Steady Flow Hemodynamic and Energy Loss Measurements in Normal and Simulated Calcified Tricuspid and Bicuspid Aortic Valves

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Clara Seaman ◽  
A. George Akingba ◽  
Philippe Sucosky
Keyword(s):  
Pressure Drop ◽  
Aortic Valve ◽  
Energy Loss ◽  
Steady Flow ◽  
Flow Rate ◽  
Maximum Flow ◽  
Maximum Flow Rate ◽  
Type I ◽  
Orifice Area ◽  
The Impact

The bicuspid aortic valve (BAV), which forms with two leaflets instead of three as in the normal tricuspid aortic valve (TAV), is associated with a spectrum of secondary valvulopathies and aortopathies potentially triggered by hemodynamic abnormalities. While studies have demonstrated an intrinsic degree of stenosis and the existence of a skewed orifice jet in the BAV, the impact of those abnormalities on BAV hemodynamic performance and energy loss has not been examined. This steady-flow study presents the comparative in vitro assessment of the flow field and energy loss in a TAV and type-I BAV under normal and simulated calcified states. Particle-image velocimetry (PIV) measurements were performed to quantify velocity, vorticity, viscous, and Reynolds shear stress fields in normal and simulated calcified porcine TAV and BAV models at six flow rates spanning the systolic phase. The BAV model was created by suturing the two coronary leaflets of a porcine TAV. Calcification was simulated via deposition of glue beads in the base of the leaflets. Valvular performance was characterized in terms of geometric orifice area (GOA), pressure drop, effective orifice area (EOA), energy loss (EL), and energy loss index (ELI). The BAV generated an elliptical orifice and a jet skewed toward the noncoronary leaflet. In contrast, the TAV featured a circular orifice and a jet aligned along the valve long axis. While the BAV exhibited an intrinsic degree of stenosis (18% increase in maximum jet velocity and 7% decrease in EOA relative to the TAV at the maximum flow rate), it generated only a 3% increase in EL and its average ELI (2.10 cm2/m2) remained above the clinical threshold characterizing severe aortic stenosis. The presence of simulated calcific lesions normalized the alignment of the BAV jet and resulted in the loss of jet axisymmetry in the TAV. It also amplified the degree of stenosis in the TAV and BAV, as indicated by the 342% and 404% increase in EL, 70% and 51% reduction in ELI and 48% and 51% decrease in EOA, respectively, relative to the nontreated valve models at the maximum flow rate. This study indicates the ability of the BAV to function as a TAV despite its intrinsic degree of stenosis and suggests the weak dependence of pressure drop on orifice area in calcified valves.

scholarly journals Finite Element Simulation of Newtonian and Non-Newtonian Fluid through the Parallel Plates Affixed with Single Screen

2020 ◽  
Vol 13 (1) ◽  
pp. 69-83
Author(s):  
Abid Ali Memon ◽  
Muhammad Asif Memon ◽  
Kaleemullah Bhatti ◽  
Gul Muhammad Shaikh
Keyword(s):  
Reynolds Number ◽  
Finite Element ◽  
Newtonian Fluid ◽  
Flow Rate ◽  
Rectangular Channel ◽  
Maximum Flow ◽  
Least Square ◽  
Maximum Flow Rate ◽  
Parallel Plates ◽  
The Impact

In the contemporary research article we have performed a numerical investigation of the non-Newtonian fluid flow through a rectangular channel with a fixed solid screen devoted at the angles 100 to 450 degrees. We have employed the power-law model for shear thickening and shear thinning fluids with the high Reynolds number between 1000 and 10,000. The obstacle has been solved by putting in the Galerkin’s least square strategy of the finite element method and the procedure has been carried out utilizing the commercial software COMSOL Multiphysics. Various flow properties such as 'maximum flow rate' and 'pressure' have been discussed in the terms of the Reynolds number and also using the linear and quadratic regressions in order to establish the relationship between them for the future analysis. Moreover the impact of turning screen in the shape of increment in the maximum flow rate and pressure is checked in terms of Reynolds number and  Satisfactory results are gained in comparison with the results available in the literature.

