Delayed thermal explosion in porous media: method of invariant manifolds

2002 ◽  
Vol 67 (3) ◽  
pp. 263-280 ◽  
Author(s):  
I. Goldfarb
2021 ◽  
pp. 1-37
Author(s):  
Yuta Tsubokura ◽  
Kyohei Noguchi ◽  
Tomomi Yagi

Abstract Airborne salt accelerates the corrosion of steel materials and, thus, must be quantitatively evaluated for the management of steel structures. In Japan, the dry gauze method, which uses a gauze embedded in a wooden frame, is often used to evaluate the amount of airborne salt. However, its collection efficiency for salt particles has not been verified owing to the complex airflows around the device. Therefore, as a first step to clarify the collection efficiency, the authors simulated the flow field around the collection device using computational fluid dynamics. In this study, the gauze was modeled as a porous medium to reduce the computational costs. Wind tunnel tests were performed to obtain the pressure loss coefficients of the gauze, which is necessary for the porous media method. Subsequently, particle tracking was performed in the calculated flow field, and the collection efficiency was evaluated under the condition of a filtration efficiency of 100%. The flow fields around the device were accurately reproduced using the porous media model, which considered both the tangential and normal resistances of the gauze. This result suggests that the tangential resistance must be considered in the porous media model when the porosity of an object is small, even if the thickness is small. The dependence of collection efficiency on wind speed and direction was quantitatively evaluated. The results showed that the collection efficiency was greatly affected by the complicated flow field around the device due to the combination of the gauze and wooden frame.


2020 ◽  
Vol 30 (06) ◽  
pp. 2050081 ◽  
Author(s):  
Karam Allali ◽  
Youssef Joundy ◽  
Ahmed Taik ◽  
Vitaly Volpert

In this paper, we study complex dynamics of the interaction between natural convection and thermal explosion in porous media. This process is modeled with the nonlinear heat equation coupled with the nonstationary Darcy equation under the Boussinesq approximation for a fluid-saturated porous medium in a rectangular domain. Numerical simulations with the Radial Basis Functions Method (RBFM) reveal complex dynamics of solutions and transitions to chaos after a sequence of period doubling bifurcations. Several periodic windows alternate with chaotic regimes due to intermittence or crisis. After the last chaotic regime, a final periodic solution precedes transition to thermal explosion.


2008 ◽  
Vol 2 (4) ◽  
pp. 247-252 ◽  
Author(s):  
Yasuhiro Maeda ◽  
◽  
Yukio Otsuka ◽  

The need to speed up calculation and improve analytical accuracy of Casting CAE has grown with optimized casting planning and speeded-up product design. A finite difference method using regular grid of Cartesian coordinates is often used in simulating mold filling because it reduces memory requirements, computation time and easier grid generation. Its disadvantage is that shape expression becomes less precise so that casting slopes and curved surfaces are replaced to stair-step shape. The mold filling simulation developed using porous media method in this paper provides uses two control volume parameters -- porosity rate of grid volume and permeability of grid surface -- to maintain shape expression and analytical accuracy. Results used larger grids than conventionally have with almost the same accuracy as analysis with fine grids. It has also advantages saving on memory and computation time.


2014 ◽  
Vol 543-547 ◽  
pp. 207-210
Author(s):  
Ning Kang ◽  
Ni Ka Mo ◽  
Wei Qi Zheng

12 kinds of automotive radiator cell models were simulated at different air inlet velocities using CFD software Fluent. The distributed drag coefficients of each cell model were obtained by least squares method. Then the whole radiator model whose fins region was replaced by the porous media was simulated. The numerical results were validated by experiments which indicate that the porous media method is reliable. The study shows that the radiator heat dissipation is significantly influenced by fin structure and the model with a fin space of 1.4mm and a louver angle of 23o has the best cooling effect.


2017 ◽  
Vol 104 ◽  
pp. 178-190 ◽  
Author(s):  
Ronghua Chen ◽  
Maolin Tian ◽  
Sen Chen ◽  
Wenxi Tian ◽  
G.H. Su ◽  
...  

Nonlinearity ◽  
2010 ◽  
Vol 23 (6) ◽  
pp. 1433-1447 ◽  
Author(s):  
Peter Gordon

2020 ◽  
Vol 188 ◽  
pp. 104227 ◽  
Author(s):  
Chuanjun Liao ◽  
Haipeng Chen ◽  
Haoran Lu ◽  
Ruitao Dong ◽  
Hailiang Sun ◽  
...  

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