scholarly journals Experimental study on the shape of plunge pool in the Horizontal Swirl Spillway Tunnel

2021 ◽  
Vol 276 ◽  
pp. 01025
Author(s):  
Heng Zhou ◽  
Hui Li ◽  
Ruijiao Xing ◽  
Xinlei Guo ◽  
Haitao Wang ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Side Wall ◽  
Western China ◽  
Physical Model Test ◽  
Inlet Section ◽  
Design Scheme ◽  
Plunge Pool ◽  
Measurement Results ◽  
Hydropower Dams ◽  
Spillway Tunnel

According to the study on the shape of plunge pool in the horizontal swirl spillway tunnel, the design scheme of a plunge pool with better energy dissipation effect is proposed. Based on the hydraulic physical model test, which includes atmospheric pressure and decompression tests, and combined with the different design scheme of a plunge pool, measurement results of fluctuating pressure. Main frequency and sidewall pressure are analysed. The results show that the inlet section of the plunge pool is connected by a gradual variable section which length of gradient segment 6m. The shape of the gradient section is a long round variable gate hole. To improve the side wall pressure, the inlet section is increasing from 6.0m to 14.0m. Finally, the proposed plunge pool has the advantages of simple design and convenient construction, and these studies provide reference and support for the design of hydropower dams in western China.

scholarly journals Synthesis and Properties of Plasma-Polymerized Methyl Methacrylate via the Atmospheric Pressure Plasma Polymerization Technique

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 396 ◽  
Author(s):  
Choon-Sang Park ◽  
Eun Jung ◽  
Hyo Jang ◽  
Gyu Bae ◽  
Bhum Shin ◽  
...  
Keyword(s):  
Methyl Methacrylate ◽  
Photoelectron Spectroscopy ◽  
Atmospheric Pressure ◽  
Secondary Ion Mass Spectrometry ◽  
Atmospheric Pressure Plasma ◽  
Thickness Measurement ◽  
Water Contact ◽  
Pressure Plasma ◽  
Measurement Results ◽  
The Fourier Transform

Pinhole free layers are needed in order to prevent oxygen and water from damaging flexible electrical and bio-devices. Although polymerized methyl methacrylate (polymethyl methacrylate, PMMA) for the pinhole free layer has been studied extensively in the past, little work has been done on synthesizing films of this material using atmospheric pressure plasma-assisted electro-polymerization. Herein, we report the synthesis and properties of plasma-PMMA (pPMMA) synthesized using the atmospheric pressure plasma-assisted electro-polymerization technique at room temperature. According to the Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and time of flight-secondary ion mass spectrometry (ToF-SIMS) results, the characteristic peaks from the pPMMA polymer chain were shown to have been detected. The results indicate that the percentage of hydrophobic groups (C–C and C–H) is greater than that of hydrophilic groups (C–O and O–C=O). The field emission-scanning electron microscope (FE-SEM) and thickness measurement results show that the surface morphology is quite homogenous and amorphous in nature, and the newly proposed pPMMA film at a thickness of 1.5 µm has high transmittance (about 93%) characteristics. In addition, the results of water contact angle tests show that pPMMA thin films can improve the hydrophobicity.

Measurement of small values of hydrostatic pressure difference / Pomiar małych wartości różnicy ciśnień hydrostatycznych

2012 ◽  
Vol 57 (1) ◽  
pp. 157-167
Author(s):  
Krzysztof Broda ◽  
Wiktor Filipek
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Distribution ◽  
Atmospheric Pressure ◽  
Free Water ◽  
Reynolds Numbers ◽  
Measurement Results ◽  
Order Of Magnitude ◽  
Hydraulic Gradients ◽  
Accuracy Of Measurement ◽  
Definition Of

In order to describe the fluid flow through the porous centre, made of identical spheres, it is necessary to know the pressure, but in fact - the pressure distribution. For the flows in the range that was traditionally called laminar flow (i. e. for Reynolds numbers (Bear, 1988; Duckworth, 1983; Troskolański, 1957) from the range 0,01 to 3) it is virtually impossible with the use of the tools directly available on the market. Therefore, many scientists who explore this problem have concentrated only on the research of the velocity distribution of the medium that penetrates the intended centre (Bear, 1988) or pressure distribution at high hydraulic gradients (Trzaska & Broda, 1991, 2000; Trzaska et al., 2005). It may result from the inaccessibility to the measurement methods that provide measurement of very low hydrostatic pressures, such as pressure resulting from the weight of liquid located in the gravitational field (Duckworth, 1983; Troskolański, 1957). The pressure value c. 10 Pa (Troskolański, 1957) can be generated even by 1 mm height difference between the two levels of the free water surface, which in fact constitutes the definition of gauging tools of today measuring the level of the hydrostatic pressure. Authors proposed a method of hydrostatic pressure measurement and devised a gauging tool. Then a series of tests was conducted aiming at establishing what is the influence of various factors, such as temperature, atmospheric pressure, velocity of measurement completion, etc. on the accuracy and method of measurements. A method for considerable reduction of hysteresis that occurs during measurement was also devised. The method of measurement of small hydrostatic difference measurements allows for the accuracy of measurement of up to 0.5 Pa. Measurement results can be improved successfully by one order of magnitude, which for sure would entail necessary temperature stabilization of the tool. It will be more difficult though to compensate the influence of atmospheric pressure on the measurement process.

