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Investigation of the Fire-Induced Smoke Flow in the Complex Geometries Using The 3d Numerical Method and the Body-Fitted Curvilinear Coordinates

Savalanpour Ardebili, Hamid Reza | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53882 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farhanieh, Bijan; Afshin, Hossein
  7. Abstract:
  8. With the process of achieving a higher state of social development and technological advances, the need for higher and more strict safety standards has been increased. In this regard, it is of great importance to have an accurate understanding of the fire phenomena and its consequences. Among the adverse effects of fire, a significant percentage of the fire fatalities is related to the fire-induced buoyant gases (smoke) flow which can lead to suffocation. Therefore, it is necessary to know the physics of the fire phenomena well. In fire investigation methods, the numerical study is an appropriate choice, because of the lower executive cost (relative to the experimental study) and the wider scope of the study (relative to the analytical study). However, the numerical method requires a deep understanding of CFD due to the complexity and coupling of the governing equations of fire. Therefore, in the present study, the governing equations of the fluid flow (momentum and continuity), turbulence (LES), buoyancy, energy, fire, radiation, and smoke emission are computationally solved using the 3D developed finite volume code. Among the enclosures, which are exposed to fire, the tunnels (either over-ground, under-ground, road, city, and mine tunnels) require special attention, due to the continual vehicular (containing combustible materials) traffic in the tunnels. Although the typical tunnel geometries are not rectangular, most of the numerical studies investigated the tunnel fire using the Cartesian grid (e.g., the FDS software). So, most of the numerical methods have significant computational errors due to the weakness of the Cartesian grid in accurately fitting the curved (non-rectangular) bodies. In the present study, in order to solve the problem, the curvilinear non-orthogonal (general) meshing is fitted well to the non-rectangular boundaries (without the grid refinement) and the governing equations are solved in the curvilinear coordinates, using the coordinate transformation relations. Thus, the computational cost reduces while the numerical accuracy increases. After developing and validating the 3D curvilinear method, a set of practical problems are investigated and the appropriate suggestions are provided in order to increase tunnel safety. According to the results, using the present method increases the accuracy of the calculation of the tunnel fire characteristics up to 30%
  9. Keywords:
  10. Numerical Method ; Fire ; Smoke Propagation ; Mesh Generation ; Three-Dimensional Simulation ; Curvilinear Coordinates ; Body-Fitted Grid

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