Radulescu Gasdynamics Laboratory

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

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.

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);...