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1
Content available Force analysis and treatments for Lidong tunnel of Renxin expressway crossing karst caves
Zhu Kai, Zhang Kui, Wu Xiang-Dong, Chen Xiang-Ge
Archives of Civil Engineering
|
2024
|
Vol. 70, nr 1
693--705
EN
There are several large karst caves at haunch part of the Lidong Tunnel during construction, together with inrush water due to high pressure within these caves. In light of it, this paper takes YK342+113 section as an example and adopts finite difference software FLAC 3D, so as to analyze tunnel deformation when crossing karst caves under six different working conditions, including with or without karst cave, before and after karst treatment, along with support locations. According to analysis results: First, the wall rock mainly had deformation at tunnel vault when evacuating at the third bench, which is a critical monitoring focus for tunnel construction; Second, karst cave treatment contributed to better conduct forces on both sides of wall rock, thus reducing vault settlement, while not affecting horizontal convergence and upturn of vaults; Third, treatment measures were proved to be effective in minimizing wall rock deformation by comparing deformation curves under different conditions; Fourth, after treatment measures, the angular points within the cave’s chamber had stress concentration, which might cause secondary collapse. Field monitoring data revealed that the final settlement of the tunnel vault was relatively consistent with the numerical analysis results, with a distinct change in daily settlement after initial support construction. By integrating numerical analysis and field monitoring, the rationality of the karst treatment plan was fully verified, providing a valuable reference for similar projects.
2
Content available Numerical study of a transient MHD flow across an oscillating vertical plate with thermal radiation and viscous dissipation
Rajaraman R., Muthucumaraswamy R.
International Journal of Applied Mechanics and Engineering
|
2023
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Vol. 28, no. 2
77--89
EN
The flow of an electrically conducting fluid across a vertically positioned oscillating semi-boundless plate with uniform mass diffusion and temperature is examined in this study in terms of the effects of thermal radiation and viscous dissipation. The dimensionless governing equations were solved using an effective and unconditionally stable implicit finite-difference approach known as the Crank-Nicolson method. Based on the numerical results, the impacts of various physical parameter values on concentration, temperature; velocity; Sherwood numbers, Nusselt numbers and skin-friction profiles are displayed graphically and their consequences thoroughly analyzed. We observed that when the magnetic field, radiation and phase angle parameters are increased, the velocity is reduced. This shows that plate oscillation, radiation and magnetic fields affect the flow pattern significantly.
3
Content available Roughness effects of textured surfaces in hydrodynamic lubrication
Bahi Youssef, El Gadari Mhammed, Rahmoune Miloud
International Journal of Applied Mechanics and Engineering
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2022
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Vol. 27, no. 3
9--21
EN
Several studies have been conducted to improve and model the lubricated contact between surfaces. The main subjects were defining the hydrodynamic parameters to reduce energy losses and protect the environment. Some of the proposed models have studied the effect of textures in hydrodynamic lubrication and have proved that adapted shapes and geometries can improve the performance of lubricated contacts. A hydrodynamic model was developed by assuming the roughness of the textured surface and considering the cavitation in a steady-state regime. The proposed model was validated and compared with the analytical model of Fowell et al. [1]. Three different textures shapes were considered. The results showed that the rough-textured thrust affects the hydrodynamic performance significantly. Thus, by increasing the arithmetic roughness of textured surfaces, the hydrodynamic pressure, and the lifting force increase depending on the texture shape. A rougher surface slightly increases the friction force for the three considered textures.
4
Content available Radiation and magnetohydrodynamic effects on convective nanofluid past an inclined plate in the presence of a chemical reaction
Palani G., Arutchelvi A.
International Journal of Applied Mechanics and Engineering
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2022
|
Vol. 27, no. 3
115--126
EN
This computational work explores the heat and mass transfer of copper water nanofluid flowing along an inclined plate with varying surface temperature and concentration in the presence of a magnetic field and radiation through a permeable medium. The dimensionless governing equations are solved numerically using an efficient finite-difference technique, which is fast convergent and unconditionally stable. The findings are reviewed and illustrated through graphs for pertinent parameters.
5
Content available Application of finite difference method for measurement simulation in ultrasound transmission tomography
Kania Konrad, Mazurek Mariusz, Rymarczyk Tomasz
Applied Computer Science
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2022
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Vol. 18, no 2
101--109
EN
In this work, we present a computer simulation model that generates the propagation of sound waves to solve a forward problem in ultrasound transmission tomography. The simulator can be used to create data sets used in the supervised learning process. A solution to the "free-space" boundary problem was proposed, and the memory consumption was significantly optimized from O(n2) to O(n). The given method of simulating wave scattering enables the control of the noise extinction time within the tomographic probe and the permeability of the sound wave. The presented version of the script simulates the classic variant of a circular probe with evenly distributed sensors around the circumference.
6
Content available Effects of pressure work over a semi-infinite vertical oscillating cylinder
Sarojini A., Palani G.
