Study on the Shape of the Aerator of High-Head Discharge Tunnel with Mild Bottom Slope

Due to the high flow velocity and easy cavitation of high-head drainage tunnels, it is usually necessary to set up aeration facilities. In particular, when the bottom slope of the tunnel is mild, the aeration facilities often have problems such as difficulty with air intake, short cavity, and serious water accumulation, which aggravate the risk of cavitation damage. In this paper, based on the Rumei hydropower station and the Gushui hydropower station, a method combining theoretical analysis and model testing is used to solve the connection problem between the aeration facility and the 3% mild bottom slope of a tunnel body, and the aeration facility shape of “lifting ridge + flat (mild) slope + steep slope” is put forward. The research shows that the steep slope section can smoothly connect the water flow over the cantilever, reduce the jet impact angle, prevent the water from backtracking, and produce a long and stable cavity in the flat (mild) slope section. The aeration concentration along the bottom of the tunnel is higher than 3% at 140 m over the top of the dam. The aeration effect of this type is better, and it can provide effective long-distance protection for a drainage tunnel with high head and a mild bottom slope.

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Numerical Simulation on Backwater Downstream of Aerators in Spillway Tunnel with Ultra-Low Frounde Number Flow

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.444-445.539 ◽

2013 ◽

Vol 444-445 ◽

pp. 539-543

Author(s):

Li Qiang Chen ◽

Jun Xing Wang ◽

Yu Ting Chen

Keyword(s):

Numerical Simulation ◽

Model Test ◽

Steep Slope ◽

Hydropower Station ◽

Bottom Slope ◽

Circular Arc ◽

Circular Arcs ◽

Number Flow ◽

Spillway Tunnel ◽

Better Than

The backtracking of flow occurs easily in cavity of aeration step in spillway tunnel with a gentle bottom slope and ultra-low Frounde number, and this influences the intake of air, so combined with the spillway tunnel of Chang heba Hydropower Station, four bodily form of aeration steps are chosen to be studied by both numerical simulation and model test based on κ-ε turbulence model, they are continuous aeration step, U-type aeration step + local steep slope, continuous aeration step + circular arc type steep slope and continuous aeration step + ogee curve steep slope, the results show that, the downstream bottom slope of aeration step with suitable ogee curve or circular arcs can efficiently inhibit the backtracking of flow in continuous aeration step, and can efficiently eliminate hydrops in cavity and in the same time can improve the efficiency of aeration. Usually, the results of bottom slope with an ogee curve are better than that with a circular arc.

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In-Line Analysis of Diffusion Processes in Micro Channels by Long Distance Raman Photometric Measurement Technology—A Proof of Concept Study

Micromachines ◽

10.3390/mi12020116 ◽

2021 ◽

Vol 12 (2) ◽

pp. 116

Author(s):

Julian Deuerling ◽

Shaun Keck ◽

Inasya Moelyadi ◽

Jens-Uwe Repke ◽

Matthias Rädle

Keyword(s):

Numerical Aperture ◽

Spot Size ◽

Measuring System ◽

Optical Systems ◽

Measurement Technology ◽

Long Distance ◽

Measuring Point ◽

Acetone Concentration ◽

Micro Channels ◽

Set Up

This work presents a novel method for the non-invasive, in-line monitoring of mixing processes in microchannels using the Raman photometric technique. The measuring set-up distinguishes itself from other works in this field by utilizing recent state-of-the-art customized photon multiplier (CPM) detectors, bypassing the use of a spectrometer. This addresses the limiting factor of integration times by achieving measuring rates of 10 ms. The method was validated using the ternary system of toluene–water–acetone. The optical measuring system consists of two functional units: the coaxial Raman probe optimized for excitation at a laser wavelength of 532 nm and the photometric detector centered around the CPMs. The spot size of the focused laser is a defining factor of the spatial resolution of the set-up. The depth of focus is measured at approx. 85 µm with a spot size of approx. 45 µm, while still maintaining a relatively high numerical aperture of 0.42, the latter of which is also critical for coaxial detection of inelastically scattered photons. The working distance in this set-up is 20 mm. The microchannel is a T-junction mixer with a square cross section of 500 by 500 µm, a hydraulic diameter of 500 µm and 70 mm channel length. The extraction of acetone from toluene into water is tracked at an initial concentration of 25% as a function of flow rate and accordingly residence time. The investigated flow rates ranged from 0.1 mL/min to 0.006 mL/min. The residence times from the T-junction to the measuring point varies from 1.5 to 25 s. At 0.006 mL/min a constant acetone concentration of approx. 12.6% was measured, indicating that the mixing process reached the equilibrium of the system at approx. 12.5%. For prototype benchmarking, comparative measurements were carried out with a commercially available Raman spectrometer (RXN1, Kaiser Optical Systems, Ann Arbor, MI, USA). Count rates of the spectrophotometer surpassed those of the spectrometer by at least one order of magnitude at identical target concentrations and optical power output. The experimental data demonstrate the suitability and potential of the new measuring system to detect locally and time-resolved concentration profiles in moving fluids while avoiding external influence.

