scholarly journals Optimised Triangular Weir Design for Assessing the Full-Scale Performance of Green Infrastructure

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 773
Author(s):  
Mohamad H. El Hattab ◽  
Ana Mijic ◽  
Dejan Vernon
Keyword(s):  
Green Infrastructure ◽  
Discharge Coefficient ◽  
Flow Regimes ◽  
Full Scale ◽  
Performance Estimation ◽  
Low Flow ◽  
Site Conditions ◽  
Flow Measurements ◽  
Flow Rates ◽  
Accuracy Of Measurements

Conventional triangular weirs have been originally developed to measure, divert, and control surface water. However, a special application of these weirs, such as for low flow measurements in full-scale monitoring of Green Infrastructure (GI), is not well investigated. Available head-discharge relationships for triangular sharp-crested weirs are only valid under a free-flow regime. Literature focusing on the V-notch weir usage for GI assessment suggests that it is necessary to calibrate the head-discharge relationship before its use. This study focuses on understanding the effects of site constraints on the measurement performance of a V-notch weir at low flow rates, and the validity of equations derived for similar applications that can be found in the literature. The variation of discharge coefficient in various flow regimes was investigated experimentally based on calibration runs covering flow rates between 0.054 l/s and 7 l/s. The results show that for 30° and 45° V-notch weirs, three flow regimes can be identified. It was observed that literature equations to calculate the discharge coefficient are valid for partially-contracted triangular weirs only at heads greater than vertex distance from the channel. However, for low flows that are expected to occur when estimating the full-scale performance of GI, the equations available from the literature for similar site conditions underestimated the flow rate between 85% and 17%. This emphasises the need for accurate calibration of a V-notch device under the site conditions to achieve the necessary level of accuracy in GI performance estimation. The procedure outlined in this work can be easily replicated to determine the optimal monitoring system configuration. Alternatively, if the site conditions would match those described in this study, the computed discharge using the proposed relations, in combination with the general V-notch weir equation, provides a significant improvement in the accuracy of measurements, expands the head applicability range of V-notch weirs, and enables better understanding of GI performance at the full scale.

Calibration of a Small Venturimeter for Wet Steam at Low Reynolds Number

1969 ◽  
Vol 184 (3) ◽  
pp. 151-153
Author(s):  
M. D. Bennett ◽  
K. Martin
Keyword(s):  
Reynolds Number ◽  
Discharge Coefficient ◽  
Thrust Bearing ◽  
Area Ratio ◽  
Low Flow ◽  
Wet Steam ◽  
Steam Quality ◽  
Design Data ◽  
Flow Rates ◽  
Machined Parts

A device was required to measure the flow rate of steam through a small thrust bearing over the range 0–1·5 kg/h at pressures varying from 4·5 to 10 bar abs. and for steam quality varying from 0·75 dry to 100°C superheat. The ranges appeared to be outside those of existing instruments and not covered by existing design data for differential pressure devices; nor could the authors find any published work on the metering of wet steam at these low flow rates. Accordingly a 12·7-mm diameter venturimeter having an area ratio of 0·25 was made from stainless steel and has been calibrated for wet steam using a compounded differential U-tube manometer. The manometer and associated equipment is extremely simple and cheap to construct, and consists entirely of easily machined parts and standard pipe fittings. The results indicate that the discharge coefficient is very low and approximately a linear function of Reynolds number over the range tested.

Control of Self-Excited Flow Oscillations in Vaneless Diffuser of Centrifugal Compression Systems

1982 ◽  
Author(s):  
A. N. Abdelhamid
Keyword(s):  
Flow Field ◽  
Performance Improvement ◽  
High Flow ◽  
Low Flow ◽  
Flow Oscillation ◽  
Vaneless Diffuser ◽  
Flow Area ◽  
Flow Measurements ◽  
Flow Rates ◽  
Flow Oscillations

