the study that the peak efficiency of the proposed radial turbine is approximately 57% and the rotational speed of this turbine is considerably lower that that of Wells turbine. Further, the effect of nozzle setting angle on the turbine performance was investigated and clarified in the study.

scholarly journals Flow Patterns in the Dog Descending Aorta under a Steady Flow Condition Simulating Mid-Systole

2004 ◽  
Vol 47 (4) ◽  
pp. 1000-1009 ◽  
Author(s):  
Shunsuke ENDO ◽  
Harry Leonardo GOLDSMITH ◽  
Takeshi KARINO
Keyword(s):  
Steady Flow ◽  
Flow Condition ◽  
Flow Patterns ◽  
Descending Aorta ◽  
Steady Flow Condition

Flow patterns in dog aortic arch under a steady flow condition simulating mid-systole

1996 ◽  
Vol 11 (4) ◽  
pp. 180-191 ◽  
Author(s):  
Shunsuke Endo ◽  
Yasunori Sohara ◽  
Takeshi Karino
Keyword(s):  
Aortic Arch ◽  
Steady Flow ◽  
Flow Condition ◽  
Flow Patterns ◽  
Steady Flow Condition

Steady-flow Cf-Nre Correlation for the Wire Gauze Regenerator Inferred from Linear Wave Analysis

1993 ◽  
Vol 207 (1) ◽  
pp. 53-62
Author(s):  
A J Organ
Keyword(s):  
Unsteady Flow ◽  
Steady Flow ◽  
Momentum Equation ◽  
Wire Mesh ◽  
Linear Wave ◽  
Wave Analysis ◽  
Flow Area ◽  
Pressure Drops ◽  
The Wire ◽  
Factor C

Linear wave analysis of unsteady flow in the wire mesh regenerator is extended to account for viscous losses (shear at the wall and abrupt change in the free-flow area). As a test of relevance to the Stirling gas circuit, the standard, unsteady-flow momentum equation is re-expressed in terms of the algebra [admittance ratios, pressure ratios) of the linear wave approach. This permits the steady-flow friction factor, Cf, to be extracted and plotted as a function of Reynolds number, Ntc. The resulting correlation is found to correspond closely to the experimentally determined counterpart. An explanation is found for the discrepancy noted between computed and observed pressure drops in the Stirling cycle machine.

scholarly journals Rapid Numerical Estimation of Pressure Drop in Hot Runner System

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 207
Author(s):  
Jae Sung Jung ◽  
Sun Kyoung Kim
Keyword(s):  
Pressure Drop ◽  
Injection Molding ◽  
Steady Flow ◽  
Design Process ◽  
Newtonian Fluid ◽  
Numerical Estimation ◽  
Generalized Newtonian Fluid ◽  
Computer Tool ◽  
Pressure Drops ◽  
Runner Design

To determine dimensions in the hot runner systems, given a material, it is necessary to predict the pressure drop according to them. Although modern injection molding simulators are able to evaluate such pressure drops, they are expensive and demanding to be employed as a design utility. This work develops a computer tool that can calculate a pressure drop from the sprue to the gate assuming a steady flow of a generalized Newtonian fluid. For a four drop hot runner system, the accuracy has been verified by comparing the obtained results with those by a commercial simulator. This paper presents how to utilize the proposed method in the hot runner design process.

Flow Measurements in an Aortocoronary Bypass Graft Casting

1996 ◽  
Vol 118 (2) ◽  
pp. 165-171
Author(s):  
E. Y. Kwack ◽  
L. H. Back ◽  
X. M. Ruan ◽  
A. Chaux
Keyword(s):  
Pressure Drop ◽  
Flow Visualization ◽  
Steady Flow ◽  
Flow Rate ◽  
Saphenous Vein ◽  
Poiseuille Flow ◽  
Flow Rates ◽  
Pressure Drops ◽  
Vein Segment ◽  
Flow Pressure

Flow visualization and pressure measurements were carried out in a single valve saphenous vein casting which was made from a saphenous vein segment obtained from a bypass patient at Cedars Sinai Medical Center. Dye was injected to understand the flow around the valve. The dye showed very complex flow patterns around the valve and in the valve sinus, and the cavity formed by a ligated branch. For steady flow, pressure drops across the valve were 0.72, 2.0 and 6.3 mmHg for the physiological flow rates of 45, 84, and 169 ml/min, respectively. Overall pressure drop across the casting (compared to Poiseuille flow for a straight tube) increased with the flow rate, being 130 to 290 percent higher over this flow rate range. In the case of pulsatile flow, pressure drops across the valve were 0.95 and 3.0 mmHg for the flow rates of 47 and 87 ml/min which were 26 and 43 percent higher than those of steady flow. Overall pressure drop was 220 and 360 percent higher for those flow rates compared to Poiseuille flow. The measured spatial pressure distributions along the casting and flow visualization indicated the global nature of the flow field with the accelerated flow through the valve separating and reattaching downstream along the wall in the pressure recovery region. Atherosclerosis may be prone to occur in the lower shear region along the wall beyond the valve tip in the reattachment region, as we have observed in vivo in rabbit experiments.

Experimental and Computational Analyses of Pressure Differentials in Flexible Ducts With Different Bent Angles

2007 ◽  
Author(s):  
Ray R. Taghavi ◽  
Wonjin Jin ◽  
Mario A. Medina
Keyword(s):  
Pressure Drop ◽  
Static Pressure ◽  
Complex Geometry ◽  
Analysis Data ◽  
Secondary Flows ◽  
Low Flow ◽  
Pressure Drops ◽  
Pressure Distributions ◽  
Geometrical Effects ◽  
Cfd Analyses

A set of experimental analyses was conducted to determine static pressure drops inside non-metallic flexible, spiral wire helix core ducts, with different bent angles. In addition, Computational Fluid Dynamics (CFD) solutions were performed and verified by comparing them to the experimental data. The CFD computations were carried out to produce more systematic pressure drop information through these complex-geometry ducts. The experimental setup was constructed according to ASHRAE Standard 120-1999. Five different bent angles (0, 30, 45, 60, and 90 degrees) were tested at relatively low flow rates (11 to 89 CFM). Also, two different bent radii and duct lengths were tested to study flexible duct geometrical effects on static pressure drops. FLUENT 6.2, using RANS based two equations - RNG k-ε model, was used for the CFD analyses. The experimental and CFD results showed that larger bent angles produced larger static pressure drops in the flexible ducts. CFD analysis data were found to be in relatively good agreement with the experimental results for all bent angle cases. However, the deviations became slightly larger at higher velocity regimes and at the longer test sections. Overall, static pressure drop for longer length cases were approximately 0.01in.H2O higher when compared to shorter cases because of the increase in resistance to the flow. Also, the CFD simulations captured more pronounced static pressure drops that were produced along the sharper turns. The stronger secondary flows, which resulted from higher and lower static pressure distributions in the outer and inner surfaces, respectively, contributed to these higher pressure drops.

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