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Micro-grooving on quartz crystals by an abrasive air jet

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406211410260 ◽

2011 ◽

Vol 225 (9) ◽

pp. 2161-2173 ◽

Cited By ~ 6

Author(s):

J Wang ◽

A Moridi ◽

P Mathew

Keyword(s):

Performance Measures ◽

Process Parameters ◽

Traverse Speed ◽

Groove Depth ◽

Impact Angle ◽

Quartz Crystals ◽

Air Jet ◽

Jet Impact ◽

Mass Flowrate ◽

Micro Grooving

An investigation of the micro-grooving performance of abrasive air jet (AAJ) on quartz crystals is presented and discussed. An experimental study was carried out first to understand the effect of process parameters on the major grooving performance measures such as groove depth, groove width, kerf taper, and surface roughness. Plausible trends for these grooving performance measures with respect to the various process variables, such as air pressure, nozzle traverse speed, jet impact angle, and abrasive mass flowrate, are discussed. It is found that AAJ is an effective technology for micromachining of quartz crystals and the grooving performance can be improved or optimized by selecting the process parameters properly. Predictive models are then developed for quantitatively estimating the micro-grooving performance. The models are finally verified by an experiment. It shows that the model predictions are in good agreement with the experimental results under the corresponding conditions.

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Colonization of depopulated crinoids by symbionts: who comes from the bottom and who from the water column?

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315415000600 ◽

2015 ◽

Vol 95 (8) ◽

pp. 1607-1612 ◽

Cited By ~ 4

Author(s):

E.S. Mekhova ◽

P.Y. Dgebuadze ◽

V.N. Mikheev ◽

T.A. Britayev

Keyword(s):

Water Column ◽

Field Experiments ◽

Dispersal Ability ◽

Long Distance ◽

Sandy Substrate ◽

Limited Dispersal ◽

Set Up ◽

Almost All ◽

High Degree

Previous experiments with the comatulid Himerometra robustipinna (Carpenter, 1881) demonstrated intensive host-to-host migration processes for almost all symbiotic species both within host aggregations and among hosts separated by several metres. The aim of this study was to check the ability of symbionts to complete long-distance migrations, by means of two in situ experiments which depopulated the crinoid host. Two different sets of field experiments were set up: exposure of depopulated crinoids (set 1) on stony ‘islands’ isolated from native crinoid assemblages by sandy substrate, and (set 2) in cages suspended in the water column. Hosts from set 1 were exposed for 1, 2, 3 and 4 weeks to assess whether substrate has an influence on the symbionts' long-distance migrations. In set 2 cages were exposed for 10–11 days, aiming to check whether symbionts were able to disperse through the water column with currents. These experiments allow the conclusion that post-settled symbionts can actively migrate among their hosts. Symbionts are able to reach their hosts by employing two different ‘transport corridors’, by drifting or swimming in water column, and by moving on the bottom. Comparison of experimental results allows the division of symbionts into two conventional groups according to the dispersal ability of their post-settled stages: (1) species able to complete long-distance migrations, (2) species unable to migrate or having limited dispersal ability. The finding of the free-living shrimp Periclimenes diversipes Kemp, 1922 in set 2 raises the question about the factors that affect such a high degree of specialization of crinoid assemblages.

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Structural Analysis of a Gas Turbine Axial Compressor Blade Eroded by Online Water Washing

Volume 2B: Turbomachinery ◽

10.1115/gt2020-15942 ◽

2020 ◽

Author(s):

Rossella Cinelli ◽

Gianluca Maggiani ◽

Serena Gabriele ◽

Alessio Castorrini ◽

Giuliano Agati ◽

...

