Changes in Carotid Artery Flow Velocities after Stent Implantation: A Fluid Dynamics Study with Laser Doppler Anemometry

2003 ◽  
Vol 10 (2) ◽  
pp. 275-284 ◽  
Author(s):  
Oliver Greil ◽  
Gottlieb Pflugbeil ◽  
Klaus Weigand ◽  
Wolfgang Weiß ◽  
Dieter Liepsch ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Flow Rate ◽  
Rate Ratio ◽  
Laser Doppler Anemometry ◽  
Flow Behavior ◽  
Laser Doppler ◽  
Flow Rate Ratio ◽  
External Carotid ◽  
Flow Profile ◽  
Separation Zones

Purpose: To study the influence of stent size and location on flow patterns in a physiological carotid model. Methods: Wallstents were positioned in silicon models of the carotid artery at various locations: 2 stents appropriately sized to the anatomy were placed in (1) the internal carotid artery (ICA) and (2) the ICA extending completely into the common carotid artery so as to cover the external carotid artery (ECA) orifice. Another 2 stents were placed in the ICA extending (1) partially and (2) completely into the bulb to simulate stent displacement and disproportion between stent size and the original vessel geometry. Measurements were performed with laser Doppler anemometry (LDA) using pulsatile flow conditions (Reynolds number=250; flow 0.431 L/min; ICA:ECA flow rate ratio 70:30) in hemodynamically relevant cross sections. The hemodynamic changes were analyzed with 1-dimensional flow profiles. Results: With the stent in the ICA, no changes of the normal flow profile were seen. For stents positioned in the ICA and extending partially or completely into the carotid bulb, the flow behavior was affected by the resistance of the stent to flow in the ECA. Hemodynamically relevant disturbances were seen in the ICA and ECA, especially in the separation zones (regions along the walls just after a bifurcation, bend, or curve). The ICA:ECA flow rate ratios shifted from 70:30 to 71.3:28.7 and from 70:30 to 75.1:24.9, respectively, in the 2 malpositioned stent models. With the stent placed in the ICA extending completely into the CCA, the ICA:ECA flow rate ratio shifted from 70:30 to 72.4:27.6. In this configuration, there were no notable flow changes in the ICA, but a clear diminishing of the separation zones in the ECA separation zones. Conclusions: Anatomically correct positioning of appropriately sized stents does not lead to relevant flow disturbances in the ICA. In the ECA, depending on the position, size, and interstices of the stent, the physiological flow was considerably disturbed when any part of the stent covered the inflow of the vessel. Disturbances were seen when the stent was positioned into the bulb. For clinical application, stent location and size must be carefully determined so that the stent covers the bifurcation completely or is in the ICA only.

Traceable Flow Rate Measurements With a Very Low Uncertainty Using Laser Doppler Anemometry

2017 ◽  
Author(s):  
Markus Juling ◽  
Jonas Steinbock ◽  
Andreas Weissenbrunner
Keyword(s):  
Flow Rate ◽  
Laser Doppler Anemometry ◽  
Volume Flow Rate ◽  
Primary Standard ◽  
Volume Flow ◽  
Laser Doppler ◽  
Maximum Deviation ◽  
Flow Profile ◽  
Rate Measurement ◽  
Flow Rate Measurement

Precise volume flow rate measurements are very important for various industrial applications. Here, one problem is that the service conditions of a flow meter used in the field differ significantly from the conditions present during calibration. The working conditions such as the pressure, the temperature and the flow profile greatly increase the uncertainty of the flow rate measurement. To address this problem, a new laser-optical flow rate standard (LFS) was developed at the Physikalisch-Technische Bundesanstalt (PTB) that allows flow meters to be calibrated on site, thus greatly reducing the uncertainty of the flow rate measurement. For the LFS, the velocity profile within the pipe is measured with laser Doppler anemometry (LDA). The profile is then integrated to calculate the volume flow rate. Various improvements to LDA have made it possible to measure the flow rate with an uncertainty of less than 0.15 % (k = 2). A comparison of the LFS with the primary standard for thermal energy at PTB, which has an uncertainty of less than 0.04 % (k = 2), revealed a maximum deviation of 0.07 % for Reynolds numbers from 105 to 106, thus verifying the uncertainty of the LFS.

