Narrow Results

Boundary approximation of planar shapes by circular arcs has quantitative and qualitative advantages compared to using straight-line segments. We demonstrate this by way of three basic and frequent computations on shapes – convex hull, decomposition, and medial axis. In particular, we propose a novel medial axis algorithm that beats existing methods in simplicity and practicality, and at the same time guarantees convergence to the medial axis of the original shape.

Detonation propagation in a confined circular arc configuration of an insensitive high explosive PBX9502 is investigated via numerical simulation in this paper. We introduce a steady detonation wave entering the explosive arc with confinements of stainless steel, and then it undergoes a transition phase and reaches a new steady state with a constant angular speed eventually. The influences of the inner and the outer confinements on the propagating detonation wave as well as the characteristics of the detonation driving zone (DDZ) in the steady state are discussed, respectively. Ignition and Growth (I&G) reaction rate and Jones–Wilkins–Lee (JWL) equations of state for the reactants and the products of PBX9502 are employed in the numerical simulations on the basis of a two-dimensional Eulerian code. The equation of state for stainless steel is in the Grüneisen form with a linear shock speed–particle speed Hugoniot relationship. Our results show that the inner confinement dominates the evolution of the detonation wave and the outer confinement only takes effect in a local region near the outer boundary within a limited initial stage during the transition phase. As for the steady state, the existence of the inner confinement makes the DDZ possess a certain width on the inner boundary. While as to the outer part of the detonation wave, the width of the DDZ decreases until the sonic locus intersects with the detonation front shock, which results in the detachment of the DDZ from the outer boundary and makes the detonation propagation fully independent of the outer confinement.