scholarly journals Optical Micro-Wire Flow-Velocity Sensor

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4025
Author(s):  
Matej Njegovec ◽  
Simon Pevec ◽  
Denis Donlagic
Keyword(s):  
Response Time ◽  
Flow Velocity ◽  
Time Constant ◽  
Gas Flow ◽  
Low Flow ◽  
Velocity Sensor ◽  
Short Response Time ◽  
Wide Range ◽  
Cost Efficient ◽  
Flow Velocities

This paper presents a short response time, all-silica, gas-flow-velocity sensor. The active section of the sensor consists of a 16 µm diameter, highly optically absorbing micro-wire, which is heated remotely by a 980 nm light source. The heated microwire forms a Fabry–Perot interferometer whose temperature is observed at standard telecom wavelengths (1550 nm). The short response time of the sensor allows for different interrogation approaches. Direct measurement of the sensor’s thermal time constant allowed for flow-velocity measurements independent of the absolute heating power delivered to the sensor. This measurement approach also resulted in a simple and cost-efficient interrogation system, which utilized only a few telecom components. The sensor’s short response time, furthermore, allowed for dynamic flow sensing (including turbulence detection). The sensor’s bandwidth was measured experimentally and proved to be in the range of around 22 Hz at low flow velocities. Using time constant measurement, we achieved a flow-velocity resolution up to 0.006 m/s at lower flow velocities, while the resolution in the constant power configuration was better than 0.003 m/s at low flow velocities. The sensing system is constructed around standard telecommunication optoelectronic components, and thus suitable for a wide range of applications.

Surface Radiation Effects on Flame Spread Over Thermally Thick Fuels in an Opposing Flow

1994 ◽  
Vol 116 (3) ◽  
pp. 646-651 ◽  
Author(s):  
J. West ◽  
S. Bhattacharjee ◽  
R. A. Altenkirch
Keyword(s):  
Flow Velocity ◽  
Gas Phase ◽  
Flame Spread ◽  
Radiation Effects ◽  
Solid Phase ◽  
Surface Radiation ◽  
Low Flow ◽  
Fuel Surface ◽  
Wide Range ◽  
Flow Velocities

A computational model of flame spread over a thermally thick solid fuel in an opposing-flow environment is presented. Unlike thermally thin fuels, for which the effect of fuel surface radiation is negligible for high levels of opposing flow, fuel surface radiation is important for thermally thick fuels for all flow levels. This result is shown to derive from the fact that the ratio of the rate of heat transfer by re-radiation from the surface to that by conduction from the gas to the solid is proportional to the length over which heat can be conducted forward of the flame to sustain spreading. For thin fuels, this length decreases with increasing flow velocity such that while radiation is important at low flow velocities it is not at the higher velocities. For thick fuels at low flow velocities, the conduction length is determined by gas-phase processes and decreases with increasing flow velocity. But at higher flow velocities, the conduction length is determined by solid-phase processes and is rather independent of the gas-phase flow. The result is that over a wide range of flow velocities, the conduction length of importance does not change substantially as it switches from one phase to another so that the ratio of radiation to conduction is of unit order throughout that wide range of flow.

scholarly journals Performance analysis of time and cost efficient data pre-fetching in mobile cloud computing

2021 ◽  
Author(s):  
Kaveh Khorramnejad ◽  
Alagan Anpalagan ◽  
Ling Guan
Keyword(s):  
Response Time ◽  
Processing Speed ◽  
Mobile Cloud Computing ◽  
Scheduling Model ◽  
Total Response Time ◽  
Wide Range ◽  
Workload Scheduling ◽  
Efficient Data ◽  
Cost Efficient ◽  
The Cost

Recently, many methods and algorithms have been proposed in pre-fetching area. However, pre-fetching integrated with workload scheduling approaches have not been investigated as much. Initially, this thesis reviews the principles of the existing pre-fetching strategies considering latency and cost factor as primary objectives. Later, it focuses on an integrated workload scheduling and pre-fetching model to enhance the performance of response time and minimize the cost. Furthermore, response time and cost problems are formulated and to overcome the total response time and cost problems a heuristic approach is proposed. Integrated model is tested for wide range of variables and, the effects of various parameters such as processing speed and pre-fetcher’s utilization are analysed and compared. Finally, based on the results integrated pre-fetching and workload scheduling model outperforms either of them, individually. Thus, this thesis can contribute to the the new solutions in this area.

