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Qiang Xiao defended his PhD thesis

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Qiang Xiao defended successfully his PhD thesis on the Dynamics of Detonations with Lateral Strain, showing that, gauged with respect to the steady ZND model, detonability in enhanced with increasing instability.   Congratulations Qiang!   Thesis details coming soon...

The shock-change equations

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I have now published a summary of the shock change-equations and their use for evolution equations of shocks.  The relations relate the shock speed, acceleration and curvature to the flow derivatives behind the shock, controlling the shock motion. Physics of Fluids 32, 056106 (2020); https://doi.org/10.1063/1.5140216 For example, the relation between the shock speed, acceleration and curvature with the rate of expansion of the gas behind the shock, essential in modelling of reactive gas dynamics along a particle path, is 1 ρ D ρ D t = 2 ( 3 M w 2 + 1 ) M ̇ w ( γ + 1 ) + c 0 κ ( M w 2 − 1 ) ( 2 + M w 2 ( γ − 1 ) ) M w ( M w 2 − 1 ) ( γ + 1 ) 2 . or for a strong shock: γ − 1 S w ρ 0 S ̇ w D ρ D t = 6 + 2 ( γ − 1 ) ( γ + 1 ) S w 2 κ S ̇ w

Detonations with lateral strain rate: piece-wise laminar detonations

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Combustion and Flame 215 (2020) 437–457 We now show that unstable detonations with long reaction zones, such as H2/O2/Ar, can be very well predicted by the ZND model, which neglects the cellular structure. This may come as a surprise, since the cellular structure takes very high amplitude perturbations, and the transverse waves are among the strongest of all detonations, i.e., they are reactive. The good agreement with ZND predictions is likely because of their very long reaction zones, as compared to the induction zones, as shown by their ZND profiles: The cellular structure locally changes the induction zone length along the front, as shown in the photos (Fig. 12) above, but leaves the much longer reaction zone non-affected.  Since the global divergence competes with the net rate of energy release in dictating the eigenvalue solution, and the latter is weakly affected by the cellular structure, then the ZND works well.

Compressible flow using the Noble-Abel Stiffened Gas model

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The Noble-Abel Stiffened Gas model e ( p , v ) = p + γ p ∞ γ − 1 v − b + q , is a simple extension of the perfect gas model to treat compressible flows in dense media, liquid and solids and obtain closed form analytical solutions. What started as an example in a gas dynamics course taught in Fall 2019, is now a complete description of the gasdynamics in closed form, now published in Physics of Fluids . Find here your favourite analytical expressions for Riemann variables, expansion and shock jump conditions, isentropes, detonations and deflagrations and the solution to the Riemann problem, as an example. Phys. Fluids  32 , 056101 (2020);  doi: 10.1063/1.5143428 Phys. Fluids  31 , 111702 (2019);  doi: 10.1063/1.5129139

Notable events of 2019 - Shem graduates and onto RMC

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It is the time of the year to reminisce over the highlights that made this year memorable. The first is of course the graduation of She-Ming Lau-Chapdelaine , with a PhD thesis on  Viscous Triple Shock Reflections Relevant to Detonation Waves, and Detonation Dynamics Predicted by the Fickett Model Shem impressed the members of his Jury (Ashwin Chinnayyaa, Bruno Savard and James McDonald), who nominated him for a thesis prize. Apparently, they weren't the only ones impressed, as he was invited to be the selected valedictorian speaker at the Convocation ceremony where students of the University of Ottawa received their diplomas. He has now left to take a job as Assistant Professor at the Royal Military College of Canada in Kingston. Congratulations Shem, we will miss you!

Happy holidays from our research group.

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Happy holidays to all from our research group at the University of Ottawa! From left, Hongxia Yang (PhD), Farzane Zangene (PhD), Willstrong Rakotarison (PhD), me, Kevin Cheevers (MASc), Aliou Sow (postdoc), Qiuang Xiao (PhD) and Ramki Murugesan (PhD).

Taiwan tour

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Just came back from a week trip to Taiwan, where I was invited by Professor Shouyin (Ian) Yang of the National Formosa University and Professor Ming-Hsun Wu of the National Cheng Kung University. with Shouyin (Ian) Yang and Ming-Hsun Wu at NCKU Had and amazing time, gave two talks.  The first at NCKU on Detonation dynamics and stability: Insights from Fickett’s toy model . and the second as a keynote lecture at the 29th National Conference on Combustion and Energy, Taiwan:   A detonation paradox: The influence of turbulent diffusive processes in controlling the burning rate in detonations. Lab tours at NCKU: and and took in some of the architecture in Tainan. Thanks again to Ian and Ming-Hsun for this wonderful opportunity.