International Journal of Applied Mechanics and Engineering
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2021
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Vol. 26, no. 1
215--225
EN
An arithmetical methodology is used to study natural convection with properties of pressure work over a semi-infinite vertical oscillating cylinder. The governing partial differential equations are set up and the resulting equations are changed into a non-dimensional form using the proper non-dimensional quantities. The set of non-dimensional partial differential equations is solved arithmetically using a well-organized method known as the Crank-Nicolson method. The velocity, as well as temperature profiles for different values of parameters are studied with the assistance of graphs.
7
Content available Fractional discrete-continuous model of heat transfer process
Oprzędkiewicz Krzysztof, Dziedzic Klaudia
Archives of Control Sciences
|
2021
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Vol. 31, No. 2
287--306
EN
The paper proposes a new, state space, finite dimensional, fractional order model of a heat transfer in one dimensional body. The time derivative is described by Caputo operator. The second order central difference describes the derivative along the length. The analytical formulae of the model responses are proved. The stability, convergence, and positivity of the model are also discussed. Theoretical results are verified by experiments.
8
Content available remote Viscoelastic wave finite difference modeling in the presence of topography with adaptive free surface boundary condition
Dong Shu-Li, Chen Jing-Bo, Li Zheng
Acta Geophysica
|
2021
|
Vol. 69, no. 6
2205--2217
EN
An accurate free-surface boundary condition is significant for seismic forward modeling and inversion. The finite-difference method (FDM) is widely used for its simplicity and efficiency. However, unlike the finite-element method (FEM) satisfying naturally the stress-free condition at the free surface, FDM needs additional treatment, particularly in the presence of irregular topography. In the elastic wave finite-difference modeling, the adaptive parameter-modified free-surface boundary condition has the advantages of high accuracy and simple operation. The viscoelastic wave equation can describe the nature of seismic waves more realistically. Based on the staggered-grid FDM, we extend the adaptive free-surface boundary condition to the viscoelastic medium with topography. This approach involves a combination of the average medium theory, vacuum approximation and limit idea. It is realized by modifying the viscoelastic constitutive relation. This method is simple enough, because three types of grid elements and in fact only two kinds of expressions are enough in the presence of topography. We only need to deal with the Lamé parameters and the density at the free surface without reconstructing the existing algorithm. Viscoelastic analysis of different quality factor settings shows the viscous effect. Numerical examples display that the results of the presented method agree well with the reference solutions of spectral-element method both in crest- and trough-like model and in simplified Foothill model with irregular topography. The simulation of original Foothill model demonstrates the feasibility of our method.
9
Content available A numerical study of dissipative chemically reactive radiative MHD flow past a vertical cone with nonuniform mass flux
Sambath P., Sankar D. S., Viswanathan K. K.
International Journal of Applied Mechanics and Engineering
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2020
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Vol. 25, no. 1
159--176
EN
A computational model is presented to explore the properties of heat source, chemically reacting radiative, viscous dissipative MHD flow of an incompressible viscous fluid past an upright cone under inhomogeneous mass flux. A numerical study has been carried out to explore the mass flux features with the help of Crank-Nicolson finite difference scheme. This investigation reveals the influence of distinct significant parameters and the obtained outputs for the transient momentum, temperature and concentration distribution near the boundary layer is discussed and portrayed graphically for the active parameters such as the Schmidt number Sc, thermal radiation Rd, viscous dissipation parameter […], chemical reaction parameter […], MHD parameter M and heat generation parameter ]…]. The significant effect of parameters on shear stress, heat and mass transfer rates are also illustrated.
10
Content available remote Numerical simulation of shear wave attenuation in borehole inserted by a horizontal fracture
Yan Binpeng, Ou Weiming, Huang Xingguo, da Silva Nuno Vieira
Acta Geophysica
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2020
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Vol. 68, no. 6
1715--1726
EN
The amplitude of shear waves is attenuated when passing through horizontal fractures crossing a borehole. In this study, we investigate the amplitude attenuation of shear waves throughout simulation of full-wave acoustic logging with the fnite-diference method. As the fracture aperture is very small, it needs to be represented in a very fne gird when carrying out fnite-diference simulation. Therefore, the variable-grids fnite-diference method is adopted to avoid over-sampling in the non-fracture regions, yielding substantial savings in computational cost. We demonstrate the accuracy of waveform modeling with the variable-grid fnite-diference by benchmarking against that obtained with the real-axis integrating method. We investigated the efects of several important parameters including fracture aperture, distance from receiver to fracture, borehole radius and extended distance utilizing that benchmarked variable-grid fnite diference code. We determined a good linear relationship between the attenuation coefcient of shear wave amplitude and the fracture aperture. Then, the efects of distance from receiver to fracture, the borehole radius and the extended distance of fracture on shear wave attenuation are also studied. The attenuation coefcient of shear wave becomes smaller with the increasing borehole radius. While, it increases as the distance from receiver to fracture and the extended distance of fracture increase. These efect characteristics are conducive to the use of shear wave to evaluate fractures.
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