Influence of geometrical parameters of chamfered or rounded orifices on head losses

Adam, Nicolas Jean; Cesare, Giovanni De; Schleiss, Anton

doi:10.1080/00221686.2018.1454518

Cited by 7 publications

(5 citation statements)

References 23 publications

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“…The first area divided by the second was used to calculate the σ 1 , and the second area divided by the third for the σ 2 . 14 In instances with the PA procedure where the first area was not present, only σ 2 was recorded. The length of the larynx between areas was also measured using the measured distance between the individual CT slice images to calculate the angle of incidence of airflow.…”

Section: Methodsmentioning

confidence: 99%

“…In the discipline of fluid mechanics, airflow within a pipe with a constricted region has been studied to determine how the narrowed region (orifice) affects flow and pressure. 14,15 Flow development for a given orifice is strongly correlated with energy loss and pressure drop, due to irregularities in the flow caused by the orifice shape. 15 In human airways, idealized versions of the vocal folds demonstrated airflow separation, wherein the jet of air breaks into eddies as it emerges into an expanded area.…”

Section: Clinical Relevancementioning

confidence: 99%

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Computed tomographic geometrical analysis of surgical treatments for equine recurrent laryngeal neuropathy

Tucker

Wilson

Reinink

et al. 2022

ajvr

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OBJECTIVES To characterize the 3-D geometry of the equine larynx replicating laryngeal hemiplegia and 4 surgical interventions by use of CT under steady-state airflow conditions. Secondly, to use fluid mechanic principles of flow through a constriction to establish the relationship between measured airflow geometries with impedance for each surgical procedure. SAMPLE 10 cadaveric horse larynges. PROCEDURES While CT scans were performed, inhalation during exercise conditions was replicated for each of the following 5 conditions: laryngeal hemiplegia, left laryngoplasty with ventriculocordectomy, left laryngoplasty with ipsilateral ventriculocordectomy and arytenoid corniculectomy, corniculectomy, and partial arytenoidectomy for each larynx while CT scans were performed. Laryngeal impedance was calculated, and selected cross-sectional areas were measured along each larynx for each test. Measured areas and constriction characteristics were analyzed with respect to impedance using a multilevel, mixed-effects model. RESULTS Incident angle, entrance coefficient, outlet coefficient, friction coefficient, orifice thickness, and surgical procedure were significantly associated with upper airway impedance in the bivariable model. The multivariate model showed a significant influence of incident angle, entrance coefficient, and surgical procedure on impedance; however, the orifice thickness became nonsignificant within the model. CLINICAL RELEVANCE Laryngeal impedance was significantly associated with the entrance configuration for each procedure. This suggested that the equine upper airway, despite having a highly complex geometry, adheres to fluid dynamic principles applying to constrictions within pipe flow. These underlying flow characteristics may explain the clinical outcomes observed in some patients, and lead to areas of improvement in the treatment of obstructive upper airway disease in horses.

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Section: Methodsmentioning

confidence: 99%

Section: Clinical Relevancementioning

confidence: 99%

Computed tomographic geometrical analysis of surgical treatments for equine recurrent laryngeal neuropathy

Tucker

Wilson

Reinink

et al. 2022

ajvr

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“…Changes in baseline operations and conditions might also lead to newer designs and thus justify the need for new testing procedures and techniques, as discussed for powertrain technology in Section 2.1.2.2. For example, some Swiss studies (Adam et al 2018;Adam, De Cesare, and Schleiss 2019) proposed the design of a throttling system to be implemented in the surge tank of a refurbished hydropower plant to handle extreme water levels that might occur as consequence of increased generation capacity. Different throttling systems were tested numerically and using scaled physical models.…”

