Numerical Analysis on the Effect of Slot Width on the Design of Vertical Slot Fishways

This paper presents the results of an experimental study on 18 designs of vertical slot fishways. Based on these results, it appears that a width of 8b0 and a length of 10b0 for the pools, where b0 is the slot width, are satisfactory, and minor variations can be made to these dimensions without affecting their satisfactory performance. In the two general groups of designs, design 6 in the first group and designs 16 and 18 in the second group are recommended for practical use. Key words: fishways, hydraulics, turbulent flow, open-channel flow, hydraulic design.

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Development of Prevention Method for Air Ingress During a Depressurization Accident of the VHTR

Volume 3: Thermal-Hydraulics ◽

10.1115/icone24-60990 ◽

2016 ◽

Author(s):

Tetsuaki Takeda ◽

Shumpei Funatani

Keyword(s):

Natural Convection ◽

Numerical Analysis ◽

Storage Tank ◽

Molecular Diffusion ◽

Fluid Layer ◽

Natural Circulation ◽

Flow Characteristics ◽

Mixing Process ◽

Vertical Slot ◽

Air Ingress

A depressurization accident is a design-basis accidents of a very high temperature reactor. When a depressurization accident occurs, air is expected to enter the reactor pressure vessel from the breach and oxidize in-core graphite structures. Therefore, it is important to know a mixing process of different kind of gases in the stable and unstable stratified fluid layer. Especially, it is also important to examine an influence of localized natural convection and molecular diffusion on mixing process from a viewpoint of safety. In order to predict and analyze the phenomena of air ingress during a depressurization accident, therefore, it is important to develop the method for prevention of air ingress during the accident. We have carried out an experiment and a numerical analysis using three-dimensional computational fluid dynamics (3D CFD) to obtain the mixing process of two component gases and flow characteristics of the localized natural convection. This study is also to investigate a control method of natural circulation of air by injection of helium gas. The numerical model consists of a storage tank and a reverse U-shaped vertical slot. They are separated by a partition plate. One side of the left wall of the left side vertical slot is heated and the other side was cooled. The right side vertical slot is cooled. The procedure of the experiment and the numerical analysis is as follows. Firstly, the storage tank was filled with heavy gas and the reverse U-shaped vertical slot was filled with light gas. In the left side vertical slot, the localized natural convection was generated by the temperature difference between the vertical walls. The flow characteristics were obtained by the experiment and steady state analysis. The unsteady state experiment and analysis were started after the partition plate was opened. The result obtained in the experiment was simulated by the numerical analysis quantitatively. The gases were mixed by molecular diffusion and natural convection. After the time elapsed, natural circulation occurred. When the temperature difference of the left vertical fluid layer was set to 100K and the combination of the mixed gas was helium and nitrogen, natural circulation produced after 110 minutes elapsed.

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Numerical analysis and experimental verification of magnetic fluid sealing for air cylinder in Aerospace Engineering

International Journal of Applied Electromagnetics and Mechanics ◽

10.3233/jae-201572 ◽

2021 ◽

pp. 1-17

Author(s):

Chen Fan ◽

Zhang Chongfeng ◽

Yang Xiaolong

Keyword(s):

Magnetic Field ◽

Numerical Analysis ◽

Service Life ◽

Permanent Magnet ◽

Magnetic Fluid ◽

Slot Width ◽

Aerospace Engineering ◽

Pole Piece ◽

The Magnetic Field ◽

Sealing Gap

In order to solve the problem of short service life (2 months) and zero leakage of air cylinder in aerospace engineering, this paper innovatively designs a magnetic fluid sealing device of air cylinder in aerospace engineering through magnetic circuit analysis and magnetic fluid sealing theory. The magnetic field finite element method is used to calculate the magnetic field distribution in the sealing gap under different key parameters such as the number of pole teeth, the height of the radial sealing gap, the thickness of the permanent magnet, the slot width, the ratio of pole piece height to shaft. And numerical analysis of the number of pole teeth, the radial sealing gap height, permanent magnet thickness, slot width, the ratio of pole piece height to shaft and other key parameters on the magnetic fluid sealing performance. Finally, the reliability of the reciprocating magnetic fluid sealing withstand voltage is verified by experimental methods. Research indicates. The pressure capabilities of magnetic fluid sealing is increasing with the increase of the number of pole teeth. The pressure capabilities of magnetic fluid sealing is decreasing with the increase of the radial sealing gap. The sealing withstand voltage increases first and then decreases with the increase of the thickness of the permanent magnet, and finally increases, and the value of the withstand voltage is the largest when the thickness of the permanent magnet is 7.8 mm. The sealing pressure capabilities increases as the slot width increases. The sealing withstand voltage increases first and then decreases as the ratio of pole piece height to shaft increases, and when the ratio of pole piece height to shaft is 0.8, the sealing withstand voltage reaches a maximum value. The pressure test finally reaches the pressure value of 6 MPa, which can meet the pressure value demand of medium pressure cylinder, indicating that the magnetic fluid sealing technology can effectively solve the leakage problem existing in the air cylinder technology of Aerospace Engineering, and improve the reliability and service life of the air cylinder.

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RIGOROUS NUMERICAL ANALYSIS AND CHARACTERIZATION OF A SILICON VERTICAL-SLOT NANO-WAVEGUIDE

Journal of Nonlinear Optical Physics & Materials ◽

10.1142/s0218863512500075 ◽

2012 ◽

Vol 21 (01) ◽

pp. 1250007 ◽

Cited By ~ 3

Author(s):

D. M. H. LEUNG ◽

N. KEJALAKSHMY ◽

B. M. A. RAHMAN ◽

K. T. V. GRATTAN

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Optical Properties ◽

Numerical Analysis ◽

Electric Field ◽

Poynting Vector ◽

Slot Waveguide ◽

Vertical Slot ◽

Power Densities

In this paper, the optical properties of a nanoscale silicon slot-waveguide has been rigorously studied by using a full vectorial H-field finite element method (VFEM) based approach. The variations of effective indices, effective areas, power densities in the slot-region and the confinement factors of the slot waveguide are thoroughly investigated. The full vectorial magnetic and electric field profiles and Poynting vector (Sz) are also presented.

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