Analysis of the Spray and Transfer Function of Swirling Spray Flames From a Multi-Jet Steam Assisted Liquid Fuel Injector

2014 ◽  
Author(s):  
Clément Mirat ◽  
Daniel Durox ◽  
Thierry Schuller
Keyword(s):  
Transfer Function ◽  
Flow Rate ◽  
Transfer Functions ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Low Frequency ◽  
Laser Doppler ◽  
Flow Rate Ratio ◽  
Fuel Injector ◽  
Spray Flames

Characterizations of the response of swirling spray flames to flow rate modulations over the entire frequency range remain scarce. This response is addressed here by determining the transfer function of spray flames stabilized on a multi-jet steam-assisted dodecane injector in a turbulent swirling flow confined by a quartz tube. This type of burner is used in some liquid fueled industrial boilers. In the absence of combustion and air flow, a phase Doppler particle analyzer is used to determine the Sauter mean diameter (SMD) of the fuel spray as a function of the atomizing gas to fuel mass flow rate ratio (GLR) injected in the nozzle. For small values of the GLR, the SMD of the generated spray decreases rapidly as the GLR increases. For GLR values above a certain threshold, the SMD reaches a constant value that is independent of the GLR. Transfer functions are measured in this second regime for swirling air flows characterized by a swirl number S = 0.92 that is determined by laser Doppler anemometry. Transfer functions defined as the normalized ratio of OH* or CH* flame chemiluminescence intensity fluctuations divided by the velocity oscillation level measured by laser Doppler velocimetry at the burner outlet are determined as a function of the forcing frequency for a small perturbation level. The response of sooty and non sooty flames at globally lean conditions are examined. Using a set of steady experiments, it is shown that the OH* signal may safely be used to confidently estimate low frequency heat release rate disturbances for both types of flames, but the CH* signal cannot be used in the sooty flame cases. The measured transfer functions of non-sooty spray flames feature many similarities with the transfer function of perfectly premixed swirling flames indicating that their dynamics is also controlled by interference mechanisms that need to be elucidated.

Determination of flow rate ratio for plate valve operating in two-phase medium

1989 ◽  
Vol 25 (7) ◽  
pp. 394-396
Author(s):  
V. E. Shcherba ◽  
I. S. Berezin ◽  
S. S. Danilenko ◽  
I. E. Titov ◽  
P. P. Filippov
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Flow Rate Ratio ◽  
Two Phase ◽  
Plate Valve ◽  
Phase Medium

Effect of the argon/monomer flow-rate ratio on the flowability trend of PECVD-processed micropowder

2017 ◽  
Vol 328 ◽  
pp. 480-487 ◽  
Author(s):  
V.R. Giampietro ◽  
M. Gulas ◽  
P. Rudolf von Rohr
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Flow Rate Ratio

Effects of Respiration and Gravity on Infradiaphragmatic Venous Flow in Normal and Fontan Patients

Circulation ◽  
2000 ◽  
Vol 102 (suppl_3) ◽  
Author(s):  
Tain-Yen Hsia ◽  
Sachin Khambadkone ◽  
Andrew N. Redington ◽  
Francesco Migliavacca ◽  
John E. Deanfield ◽  
...  
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Venous Return ◽  
Fontan Circulation ◽  
Flow Rate Ratio ◽  
Venous Flow ◽  
Beneficial Effects ◽  
In Series ◽  
Expiratory Flow ◽  
Fontan Patients

