Step-Pool Streams: Adjustment to Maximum Flow Resistance

1995 ◽  
Vol 31 (10) ◽  
pp. 2593-2602 ◽  
Author(s):  
Athol D. Abrahams ◽  
Gang Li ◽  
Joseph F. Atkinson
Keyword(s):  
Flow Resistance ◽  
Maximum Flow

scholarly journals A Biomechanical Evaluation of the Epidural Neurolysis Procedure

2012 ◽  
Vol 1;15 (1;1) ◽  
pp. E89-E97
Author(s):  
Christof Birkenmaier
Keyword(s):  
Experimental Study ◽  
Epidural Space ◽  
Flow Resistance ◽  
Maximum Flow ◽  
Mechanical Effect ◽  
Treatment Situation ◽  
Axial Forces ◽  
Key Words Epidural ◽  
Surgery Department

Background: The epidural lysis of adhesions (ELOA) procedure supposedly has a biomechanical component in addition to the targeted injection of medications into the epidural space. It is assumed that the catheters used for the ELOA procedure can release epidural scars and adhesions. Objectives: To evaluate the possible biomechanical effects of the typically used catheters and to put these effects into clinical perspective. Study Design: Experimental study. Setting: The biomechanical laboratory of an academic orthopedic surgery department. Methods: Experimental setups were devised that allow for the measurement of the 3 main forces that can be exerted by manipulating a catheter in the epidural space or by injecting fluids through such a catheter: axial forces, torsional forces, and hydraulic effects. Results: The maximum axial forces measured under extremely tight catheter guidance were 7 newton (N), whereas the maximum forces under conditions that more likely reflect a real treatment situation were between 1 and 2 N. The maximum torsional forces measured were 0.3 N under extremely tight catheter guidance and 0.01 N under more realistic conditions. The maximum flow that could be achieved through the typical catheter using normal saline and the maximum possible thumb pressure onto a 5 mL or a 10 mL Luer-Lock syringe was 0.48 mL/ s. Given these results and other data available to us, it appears impossible that the ELOA procedure with typically used catheters has any relevant mechanical effect. Limitations: Like with any experimental study, the realities of an in vivo situation can only be modeled to a limited degree. The main limitation of our study is that we cannot calculate, measure, or simulate neither the flow resistance between an epidural adhesion pocket and the open, local epidural space nor the flow resistance between the open, local epidural space and the larger epidural space as well as the retroperitoneal space. Conclusions: According to our findings and arguments, the ELOA procedure is predominantly a method for the highly targeted application of epidural medications and possibly also has a lavage effect. A mechanical lysis of scars or adhesions appears unlikely. Key words: epidural lysis of adhesions, epidural neurolysis, epidural neuroplasty, biomechanical, experimental, epidural, catheter, back pain, sciatica

scholarly journals Design and Experimental Verification of a PZT Pump with Streamlined Flow Tubes

2019 ◽  
Vol 9 (18) ◽  
pp. 3881 ◽  
Author(s):  
Ming Tang ◽  
Qibo Bao ◽  
Jianhui Zhang ◽  
Qingshuang Ning ◽  
Chaobin Chen ◽  
...  
Keyword(s):  
Flow Rate ◽  
Flow Resistance ◽  
Maximum Amplitude ◽  
Maximum Flow ◽  
Flow Stability ◽  
Rate Equations ◽  
Flow Tube ◽  
Piezoelectric Pump ◽  
Streamlined Flow ◽  
Frequency Relationship

