Characterizing positive pressure ventilation using computational fluid dynamics

Vascular rings, congenital intracardic anomalies of the aortic arch and the vessels emerging from the heart, completely encircle the trachea and esophagus [1]. The vascular ring results in narrowing and obstruction of the trachea and the esophagus. Due to the existence of a complete or partial vascular ring compressing either the trachea or esophagus, symptoms of a vascular ring in children include cough, stridor, chronic cough, dysphagia, persistent wheeze, and noisy breathing [2]. Some studies reported that the vascular ring surgery provides an excellent chance to improve the patient respiration conditions, especially for relief of symptoms [1–3]. Al-Bassam et al. reported that the thoracoscopic division of vascular rings in infants and children is a safe and effective surgery rather than an open thoracotomy[4]. Even after the treatment of a surgical division of the vascular ring, however, the fixed obstruction is relieved but the patient continues to have dynamic collapse because the compressed trachea segment is always malacic. Airway resistance to flow in the airway, thus, is a key factor for not only clinical diagnosis severity assessment but also therapeutic decision in tracheal stenosis. Furthermore, Malvè et al. (2011) utilized the finite element-based commercial software code (ADINA R&D Inc.) to model the fluid structure interaction of a human trachea under different ventilation conditions [5]. They also found that the positive pressure in the trachea does not result in the airway collapse during the time period of mechanical breathing. Therefore, the purpose of this study is to use the computational fluid dynamics (CFD) technique to calculate the local pressure drops in the tracheal segment for different inspiratory and expiratory flow rates due to preoperative and preoperative vascular ring surgery.

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Optimization of Positive Pressure Ventiliation Tactic for Wind Driven High Rise Fires

Volume 4: Energy Systems Analysis, Thermodynamics and Sustainability; Combustion Science and Engineering; Nanoengineering for Energy, Parts A and B ◽

10.1115/imece2011-62908 ◽

2011 ◽

Cited By ~ 2

Author(s):

Prabodh Panindre ◽

Sunil Kumar ◽

Atulya Narendranath ◽

Vinay Kanive Manjunath ◽

Venkata Pushkar Chintaluri ◽

...

Keyword(s):

Fluid Dynamics ◽

Close Agreement ◽

Positive Pressure Ventilation ◽

Combustion Products ◽

Positive Pressure ◽

High Rise ◽

Fire Scenarios ◽

Dynamic Simulator ◽

Fire Dynamic Simulator ◽

Fire Location

Positive Pressure Ventilation (PPV) is a firefighting tactic that can mitigate the spread of fire and the combustion products to improve the safety of firefighters and civilians in wind-driven high-rise fires than without PPV. The performance of a PPV tactic in wind-driven high-rise fires depends on various parameters that include wind speed, control of stairwell doors, number of fans, fan positions and placements, fire location etc. This paper describes the influence of these parameters on the efficacy of PPV operation that was studied by simulating wind-driven high-rise fire scenarios using computational fluid dynamics softwares Fluent 12.0 and NIST’s Fire dynamic simulator (FDS 5.0). The results obtained from Fluent and FDS found to be in close agreement with each other and have been used to optimize the PPV operation for better performance.

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Three-Dimensional Numerical Study of a Kitchen Extractor Adopting Nearby Pumping Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.629.495 ◽

2012 ◽

Vol 629 ◽

pp. 495-500

Author(s):

Jing Deng ◽

Chong Guang Hong ◽

Gui Quan Wang ◽

Hong Zhi Sheng

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Negative Pressure ◽

Energy Cost ◽

Collection Efficiency ◽

Numerical Study ◽

Three Dimensional ◽

Low Energy ◽

Positive Pressure ◽

Third Generation

A third generation kitchen extractor adopting nearby pumping method is investigated by using the computational fluid dynamics software. The numerical results are close to the experiment results, which can be used for supporting the optimum design of the equipment. The important parameters such as the particular distributions of velocity, temperature, and species fraction are obtained, which can supply more information about the pumping mechanism of this equipment. It is concluded that the gas-film-jet-cover technology significantly contributed to guaranteeing the pumping effect. Furthermore, decreasing negative pressure of pumping circle and/or the increasing positive pressure of gas-film-inlet could increase the collection efficiency of the equipment. However, it is necessary to choose the most appropriate pressure for getting enough collection efficiency with relatively low energy cost and working noise.

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A Numerical Investigation into the Effectiveness of Multi-Element Pressure Screen Rotor Foils

Journal of Fluids Engineering ◽

10.1115/1.2979002 ◽

2008 ◽

Vol 131 (1) ◽

Author(s):

Sean Delfel ◽

Carl Ollivier-Gooch ◽

James Olson

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Numerical Investigation ◽

Negative Pressure ◽

Pressure Pulse ◽

Angle Of Attack ◽

Positive Pressure ◽

Single Element ◽

Past Work

Pressure screening is an efficient way to remove unwanted debris from a pulp stream, which improves the quality of the end product paper. Past work has found that increased foil camber and angle-of-attack improve the performance of pressure screen foil rotors by increasing the magnitude and width of the negative pressure pulse on the screen cylinder while at the same time reducing the magnitude of the positive pressure pulse on the screen cylinder. Too large an angle-of-attack or too much camber leads to separation of the flow over the foil and a loss in rotor performance, however. This study therefore investigates, using computational fluid dynamics, the ability of multi-element rotor foils to delay stall over the foil and improve upon the performance of an existing pressure screen rotor foil. In this study, the effect of foil angle-of-attack, flap angle, the geometry of the trailing edge of the main foil, and the positioning of the flap relative to the main foil were studied. A multi-element foil was developed based on the NACA 8312, a foil used in industrial pressure screen rotors. In general, stall was delayed and a larger angle-of-attack was obtained than the single-element foil, and increased camber was added to the foil by deflecting the flap. Positive pressure pulse on the screen cylinder approached a negligible value with both increasing angle-of-attack and increasing flap angle, while the negative pressure pulse increased in magnitude with both increasing angle-of-attack and flap angle before the foil began to separate and the suction was lost. The x-positioning of the flap was shown to have less of an effect on the foil performance than the y-positioning. All told, the magnitude of the negative pressure pulse was increased by 15% while at the same time eliminating the positive pressure pulse.

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