Background —In the Fontan circulation, pulmonary and systemic vascular resistances are in series. The implications of this unique arrangement on infradiaphragmatic venous physiology are poorly understood. Methods and Results —We studied the effects of respiration and gravity on infradiaphragmatic venous flows in 20 normal healthy volunteers (control) and 48 Fontan patients (atriopulmonary connection [APC] n=15, total cavopulmonary connection [TCPC] n=30). Hepatic venous (HV), subhepatic inferior vena caval (IVC), and portal venous (PV) flow rates were measured with Doppler ultrasonography during inspiration and expiration in both the supine and upright positions. The inspiratory-to-expiratory flow rate ratio was calculated to reflect the effect of respiration, and the supine-to-upright flow rate ratio was calculated to assess the effect of gravity. HV flow depended heavily on inspiration in TCPC compared with both control and APC subjects (inspiratory-to-expiratory flow rate ratio 3.4, 1.7, and 1.6, respectively; P <0.0001). Normal PV flow was higher in expiration, but this effect was lost in TCPC and APC patients (inspiratory-to-expiratory flow rate ratio 0.8, 1.0, and 1.1, respectively; P =0.01). The respiratory influence on IVC flow was the same in all groups. Gravity decreased HV flow more in APC than in TCPC patients (supine-to-upright flow rate ratio 3.2 versus 2.1, respectively; P <0.04) but reduced PV flow equally in all groups. Conclusions —Gravity and respiration have important influences on infradiaphragmatic venous return in Fontan patients. Although gravity exerts a significant detrimental effect on lower body venous return, which is more marked in APC than in TCPC patients, the beneficial effects of respiration in TCPC patients are mediated primarily by an increase in HV flow. These effects may have important short- and long-term implications for the hemodynamics of the Fontan circulation.

scholarly journals Numerical and experimental investigation on the depressurization capacity of a new type of depressure-dominated jet mill bit

2020 ◽  
Vol 17 (6) ◽  
pp. 1602-1615
Author(s):  
Xu-Yue Chen ◽  
Tong Cao ◽  
Kai-An Yu ◽  
De-Li Gao ◽  
Jin Yang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Area Ratio ◽  
Low Flow ◽  
Flow Rate Ratio ◽  
Cuttings Transport ◽  
Horizontal Drilling ◽  
Hole Cleaning ◽  
Bottom Hole ◽  
New Type

AbstractEfficient cuttings transport and improving rate of penetration (ROP) are two major challenges in horizontal drilling and extended reach drilling. A type of jet mill bit (JMB) may provide an opportunity to catch the two birds with one stone: not only enhancing cuttings transport efficiency but also improving ROP by depressuring at the bottom hole. In this paper, the JMB is further improved and a new type of depressure-dominated JMB is presented; meanwhile, the depressurization capacity of the depressure-dominated JMB is investigated by numerical simulation and experiment. The numerical study shows that low flow-rate ratio helps to enhance the depressurization capacity of the depressure-dominated JMB; for both depressurization and bottom hole cleaning concern, the flow-rate ratio is suggested to be set at approximately 1:1. With all other parameter values being constant, lower dimensionless nozzle-to-throat-area ratio may result in higher depressurization capacity and better bottom hole cleaning, and the optimal dimensionless nozzle-to-throat-area ratio is at approximately 0.15. Experiments also indicate that reducing the dimensionless flow-rate ratio may help to increase the depressurization capacity of the depressure-dominated JMB. This work provides drilling engineers with a promising tool to improve ROP.

Cold Flow Investigation of Silicon Carbide Cylindrical Filter Element

2002 ◽  
Author(s):  
M. H. Al-Hajeri ◽  
Raed Al-Saleh ◽  
Adel Al-Hebeshi ◽  
Ali Witry
Keyword(s):  
Silicon Carbide ◽  
Laser Doppler Anemometry ◽  
Flow Behavior ◽  
Vertical Channel ◽  
Filter Element ◽  
Laser Doppler ◽  
Performance Standard ◽  
Cold Flow ◽  
Flow Investigation

Silicon carbide cylindrical filter elements have proven to be an effective mean of removing particulates to levels exceeding the new source performance standard. This paper reports a Laser Doppler anemometry (LDA) investigation to study the flow behavior in the vicinity of the cylindrical filter. A single cylindrical filter has based in vertical channel. The flow enters from the bottom of the channel towards the filter element passing through to the outlet at the top of the channel. The particles deposition distribution around the filter element is studied using different face velocities.