scholarly journals Design of A Streamwise-Lateral Ski-Jump Flow Discharge Spillway

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1585 ◽  
Author(s):  
Jun Deng ◽  
Wangru Wei ◽  
Zhong Tian ◽  
Faxing Zhang
Keyword(s):  
Side Wall ◽  
Hydraulic Engineering ◽  
Limited Area ◽  
Lateral Direction ◽  
Flow Discharge ◽  
Free Jet ◽  
Plunge Pool ◽  
New Type ◽  
Solid Walls ◽  
Large Discharge

Spillway outlet design is a major issue in hydraulic engineering with high head and large discharge conditions. A new type of design for a streamwise-lateral spillway is proposed for ski-jump flow discharge and energy dissipation in hydraulic engineering. The water in the spillway outlet is constrained by three solid walls with an inclined floor, a horizontal floor on the bottom and a deflected side wall in the lateral direction. The water flow releases in a lateral direction into the plunge pool along the streamwise direction. It generates a free jet in the shape of “∩” in a limited area, causing the water to fully diffuse and stretch in the air simultaneously, and drop into the plunge pool to avoid excessive impact in the plunge pool. The formation mechanism for the flow pattern is analyzed, and the results show that the optimum inclination is an angle range of 30°~45° for a good performance of free ski-jump jet diffusion shape.

Analysis of Developing and Fully Developed Turbulent Flow and Heat Transfer in a Square-Sectioned U-Bend Duct

2005 ◽  
Author(s):  
Sassan Etemad ◽  
Bengt Sunde´n
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulent Flow ◽  
Side Wall ◽  
Outer Wall ◽  
Industrial Applications ◽  
Inlet Section ◽  
Lower Velocity ◽  
Fully Developed Turbulent Flow ◽  
Inlet Length

Turbulent flow and thermal field were predicted in a square-sectioned 180° bend at a Reynolds number of 56000. Suga’s low-Re cubic k-ε model [5–6] and the RSM [7–8] were used. The results were compared to experimental data [1]. Identical inlet boundary conditions were used in both cases. The inlet length impact on the flow-heat transfer in the bend was investigated. The velocities are higher near the inner wall and lower near the outer wall when a short inlet section is used. As the inlet length increases, the boundary layer grows thicker and the pressure-driven secondary vortex near the side wall becomes stronger. This vortex contributes significantly to the mixing process and heat transfer. It also alters the velocity distribution to a higher velocity near the outer wall and a lower velocity near the inner wall. When using a very long inlet length the vortex grows so strong that it generates a second counter-rotating vortex which isolates the fluid near the inner wall and prevents from further mixing. Consequently the local Nusselt number decreases. Both models reproduced the experimental data fairly well. Suga’s model performed better and converged without problems. It is believed that Suga’s model would be more suitable for industrial applications.

scholarly journals A Broadband Single-Feed Circularly Polarized Patch Antenna with Wide Beamwidth

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Changhong Zhang ◽  
Junping Geng ◽  
Bin Zhou ◽  
Xianling Liang ◽  
Ronghong Jin
Keyword(s):  
Reflection Coefficient ◽  
Patch Antenna ◽  
Ground Plane ◽  
Side Wall ◽  
Axial Ratio ◽  
Resistive Load ◽  
Circularly Polarized ◽  
Measurement Results ◽  
Microstrip Ring ◽  
Matching Load

A broadband single-feed circularly polarized patch antenna with wide beamwidth is presented. The patch is coupled to four asymmetric cross slots via a microstrip ring with eight matching segments underneath the ground plane, traversing through the arms of the cross slots in a serial manner. And a coupling slice instead of a resistive load is used as matching load of the microstrip ring for higher gain. Furthermore, a metal side wall surrounding the antenna is used to improve the isolation between adjacent elements in an array. Through optimizing the four asymmetric cross slots and eight matching segments, excellent performances are achieved by the proposed antenna, especially for the broadband and wide beamwidth. Measurement results show that the antenna has −10 dB reflection coefficient bandwidth of 29.7%, 3-dB axial-ratio bandwidth of 21.6%, and beamwidth of more than 90°. It can be considered as a good candidate for the element of arrays.

