The Study of the Depression Occurred under Different Types of Impellers

2016 ◽  
Vol 841 ◽  
pp. 116-121 ◽  
Author(s):  
Lucian Mândrea ◽  
Gabriela Oprina ◽  
Corina Băbuţanu ◽  
Dorian Marin ◽  
Gabriel Negreanu
Keyword(s):  
Analytical Solution ◽  
Theoretical Approach ◽  
Numerical Results ◽  
Variable Radius ◽  
Different Types ◽  
Hydraulic Turbines ◽  
Theoretical Results ◽  
Good Agreement

The paper presents the analytical solution used to calculate the depression which appears under different types of impellers. This solution can be useful as a preliminary calculus to estimate the magnitude of the depression created at different rotational speeds, in order not to damage the equipment from different systems, such as hydraulic turbines. The authors obtain the variable radius of the depression zone, the pressure inside the depression zone and the depression height. The theoretical approach, the calculus itself and the numerical results presented in the article are original. In order to validate the proposed calculus, experiments were carried out using two experimental setups. The performed measurements showed a good agreement of the experimental and theoretical results.

Vibration Characteristics of Straight Blades of Asymmetrical Aerofoil Cross-Section

1969 ◽  
Vol 20 (2) ◽  
pp. 178-190 ◽  
Author(s):  
W. Carnegie ◽  
B. Dawson
Keyword(s):  
Analytical Solution ◽  
Cross Section ◽  
Natural Frequencies ◽  
Equations Of Motion ◽  
Limited Range ◽  
First Order ◽  
Special Cases ◽  
Theoretical Results ◽  
Theoretical Procedure ◽  
Good Agreement

SummaryTheoretical and experimental natural frequencies and modal shapes up to the fifth mode of vibration are given for a straight blade of asymmetrical aerofoil cross-section. The theoretical procedure consists essentially of transforming the differential equations of motion into a set of simultaneous first-order equations and solving them by a step-by-step finite difference procedure. The natural frequency values are compared with results obtained by an analytical solution and with standard solutions for certain special cases. Good agreement is shown to exist between the theoretical results for the various methods presented. The equations of motion are dependent upon the coordinates of the axis of the centre of flexure of the beam relative to the centroidal axis. The effect of variations of the centre of flexure coordinates upon the frequencies and modal shapes is shown for a limited range of coordinate values. Comparison is made between the theoretical natural frequencies and modal shapes and corresponding results obtained by experiment.

Stability of Unsymmetrical Rigid Rotor Supported by Self-Acting Gas-Lubricated Journal Bearings

1983 ◽  
Vol 105 (4) ◽  
pp. 656-661 ◽  
Author(s):  
S. Yoshimoto ◽  
Y. Nakano
Keyword(s):  
Theoretical Approach ◽  
Journal Bearings ◽  
Center Of Gravity ◽  
Rigid Rotor ◽  
Load Bearing ◽  
Bearing Clearance ◽  
Axial Deviation ◽  
Bearing Load ◽  
Theoretical Results ◽  
Good Agreement

In order to determine the threshold of instability for an unsymmetrical rigid rotor supported by two identical self-acting, plain-cylindrical gas journal bearings, a theoretical approach is made by the use of the quasi-static nonliner PH method. Influence of various parameters affecting the threshold of instability of the unsymmetrical rotor is experimentally shown and compared with the theoretical results. The experimental variables considered in this paper include bearing load, bearing length, bearing clearance, the axial deviation of the center of gravity from the center of the rotor span. Good agreement was obtained between the experimental and theoretical results.

The Effectiveness of Pre-Cast Wall-Piles in Reducing Ground Vibration

1998 ◽  
Vol 5 (3) ◽  
pp. 185-199
Author(s):  
K. Hayakawa ◽  
Y. Kani ◽  
N. Matsubara ◽  
R.D. Woods
Keyword(s):  
Vibration Reduction ◽  
Field Tests ◽  
Ground Vibration ◽  
Field Measurements ◽  
Ground Vibrations ◽  
Different Types ◽  
Theoretical Results ◽  
Good Agreement

This paper presents the results of a study of the effectiveness of pre-cast wall-piles for controlling ground vibrations. Field measurements have been performed for five cases of different types of pre-cast wall-piles. A method for estimation of vibration reduction by pre-cast wall-piles has been developed, based on wave penetration theory. Vibration levels as registered on the off-side of the PC wall-piles barrier were 5 to 7 dB lower than that recorded at the site with no such barrier. Theoretical results, using the wave penetration theory showed good agreement with the field tests.