In this paper, a streamlined flow tube valveless piezoelectric pump (SLFT PZT pump) is proposed to modify the single flow trend and improve the fluid flow stability. Firstly, the structural and working principle of the streamlined flow tube, which accounts for changing the flow trend and improving the flow stability, were analyzed. The flow resistance and flow rate equations were established. Secondly, the pressure and velocity fields of the tube were simulated. These simulated results were consistent with the theoretical results. Thirdly, the flow resistance of the flow tube was tested with pressure differences of 1000 Pa, 1200 Pa, 1400 Pa and 1600 Pa respectively. The trend of the result curves was consistent with the simulated results. The amplitude-frequency relationship and the flow-rate-frequency relationship were also tested, both result curves highly corelate. The maximum amplitude was 0.228 mm (10 Hz, 120 V), and the maximum flow rate was 17.01 mL/min (10 Hz, 100 V). Finally, the theoretical flow rate of the SLFT PZT pump was calculated at 100 V and 120 V. These results roughly fitted with the experimental results. The streamlined flow tube could change the internal flow trend that remarkably improved the flow stability. Therefore, it promoted the application of the valveless PZT pump in living cells, biomedical and polymer delivery.

scholarly journals Constructal Law: Optimization as Design Evolution

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Adrian Bejan
Keyword(s):  
Entropy Production ◽  
Flow Resistance ◽  
Ad Hoc ◽  
Human Life ◽  
Maximum Flow ◽  
Minimum Entropy ◽  
Design Evolution ◽  
Constructal Law ◽  
And Migration ◽  
Design In Nature

Here, I review the physics meaning of optimization, knowledge and design evolution, and why these concepts and human activities are profoundly useful for human life. A law of physics is a concise statement that summarizes a phenomenon that occurs in nature. A phenomenon is a fact, circumstance, or experience that is apparent to the human senses and can be described. The design in nature phenomenon facilitates access for everything that flows, evolves, spreads, and is collected: river basins, atmospheric and ocean currents, animal life and migration, and technology (the evolution of the “human-and-machine species,” wealth, life). This phenomenon is summarized by the constructal law: the occurrence and evolution of designs in nature, its time direction. Based on its record, the constructal law accounts for the design phenomenon and also for all the phenomena that have been described individually (ad-hoc) with end-design (destiny) statements of “optimality” (min, max). Most notably, the constructal law accounts for contradictory end-design statements such as minimum entropy production and maximum entropy production, and minimum flow resistance and maximum flow resistance.

scholarly journals The constructal law of design and evolution in nature

2010 ◽  
Vol 365 (1545) ◽  
pp. 1335-1347 ◽  
Author(s):  
Adrian Bejan ◽  
Sylvie Lorente
Keyword(s):  
Entropy Generation ◽  
Flow Resistance ◽  
Scaling Laws ◽  
Minimum Weight ◽  
Finite Size ◽  
Maximum Flow ◽  
Constructal Theory ◽  
Minimum Entropy ◽  
Constructal Law ◽  
Flow Systems

Constructal theory is the view that (i) the generation of images of design (pattern, rhythm) in nature is a phenomenon of physics and (ii) this phenomenon is covered by a principle (the constructal law): ‘for a finite-size flow system to persist in time (to live) it must evolve such that it provides greater and greater access to the currents that flow through it’. This law is about the necessity of design to occur, and about the time direction of the phenomenon: the tape of the design evolution ‘movie’ runs such that existing configurations are replaced by globally easier flowing configurations. The constructal law has two useful sides: the prediction of natural phenomena and the strategic engineering of novel architectures, based on the constructal law, i.e. not by mimicking nature. We show that the emergence of scaling laws in inanimate (geophysical) flow systems is the same phenomenon as the emergence of allometric laws in animate (biological) flow systems. Examples are lung design, animal locomotion, vegetation, river basins, turbulent flow structure, self-lubrication and natural multi-scale porous media. This article outlines the place of the constructal law as a self-standing law in physics, which covers all the ad hoc (and contradictory) statements of optimality such as minimum entropy generation, maximum entropy generation, minimum flow resistance, maximum flow resistance, minimum time, minimum weight, uniform maximum stresses and characteristic organ sizes. Nature is configured to flow and move as a conglomerate of ‘engine and brake’ designs.

scholarly journals The Influence of Groove Structure Parameters on the Maximum Flow Resistance of a Rectangular Narrow Channel