Comparative Analysis of Wind Speed in Ventilation Hole Simulated by VOF and Euler Model

2014 ◽  
Vol 624 ◽  
pp. 643-646
Author(s):  
Hong Qing Zhang ◽  
Xian Tang Zhang ◽  
Yi Long Lou ◽  
Wei Ping Xing
Keyword(s):  
Wind Speed ◽  
Outlet Section ◽  
Inlet Section ◽  
Two Phase ◽  
Vof Model ◽  
Wind Speed Distribution ◽  
Euler Model ◽  
Spillway Tunnel ◽  
Ventilation Hole ◽  
Large Discharge

In order to analysis the applicability of VOF and Euler models to simulate water-air two-phase flow, VOF model and Euler model, respectively combining turbulent model, were used to simulate wind speed in ventilation hole of working gate in a hydropower station spillway tunnel with high head and large discharge in China. The results show that the dragging force simulated by Euler model is much more effective than that simulated by VOF model, causing significant increase of airflow in ventilation hole. It is obviously that wind speed simulated by Euler model is more close to the measured one, which may also provide evidence for design of ventilation hole. So Euler model is a better method to simulate the characteristic of aerated flow than VOF model. Meanwhile, the maximum wind speed occur near the inlet of ventilation hole, and the maximum value of wind speed is close to 120 m/s, which can cause loud noise. And wind speed distribution on the inlet section and outlet section of ventilation hole is respectively the most non-uniform and uniform. The conclusions obtained can improve the design of ventilation hole.

A High-Voltage Terminal for a Field-Emission Gun

1972 ◽  
Vol 30 ◽  
pp. 428-429
Author(s):  
N. F. Ziegler
Keyword(s):  
Field Emission ◽  
High Voltage ◽  
Atmospheric Pressure ◽  
Power Supplies ◽  
High Coherence

A high-voltage terminal has been constructed for housing the various power supplies and metering circuits required by the field-emission gun (described elsewhere in these Proceedings) for the high-coherence microscope. The terminal is cylindrical in shape having a diameter of 14 inches and a length of 24 inches. It is completely enclosed by an aluminum housing filled with Freon-12 gas at essentially atmospheric pressure. The potential of the terminal relative to ground is, of course, equal to the accelerating potential of the microscope, which in the present case, is 150 kilovolts maximum.

Electron microscope characterization of MOCVD-grown gap layers on Si

1986 ◽  
Vol 44 ◽  
pp. 724-725
Author(s):  
K.M. Jones ◽  
M.M. Al-Jassim ◽  
J.M. Olson
Keyword(s):  
Atmospheric Pressure ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Organic Chemical ◽  
Lattice Match ◽  
Si Substrates ◽  
Metal Organic ◽  
Good Lattice ◽  
Antiphase Domains

The epitaxial growth of III-V semiconductors on Si for integrated optoelectronic applications is currently of great interest. GaP, with a lattice constant close to that of Si, is an attractive buffer between Si and, for example, GaAsP. In spite of the good lattice match, the growth of device quality GaP on Si is not without difficulty. The formation of antiphase domains, the difficulty in cleaning the Si substrates prior to growth, and the poor layer morphology are some of the problems encountered. In this work, the structural perfection of GaP layers was investigated as a function of several process variables including growth rate and temperature, and Si substrate orientation. The GaP layers were grown in an atmospheric pressure metal organic chemical vapour deposition (MOCVD) system using trimethylgallium and phosphine in H2. The Si substrates orientations used were (100), 2° off (100) towards (110), (111) and (211).

Microstructure and reactivity of small metal particles: The role of Ce additives

1992 ◽  
Vol 50 (1) ◽  
pp. 318-319
Author(s):  
L.D. Schmidt ◽  
K. R. Krause ◽  
J. M. Schwartz ◽  
X. Chu
Keyword(s):  
Atmospheric Pressure ◽  
Noble Metals ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Chemical Shifts ◽  
Catalytic Converter ◽  
Structural Evolution ◽  
Single Particles ◽  
Small Metal Particles

The evolution of microstructures of 10- to 100-Å diameter particles of Rh and Pt on SiO2 and Al2O3 following treatment in reducing, oxidizing, and reacting conditions have been characterized by TEM. We are able to transfer particles repeatedly between microscope and a reactor furnace so that the structural evolution of single particles can be examined following treatments in gases at atmospheric pressure. We are especially interested in the role of Ce additives on noble metals such as Pt and Rh. These systems are crucial in the automotive catalytic converter, and rare earths can significantly modify catalytic properties in many reactions. In particular, we are concerned with the oxidation state of Ce and its role in formation of mixed oxides with metals or with the support. For this we employ EELS in TEM, a technique uniquely suited to detect chemical shifts with ∼30Å resolution.

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