Experiments were conducted to evaluate the effectiveness of axisymmetric diffuser exit throttle in delaying the occurrence of self-excited flow oscillation in vaneless diffusers. Sharp edge rings were installed at diffuser exit in order to change the exit flow area. Tests were carried out with the rings attached to one or both of the diffuser walls. Steady and unsteady flow measurements were used to determine the flow field in the diffuser at the onset of the flow oscillations. Results showed that the occurrence of flow oscillation was continuously delayed as the diffuser exit flow area was reduced for all these configurations and impeller speeds. Comparison between the performance of the compression system with and without diffuser exit blockage indicated that although large losses occur at high flow rates, the use of diffuser exit rings resulted in overall diffuser performance improvement at low flow rates. Retractable diffuser exit rings would therefore be ideal for centrifugal compression systems with vaneless diffuser.

Numerical and Experimental Analysis of the Flow in a Centrifugal Pump at Nominal and Partial Flow Rate

1992 ◽  
Author(s):  
J. F. Combes ◽  
E. Rieutord
Keyword(s):  
Turbulent Flow ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Suction Side ◽  
Design Flow ◽  
Low Flow ◽  
Laser Doppler Velocimeter ◽  
Finite Element Code ◽  
Flow Measurements ◽  
Flow Rates

Detailed flow measurements in the impeller and the diffuser of an industrial centrifugal pump have been performed with a 2-component laser Doppler velocimeter. Measurements were made at 8 radial positions for flow rates ranging from 50% to 100% of design flow. The experimental results were compared to 3D turbulent flow calculations performed with a finite element code. At nominal flow rate, both measurements and calculations show a wake pattern along the suction side at the shroud. The flow is separated in the diffuser on the hub, and on the shroud at low flow rate. The inlet recirculation, occurring at 0.65 Qn is well predicted by the turbulent flow calculation.

Morphological dynamics of ureteral transport. II. Peristaltic patterns in relation to flow rate

1989 ◽  
Vol 256 (1) ◽  
pp. R29-R34 ◽  
Author(s):  
L. Ohlson
Keyword(s):  
Flow Rate ◽  
Flow Regimes ◽  
High Flow ◽  
Low Flow ◽  
Contact Period ◽  
Tube Flow ◽  
Flow Rates ◽  
Open Tube ◽  
Normal Human ◽  
Points Of Resistance

To study in the human the conditions for the flow regimes inherent in urinary systems with a dependence of the contraction interval on urine flow rate (boluses-in-contact, leaky-bolus, and open-tube flow regimes), 50 urinary systems were examined at low and high flow rates. Morphometry and volumetry were applied to eight urinary systems. The bolus frequently contacted the preceding contraction ring but the mechanisms differed categorically from that conventionally postulated. Thus the contraction interval proved independent of flow rate, leading to boluses in contact not only at high but also at low flow rates, which is impossible in flow-dependent urinary systems. Likewise, contact proved possible with small as well as large boluses. Furthermore, the contact was invariably interrupted at the points of resistance to flow, the total contact period being only 4% of the ureteral transit. Leaky-bolus flow and open-tube flow were absent. The flow regimes as conventionally defined thus proved to be absent from and inconsistent with normal human urinary transport.

Fabrication and Testing of a MEMS Low-Flow Meter

2002 ◽  
Author(s):  
Jason Sheppard ◽  
Jason Clendenin ◽  
Edward Chiu ◽  
Steve Tung
Keyword(s):  
Shear Stress ◽  
Pressure Sensors ◽  
Low Flow ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Flow Measurements ◽  
Flow Rates ◽  
Stress Sensors ◽  
Shear Stress Sensors ◽  
Small Flow

A compact MEMS flowmeter was fabricated and tested for small gas flow rates from 0.5 to 10 sccm. The flowmeter was fabricated by integrating a silicon chip consisting of three surface-micromachined sensor clusters with a 60μm tall, 1.25 mm wide, and 10 mm long flow channel. Each sensor cluster in the chip consists of a pressure sensor, a surface shear stress sensor, and a temperature sensor. As gas flows through the channel, the volumetric flow rate is determined by measuring either the pressure drop in the flow direction or the local surface shear stress. The temperature sensors in the clusters mainly function as a reference for temperature compensating of the thermally based shear stress sensors. The flowmeter was calibrated in an open-loop pipe-flow facility using nitrogen as the gas medium. Based on the test results, it is clear that the pressure sensors, while capable of handling high flow rates, do not have the necessary precision level for small flow measurements. By comparison, the shear stress sensors, after proper temperature compensation, provide consistent and repeatable measurements for small flow rates. Additionally, the voltage output of the shear stress sensors also follows the 1/3 power trend, previously predicted for macro flow situations, in the small flow range tested.

