scholarly journals Simulation of a Chain of Collapsible Contracting Lymphangions With Progressive Valve Closure

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
C. D. Bertram ◽  
C. Macaskill ◽  
J. E. Moore
Keyword(s):  
Flow Rate ◽  
Flow Direction ◽  
Maximum Flow ◽  
Transmural Pressure ◽  
Maximum Flow Rate ◽  
Smooth Transition ◽  
Maximum Pressure ◽  
Mean Flow ◽  
Forward Flow ◽  
In Series

The aim of this investigation was to achieve the first step toward a comprehensive model of the lymphatic system. A numerical model has been constructed of a lymphatic vessel, consisting of a short series chain of contractile segments (lymphangions) and of intersegmental valves. The changing diameter of a segment governs the difference between the flows through inlet and outlet valves and is itself governed by a balance between transmural pressure and passive and active wall properties. The compliance of segments is maximal at intermediate diameters and decreases when the segments are subject to greatly positive or negative transmural pressure. Fluid flow is the result of time-varying active contraction causing diameter to reduce and is limited by segmental viscous and valvular resistance. The valves effect a smooth transition from low forward-flow resistance to high backflow resistance. Contraction occurs sequentially in successive lymphangions in the forward-flow direction. The behavior of chains of one to five lymphangions was investigated by means of pump function curves, with variation of valve opening parameters, maximum contractility, lymphangion size gradation, number of lymphangions, and phase delay between adjacent lymphangion contractions. The model was reasonably robust numerically, with mean flow-rate generally reducing as adverse pressure was increased. Sequential contraction was found to be much more efficient than synchronized contraction. At the highest adverse pressures, pumping failed by one of two mechanisms, depending on parameter settings: either mean leakback flow exceeded forward pumping or contraction failed to open the lymphangion outlet valve. Maximum pressure and maximum flow-rate were both sensitive to the contractile state; maximum pressure was also determined by the number of lymphangions in series. Maximum flow-rate was highly sensitive to the transmural pressure experienced by the most upstream lymphangions, suggesting that many feeding lymphatics would be needed to supply one downstream lymphangion chain pumping at optimal transmural pressure.

Development of Piezoelectric Diaphragm Pump

2012 ◽  
Vol 185 ◽  
pp. 18-20
Author(s):  
Tao Li ◽  
Chin Foo Goh ◽  
Jan Ma
Keyword(s):  
Flow Rate ◽  
Flow Direction ◽  
Maximum Flow ◽  
Pressure Head ◽  
Maximum Flow Rate ◽  
Pump Performance ◽  
Diaphragm Pump

In the present work, a piezoelectric diaphragm pump was designed and investigated. The pump uses a piezoelectric diaphragm transducer as the driving component, and two check valves located at the inlet and outlet to control the flow direction. The displacement of the transducer was first measured statically and dynamically. Then the vibration of check valves and the effects of chamber depth were investigated. Finally the pump performance was characterized. Maximum flow rate of 200 mL/min and pressure head of 5 mH2O can be achieved.

Propose and Characteristics Study of a New Actuation Method for Micropumps, Using Membrane Buckling

2005 ◽  
Author(s):  
Mohammad H. Saghafi ◽  
Mohammad T. Ahmadian ◽  
Hadi Salehi ◽  
R. Monazami ◽  
Azad Q. Zade
Keyword(s):  
Flow Rate ◽  
Outer Space ◽  
Maximum Flow ◽  
Maximum Flow Rate ◽  
Maximum Pressure ◽  
High Frequencies ◽  
Actuation System ◽  
Good Ability ◽  
Analytical Proof ◽  
Mechanical Actuation