scholarly journals Vibration analysis of submerged rectangular microplates with distributed mass loading

2009 ◽  
Vol 465 (2104) ◽  
pp. 1323-1336 ◽  
Author(s):  
Zhangming Wu ◽  
Xianghong Ma ◽  
Peter N Brett ◽  
Jinwu Xu
Keyword(s):  
Analytical Solution ◽  
Natural Frequencies ◽  
Isotropic Plate ◽  
Numerical Results ◽  
Previous Literature ◽  
Mode Shapes ◽  
Mass Loading ◽  
Coupling System ◽  
Different Types ◽  
Loaded Structure

This paper investigates the vibration characteristics of the coupling system of a microscale fluid-loaded rectangular isotropic plate attached to a uniformly distributed mass. Previous literature has, respectively, studied the changes in the plate vibration induced by an acoustic field or by the attached mass loading. This paper investigates the issue of involving these two types of loading simultaneously. Based on Lamb's assumption of the fluid-loaded structure and the Rayleigh–Ritz energy method, this paper presents an analytical solution for the natural frequencies and mode shapes of the coupling system. Numerical results for microplates with different types of boundary conditions have also been obtained and compared with experimental and numerical results from previous literature. The theoretical model and novel analytical solution are of particular interest in the design of microplate-based biosensing devices.

Study of Electrical Conductivity in WO3-doped Nonstoichiometric LiTaO3

2012 ◽  
Vol 57 (8) ◽  
pp. 834
Author(s):  
M. Tahiri ◽  
N. Masaif ◽  
A. Jennane ◽  
E.M. Lotfi
Keyword(s):  
Experimental Data ◽  
Electrical Conductivity ◽  
Ternary System ◽  
Curie Temperature ◽  
Solid Solutions ◽  
Theoretical Approach ◽  
Defect Structure ◽  
Experimental Conductivity ◽  
Theoretical Results ◽  
Good Agreement

The results of experimental and analytical studies of the electrical conductivity for different solid solutions synthesized in a vicinity of LiTaO3 in the ternary system Li2O–Ta2O5–(WO3)2 are presented. It is shown that the electrical conductivity increases linearly with the Curie temperature. The experimental conductivity between 200 and 700 ºC was measured using an LCR bridge HP4192A on ceramics sintered at 1250 ºC. Within the theoretical approach to the defect structure analysis combined with our proposed vacancy models, the theoretical results are in a good agreement with the experimental data.

On the Propagation Buckling and Effects in Ultra-Long Deep Subsea Pipelines

2011 ◽  
Author(s):  
Hossein Khalilpasha ◽  
Faris Albermani
Keyword(s):  
Experimental Investigation ◽  
Analytical Solution ◽  
Analytical Solutions ◽  
Numerical Results ◽  
Series Of Experiments ◽  
Buckle Propagation ◽  
Subsea Pipelines ◽  
Good Agreement

This paper considers buckling propagation in ultra-long deep subsea pipelines. Experimental investigation of buckle propagation in ultra-deep pipelines was conducted to verify the analytical solutions proposed by the authors in a previous paper [1]. A series of experiments were designed and conducted to calibrate the equations and verify the analytical and numerical results. The tests include tensile coupon tests, ring squash tests and buckle propagation tests on intact and dented Aluminum pipes with three different D/t ratios. The results are in good agreement with the proposed analytical solution.

A Rotary Magnetic Damper or Brake Consisting of a Number of Sector Magnets and a Circular Conductor

1989 ◽  
Vol 111 (1) ◽  
pp. 97-104 ◽  
Author(s):  
Kosuke Nagaya ◽  
Yasuo Karube
Keyword(s):  
Analytical Solution ◽  
Magnetic Flux ◽  
Eddy Current ◽  
Experimental Tests ◽  
Numerical Calculations ◽  
Damping Coefficient ◽  
Braking Force ◽  
Theoretical Results ◽  
Good Agreement

This paper is concerned with a method for analyzing a rotary magnetic damper (eddy current brake) consisting of a number of sector magnets and a circular conductor. The analytical solution to obtain an eddy current, a braking force, and a damping coefficient is obtained by dividing the magnetic flux into the narrow sectors. Numerical calculations have been carried out for the variation of the flux range, the position, and the number of the magnets. Experimental tests are also carried out to verify the present theoretical results. The theoretical results are in good agreement wtih the experimental ones.