Effects of flow velocity on fitness-related behaviours of the sea urchin Mesocentrotus nudus: new information on stock enhancement

2020 ◽  
Vol 100 (6) ◽  
pp. 963-967
Author(s):  
Dongtao Shi ◽  
Donghong Yin ◽  
Yang Chen ◽  
Jiangnan Sun ◽  
Mingfang Yang ◽  
...  
Keyword(s):  
Response Time ◽  
Flow Velocity ◽  
Stock Enhancement ◽  
Long Term Effects ◽  
Movement Velocity ◽  
Righting Response ◽  
New Information ◽  
Mesocentrotus Nudus ◽  
Flow Velocities

AbstractThe effects of flow velocity on the fitness-related behaviours of Mesocentrotus nudus remain largely unknown, greatly hampering the efficiency of stock enhancement. To explore the appropriate velocities for stock enhancement, we investigated dislodgement and immobilization velocities up to 90 cm s−1. The experimental results showed that M. nudus (test diameter of ~30 mm) were dislodged at 73.50 ± 7.7 cm s−1 and that M. nudus movement occurred only when the flow velocity was less than 33.40 ± 2.7 cm s−1. Three flow velocities less than 33.40 ± 2.7 cm s−1 (2, 10 and 20 cm s−1) were subsequently used to study the effects of flow velocities on covering behaviour and the righting response time of M. nudus. The downstream movement velocity of M. nudus was significantly larger than that upstream at 2 cm s−1 (P = 0.016) and 10 cm s−1 (P = 0.008), but not at 20 cm s−1 (P = 0.222). The righting response time of M. nudus was significantly longer at 20 cm s−1 than that at 2 cm s−1 (P = 0.015). The present study indicates that a flow velocity less than 20 cm s−1, preferably 2–10 cm s−1, is probably appropriate for the stock enhancement of M. nudus. Notably, the current study is a laboratory investigation without considering the hydrographic complexity in the field. Further studies should be carried out to investigate the long-term effects of water flow on feeding and growth of M. nudus both in the laboratory and the field.

scholarly journals Experimental Investigation of Reactive-Inert Particulate Matter Detachment from Metal Fibres at Low Flow Velocities and Different Gas Temperatures

2020 ◽  
Author(s):  
Julian Zoller ◽  
Amin Zargaran ◽  
Kamil Braschke ◽  
Jörg Meyer ◽  
Uwe Janoske ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Gas Flow ◽  
Low Flow ◽  
Inert Particle ◽  
Particle Structure ◽  
Inert Component ◽  
Reactive Component ◽  
Glass Spheres ◽  
Single Fibres ◽  
Flow Velocities

Abstract The detachment of particle structures from single fibres in gas flow has been investigated only for inert particle structures yet. This study investigates the detachment of particle structures containing reactive components. These reactive components disappear during the reaction and enhance detachment at low flow velocities. Soot was used as the reactive component and glass spheres as the inert component of the particle structure. The soot disappears due to combustion with oxygen leaving only the glass spheres on the fibre. Without reaction, the detachment phenomenon was observed at superficial flow velocities above 1.9 m/s and with reaction at 0.5 m/s. This shows that reacting and disappearing components of the particle structure can enhance detachment.

scholarly journals Relative impacts of the invasive Pacific oyster, Crassostrea gigas, over the native blue mussel, Mytilus edulis, are mediated by flow velocity and food concentration

NeoBiota ◽  
2019 ◽  
Vol 45 ◽  
pp. 19-37 ◽  
Author(s):  
Patrick W.S. Joyce ◽  
Louise Kregting ◽  
Jaimie T.A. Dick
Keyword(s):  
Flow Velocity ◽  
Pacific Oyster ◽  
Food Concentration ◽  
Ecological Impacts ◽  
Low Flow ◽  
Relative Impact ◽  
Clearance Rates ◽  
Mussel Beds ◽  
Food Concentrations ◽  
Flow Velocities

