L'explosion isotherme

1982 ◽  
Vol 60 (2) ◽  
pp. 168-178
Author(s):  
L. Brun ◽  
R. Roguet

The isothermal explosion model of Korobeinikov has been generalized to include the specific heat varying as temperature to the power k. Unlike Korobeinikov the different phases of the motion arc considered. The eventual self-similar solutions only exist for k > −1/2 and resemble that for k = 0 (the Korobeinikov value). For all k ≥ 0 the limiting expansion velocity is given by the von Neumann–Taylor–Sedov result (independent of k) and for k > 0 the internal energy decreases steadily. For k > 1/2 there is first an intermediate detonation phase. For −1/2 < k < 0 the kinetic energy first increases, then decreases, and the expansion law depends on k.

Author(s):  
Yu. V. Nuzhnov

The statistical modeling of fluctuating kinetic energy in turbulent and non-turbulent fluid of a turbulent flow are presented and self-similar solutions applied to budget equations of conditionally averaged fluctuating kinetic energy are obtained. The equations were constructed on basis of the method of autonomous statistical modeling of turbulent flows (ASMTurb method) and allow to calculate the conditional averages both fluctuating kinetic energy and terms of the budget equations. The total statistical averages are found with help algebraic ratios between total and conditional averages through the agency of external intermittency factor. Testing the ASMTurb method is presented in the form of ASMTurb model for self-similar region of the two-stream plane mixing layer. Test results showed that the constructed here ASMTurb model is deeper and more accurate than RANS model. A comparison is performed between predictions and known experimental data for energy-containing fluctuating structure of the turbulent flow in mixing layer and excellent agreements are noted.


Entropy ◽  
2021 ◽  
Vol 23 (3) ◽  
pp. 314
Author(s):  
Tianyu Jing ◽  
Huilan Ren ◽  
Jian Li

The present study investigates the similarity problem associated with the onset of the Mach reflection of Zel’dovich–von Neumann–Döring (ZND) detonations in the near field. The results reveal that the self-similarity in the frozen-limit regime is strictly valid only within a small scale, i.e., of the order of the induction length. The Mach reflection becomes non-self-similar during the transition of the Mach stem from “frozen” to “reactive” by coupling with the reaction zone. The triple-point trajectory first rises from the self-similar result due to compressive waves generated by the “hot spot”, and then decays after establishment of the reactive Mach stem. It is also found, by removing the restriction, that the frozen limit can be extended to a much larger distance than expected. The obtained results elucidate the physical origin of the onset of Mach reflection with chemical reactions, which has previously been observed in both experiments and numerical simulations.


2002 ◽  
Vol 20 (2) ◽  
pp. 263-268 ◽  
Author(s):  
X. FLEURY ◽  
S. BOUQUET ◽  
C. STEHLÉ ◽  
M. KOENIG ◽  
D. BATANI ◽  
...  

In this article, we present a laboratory astrophysics experiment on radiative shocks and its interpretation using simple modelization. The experiment is performed with a 100-J laser (pulse duration of about 0.5 ns) which irradiates a 1-mm3 xenon gas-filled cell. Descriptions of both the experiment and the associated diagnostics are given. The apparition of a radiation precursor in the unshocked material is evidenced from interferometry diagrams. A model including self-similar solutions and numerical ones is derived and fairly good agreements are obtained between the theoretical and the experimental results.


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