Fabrication and Testing of a MEMS Low-Flow Meter

2002 ◽  
Author(s):  
Jason Sheppard ◽  
Jason Clendenin ◽  
Edward Chiu ◽  
Steve Tung
Keyword(s):  
Shear Stress ◽  
Pressure Sensors ◽  
Low Flow ◽  
Surface Shear Stress ◽  
Surface Shear ◽  
Flow Measurements ◽  
Flow Rates ◽  
Stress Sensors ◽  
Shear Stress Sensors ◽  
Small Flow

A compact MEMS flowmeter was fabricated and tested for small gas flow rates from 0.5 to 10 sccm. The flowmeter was fabricated by integrating a silicon chip consisting of three surface-micromachined sensor clusters with a 60μm tall, 1.25 mm wide, and 10 mm long flow channel. Each sensor cluster in the chip consists of a pressure sensor, a surface shear stress sensor, and a temperature sensor. As gas flows through the channel, the volumetric flow rate is determined by measuring either the pressure drop in the flow direction or the local surface shear stress. The temperature sensors in the clusters mainly function as a reference for temperature compensating of the thermally based shear stress sensors. The flowmeter was calibrated in an open-loop pipe-flow facility using nitrogen as the gas medium. Based on the test results, it is clear that the pressure sensors, while capable of handling high flow rates, do not have the necessary precision level for small flow measurements. By comparison, the shear stress sensors, after proper temperature compensation, provide consistent and repeatable measurements for small flow rates. Additionally, the voltage output of the shear stress sensors also follows the 1/3 power trend, previously predicted for macro flow situations, in the small flow range tested.

scholarly journals Forensic Investigation of Four Monitored Green Infrastructure Inlets

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1787
Author(s):  
Leena J. Shevade ◽  
Franco A. Montalto
Keyword(s):  
Measurement Uncertainty ◽  
Green Infrastructure ◽  
Stormwater Management ◽  
Catchment Area ◽  
Low Flow ◽  
Inflow Rate ◽  
Forensic Investigation ◽  
Flow Conditions ◽  
The Mean

Green infrastructure (GI) is viewed as a sustainable approach to stormwater management that is being rapidly implemented, outpacing the ability of researchers to compare the effectiveness of alternate design configurations. This paper investigated inflow data collected at four GI inlets. The performance of these four GI inlets, all of which were engineered with the same inlet lengths and shapes, was evaluated through field monitoring. A forensic interpretation of the observed inlet performance was conducted using conclusions regarding the role of inlet clogging and inflow rate as described in the previously published work. The mean inlet efficiency (meanPE), which represents the percentage of tributary area runoff that enters the inlet was 65% for the Nashville inlet, while at Happyland the NW inlet averaged 30%, the SW inlet 25%, and the SE inlet 10%, considering all recorded events during the monitoring periods. The analysis suggests that inlet clogging was the main reason for lower inlet efficiency at the SW and NW inlets, while for the SE inlet, performance was compromised by a reverse cross slope of the street. Spatial variability of rainfall, measurement uncertainty, uncertain tributary catchment area, and inlet depression characteristics are also correlated with inlet PE. The research suggests that placement of monitoring sensors should consider low flow conditions and a strategy to measure them. Additional research on the role of various maintenance protocols in inlet hydraulics is recommended.

