Radulescu Gasdynamics Laboratory

Come and join us at ICDERS 2015 to discuss the latest discoveries in the field of reactive compressible fluid dynamics. The upcoming  International Colloquium on the Dynamics of Explosions and Reactive Systems  ( ICDERS ) will be held in  Leeds, UK, 2-7 August 2015 .   Extended abstracts are  due on 15 December 2014 9th January 2015 . Five  plenary sessions  will be given: Paul Clavin Nonlinear dynamics of shock waves and cellular detonations in gases Vladimir Fortov   High explosives for extreme states of matter generation Andrew Higgins   Approaching detonation dynamics as an ensemble of interacting waves Richard Saurel   Modelling shocks and detonations in heterogeneous high explosives Richard Yetter  Nanoenergetics and combustion Topical reviews  and  special sessions  will be: Detonation applications in propulsion - Sergey Frolov & Jiro Kasahara Progr...

Geoff Maines was instrumental in our efforts to characterize thermites for use in cellular injury studies.  His work addressed the underwater shock performance of ball-milled activated thermites and the ability to control the pressure pulse amplitude and widths.   He has now graduated with a MASc degree from our group - unfortunately someone else will benefit in the future from his enthusiasm for research, ambition and meticulousness in setting up experiments.  Ongoing work with Kadeem Dennis studies the interaction of these pressure waves with cells.  Geoff's thesis:  Underwater Pressure Pulses Generated by Mechanically Alloyed Intermolecular Composites Recently, the use of thermite-based pressure waves for applications in cellular transfection and drug delivery have shown significant improvements over previous technologies. In the present study, a new technique for producing thermite-generated pressure pulses using fully-dense nano-scale therm...

The key question in detonation research is being able to predict limits. How easy is it to initiate a detonation? What are the limits of propagation in the presence of attenuating boundary conditions? Most models developed over the past decades rely on one-dimensional formulations - resulting in simple models. Nevertheless, detonations in reality are plagued by instability, which takes the form of cellular structures in gases and localized heterogeneities involving hot spots in condensed media. The question that arises, is what role do these non-homogeneities have on the limits of detonations ? A very recent study from Li, Mi and Higgins tackles this central issue in detonation science. By introducing non-heterogeneities in their explosive medium, they find that the detonation limits become wider. Localized unsteady effects sensitize the propagation of detonations. The problem they address is the detonation propagation in a unconfined charge, the so-called critical tube pr...

The Daily Planet show on Discovery Channel featured our experiments with non-homogeneous mixtures using the soap bubble technique on Monday February 10th, 2014.  Here is a link to the video . (4:38- 7:53) Logan Maley, master's student in Applied Science and Mechanical Engineering, shares his research that includes experimenting with reactive gas filled bubbles. The study is being conducted in an effort to gain a better understanding of explosions, and how to prevent a potentially catostrophic explosion in real life. Logan in front of the large scale shadowgraph system he designed with Kadeem Dennis, now used by Maha Manoubi and Maxime La Flèche in their research with the soap bubbles. More results upcoming soon from this work sponsored by Atomic Energy Canada Limited.

Geoff and Nick #Canadasgame #odr #doubledion Geoff Maines submitted his Master's thesis.  Given he will miss the Canadian winters from Cali, we organized a group hockey outing.    Wentian in top shape Kadeem and Logan Nick and Shem - Leafs fans Geoff and Karl Maxime and Mama

Our new detonation driven shock tube is now up and running.  Modular length, 12 inch internal diameter, rated for atmospheric pressure detonations, modular reactive driver volume, and outfitted with the Yellow Submarine as receptor/dump tank with optical access.  Jonathan Armstrong, its creator

We just submitted our new paper on the fast flame supersonic regime in gases. A pre-print , along with the high speed videos , are available on ArXiv. Our work investigates the structure of fast supersonic turbulent flames typically observed as precursors to the onset of detonation. These high speed deflagrations are obtained after the interaction of a detonation wave with cylindrical obstacles. Two mixtures having the same propensity for local hot spot formation were considered, namely hydrogen-oxygen (2H 2 +O 2 ) and methane-oxygen (CH 4 +2O 2 ). We show that the methane mixture sustains turbulent fast flames, while the hydrogen mixture does not. An incident detonation wave in 2H 2 +O 2 coming from the left interacts with a row of cylinders.  The subsequent fast flame, consisting of a system of discrete hot spots and transverse shock system, fails; the figure consists of an overlay of frames showing the evolution; See Video . A supersonic turbulent fast flame is es...

Self-similar inviscid flows in gas dynamics abound, e.g., strong Taylor-Sedov blast waves, shock diffraction and reflection at a compressive or expansion corner, and many other shock/shock interactions, shock slip lines interactions. With the neglect of viscous effects and the corresponding dissipation length and time scales, problems of shock dynamics are self-similar.   Simple magnification of the length scales of observation can be obtained at correspondingly scaled evolution times.  In reality, such problems are never self-similar at a young age.  Characteristic length scales exist in these problems, often at the smallest scales (boundary layers, shear layers, shock structure, etc...). Our numerical experiments address how the introduction of small characteristic length scales affect the asymptotically self-similar solution at much later times.  We pose the question: How does an early injury of the self-similar regime affect the solution at later t...

Our paper “ Detonation re-initiation mechanism following the Mach reflection of a quenched detonation ” was selected as the Distinguished Paper in the Detonation colloquium of the 34th International Symposium on Combustion.    Congratulations to Rohit Bhattacharjee, She-Ming Lau-Chapdelaine, Logan Maley and Geoff Maines. Fig. 4 in paper - Re-ignition behind the Mach shock over a rough plate and entrainment of flame in the jet associated with this type of "jetting" Mach reflection.

Last week, Logan Maley, Hesam Akbarnejad,  Maha Manoubi and myself were attending the ICDERS conference in Taipei, Taiwan. Maha, Matei, Hesam and Logan Structure of high speed deflagrations, DDT and self-generated turbulence Logan presented his study on the structure of supersonic turbulent deflagrations and DDT.  Strong pressure waves are driven by the rapid ignition of hot-spots.  The driven hydrodynamic instabilities along shear layers permit to rapidly burn the gases.  Onset of detonation in a Ch4-O2 high speed deflagration A detonation in the detonation ?  Very similar to self-sustained detonations, just slower.  The session was closed by a panel discussion on DDT.  The concept of self-turbulization of the flame came out as the outstanding theme for future research.  Logan pursued discussions with Joe Shepherd...  Hesam on bimetallic flames Hesam presented his thesis work on the flame speed in bi-metallic mixtu...