Numerical study on the steady flow characteristics of proximal anastomotic models

Abdominal aortic aneurysm (AAA) is a degenerative disease defined as the abnormal ballooning of the abdominal aorta (AA) wall which is usually caused by atherosclerosis. The aneurysm grows larger and eventually ruptures if it is not diagnosed and treated. Aneurysms occur mostly in the aorta, the main artery of the chest and abdomen. The aorta carries blood flow from the heart to all parts of the body, including the vital organs, the legs, and feet. The objective of the present study is to investigate the combined effects of aneurysm and curvature on flow characteristics in S-shaped bends with sweep angle of 90° at Reynolds number of 900. The fluid mechanics of blood flow in a curved artery with abnormal aortic is studied through a mathematical analysis and employing Cosmos flow simulation. Blood is modeled as an incompressible non-Newtonian fluid and the flow is assumed to be steady and laminar. Hemodynamic characteristics are analyzed. Grid independence is tested on three successively refined meshes. It is observed that the abrupt expansion induced by AAA results in an immensely disturbed regime. The results may have implications not only for understanding the mechanical behavior of the blood flow inside an aneurysm artery but also for investigating the mechanical behavior of the blood flow in different arterial diseases, such as atherosclerosis.

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Numerical study on flow characteristics at blade passage and tip clearance in a linear cascade of high performance turbine blade

KSME International Journal ◽

10.1007/bf02984462 ◽

2003 ◽

Vol 17 (4) ◽

pp. 606-616 ◽

Cited By ~ 2

Author(s):

Hyon Kook Myong ◽

Seung Yong Yang

Keyword(s):

Turbine Blade ◽

High Performance ◽

Numerical Study ◽

Flow Characteristics ◽

Tip Clearance ◽

Blade Passage ◽

Linear Cascade

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A Numerical Study of the Flow Characteristics and Separation Efficiency of a Hydrocyclone

KSCE Journal of Civil Engineering ◽

10.1007/s12205-018-1780-1 ◽

2018 ◽

Vol 22 (11) ◽

pp. 4272-4281 ◽

Cited By ~ 4

Author(s):

Ik-Tae Im ◽

Gyu Dong Gwak ◽

Se Min Kim ◽

Young Ki Park

Keyword(s):

Separation Efficiency ◽

Numerical Study ◽

Flow Characteristics

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Numerical Study of Heat Transfer Intensification in a Circular Tube Using a Thin, Radiation-Absorbing Insert. Part 1: Thermo-Hydraulic Characteristics

Energies ◽

10.3390/en14154596 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4596

Author(s):

Piotr Bogusław Jasiński

Keyword(s):

Heat Transfer ◽

Flow Resistance ◽

Numerical Study ◽

Flow Characteristics ◽

Cylindrical Tube ◽

Radiation Absorption ◽

Fluid Temperature ◽

Gas Temperature ◽

Insert Size ◽

Channel Diameter

The presented paper, which is the first of two parts, shows the results of numerical investigations of a heat exchanger channel in the form of a cylindrical tube with a thin insert. The insert, placed concentrically in the pipe, uses the phenomenon of thermal radiation absorption to intensify the heat transfer between the pipe wall and the gas. Eight geometric configurations of the insert size were numerically investigated using CFD software, varying its diameter from 20% to 90% of the pipe diameter and obtaining the thermal-flow characteristics for each case. The tests were conducted for a range of numbers Re = 5000–100,000 and a constant temperature difference between the channel wall and the average gas temperature of ∆T = 100 °C. The results show that the highest increase in the Nu number was observed for the inserts with diameters of 0.3 and 0.4 of the channel diameter, while the highest flow resistance was noted for the inserts with diameters of 0.6–0.7 of the channel diameter. The f/fs(Re) and Nu/Nus(Re) ratios are shown on graphs indicating how much the flow resistance and heat transfer increased compared to the pipe without an insert. Two methods of calculating the Nu number are also presented and analysed. In the first one, the average fluid temperature of the entire pipe volume was used to calculate the Nu number, and in the second, only the average fluid temperature of the annular portion formed by the insert was used. The second one gives much larger Nu/Nus ratio values, reaching up to 8–9 for small Re numbers.

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A particle image velocimetry study on the pulsatile flow characteristics in straight tubes with an asymmetric bulge

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/0954406001523678 ◽

2000 ◽

Vol 214 (5) ◽

pp. 655-671 ◽

Cited By ~ 10

Author(s):

S C M Yu ◽

J B Zhao

Keyword(s):

Particle Image Velocimetry ◽

Steady Flow ◽

Pulsatile Flow ◽

Flow Condition ◽

Particle Image ◽

Flow Characteristics ◽

Reynolds Numbers ◽

Working Fluid ◽

Flow Conditions ◽

Image Velocimetry

Flow characteristics in straight tubes with an asymmetric bulge have been investigated using particle image velocimetry (PIV) over a range of Reynolds numbers from 600 to 1200 and at a Womersley number of 22. A mixture of glycerine and water (approximately 40:60 by volume) was used as the working fluid. The study was carried out because of their relevance in some aspects of physiological flows, such as arterial flow through a sidewall aneurysm. Results for both steady and pulsatile flow conditions were obtained. It was found that at a steady flow condition, a weak recirculating vortex formed inside the bulge. The recirculation became stronger at higher Reynolds numbers but weaker at larger bulge sizes. The centre of the vortex was located close to the distal neck. At pulsatile flow conditions, the vortex appeared and disappeared at different phases of the cycle, and the sequence was only punctuated by strong forward flow behaviour (near the peak flow condition). In particular, strong flow interactions between the parent tube and the bulge were observed during the deceleration phase. Stents and springs were used to dampen the flow movement inside the bulge. It was found that the recirculation vortex could be eliminated completely in steady flow conditions using both devices. However, under pulsatile flow conditions, flow velocities inside the bulge could not be suppressed completely by both devices, but could be reduced by more than 80 per cent.

