Numerical Study of the Direct Initiation of Spherical and Cylindrical Detonations by an Energy Source

1995 ◽  
pp. 443-448 ◽  
Author(s):  
Longting He ◽  
Paul Clavin
Keyword(s):  
Energy Source ◽  
Numerical Study ◽  
Direct Initiation

On the direct initiation of gaseous detonations by an energy source

1994 ◽  
Vol 277 ◽  
pp. 227-248 ◽  
Author(s):  
Longting He ◽  
Paul Clavin
Keyword(s):  
Energy Source ◽  
Critical Radius ◽  
Critical Value ◽  
Blast Waves ◽  
Initiation Energy ◽  
Point Energy ◽  
Gaseous Detonations ◽  
Curvature Effects ◽  
Direct Initiation ◽  
Steady Solutions

A new criterion for the direct initiation of cylindrical or spherical detonations by a localized energy source is presented. The analysis is based on nonlinear curvature effects on the detonation structure. These effects are first studied in a quasi-steady-state approximation valid for a characteristic timescale of evolution much larger than the reaction timescale. Analytical results for the square-wave model and numerical results for an Arrhenius law of the quasi-steady equations exhibit two branches of solutions with a C-shaped curve and a critical radius below which generalized Chapman–Jouguet (CJ) solutions cannot exist. For a sufficiently large activation energy this critical radius is much larger than the thickness of the planar CJ detonation front (typically 300 times larger at ordinary conditions) which is the only intrinsic lengthscale in the problem. Then, the initiation of gaseous detonations by an ideal point energy source is investigated in cylindrical and spherical geometries for a one-step irreversible reaction. Direct numerical simulations show that the upper branch of quasi-steady solutions acts as an attractor of the unsteady blast waves originating from the energy source. The critical source energy, which is associated with the critical point of the quasi-steady solutions, corresponds approximately to the boundary of the basin of attraction. For initiation energy smaller than the critical value, the detonation initiation fails, the strong detonation which is initially formed decays to a weak shock wave. A successful initiation of the detonation requires a larger energy source. Transient phenomena which are associated with the intrinsic instability of the quasi-steady detonations branch develop in the induction timescale and may induce additional mechanisms close to the critical condition. In conditions of stable or weakly unstable planar detonations, these unsteady phenomena are important only in the vicinity of the critical conditions. The criterion of initiation derived in this paper works to a good approximation and exhibits the huge numerical factor, 106–108, which has been experimentally observed in the critical value of the initiation energy.

scholarly journals Instability Attenuation And Bifurcation Studies of A Non-Ideal Rotor Involving Time Delayed Feedback

2021 ◽  
Author(s):  
Sovan Sundar Dasgupta
Keyword(s):  
Energy Source ◽  
Time Delay ◽  
Numerical Study ◽  
Critical Role ◽  
Nonlinear Function ◽  
Delayed Feedback ◽  
Rotor System ◽  
System Response ◽  
Jump Phenomena ◽  
Time Delayed Feedback

Abstract In non-ideal vibratory system, the excitation is a nonlinear function of system response. The dynamic behavior of such system is often characterized by an energy source with limited power. The study of instability phenomena in non-ideal rotor driven through a non-ideal energy source is of considerable current interest. The non-ideal rotor system often gets destabilized on exceeding a critical input power near the resonance. This kind of instability is termed as Sommerfeld effect marked with nonlinear jump phenomena. This paper investigates the attenuation of nonlinear jump phenomena and numerical study of bifurcations of a non-ideal unbalanced rotor system with internal damping using time delayed feedback via active magnetic bearings. The results show that the time delay indeed plays a critical role on the suppression of the jump phenomena. Following, some new insights are also revealed through a numerical study of saddle node, Hopf and trans-critical bifurcations with time delay as a bifurcation parameter. The transient analysis confirms the results obtained analytically through the steady-state consideration.

Numerical Study on Direct Initiation of Cylindrical Detonation in H2/O2 Mixtures: Effect of Higher-Order Schemes on Detonation Propagation

2016 ◽  
Vol 188 (11-12) ◽  
pp. 2044-2059 ◽  
Author(s):  
Tomotaka Niibo ◽  
Youhi Morii ◽  
Makoto Ashahara ◽  
Nobuyuki Tsuboi ◽  
A. Koichi Hayashi
Keyword(s):  
Numerical Study ◽  
Higher Order ◽  
Detonation Propagation ◽  
Direct Initiation

Numerical study of the low-frequency atomic dynamics in a Lennard-Jones glass

1998 ◽  
Vol 77 (2) ◽  
pp. 473-484 ◽  
Author(s):  
M. Sampoli, P. Benassi, R. Dell'Anna,
Keyword(s):  
Numerical Study ◽  
Low Frequency ◽  
Lennard Jones

Experimental and numerical study of the response of steel sheet Hopkinson specimens

2006 ◽  
Vol 134 ◽  
pp. 541-546 ◽  
Author(s):  
P. Verleysen ◽  
J. Degrieck
Keyword(s):  
Steel Sheet ◽  
Numerical Study

12-months late procedural success after ablation of atrial fibrillation correlates with energy source and patient characteristics

2014 ◽  
Vol 62 (S 01) ◽  
Author(s):  
B. Niemann ◽  
E. Dominik ◽  
S. Rohrbach ◽  
P. Roth ◽  
C. Orhan ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Energy Source ◽  
Patient Characteristics ◽  
Procedural Success
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