In this paper, we present a novel idea on actuation system in micropumps. The prominent goal of this paper is to propose and prove a mechanical actuation system which works in high frequency and has good ability in producing flow and pressure in micro actuation system. As like as other common micropumps, the proposed scheme is consisted of two check valves and an actuation space. The actuation space includes a volume of liquid in a chamber and a cylindrical membrane as the actuator. The main aspect of this idea is employment of buckling as a consequence of incensement of its internal pressure caused by temperature rising in the membrane. Rise of temperature is done by passing a controllable current through the membrane and it looses its temperature to its outer space in the chamber. Frequency and amperage of the current are the elements identifying the temperatures membrane vacillates between them. Meanwhile, a nice idea is setting these values in such a way that minimum temperature of the membrane becomes equal to the temperature which membrane starts buckling at. Thermal, elastic and thermoelastic equations of the membrane and fluids dynamic equations is obtained and studied. Using these equations, the validity of the scheme is proved by showing its ability of getting and loosing temperature and also fatigue resistance of the membrane, in high frequencies. The analytical proof is done for a specific design. In the proposed design, Aluminum 1100 is adopted as membrane material and thickness and radius of the membrane are 1 μm and 100 μm, respectively. Maximum flow rate and frequency of the system according to highest temperature of the membrane are depicted in diagrams. According to this design, maximum flow rate in rational frequency and amperage of the current is 8.25 μL/min. Maximum pressure in that design is 3.5Kpa.

Lichen sclerosis–induced long segment anterior urethral stricture: The early outcome of one-stage repair using dorsolateral onlay buccal mucosa graft

2021 ◽  
pp. 039156032110033
Author(s):  
Atef Fathi ◽  
Omar Mohamed ◽  
Osama Mahmoud ◽  
Gamal A Alsagheer ◽  
Ahmed M Reyad ◽  
...  
Keyword(s):  
Success Rate ◽  
Urethral Stricture ◽  
Flow Rate ◽  
Urine Volume ◽  
Maximum Flow ◽  
Maximum Flow Rate ◽  
P Value ◽  
Onlay Graft ◽  
Voiding Symptoms ◽  
Stricture Recurrence

Background: Substitution urethroplasty using buccal mucosal grafts can be performed by several approaches including ventral onlay graft, dorsal onlay graft, or ventral urethrotomy with dorsal inlay graft. Our study aims to evaluate the surgical outcome of dorsolateral buccal mucosal graft for long segment anterior urethral stricture >6 cm in patients with Lichen sclerosus (LS). Methods: A retrospective study included patients who underwent repair for long segment anterior urethral stricture >6 cm due to LS between January 2013 and April 2019. All patients were followed-up at 3, 6, 9, and 12 months postoperatively and then yearly by clinical symptoms, uroflowmetry, and calculation of post-void residual urine volume. Retrograde urethrogram was requested for patients with voiding symptoms or decreased maximum flow rate. Stricture recurrence that required subsequent urethrotomy or urethroplasty was considered failure. The success rate and surgical complications were collected and analyzed. Results: Thirty patients were identified. The median age (range) was 39 (25–61) years and a median (range) stricture length was 8 (6–14) cm. Most of postoperative complications were of minor degree. The success rate at median follow-up of 15 (12–24) months was 86.5%. The median maximum flow rate increased significantly from 6 (2–11) ml/s preoperatively to 18 (range: 6–23) ml/s at the 6th month ( p value < 0.001). Conclusion: Dorsolateral buccal mucosal grafts urethroplasty for long anterior urethral stricture caused by LS has a high success rate and low risk of complications including stricture recurrence.

scholarly journals Maximum Flow Rate of a Single Component, Two-Phase Mixture

1965 ◽  
Vol 87 (1) ◽  
pp. 134-141 ◽  
Author(s):  
F. J. Moody
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Maximum Flow ◽  
Single Component ◽  
Maximum Flow Rate ◽  
Vapor Flow ◽  
Two Phase ◽  
Slip Ratio ◽  
Phase Mixture ◽  
Local Slip

A theoretical model is developed for predicting the maximum flow rate of a single component, two-phase mixture. It is based upon annular flow, uniform linear velocities of each phase, and equilibrium between liquid and vapor. Flow rate is maximized with respect to local slip ratio and static pressure for known stagnation conditions. Graphs are presented giving maximum steam/water flow rates for: local static pressures between 25 and 3,000 psia, with local qualities from 0.01 to 1.00; local stagnation pressures and enthalpies which cover the range of saturation states.

