scholarly journals Numerical analyses of embankment dams containing plastic concrete cut-off walls using finite difference method (A case study: The Karkheh Embankment Dam)

2021 ◽  
Vol 9 (3) ◽  
pp. 143-153
Author(s):  
Yadolah Pashang Pisheh ◽  
Seyd Majdeddin Mir Mohammad Hosseini
Keyword(s):  
Steady State ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
The Other ◽  
Numerical Analyses ◽  
Maximum Magnitude ◽  
Embankment Dam ◽  
Plastic Concrete ◽  
Clay Core

In this paper, numerical analyses have been performed on the Karkheh embankment dam with a clayey core and plastic concrete cut-off wall during construction, impounding, and permanent seepage stages. The dam has 127 meters height and is located in a high seismic hazard zone in Iran. Different stages of construction, water impounding, and steady state seepage were modelled and analyzed using the hyperbolic and Mohr-Coulomb models with the two dimensional finite difference method (FDM). So, nonlinear analyses were performed using FLAC 2D to investigate the settlements and the pore water pressure changes in different zones of the dam during above-mentioned stages and the results were compared to those of the other studies. The results show that at the end of the construction stage, the maximum settlement equal to 1.45m occurs inside the clay core at the height of 65m. Then, after impounding of the reservoir and steady state stage, the maximum magnitude of the horizontal deformations occurs in the downstream of the dam equal to 0.55m; however, these magnitudes reach to 0.17m at the crest of the dam. Moreover, it was shown that the maximum horizontal displacement of the plastic concrete cut-off wall has happened at the top of the wall in the clay core which is in a good agreement with the other studies’ result.

Boundary-layer flow between nodal and saddle points of attachment

1970 ◽  
Vol 41 (4) ◽  
pp. 823-835 ◽  
Author(s):  
J. C. Cooke ◽  
A. J. Robins
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Saddle Point ◽  
Difference Method ◽  
Series Solution ◽  
Nodal Point ◽  
Saddle Points ◽  
The Other ◽  
The Finite Difference Method ◽  
Layer Flow

A simplified example of this type of flow was examined in detail by developing two series, eventually matched, one about the nodal point and the other about the saddle point, and also by finite differences, marching from the nodal point to the saddle point. It was found that the results of marching the two series were in agreement with the finite difference method. The series solution near the saddle point is not unique, but numerical evidence indicates that the correct solution is that which has ‘exponential decay’ at infinity, and that this type of solution, if such exists, automatically emerges when the finite difference method is used.

Influence of Rotational Speed on Thermal Performance of Tri-Sector Rotary Regenerative Air Preheater

2016 ◽  
Author(s):  
Xun Chen ◽  
Xue-nong Duan ◽  
Li-min Wang ◽  
Yi Yang ◽  
Dun-dun Wang ◽  
...  
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
Rotational Speed ◽  
The Other ◽  
Heating Period ◽  
Height Range ◽  
Rotational Angle ◽  
Air Preheater ◽  
Deposition Area

This paper provides a detailed analysis of how a rotary regenerative air preheater’s performance parameters such as effectiveness, fluid and metal temperature fields, and ammonium bisulfate (ABS) deposition area vary with rotor rotational speed. A tri-sector rotary regenerative air preheater for a 600MW unit was studied as an example by use of effectiveness–modified number of transfer units (ε-NTU0) method and a finite difference method. The findings of the research are as follows: (1) There is a nonlinear relationship between matrix temperature distribution and rotational angle, and the degree of nonlinearity, represented by unsteady heat transfer correction factor Π, increases with decreasing rotational speed and varies between sectors; (2) There exist two equilibrium positions around the intersection points of matrix temperature curves for different rotational speeds, one occurring in the heating period and the other in the cooling period; (3) The act of reducing the rotor speed has two effects on ABS deposition. On the one hand, the height range of possible ABS deposition area will expand as the matrix temperature within the first third of gas sector’s angle range further decreases with decreasing rotational speed. On the other hand, after the rotational speed falls below a certain level, the hot-end matrix temperature climbs above the ABS formation temperature during part of the heating period, resulting in gasification and decomposition of the condensed product. The combined effect is yet to be examined through further theoretical and empirical analyses. (4) The trends of average outlet temperatures of primary and secondary air depend on rotor rotation direction and angles of sectors. (5) The effectiveness values calculated by ε-NTU0 method are greater than those acquired by the finite difference method, especially at low rotor rotational speeds.

Determination of the Steady-State Response of Viscoelastically Supported Rectangular Orthotropic Mass Loaded Plates by an Energy-Based Finite Difference Method

2005 ◽  
Vol 11 (12) ◽  
pp. 1535-1552 ◽  
Author(s):  
Gökhan Altintaş ◽  
Muhiddin Bağci
Keyword(s):  
Steady State ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
Plate Theory ◽  
Steady State Response ◽  
Algebraic Equations ◽  
State Response ◽  
Elastic Rectangular Plate ◽  
Spring Coefficient

A method based on a variational procedure in conjunction with a finite difference method is used to examine the free vibration characteristics and steady-state response to a sinusoidally varying force applied orthotropic elastic rectangular plate carrying masses. Using the energy-based finite difference method, the problem reduced to the solution of a system of algebraic equations. Due to the significance of the fundamental natural frequency of the plate, its variation is investigated with respect to the mechanical properties of the plate material, the translational spring coefficient of the supports, the mass distribution, the mass locations and the quantity of mass. The steady-state response of the viscoelastically supported plates was also investigated numerically for the damping coefficient of the supports and the force distribution in addition to the characteristics of the plate system. Many new results are presented and the validity of the present approach is demonstrated by comparing the results with other solutions based on the Kirchhoff-Love plate theory.

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