Section: Changing Conditionsmentioning

confidence: 99%

Needs and Opportunities for Testing of Hydropower Technology Innovations

Musa

Smith²,

Sasthav

et al. 2022

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Despite hydropower's status as a well-established technology, changes in the global energy sector have prompted a variety of necessary hydropower technological innovations. Examples include efficient lowhead turbines, more flexible and dispatchable hydropower and pumped storage systems to complement variable and intermittent renewable resources, and technologies providing higher environmental performance. However, while innovative technologies are currently being proposed to meet these development challenges, small hydropower facility owners do not have sufficient risk-bearing capacity to adopt new, unvalidated technologies. This discourages manufacturers from bringing nascent technologies to market and stalls the technological growth of the sector. To reduce the risks associated with new technologies and promote further innovation, systemic (and sometimes unconventional) validation activities and new testing capabilities for hydropower are highly desired. These testing capabilities must demonstrate the safety, environmental acceptability, reliability, and performance of innovative technologies to quantify their value compared with existing technologies. Establishing these capabilities through dedicated testing facilities will be key to promoting hydropower growth in the United States.Following direction from the House Energy and Water Development Committee, the US Department of Energy's Water Power Technologies Office (WPTO) has been tasked with understanding the state of hydropower testing in the United States. This scoping report discusses the needs and opportunities of hydropower testing in the United States, with a specific focus on small hydropower. Future developments will likely mostly target low-head sites with less than 30 ft (9.1 m) from new stream-reach developments, non-powered dam retrofits, and rehabilitation/upgrade of existing plants.Based on emerging technology trends, testing gaps evaluation, and stakeholder inputs, four overarching thematic challenges were identified for testing hydropower innovations: 10

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“…There exists a considerable body of literature on throttles, where the orifice type is addressed. Several authors derived analytical formulations to get head loss coefficients for orifices in one flow direction (mainly sharp flow direction) while others adapted or extended the existing ones to account for both flow directions for particular orifice shapes such as rounded or chamfered orifices [10]. Some analytical formulations are also available to estimate asymmetrical head losses in simple diaphragm configurations such as T-junctions [11].…”

Section: Introductionmentioning

confidence: 99%

Holistic Design Approach of a Throttled Surge Tank: The Case of Refurbishment of Gondo High-Head Power Plant in Switzerland

Seyfeddine

Vorlet

Adam³

et al. 2020

Water

Self Cite

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In order to increase the installed capacity, the refurbishment of Gondo high-head power plant required a modification of the existing surge tank by installing a throttle at its entrance. In a previous study, the geometry of this throttle was optimized by physical modeling to achieve the target loss coefficients as identified by a transient 1D numerical analysis. This study complements previous analyses by means of 3D numerical modeling using the commercial software ANSYS-CFX 19 R1. Results show that: (i) a 3D computational fluid dynamics (CFD) model predicts sufficiently accurate local head loss coefficients that agree closely with the findings of the physical model; (ii) in contrast to a standard surge tank, the presence of an internal gallery in the surge tank proved to be of insignificant effect on a surge tank equipped with a throttle, as the variations in the section of the tank cause negligible local losses compared to the ones induced by the throttle; (iii) CFD investigations of transient flow regimes revealed that the head loss coefficient of the throttle only varies for flow ratios below 20% of the total flow in the system, without significantly affecting the conclusions of the 1D transient analysis with respect to minimum and maximum water level in the surge tank as well as pressure peaks below the surge tank. This study highlights the importance of examining the characteristics of a hydraulic system from a holistic approach involving hybrid modeling (1D, 3D numerical and physical) backed by calibration as well as validation with in-situ measurements. This results in a more rapid and economic design of throttled surge tanks that makes full use of the advantages associated with each modeling strategy.

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Influence of geometrical parameters of chamfered or rounded orifices on head losses

Cited by 7 publications

References 23 publications

Computed tomographic geometrical analysis of surgical treatments for equine recurrent laryngeal neuropathy

Computed tomographic geometrical analysis of surgical treatments for equine recurrent laryngeal neuropathy

Needs and Opportunities for Testing of Hydropower Technology Innovations

Holistic Design Approach of a Throttled Surge Tank: The Case of Refurbishment of Gondo High-Head Power Plant in Switzerland

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