Visually believable explosions in real time

2017

In the late 1970’s Fickett and Majda introduced qualitative models for supersonic combustion, in an attempt to produce simple equations describing reactive shocks [1, 2]. The rationale was to strip the compressible reactive Euler/Navier-Stokes equations of their non-essential difficulties, in order to gain a deeper mathematical (as well as physical) understanding of the dynamics of shock waves propagating in a reactive medium. Not surprisingly, both Fickett and Majda chose as the starting point Burgers’ equation (already known to represent the generic behavior of weakly non-linear hyperbolic waves), and modified it in order to account for the energy released by a chemical reaction. A few years later, Rosales and Majda [3] showed that the Burgers-like “toy” models invented in the late 1970’s were closely related to a rational asymptotic approximation, starting from the full reactive Navier-Stokes equations, of weak heat release gaseous detonations. The weak heat release limit was als...

IEEE Access

Explosion phenomena today are considered a significant concern that needs to be detected and analyzed with a prompt response. We develop a multiclass categorization system for explosion phenomena using color images. Consequently, we describe four patterns of explosion phenomena, including pyroclastic density currents, lava fountains, lava and tephra fallout, and nuclear explosions, against three patterns of nonexplosion phenomena, including wildfires, fireworks, and sky clouds. The classification task was handled through extracting different types of features, including texture features, amplitude features, frequency features, and histogram features. Then, these features were fed into several multiclass classification methods. In addition, we present a new data set for volcanic and nuclear explosions that includes 10 654 samples. Evaluation results show the one-against-one multiclass support vector machine with degree 3 polynomial kernel outperforms other classification methods. It produces the highest classification rate of 90.85% to categorize 5327 images of the data set. A reasonable execution time of approximately 117 ms was accomplished to classify one input test image. INDEX TERMS Explosions, frequency-domain image analysis, image classification, image color analysis, image histogram analysis, image texture analysis, nuclear explosions, support vector machines, volcanoes.

2007

Prior to this work, a phenomenological description of mid-wave infrared (MWIR) emissions from highexplosive (HE) detonation fireballs did not exist, hampering efforts to classify the type and size of HEs from their electro-optical signatures. In recent field tests, temporally-resolved infrared spectra (0.05 ≤ t ≤ 0.12 s, 2 ≤ ν ≤ 8 cm −1) were collected via a Fourier-transform spectrometer (FTS) from the detonation fireballs of two types of conventional military munitions (CMM) as well as uncased TNT and four types of enhanced novel explosives (ENEs). The FTS data is not appreciably corrupted by artifacts due to scene changes resulting from the fast transient events. The CMM spectra are dominated by continuum emission, and a single-temperature Planckian distribution, modified for atmospheric attenuation, captures most of the variation in the data. Fitted CMM temperatures are well described by an exponential decay to ambient at an approximate rate of 0.8 s −1. A two-temperature fit to CMM spectra improved results, suggesting variations in the temperature field are important. Some evidence of selective emission is identified by systematic patterns First, I am deeply indebted to my wife and three children for gracefully enduring this lengthy process and providing the needed support throughout. Without them, the stresses and difficulties encountered during this extended effort would have seemed much greater. Next, I extend my gratitude to Glen Perram who provided excellent guidance when needed and appropriate distance when lessons were better learned the hard way. From him I learned a variety of good things, many related to this work, others about broader aspects of science, and still others about life in general. Ronald Tuttle is to be thanked for both his academic advice and necessary support to see this project to its completion. The remaining committee members-Jim Engel, Stephen Cain, and Meir Pachter-also deserve recognition for their thoughtful contributions which improved the quality of this work. Thanks are extended to Greg Smith (technician) and Mark Houle (bureaucratic ninja) for their help in the planning, execution, and successful completion of several field tests. Of course friendships forged along the way made for a more enjoyable expericence: thanks (in no particular order) Bryan Steward,

Monitoring a Comprehensive Test Ban Treaty, 1996

Bulletin of Volcanology, 2007

Forward Looking Infrared Radiometer (FLIR) cameras offer a unique view of explosive volcanism by providing an image of calibrated temperatures. In this study, 344 eruptive events at Stromboli volcano, Italy, were imaged in 2001–2004 with a FLIR camera operating at up to 30 Hz. The FLIR was effective at revealing both ash plumes and coarse ballistic scoria, and a wide range of eruption styles was recorded. Eruptions at Stromboli can generally be classified into two groups: Type 1 eruptions, which are dominated by coarse ballistic particles, and Type 2 eruptions, which consist of an optically-thick, ash-rich plume, with (Type 2a) or without (Type 2b) large numbers of ballistic particles. Furthermore, Type 2a plumes exhibited gas thrust velocities (>15 m s−1) while Type 2b plumes were limited to buoyant velocities (−1) above the crater rim. A given vent would normally maintain a particular gross eruption style (Type 1 vs. 2) for days to weeks, indicating stability of the uppermost conduit on these timescales. Velocities at the crater rim had a range of 3–101 m s−1, with an overall mean value of 24 m s−1. Mean crater rim velocities by eruption style were: Type 1 = 34 m s−1, Type 2a = 31 m s−1, Type 2b = 7 m s−1. Eruption durations had a range of 6–41 s, with a mean of 15 s, similar among eruption styles. The ash in Type 2 eruptions originates from either backfilled material (crater wall slumping or ejecta rollback) or rheological changes in the uppermost magma column. Type 2a and 2b behaviors are shown to be a function of the overpressure of the bursting slug. In general, our imaging data support a broadening of the current paradigm for strombolian behavior, incorporating an uppermost conduit that can be more variable than is commonly considered.