scholarly journals Numerical Analysis of Urine Flow with Multiple Sizes of Double-J Stents

2020 ◽  
Vol 10 (12) ◽  
pp. 4291 ◽  
Author(s):  
Hyoung-Ho Kim ◽  
Kyung-wuk Kim ◽  
Young Ho Choi ◽  
Seung Bae Lee ◽  
Yasutaka Baba
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Urine Flow ◽  
Total Flow ◽  
Total Flow Rate ◽  
Flow Rates ◽  
Double J Stent ◽  
Luminal Flow ◽  
Flow Through

This study investigated which sizes of double-J stents are more effective in achieving an acceptable urine flow through stenotic and stented ureters. Sixty four computational fluid dynamics models of the combinations of two different gauge ureters (4.57 mm and 5.39 mm in diameter) with four different levels of ureteral and four different sizes of double-J stents were developed for the numerical analysis of urine flow in the ureter. Luminal, extraluminal, and total flow rates along the ureter were measured, and the flow patterns around the ports and side holes were investigated. For the 4.57-mm ureter, the total flow rate for each gauge of stent was 23–63 mL/h (5 Fr), 20–47 mL/h (6 Fr), 17–35 mL/h (7 Fr), and 16–26 mL/h (8 Fr) and for the 5.39-mm ureter, the total flow rate for each gauge of stent was 43–147 mL/h (5 Fr), 36–116 mL/h (6 Fr), 29–92 mL/h (7 Fr), and 26–71 mL/h (8 Fr). With a 74% stenosis, all stents allowed a low flow rate, and the differences in flow rates between the stents were small. At the other levels of stenosis, 5 Fr stents allowed greater flow rates than the 8 Fr stents. The luminal flow rate increased just before the area of stenosis and decreased after the stenosis because of the increase and decrease in the luminal flow through the side holes before and after the stenosis. Therefore, a larger double-J stent is not favorable in achieving an acceptable urine flow through the stenotic and stented ureters. The results in this study could not be necessarily correlated with clinical situation because peristalsis, viscosity of the urine and real format of the ureter were not considered in our model. In vivo experiments are necessary for confirmation of our findings. Double J stents are commonly used in the ureteral stenosis or occlusion, especially due to ureter stones which obstruct the flow of urine. Clinicians choose the size of double J stent on the basis of their clinical experience. Here, we tried to know which sizes of double J stents are better for sufficient urine flow. According to various documents that try to determine the optimal shape of double J stents to increase the urine flow through the ureter, mostly bigger stent is recommended to occur maximum urine flow. However, in case of ureter with stenosis or occlusion, the right size of the double J stent may vary depending on the degree of stenosis in the ureter. To find appropriate stent size for the ureter with stenosis, computational fluid dynamics was conducted. This study shows that smaller diameter stents are more appropriate than larger diameter stents depending on the situation.

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.

scholarly journals Computational fluid dynamics analysis of flow through immobilized catalyzed packed bed reactor for removal of 4-chlorophenol from wastewater

2019 ◽  
Vol 25 (6) ◽  
pp. 878-889 ◽  
Author(s):  
Sudhansu Sandhibigraha ◽  
Soumya Sasmal ◽  
Tarun Kanti Bandyopadhyay ◽  
Biswanath Bhunia
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Packed Bed ◽  
Packed Bed Reactor ◽  
Inlet Concentration ◽  
Bed Height ◽  
Fluent Software ◽  
Flow Through

The computational fluid dynamics (CFD) simulation of the packed bed reactor (PBR) was carried out using ANSYS Fluent software. The various process parameters, such as inlet concentration of 4-chlorophenol (4-CP), flow rate, bed height, and porosity, were optimized to predict maximum biodegradation of 4-CP in immobilized catalyzed PBR. The geometrical mesh of the PBR was constructed using Gambit software, and a mesh size of 236995 was selected from the grid-independent study. A laminar flow model was used to understand the hydrodynamics as well as concentration profile of 4-CP inside the PBR using Fluent software. Through CFD, the effect of the flow rate, inlet concentration, and the bed height and porosity of the immobilized catalyst bed on the static pressure, mass imbalance, velocity, and stress-strain field inside the PBR was visualized. CFD simulation study predicted that maximum biodegradation of 4-CP was found in the presence of 500 mg/L of inlet concentration of 4-CP, 4 mL/min of flow rate, 18 cm of bed height and 0.375 of porosity. An experimental study was conducted for wastewater flow through the <i>B. subtilis MF447840.1</i> immobilized catalyzed PBR to remove the 4-CP in the laminar flow region. It was evident that CFD simulated results agreed well with experimental values.