The ecological impacts of invasive species can be severe, but are generally viewed as highly unpredictable. Recent methods combining per capita feeding rates, population abundances and environmental contexts have shown great utility in predicting invader impacts. Here, clearance rates of the invasive Pacific oyster, Crassostreagigas, and native mussel, Mytilusedulis, were investigated in a laboratory experiment where oscillatory water flow and algal food concentrations were manipulated. Invasive oysters had lower clearance rates than native mussels in all experimental groups and did not differ among flow velocities or food concentrations. Native mussel clearance rates were higher at 5 cm s-1 compared to 0 and 15 cm s-1 flow velocities and increased with increasing food concentration. The Relative Impact Potential (RIP) metric was used to assess (i) the influence of flow velocity and food concentration on potential impacts of C.gigas on plankton resources and, (ii) the impacts of coexisting reefs, containing both species, on resources compared to monospecific native mussel beds. Greatest Relative Impact Potential of invasive oysters was seen at the lowest flow velocity, but became reduced with increasing flow velocity and food concentration. Relative Impact Potentials of coexisting reefs were generally greater than monospecific native mussel beds, with greatest impacts predicted at lowest flow velocity. We suggest that the greatest ecological impacts and competition potential of C.gigas will occur in areas with low flow velocity, but that increased flow will mediate co-existence between the two species.

scholarly journals Experimental Study on Hydroelectric Energy Harvester Based on a Hybrid Qiqi and Turbine Structure

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7601
Author(s):  
Bin Bao ◽  
Quan Wang ◽  
Yufei Wu ◽  
Pengda Li
Keyword(s):  
Energy Harvesting ◽  
Flow Velocity ◽  
Water Flow ◽  
Energy Harvester ◽  
Hybrid Structure ◽  
High Flow ◽  
Low Flow ◽  
Flow Rates ◽  
Hydroelectric Energy ◽  
Wide Range

The Qiqi structure design can automatically upset and spill its content once it arrives at limit capacity under vertical water flow excitation. Considering this function, the Qiqi structure has been utilized for small hydroelectric energy harvesting lately. To investigate the tradeoff between the Qiqi structure and the turbine structure for small hydroelectric energy harvesting, an energy harvester based on a hybrid Qiqi and turbine structure is proposed for vertical water flow hydroelectric applications. The hybrid structure is composed of a rectangular Qiqi structure, with two blades inserted on both sides. Self-tipping function of the hybrid Qiqi structure and working principle of the structure is investigated in detail. The proposed structure has both the advantages of low flow velocity energy harvesting of the Qiqi structure and high flow velocity energy harvesting of the turbine structure. A hydroelectric energy harvesting application using the hybrid structure is given to demonstrate that the hybrid structure had a higher rotational speed than the Qiqi structure under vertical low water flow excitation and was able to work at relatively high flow rates. Thus, the investigated hybrid structure can help small rotational hydropower achieve better energy harvesting performance and work at wide-range flow rates under vertical ultra-low water flow applications. At 600 mL/min, 902 μJ of electrical energy was charged by the investigated structure, which is six times higher than that using the Qiqi structure alone.

Interaction of neutrophils and endothelium in isolated coronary venules and arterioles

1995 ◽  
Vol 268 (1) ◽  
pp. H490-H498 ◽  
Author(s):  
Y. Yuan ◽  
R. A. Mier ◽  
W. M. Chilian ◽  
D. C. Zawieja ◽  
H. J. Granger
Keyword(s):  
Flow Velocity ◽  
Shear Force ◽  
Low Flow ◽  
Microvascular Endothelium ◽  
Neutrophil Adherence ◽  
Flow Velocities