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Numerical Study on Flow Characteristics in High Multi-Stage Pressure Reducing Valve

Volume 1A, Symposia: Keynotes; Advances in Numerical Modeling for Turbomachinery Flow Optimization; Fluid Machinery; Industrial and Environmental Applications of Fluid Mechanics; Pumping Machinery ◽

10.1115/fedsm2017-69210 ◽

2017 ◽

Author(s):

Fu-qiang Chen ◽

Zhi-xin Gao ◽

Jin-yuan Qian ◽

Zhi-jiang Jin

Keyword(s):

Energy Consumption ◽

Numerical Study ◽

Research Work ◽

Flow Characteristics ◽

Temperature Fields ◽

Turbulent Dissipation ◽

Technological Support ◽

Multi Stage ◽

Valve Opening ◽

Pressure Reducing Valve

In this paper, a new high multi-stage pressure reducing valve (HMSPRV) is proposed. The main advantages include reducing noise and vibration, reducing energy consumption and dealing with complex conditions. As a new high pressure reducing valve, its flow characteristics need to be investigated. For that the valve opening has a great effect on steam flow, pressure reduction and energy consumption, thus different valve openings are taken as the research points to investigate the flow characteristics. The analysis is conducted from four aspects: pressure, velocity, temperature fields and energy consumption. The results show that valve opening has a great effect on flow characteristics. No matter for pressure, velocity or temperature field, the changing gradient mainly reflects at those throttling components for all valve openings. For energy consumption, in the study of turbulent dissipation rate, it can be found that the larger of valve opening, the larger of energy consumption. It can be concluded that the new high multi-stage pressure reducing valve works well under complex conditions. This study can provide technological support for achieving pressure regulation, and benefit the further research work on energy saving and multi-stage design of pressure reducing devices.

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Numerical study on the flow characteristics of tidal jets induced by a tidal-jet-generator

Ocean Engineering ◽

10.1016/j.oceaneng.2005.10.024 ◽

2006 ◽

Vol 33 (14-15) ◽

pp. 1896-1918 ◽

Cited By ~ 1

Author(s):

J.-C. Park ◽

T. Okada ◽

K. Furukawa ◽

K. Nakayama

Keyword(s):

Numerical Study ◽

Flow Characteristics

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Experimental and Numerical Study of Honeycomb Tip on Suppressing Tip Leakage Flow in Turbine Cascade

Volume 2A: Turbomachinery ◽

10.1115/gt2017-64942 ◽

2017 ◽

Cited By ~ 4

Author(s):

Yunfeng Fu ◽

Fu Chen ◽

Huaping Liu ◽

Yanping Song

Keyword(s):

Numerical Study ◽

Flow Characteristics ◽

Leakage Flow ◽

Exit Section ◽

Turbine Cascade ◽

Tip Leakage Flow ◽

Physical Processes ◽

Tip Leakage ◽

Gap Height ◽

Positive Effect

In this paper, the effect of a novel honeycomb tip on suppressing tip leakage flow in a highly-loaded turbine cascade has been experimentally and numerically studied. The research focuses on the mechanisms of honeycomb tip on suppressing tip leakage flow and affecting the secondary flow in the cascade, as well as the influences of different clearance heights on leakage flow characteristics. In addition, two kinds of local honeycomb tip structures are pro-posed to explore the positive effect on suppressing leakage flow in simpler tip honeycomb structures. Based on the experimental and numerical results, the physical processes of tip leakage flow and its interaction with main flow are analyzed, the following conclusions can be obtained. Honeycomb tip rolls up a number of small vortices and radial jets in regular hexagonal honeycomb cavities, increasing the flow resistance in the clearance and reducing the velocity of leakage flow. As a result, the structure of honeycomb tip not only suppresses the leakage flow effectively, but also has positive effect on reducing the associated losses in cascade by reducing the strength of leakage vortex. Compare to the flat tip cascade at 1%H gap height, the relative leakage flow in honeycomb tip cascade reduces from 3.05% to 2.73%, and the loss at exit section is also decreased by 10.63%. With the increase of the gap height, the tip leakage flow and loss have variations of direct proportion with it, but their growth rates in the honeycomb tip cascade are smaller. Consider the abradable property of the honeycomb seal, a smaller gap height is allowed in the cascade with honeycomb tip, and that means honeycomb tip has better effect on suppressing leakage flow. Two various local honeycomb tip structures has also been discussed. It shows that local raised honeycomb tip has better suppressing leakage flow effect than honeycomb tip, while local concave honeycomb tip has no more effect than honeycomb tip. Compare to flat tip cascade, the leakage flow in honeycomb tip cascade, local concave tip cascade and local raised honeycomb tip cascade decrease by nearly 17.33%, 15.51% and 30.86% respectively, the losses at exit section is reduced by 13.38%, 12% and 28.17% respectively.

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