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Formation and Evolution of Cellular Structures in Two Dimensional Weakly Unstable Detonation Waves

Pourmohammad Hadi Farshami, Fatemeh | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40470 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Farshchi, Mohammad
  7. Abstract:
  8. In this investigation, cellular structure of a weakly unstable detonation wave in H2/O2/Ar mixture is studied. The detonation is simulated using 2D reactive Euler equations and one step Arrhenius type reaction model developed by Mr. Barkhordari. The numerical technique is the high order Piecewise Parabolic Method on the basis of Godonov method. The numerical fluxes are computed based on a high-order extension of the Godunov's method; the piecewise parabolic method (PPM). The initial cell formation processes and different machanisms involved in cell size changes are studied. This study shows that the form of initial perturbation used to intrigate the instability of detonation is not important because the structures formed by initial disturbances after a short time enter the dead zone and the only effect of them is to leave the shock front curvatured. Some of the mechanisms that change the number of transverse wanves in channel width rapidly give rise to the change in cell numbers but in some cases, neighboring transverse waves move in the same direction, for these kinds of transverse waves other processes take place to alter the number of cells. The important mechanism which is responsible for the increase in the cell numbers is the instability of much stem. Mostly, when the number of cells in the channel width is decearsing, weaker transverse waves slow dowm and then disappear. The instability of much stems produce transverse waves. At first these new transverse waves meruly contribute in the cellular structure but after a few collisions between the weak and storng transverse waves a uniform structure will form. The comparison of initial cell formation processe and those which are reported in experimental studies shows that they are similar in spite of the fact that some physics are neglected in numerical simulation
  9. Keywords:
  10. Cellular Structure ; Weakly Unstable Detonation Wave ; Transverse Waves

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