This study reports measurements of porcine neutrophil dynamics in isolated microvessels. Porcine coronary venules and arterioles were isolated, cannulated, and perfused with fluorescently labeled neutrophils at a series of flow velocities. In venules (62.50 +/- 5.41 microns diam) under control conditions, rolling neutrophils were often observed at intraluminal flow velocities ranging from 600 to 6,000 microns/s, and the rolling fraction varied inversely as a function of flow velocity. There was no significant adherence under the control conditions at any of the various flow velocities. Pretreatment of the neutrophils with human recombinant complement 5a (C5a, 10(-8) M) increased adherence at low flow velocities but did not alter the rolling fraction. In contrast to venules, rolling neutrophils were not observed in arterioles (58.80 +/- 5.6 microns diam). Furthermore, neutrophils that were pretreated with C5a did not adhere to the arteriolar endothelium even at low flow velocities. We suggest that 1) isolated microvessels perfused with fluorescently labeled neutrophils are suitable models for the study of the interaction between neutrophils and the microvascular endothelium, 2) shear force plays an important role in neutrophil rolling in coronary venules but is not the major factor that prevents neutrophil rolling and adherence in arterioles, and 3) C5a causes neutrophil adherence in venules but not in arterioles, indicating that different mechanisms underlie the interaction between neutrophils and endothelium in venules and arterioles.

Experimental Investigation of the Acoustic Power Around Two Tandem Cylinders

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
S. L. Finnegan ◽  
C. Meskell ◽  
S. Ziada
Keyword(s):  
Flow Field ◽  
Flow Velocity ◽  
Vortex Shedding ◽  
Acoustic Resonance ◽  
Low Flow ◽  
Interaction Mechanisms ◽  
Tandem Cylinders ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
Flow Velocities

Aeroacoustic resonance of bluff bodies exposed to cross flow can be problematic for many different engineering applications and knowledge of the location and interaction of acoustic sources is not well understood. Thus, an empirical investigation of the acoustically coupled flow around two tandem cylinders under two different resonant conditions is presented. It is assumed that the resonant acoustic field could be decoupled from the hydrodynamic flow field, resolved separately, and then recoupled to predict the flow/sound interaction mechanisms using Howe's theory of aerodynamic sound. Particle image velocimetry was employed to resolve the phase-averaged flow field characteristics around the cylinders at various phases in an acoustic wave cycle. It was found that the vortex shedding patterns of the two resonant conditions exhibit substantial differences. For the first condition, which occurred at low flow velocities where the natural vortex shedding frequency was below the acoustic resonance frequency, fully developed vortices formed in both the gap region between the cylinders and in the wake. These vortices were found to be in phase with each other. For the second resonant condition, which occurred at higher flow velocities where the natural vortex shedding frequency was above the acoustic resonant frequency, fully developed vortices only formed in the wake and shedding from the two cylinders were not in phase. These differences in the flow field resulted in substantial variation in the flow-acoustic interaction mechanisms between the two resonant conditions. Corresponding patterns of the net acoustic energy suggest that acoustic resonance at the lower flow velocity is due to a combination of shear layer instability in the gap and vortex shedding in the wake, while acoustic resonance at the higher flow velocity is driven by the vortex shedding in the wake of the two cylinders.

scholarly journals Performance analysis of time and cost efficient data pre-fetching in mobile cloud computing

2021 ◽  
Author(s):  
Kaveh Khorramnejad ◽  
Alagan Anpalagan ◽  
Ling Guan
Keyword(s):  
Response Time ◽  
Processing Speed ◽  
Mobile Cloud Computing ◽  
Scheduling Model ◽  
Total Response Time ◽  
Wide Range ◽  
Workload Scheduling ◽  
Efficient Data ◽  
Cost Efficient ◽  
The Cost

Recently, many methods and algorithms have been proposed in pre-fetching area. However, pre-fetching integrated with workload scheduling approaches have not been investigated as much. Initially, this thesis reviews the principles of the existing pre-fetching strategies considering latency and cost factor as primary objectives. Later, it focuses on an integrated workload scheduling and pre-fetching model to enhance the performance of response time and minimize the cost. Furthermore, response time and cost problems are formulated and to overcome the total response time and cost problems a heuristic approach is proposed. Integrated model is tested for wide range of variables and, the effects of various parameters such as processing speed and pre-fetcher’s utilization are analysed and compared. Finally, based on the results integrated pre-fetching and workload scheduling model outperforms either of them, individually. Thus, this thesis can contribute to the the new solutions in this area.

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