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3716
Author(s):  
Guodong Li ◽  
Dandan Cai ◽  
Shanshan Li ◽  
Xiaogang Li ◽  
Pengfeng Li ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flow Resistance ◽  
Unit Length ◽  
Maximum Flow ◽  
Narrow Channel ◽  
Critical Value ◽  
Structure Parameters ◽  
Liquid Suspension ◽  
High Turbulence ◽  
Groove Structure

In the hydraulically suspended passive shutdown assembly, in order to prevent the liquid suspension rod falling too fast and the outer tube from violent impact, it is necessary to study the way to increase flow resistance. This study added grooves to the wall of the narrow channel to increase its flow resistance. Using the RNG k-ε turbulence model in Fluent, the influence of the groove structure parameters and the Reynolds number on the flow resistance of the narrow channel was discussed to find the optimal groove structure parameters. The results showed that the flow resistance of the narrow channel increased with the increase in the concave–convex ratio, and when the concave–convex ratio was small, the flow resistance decreased with increased groove thickness, while when the concave–convex ratio exceeded a certain critical value, the flow resistance increased with increased groove thickness. Additionally, the growth rate slowed down when the concave–convex ratio was greater than 3:1. As the unit length decreased, the flow resistance first increased and then decreased. When the unit length was 6 mm, the flow resistance reached the maximum. With the increase in the Reynolds number, the intensity of the local high-turbulence kinetic energy clearly increased.

Outcome of Buccal Mucosal Graft Urethroplasty in Long Segment Anterior Urethral Stricture

2020 ◽  
Vol 19 (2) ◽  
pp. 64-68
Author(s):  
Mrinmoy Biswas ◽  
Sudip Das Gupta ◽  
Mohammed Mizanur Rahman ◽  
Sharif Mohammad Wasimuddin
Keyword(s):  
Urethral Stricture ◽  
Flow Rate ◽  
Surgical Outcome ◽  
Simple Technique ◽  
Anterior Segment ◽  
Maximum Flow ◽  
Anastomotic Site ◽  
Buccal Mucosal Graft ◽  
Male Patients

Objective: To assess the success of BMG urethroplasty in long segment anterior urethral stricture. Method: From January 2014 to December 2015, twenty male patients with long anterior segment urethral stricture were managed by BMG urethroplasty. After voiding trial they were followed up at 3 month with Uroflowmetry, RGU & MCU and PVR measurement by USG. Patients were further followed up with Uroflowmetry and PVR at 6 months interval.Successful outcome was defined as normal voiding with a maximum flow rate >15ml /sec and PVR<50 ml with consideration of maximum one attempt of OIU after catheter removal. Results: Mean stricture length was 5.2 cm (range 3-9 cm) and mean follow-up was 15.55 months (range 6-23 months). Only two patients developed stricture at proximal anastomotic site during follow-up. One of them voided normally after single attempt of OIU. Other one required second attempt of OIU and was considered as failure (5%). Conclusion: BMG urethroplasty is a simple technique with good surgical outcome. Bangladesh Journal of Urology, Vol. 19, No. 2, July 2016 p.64-68

Tidal Flow: A Fast and Teachable Maximum Flow Algorithm

2018 ◽  
Vol 12 ◽  
pp. 25-41
Author(s):  
Matthew C. FONTAINE
Keyword(s):  
Computer Science ◽  
Tidal Flow ◽  
Maximum Flow ◽  
Efficient Algorithms ◽  
Science Students ◽  
Flow Algorithm ◽  
Maximum Flows

Among the most interesting problems in competitive programming involve maximum flows. However, efficient algorithms for solving these problems are often difficult for students to understand at an intuitive level. One reason for this difficulty may be a lack of suitable metaphors relating these algorithms to concepts that the students already understand. This paper introduces a novel maximum flow algorithm, Tidal Flow, that is designed to be intuitive to undergraduate andpre-university computer science students.

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