Investigating the Nonlinear Optical Response of Pepper Oil under Low Power Irradiation with Continuous Wave Visible Laser Beam

2020 ◽  
pp. 131-138
Keyword(s):  
Refractive Index ◽  
Nonlinear Refractive Index ◽  
Nonlinear Optical ◽  
Continuous Wave ◽  
Diffraction Integral ◽  
Visible Laser ◽  
Limiting Property ◽  
Kirchhoff Diffraction Integral ◽  
Theoretical Results ◽  
Good Agreement

The nonlinear optical properties of pepper oil are studied by diffraction ring patterns and Z-scan techniques with continuous wave beam from solid state laser at 473 nm wavelength. The nonlinear refractive index of the sample is calculated by both techniques. The sample show high nonlinear refractive index. Based on Fresnel-Kirchhoff diffraction integral, the far-field intensity distributions of ring patterns have been calculated. It is found that the experimental results are in good agreement with the theoretical results. Also the optical limiting property of pepper oil is reported. The results obtained in this study prove that the pepper oil has applications in nonlinear optical devices.

scholarly journals Semi-Analytical Solution to Assess CO2 Leakage in the Subsurface through Abandoned Wells

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2452
Author(s):  
Tian Qiao ◽  
Hussein Hoteit ◽  
Marwan Fahs
Keyword(s):  
Analytical Solution ◽  
Storage Site ◽  
Co2 Leakage ◽  
Transient Pressure ◽  
Flow Paths ◽  
Abandoned Wells ◽  
Diffusivity Equation ◽  
Carbon Dioxide Co2 ◽  
Good Agreement

Geological carbon storage is an effective method capable of reducing carbon dioxide (CO2) emissions at significant scales. Subsurface reservoirs with sealing caprocks can provide long-term containment for the injected fluid. Nevertheless, CO2 leakage is a major concern. The presence of abandoned wells penetrating the reservoir caprock may cause leakage flow-paths for CO2 to the overburden. Assessment of time-varying leaky wells is a need. In this paper, we propose a new semi-analytical approach based on pressure-transient analysis to model the behavior of CO2 leakage and corresponding pressure distribution within the storage site and the overburden. Current methods assume instantaneous leakage of CO2 occurring with injection, which is not realistic. In this work, we employ the superposition in time and space to solve the diffusivity equation in 2D radial flow to approximate the transient pressure in the reservoirs. Fluid and rock compressibilities are taken into consideration, which allow calculating the breakthrough time and the leakage rate of CO2 to the overburden accurately. We use numerical simulations to verify the proposed time-dependent semi-analytical solution. The results show good agreement in both pressure and leakage rates. Sensitivity analysis is then conducted to assess different CO2 leakage scenarios to the overburden. The developed semi-analytical solution provides a new simple and practical approach to assess the potential of CO2 leakage outside the storage site. This approach is an alternative to numerical methods when detailed simulations are not feasible. Furthermore, the proposed solution can also be used to verify numerical codes, which often exhibit numerical artifacts.

scholarly journals Constitutive Modeling of the Densification Behavior in Open-Porous Cellular Solids

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2731
Author(s):  
Ameya Rege
Keyword(s):  
Constitutive Model ◽  
Cell Walls ◽  
Compressive Strain ◽  
Pore Collapse ◽  
Compressive Response ◽  
Linear Elastic ◽  
Nonlinear Springs ◽  
Different Types ◽  
Point Of Intersection ◽  
Good Agreement

The macroscopic mechanical behavior of open-porous cellular materials is dictated by the geometric and material properties of their microscopic cell walls. The overall compressive response of such materials is divided into three regimes, namely, the linear elastic, plateau and densification. In this paper, a constitutive model is presented, which captures not only the linear elastic regime and the subsequent pore-collapse, but is also shown to be capable of capturing the hardening upon the densification of the network. Here, the network is considered to be made up of idealized square-shaped cells, whose cell walls undergo bending and buckling under compression. Depending on the choice of damage criterion, viz. elastic buckling or irreversible bending, the cell walls collapse. These collapsed cells are then assumed to behave as nonlinear springs, acting as a foundation to the elastic network of active open cells. To this end, the network is decomposed into an active network and a collapsed one. The compressive strain at the onset of densification is then shown to be quantified by the point of intersection of the two network stress-strain curves. A parameter sensitivity analysis is presented to demonstrate the range of different material characteristics that the model is capable of capturing. The proposed constitutive model is further validated against two different types of nanoporous materials and shows good agreement.

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