Computational Study of Single-Sided Ventilation Through a 3-Dimensional Room

2012 ◽  
Author(s):  
A. Idris ◽  
B. P. Huynh
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Speed ◽  
Flow Rate ◽  
Software Package ◽  
Computational Study ◽  
Ventilation Rate ◽  
3 Dimensional ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through

Ventilation flow through a 3-dimensional rectangular-box room is investigated numerically, by using a commercial Computational Fluid Dynamics (CFD) software package. The room has all its window openings located on one wall, and the wind is assumed to blow parallel to this wall. The standard K-epsilon turbulence model is used. Air’s flow rate and flow pattern are considered in terms of wind speed and the openings’ characteristics, such as their number, location, size and shape. For a constant total area of the openings, it is found that ventilation rate increases with more openings, especially when they are widely separated or positioned at different heights.

scholarly journals Design of a Novel Axial Gas Pulses Micromixer and Simulations of its Mixing Abilities via Computational Fluid Dynamics

Micromachines ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 205 ◽  
Author(s):  
Florian Noël ◽  
Christophe Serra ◽  
Stéphane Le Calvé
Keyword(s):  
Fluid Dynamics ◽  
Air Pollution ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Inert Gas ◽  
Flow Rates ◽  
Carrier Gas ◽  
Mixing Ratios ◽  
Multi Stage ◽  
Fast Development

Following the fast development of microfluidics over the last decade, the need for methods for mixing two gases in flow at an overall flow rate ranging from 1 to 100 NmL·min−1 with programmable mixing ratios has been quickly increasing in many fields of application, especially in the calibration of analytical devices such as air pollution sensors. This work investigates numerically the mixing of pure gas pulses at flow rates in the range 1–100 NmL·min−1 in a newly designed multi-stage and modular micromixer composed of 4 buffer tanks of 300 µL each per stage. Results indicate that, for a 1 s pulse of pure gas (formaldehyde) followed by a 9 s pulse of pure carrier gas (air), that is a pulses ratio of 1/10, an effective mixing up to 94–96% can be readily obtained at the exit of the micromixer. This is achieved in less than 20 s for any flow rate ranging from 1 to 100 NmL·min−1 simply by adjusting the number of stages, 1 to 16 respectively. By using an already diluted gas bottle containing 100 ppm of a given compound in an inert gas same as the carrier gas, concentrations ranging from 10 to 90 ppm should be obtained by adjusting the pulses ratio between 1/10 and 9/10 respectively.

scholarly journals Analysis of Urine Flow in Three Different Ureter Models

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Kyung-Wuk Kim ◽  
Young Ho Choi ◽  
Seung Bae Lee ◽  
Yasutaka Baba ◽  
Hyoung-Ho Kim ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Hydrostatic Pressure ◽  
Flow Rate ◽  
Urine Flow ◽  
Human Anatomy ◽  
Urine Flow Rate ◽  
Ureteral Stenosis ◽  
Double J Stent ◽  
Different Types ◽  
Luminal Flow

The ureter provides a way for urine to flow from the kidney to the bladder. Peristalsis in the ureter partially forces the urine flow, along with hydrostatic pressure. Ureteral diseases and a double J stent, which is commonly inserted in a ureteral stenosis or occlusion, disturb normal peristalsis. Ineffective or no peristalsis could make the contour of the ureter a tube, a funnel, or a combination of the two. In this study, we investigated urine flow in the abnormal situation. We made three different, curved tubular, funnel-shaped, and undulated ureter models that were based on human anatomy. A numerical analysis of the urine flow rate and pattern in the ureter was performed for a combination of the three different ureters, with and without a ureteral stenosis and with four different types of double J stents. The three ureters showed a difference in urine flow rate and pattern. Luminal flow rate was affected by ureter shape. The side holes of a double J stent played a different role in detour, which depended on ureter geometry.

Automatic optimization of a centrifugal pump based on impeller–diffuser interaction

2018 ◽  
Vol 232 (8) ◽  
pp. 1004-1018 ◽  
Author(s):  
KM Guleren
Keyword(s):  
Fluid Dynamics ◽  
Genetic Algorithm ◽  
Computational Fluid Dynamics ◽  
Centrifugal Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Increase ◽  
Flow Rates ◽  
Automatic Optimization ◽  
Mass Flow Rates

In this study, a centrifugal pump has been optimized using the genetic algorithm coupled with computational fluid dynamics considering the flow physics for various impeller–diffuser configurations. During the automatic optimization process, the population was selected from a pool of pump geometries generated by four design variables; namely the relative diffuser vane angle, number of diffuser vanes, number of impeller blades, and the impeller wrap angle. The genetic algorithm was combined with a flow solver and a computer aided design software which was used also to create the mesh for the generated geometry. Two objective functions were adopted for the optimization: maximum pressure increase and minimum relative flow angle, which is an indication of reverse flow in the impeller. The iteration history of the optimization for the design (2.4 kg/s) and off-design (3.6 kg/s) flow rate showed that the optimization has been converged to an impeller–diffuser configuration within approximately 250 computational fluid dynamics analyses. Three geometries from each optimization with the highest pressure increase were studied for various mass flow rates and the results were compared with those of the original pump. The results show that the first optimization indicates a significant improvement of pressure increase at design flow rate (15.5%) but decrease at larger flow rates. The second optimization which was required after the results of the first optimization enhanced the head for the entire mass flow rates with an average increase of 25.74%.