Assessment of the Use of Humidified Nasal Cannulas for Oxygen Therapy in Patients with Epistaxis

ORL ◽  
2021 ◽  
pp. 1-5
Author(s):  
Jingjing Liu ◽  
Tengfang Chen ◽  
Zhenggang Lv ◽  
Dezhong Wu
Keyword(s):  
Flow Rate ◽  
Oxygen Therapy ◽  
Preliminary Investigation ◽  
Nasal Cannula ◽  
Low Flow ◽  
Antiplatelet Drugs ◽  
Flow Rates ◽  
The Past ◽  
Oxygen Inhalation ◽  
Significant Difference

<b><i>Introduction:</i></b> In China, nasal cannula oxygen therapy is typically humidified. However, it is difficult to decide whether to suspend nasal cannula oxygen inhalation after the nosebleed has temporarily stopped. Therefore, we conducted a preliminary investigation on whether the use of humidified nasal cannulas in our hospital increases the incidence of epistaxis. <b><i>Methods:</i></b> We conducted a survey of 176,058 inpatients in our hospital and other city branches of our hospital over the past 3 years and obtained information concerning their use of humidified nasal cannulas for oxygen inhalation, nonhumidified nasal cannulas, anticoagulant and antiplatelet drugs, and oxygen inhalation flow rates. This information was compared with the data collected at consultation for epistaxis during these 3 years. <b><i>Results:</i></b> No significant difference was found between inpatients with humidified nasal cannulas and those without nasal cannula oxygen therapy in the incidence of consultations due to epistaxis (χ<sup>2</sup> = 1.007, <i>p</i> &#x3e; 0.05). The same trend was observed among hospitalized patients using anticoagulant and antiplatelet drugs (χ<sup>2</sup> = 2.082, <i>p</i> &#x3e; 0.05). Among the patients with an inhaled oxygen flow rate ≥5 L/min, the incidence of ear-nose-throat (ENT) consultations due to epistaxis was 0. No statistically significant difference was found between inpatients with a humidified oxygen inhalation flow rate &#x3c;5 L/min and those without nasal cannula oxygen therapy in the incidence of ENT consultations due to epistaxis (χ<sup>2</sup> = 0.838, <i>p</i> &#x3e; 0.05). A statistically significant difference was observed in the incidence of ENT consultations due to epistaxis between the low-flow nonhumidified nasal cannula and nonnasal cannula oxygen inhalation groups (χ<sup>2</sup> = 18.428, <i>p</i> &#x3c; 0.001). The same trend was observed between the 2 groups of low-flow humidified and low-flow nonhumidified nasal cannula oxygen inhalation (χ<sup>2</sup> = 26.194, <i>p</i> &#x3c; 0.001). <b><i>Discussion/Conclusion:</i></b> Neither high-flow humidified nasal cannula oxygen inhalation nor low-flow humidified nasal cannula oxygen inhalation will increase the incidence of recurrent or serious epistaxis complications; the same trend was observed for patients who use anticoagulant and antiplatelet drugs. Humidification during low-flow nasal cannula oxygen inhalation can prevent severe and repeated epistaxis to a certain extent.

Effect of Tip Clearance on Suction Performance at Different Flow Rates in a Mixed Flow Pump

2014 ◽  
Author(s):  
Yo Han Jung ◽  
Young Uk Min ◽  
Jin Young Kim
Keyword(s):  
Performance Test ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Tip Clearance ◽  
Low Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Flow Rates ◽  
Suction Performance ◽  
Flow Pump

This paper presents a numerical investigation of the effect of tip clearance on the suction performance and flow characteristics at different flow rates in a vertical mixed-flow pump. Numerical analyses were carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations. Steady computations were performed for three different tip clearances under noncavitating and cavitating conditions at design and off-design conditions. The pump performance test was performed for the mixed-flow pump and numerical results were validated by comparing the experimental data for a system characterized by the original tip clearance. It was shown that for large tip clearance, the head breakdown occurred earlier at the design and high flow rates. However, the head breakdown was quite delayed at low flow rate. This resulted from the cavitation structure caused by the tip leakage flow at different flow rates.

Sign in / Sign up

Export Citation Format

Share Document