Keyword(s):

Structural Analysis ◽

Gas Turbine ◽

Axial Compressor ◽

Compressor Blades ◽

Performance Levels ◽

Water Washing ◽

Critical Issues ◽

Air Intake ◽

Set Up ◽

The Impact

Abstract The Gas Turbine (GT) Axial Compressor (AXCO) can absorb up to the 30% of the power produced by the GT, being the component with the largest impact over the performances. The axial compressor blades might undergo the fouling phenomena as a consequence of the unwanted material locally accumulating during the machine operations. The presence of such polluting substances reduces the aerodynamic efficiency as well as the air intake causing the drop of performances and the increase of the fuel consumption. To address the above-mentioned critical issues, several washing strategies have been implemented so far, among the most promising ones, High Flow On-Line Water Washing (HFOLWW) is worth to mention. Exploiting this technique, the performance levels are preserved, whereas the stops for maintenance should be reduced. Nevertheless, this comes at the cost of a long-term erosion exposure caused by the impact of water washing droplets. Hence, it was deemed necessary to carry out a finite element method (FEM) structural analysis of the first rotor stage of the compressor of an aeroderivative GT, integrated into the HFOLWW scheme, in order to evaluate the fatigue strength of the component subjected to the erosion; possibly along with its acceptability limits. The first step requires the determination of the blade areas affected by erosion, using computational fluid dynamics (CFD) simulations, followed by the creation and the 3D modelling of the damaged geometry. The final step consists in the evaluation of the static stress and the dynamic agents, to perform a fatigue analysis through the Goodman relation and carrying out a simulation of damage propagation exploiting the theory of fracture mechanics. This procedure has been extended to the damage-free baseline component to set-up a model suitable for comparison. The structural analysis confirms the design of the blade, moreover dynamic and static evaluation of the eroded profiles haven’t outlined any working, nor mechanical, issue. This entitles the structural choice of HFOLWW as a system which guarantees full performance levels of the compressor.

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Next Generation Emergency Services Based on the Pan-European Mobile Emergency Application (PEMEA) Protocol: Leveraging Mobile Positioning and Context Information

Wireless Communications and Mobile Computing ◽

10.1155/2019/1408784 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Urban Sedlar ◽

James Winterbottom ◽

Bostjan Tavcar ◽

Janez Sterle ◽

Jaka Cijan ◽

...

Keyword(s):

Public Service ◽

Emergency Services ◽

User Acceptance ◽

Next Generation ◽

The Road ◽

Cross Border ◽

Location Aware ◽

Set Up ◽

Cell Tower ◽

Over The Top

In this paper, we analyze requirements of next generation 112 emergency services in the era of ubiquitous mobile devices and sensors and present the design, implementation, and piloting results of our testbed, which was developed within the H2020 project NEXES. The system leverages a multihop location-aware PEMEA routing network that finds the geographically closest responsible public service answering point (PSAP) and supports cross-border application roaming. Our reference mobile implementation utilizes multiple device and network-based positioning technologies, which, combined, both outperform traditional cell-tower based positioning and provide a means for detecting fraudulent calls. The system is extensible and can establish a variety of communication channels after the initial emergency session is set up; we demonstrate this with an interoperable WebRTC-based video call. The obtained results demonstrate the viability and flexibility of PEMEA-based over-the-top emergency services, show high user acceptance when comparing them with existing solutions, and thus pave the road for further rollout of such systems.

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Experimental Study on Skin Friction Reduction With Micro-Blowing

Volume 4 ◽

10.1115/ht-fed2004-56218 ◽

2004 ◽

Cited By ~ 2

Author(s):

Song Liu ◽

Hongmin Li ◽

Minel J. Braun

Keyword(s):

Boundary Layer ◽

Shear Stress ◽

Skin Friction ◽

Full Range ◽

Experimental System ◽

Main Flow ◽

Friction Reduction ◽

Long Distance ◽

Full Field ◽

Set Up

Reducing skin friction, such as friction on a car hood or a plane wing, can significantly reduce the drag force and decrease specific fuel consumption. Many techniques and methods have been tried. The Micro-blowing Technique (MBT) is an innovative way to reduce skin friction. Suggested by early research in boundary layer injection in 1950s, MBT was actually brought to effective use in 1994 by Hwang [1]. The basic idea is that by blowing fluid, same as or different from the mainstream flow, at an angle with that of the main flow, a decrease in the velocity gradient at the wall can be achieved, and thus the shear stress on the surface is reduced. Although the experimental data on boundary layer with micro blowing show a significant friction reduction, the mechanism of MBT is still not well understood and thus its full range of application is not yet established. In this paper, we further the understanding of the MBT mechanism. An experimental system is set up to visualize the flow structure on a plate with and without micro blowing in a tunnel. A long distance microscope is combined with a Full Field Flow Tracking visualization method in order to elucidate the nature of the flow interaction and mixing between the blowing flow and the main flow. The flow above the porous plates is visualized and velocities both in the blowing layer immediately adjacent to the plate and in the main flow are quantified using the PIV procedure. The flow and shear stress analysis shows that MTB has significantly different effects on a flow with a boundary layer and fully developed internal flows.

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