Spray Outputs from a Variable-Rate Sprayer Manipulated with PWM Solenoid Valves

2018 ◽  
Vol 34 (3) ◽  
pp. 527-534
Author(s):  
Joao Eduardo Silva ◽  
Heping Zhu ◽  
João Paulo Arantes Rodrigues da Cunha
Keyword(s):  
Flow Rate ◽  
Duty Cycle ◽  
Pressure Fluctuations ◽  
Control Flow ◽  
Operating Pressure ◽  
Regression Equations ◽  
Variable Rate ◽  
Total Flow ◽  
Total Flow Rate ◽  
Flow Rates

Abstract. Pressure fluctuations from air-assisted orchard sprayers can cause nozzles to discharge inaccurate flow rates during variable-rate spray applications. Variations in total flow rate discharged from 40 nozzles, each coupled with a pulse-width-modulated (PWM) solenoid valve, were determined for a variable-rate air-assisted sprayer. Variables for the total flow rate measurements were number of active nozzles ranging from 1 to 40 and PWM duty cycle ranging from 10% to 100%. Experiments were conducted under conditions with and without operating pressure adjustments. Under the no-pressure-adjustment condition, the operating pressure in the spray line was not adjusted for compensation when either the number of active nozzles or PWM duty cycle was changed. Under the pressure-adjustment condition, the operating pressure was adjusted to retain at 242 kPa. The total flow rate increased as duty cycle and/or number of active nozzles increased under both pressure conditions. However, the operating pressure in the spray line dropped considerably as either the number of active nozzles or duty cycle increased under the no-pressure-adjustment condition, resulting in significant lower total flow rates compared to the pressure-adjustment condition. The differences in total flow rates between the two pressure conditions increased as duty cycle and number of active nozzles increased. To improve future intelligent sprayer accuracy, two-variable regression equations were established to predict and control total flow rates with different duty cycles and numbers of active nozzles operated simultaneously. Keywords: Flow control, Flow rate, Hydraulic nozzle, Pesticide, Precision sprayer.

scholarly journals Effects of water salinity on the foam dynamics for EOR application

2021 ◽  
Author(s):  
Svetlana Rudyk ◽  
Sami Al-Khamisi ◽  
Yahya Al-Wahaibi
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Apparent Viscosity ◽  
Liquid Flow Rate ◽  
Salinity Range ◽  
Porous System ◽  
Foam Formation ◽  
Total Flow ◽  
Total Flow Rate ◽  
Foam Flow

AbstractFactors limiting foam injection for EOR application are exceptionally low rock permeability and exceedingly high salinity of the formation water. In this regard, foam formation using internal olefin sulfonate is investigated over a wide salinity range (1, 5, 8, 10, and 12% NaCl) through 10 mD limestone. The relationships between pressure drop (dP), apparent viscosity, liquid flow rate, total flow rate, salinity, foam texture, and length of foam drops at the outlet used as an indicator of viscosity are studied. Foaming is observed up to 12% NaCl, compared to a maximum of 8% NaCl in similar core-flooding experiments with 50 mD limestone and 255 mD sandstone. Thus, the salinity limit of foam formation has increased significantly due to the low permeability, which can be explained by the fact that the narrow porous system acts like a membrane with smaller holes. Compared to the increasing dP reported for highly permeable rocks, dP linearly decreases in almost the entire range of gas fraction (fg) at 1–10% NaCl. As fg increases, dP at higher total flow rate is higher at all salinities, but the magnitude of dP controls the dependence of apparent viscosity on total flow rate. Low dP is measured at 1% and 10% NaCl, and high dP is measured at 5, 8, and 12% NaCl. In the case of low dP, the apparent viscosity is higher at higher total flow rate with increasing gas fraction, but similar at two total flow rates with increasing liquid flow rate. In the case of high dP, the apparent viscosity is higher at lower total flow rate, both with an increase in the gas fraction and with an increase in the liquid flow rate. A linear correlation is found between dP or apparent viscosity and liquid flow rate, which defines it as a governing factor of foam flow and can be considered when modeling foam flow.

scholarly journals A Simple Transient Poiseuille-Based Approach to Mimic the Womersley Function and to Model Pulsatile Blood Flow

Dynamics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 9-17
Author(s):  
Andrea Natale Impiombato ◽  
Giorgio La Civita ◽  
Francesco Orlandi ◽  
Flavia Schwarz Franceschini Zinani ◽  
Luiz Alberto Oliveira Rocha ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Quadratic Function ◽  
Pulsatile Blood Flow ◽  
Flow Through ◽  
Simplified Analysis ◽  
Function Models ◽  
Flow Reversals

As it is known, the Womersley function models velocity as a function of radius and time. It has been widely used to simulate the pulsatile blood flow through circular ducts. In this context, the present study is focused on the introduction of a simple function as an approximation of the Womersley function in order to evaluate its accuracy. This approximation consists of a simple quadratic function, suitable to be implemented in most commercial and non-commercial computational fluid dynamics codes, without the aid of external mathematical libraries. The Womersley function and the new function have been implemented here as boundary conditions in OpenFOAM ESI software (v.1906). The discrepancy between the obtained results proved to be within 0.7%, which fully validates the calculation approach implemented here. This approach is valid when a simplified analysis of the system is pointed out, in which flow reversals are not contemplated.

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