The Characteristics of CH4-Vapor Catalytic Reforming Reaction Considering CO2 and CH4 Reaction in the Micro-Chamber

2007 ◽  
Author(s):  
Jing-Yu Ran ◽  
Li-Xiang Niu ◽  
Qiang Tang ◽  
Li Zhang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rate Ratio ◽  
Reaction System ◽  
Conversion Ratio ◽  
Flow Rate Ratio ◽  
Ni Catalyst ◽  
Complex Reaction ◽  
Catalytic Reforming

Methane and vapor catalytic-reaction is a complex reaction system, and especially CH4/CO2 reaction has an important influence to the methane/vapor reforming reaction. In this paper, the reaction character for methane and vapor catalytic reforming reaction in the micro-chamber wall with Ni catalyst is numerically investigated. The results show that the CH4/CO2 reaction has a vital influence on reactive characteristics in the different H2O/CH4 mole ratio and the mass flow-rate. With increasing the H2O/CH4 mole ratio, the concentration of H2 and CO2 increases, the concentration of CO increases and then decreases, but if the H2O/CH4 mole ratio is more than 2.5, the result is different. The reaction efficiency will descend while the flow-rate increases. The results also display that the methane conversion ratio, the vapor conversion ratio, and the hydrogen concentrations can be up to 81.73%, 69.42%, and 4.29%, while the H2O/CH4 mole ratio, flow-rate and methane/vapor mass flow-rate ratio are 2.5, 7 g/h and 0.1 respectively.

Effect of CS2 Flow Rate on the Formation of Aligned Carbon Microcoils

2019 ◽  
Vol 947 ◽  
pp. 40-46
Author(s):  
Hyun Ji Kim ◽  
Sung Hoon Kim
Keyword(s):  
Flow Rate ◽  
Vapor Deposition ◽  
Rate Ratio ◽  
Chemical Vapor ◽  
Regular Structure ◽  
Flow Rate Ratio ◽  
Total Flow ◽  
Total Flow Rate ◽  
Flow Rates ◽  
Thermal Chemical Vapor Deposition

The formation of aligned carbon microcoils could be achieved using C2H2 as a source gas and CS2 as an incorporated additive gas under thermal chemical vapor deposition system. To elucidate the ratio of C2H2/CS2 for the formation of the aligned carbon microcoils, the CS2 flow rate was first manipulated under the identical C2H2 flow rate (500sccm) condition. The formation and the alignment of carbon microcoils could be only achieved under the ratio of C2H2/CS2 = 33.3 condition, namely the flow rates of CS2 = 15sccm and C2H2= 500sccm. The total flow rate of the used gases was varied under the identical C2H2/CS2 flow rate ratio (33.3) condition. The C2H2 flow rate was manipulated under the identical CS2 flow rate (15sccm) condition. It was found that the formation and the alignment of carbon microcoils could be only achieved under the condition of 15sccm of CS2 flow rate in the range of 200 ~ 500sccm of C2H2 flow rate, regardless of the flow rate ratio of C2H2/CS2 and the total flow rate. The crystal structure of the well-aligned CMCs reveals the increase in the (002) peak in XRD spectrum for the aligned carbon microcoils, indicating the existence of the more regular structure in the aligned carbon microcoils. Based on these results, the cause for the formation of the aligned carbon microcoils only in the case of the CS2 flow rate = 15sccm with the imaginary pictures for the flow rate ratio of C2H2/CS2 just above the substrate were proposed.

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