The Impact of Emergency Release in LNG Transfer

2014 ◽  
Author(s):  
Evert van Bokhorst ◽  
Tony Webber ◽  
Jesper van der Putte ◽  
Jan Smeulers ◽  
David Remans
Keyword(s):  
Flow Rate ◽  
Propagation Speed ◽  
Maximum Flow ◽  
Maximum Flow Rate ◽  
Shock Loads ◽  
Acoustic Damping ◽  
Pressure Transients ◽  
Flow Test ◽  
Pressure Surge ◽  
The Impact

This paper describes the results of experimental work and simulations of pressure surges resulting from fast closing valves and activation of an emergency release coupling (ERC) in ship-to-ship LNG transfer. The first part presents the results of an ambient water flow test with a fast closing 4-inch full bore valve in combination with a 4-inch flexible multi-composite hose. High amplitude pressure surges up to 4 times the working pressure occur upstream of the valve. Pressure surge amplitudes strongly depend on valve closing time and flow rate. The propagation speed in the upstream hose is lowered considerably due to the hose flexibility. Furthermore the temporarily deformation of the hose results in loss of energy and acoustic damping of the pressure surge amplitudes. The measurement results are compared to the results of modeling. Acoustic damping and propagation speed of sound show a non-linear behavior of the hose, due to a varying internal pressure, which is not captured in the present modeling techniques. The second part of the paper describes the results of a full scale flow test on an 8-inch ERC (KLAW make) for LNG ship-to-ship transfer (Figure 1). The ERC in the test is located downstream of an 8-inch 15-meter long multi-composite flexible hose. The test is intended to investigate operational and mechanical integrity, spill rate and the impact of pressure transients and shock loads on the ERC including upstream hose and downstream piping. Upon hydraulic activation the ERC separates in two parts, each provided with a fast closing butterfly valve. The complete operation takes about 0.2 s and the actual valve closure duration is about 0.02 s resulting in a negligible spill of less than 0.002 m3. Pressure transients from 34 to 100 bar, over 10 times the operating pressure, occur at the maximum flow rate of 1000 m3/hr, resulting in shock loads and high acceleration levels. The mechanical integrity remains intact even after four successive releases at the maximum flow rate of 1000 m3/hr. The results contribute to the certification of the ERC by Lloyds B.V. Further development in modeling is necessary to obtain a validated model for the calculation of pressure surges due to emergency shutdown in a LNG transfer.

scholarly journals The existence of steady flow in a collapsed tube

1989 ◽  
Vol 206 ◽  
pp. 339-374 ◽  
Author(s):  
O. E. Jensen ◽  
T. J. Pedley
Keyword(s):  
Pressure Drop ◽  
Energy Loss ◽  
Steady Flow ◽  
Flow Rate ◽  
Transmural Pressure ◽  
Tube Model ◽  
Collapsible Tube ◽  
One Dimensional ◽  
Flow Through ◽  
Range Of Values

Self-excited oscillations arise during flow through a pressurized segment of collapsible tube, for a range of values of the time-independent controlling pressures. They come about either because there is an (unstable) steady flow corresponding to these pressures, or because no steady flow exists. We investigate the existence of steady flow in a one-dimensional collapsible-tube model, which takes account of both longitudinal tension and jet energy loss E downstream of the narrowest point. For a given tube, the governing parameters are flow-rate Q, and transmural pressure P at the downstream end of the collapsible segment. If E = 0, there exists a range of (Q, P)-values for which no solutions exist; when E ≠ 0 a solution is always found. For the case E ≠ 0, predictions are made of pressure drop along the collapsible tube; these solutions are compared with experiment.

scholarly journals Finite Element Simulation of Newtonian and Non-Newtonian Fluid through the Parallel Plates Affixed with Single Screen

2020 ◽  
Vol 13 (1) ◽  
pp. 69-83
Author(s):  
Abid Ali Memon ◽  
Muhammad Asif Memon ◽  
Kaleemullah Bhatti ◽  
Gul Muhammad Shaikh
Keyword(s):  
Reynolds Number ◽  
Finite Element ◽  
Newtonian Fluid ◽  
Flow Rate ◽  
Rectangular Channel ◽  
Maximum Flow ◽  
Least Square ◽  
Maximum Flow Rate ◽  
Parallel Plates ◽  
The Impact

In the contemporary research article we have performed a numerical investigation of the non-Newtonian fluid flow through a rectangular channel with a fixed solid screen devoted at the angles 100 to 450 degrees. We have employed the power-law model for shear thickening and shear thinning fluids with the high Reynolds number between 1000 and 10,000. The obstacle has been solved by putting in the Galerkin’s least square strategy of the finite element method and the procedure has been carried out utilizing the commercial software COMSOL Multiphysics. Various flow properties such as 'maximum flow rate' and 'pressure' have been discussed in the terms of the Reynolds number and also using the linear and quadratic regressions in order to establish the relationship between them for the future analysis. Moreover the impact of turning screen in the shape of increment in the maximum flow rate and pressure is checked in terms of Reynolds number and  Satisfactory results are gained in comparison with the results available in the literature.

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.

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