Effect of Blade Angle of Attack and Hub to Tip Ratio on Mass Flow Rate in an Axial Fan at a Fixed Rotational Speed

2008 ◽  
Author(s):  
Mohammad J. Izadi ◽  
Alireza Falahat
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Angle Of Attack ◽  
Maximum Flow ◽  
Maximum Flow Rate ◽  
Maximum Mass ◽  
Blade Angle ◽  
Axial Fan

In this investigation an attempt is made to find the best hub to tip ratio, the maximum number of blades, and the best angle of attack of an axial fan with flat blades at a fixed rotational speed for a maximum mass flow rate in a steady and turbulent conditions. In this study the blade angles are varied from 30 to 70 degrees, the hub to tip ratio is varied from 0.2 to 0.4 and the number of blades are varied from 2 to 6 at a fixed hub rotational speed. The results show that, the maximum flow rate is achieved at a blade angle of attack of about 45 degrees for when the number of blades is set equal to 4 at most rotational velocities. The numerical results show that as the hub to tip ratio is decreased, the mass flow rate is increased. For a hub to tip ratio of 0.2, and an angle of attack around 45 degrees with 4 blades, a maximum mass flow rate is achieved.

The characters exploration of a piezoelectric pump with fishtail-shaped bluffbody

2021 ◽  
pp. 1045389X2110386
Author(s):  
Yi Hou ◽  
Lipeng He ◽  
Zheng Zhang ◽  
Baojun Yu ◽  
Hong Jiang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Preliminary Investigation ◽  
Maximum Flow ◽  
Theoretical Explanation ◽  
Maximum Flow Rate ◽  
Bluff Bodies ◽  
Conical Flow ◽  
Piezoelectric Pump ◽  
Valveless Piezoelectric Pump ◽  
Shape And Size

This paper focuses on a new structure in the valveless piezoelectric pump, which has a combination structure of the conical flow channel and two fishtail-shaped bluffbodies in the chamber of the pump. The fishtail-shaped bluffbody is inspired by the shape of the swimming fish to diminish the backflow and optimize the performance of the pump. The performance is studied by changing the shape and size of the inlet and outlet, the bluff bodies’ height and the space between two bluff bodies. The results show that the 3 mm × 3 mm square inlet, 3 mm diameter round outlet, 3 mm height of bluffbodies, 6.8 mm pitch of bluffbodies has a best performance in all 10 prototypes, which implements a maximum flow rate of 87.5 ml/min at 170 V 40 Hz with a noise of 42.6 dB. This study makes a preliminary investigation and theoretical explanation for the subsequent optimization of this structure, improved the performance of the valveless piezoelectric pump, broaden the thinking of the design for the bluffbody for better performance of the valveless piezoelectric pump.

Transport of Particle-Laden Fluids Through Fixed-Valve Micropumps

1999 ◽  
Author(s):  
Ling-Sheng Jang ◽  
Christopher J. Morris ◽  
Nigel R. Sharma ◽  
Ron L. Bardell ◽  
Fred K. Forster
Keyword(s):  
Surface Charge ◽  
Surface Area ◽  
Flow Rate ◽  
Pure Water ◽  
Maximum Flow ◽  
Total Surface Area ◽  
Maximum Flow Rate ◽  
Number Density ◽  
Polystyrene Microspheres ◽  
Negative Surface

Abstract Micropumps designed for the flow-rate range of 100–1000μl/min have been developed by a number of research groups. However, little data is available regarding the ability of various designs to directly transport liquids containing particles such as cells, microspheres utilized for bead chemistry, or contaminants. In this study the ability of pumps with no-moving-parts valves (NMPV) to transport particles was investigated. The results showed that a NMPV micropump was able to directly pump suspensions of polystyrene microspheres from 3.1 to 20.3μm in diameter. The pump functioned without clogging at microsphere number densities as high as 9000 particles/μl of suspension, which corresponded to over 90,000 particles per second passing through the pump at a flow rate of 600μl/min. Performance with polystyrene microspheres was the same as pure water up to the point of cavitation. Microspheres manufactured with negative surface charge cavitated less readily that other microspheres studied that were manufactured without surface charge. However, cavitation did not appear to be a function of microsphere size, total surface area or number density. Thus pumping polystyrene microspheres was found to be more affected by surface effects than by size, surface area or number density within the range of parameters considered. In the case of charged microspheres, the maximum flow rate was reduced by 30% compared to pure water whereas for uncharged microspheres the maximum flow rate was reduced by approximately 80%.

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