Recent advances in nonlinear passive vibration isolators

Force and displacement transmissibility of a nonlinear isolator with high-static-low-dynamic-stiffness

Approximate Riemann Solvers

On the characteristics of a quasi-zero stiffness isolator using Euler buckled beam as negative stiffness corrector

Rotating detonation combustors and their similarities to rocket instabilities

Formation and evolution of distorted tulip flames

A low-dissipation and time-accurate method for compressible multi-component flow with variable specific heat ratios

Numerical simulations were performed to study the effects of pressure waves on the evolution and stability of flames propagating in tubes. The model is the fully compressible reactive Navier–Stokes equations coupled to a calibrated one-step chemical-diffusive model for combustion in a stoichiometric hydrogen–air mixture. The numerical solution method is high order in space and time, and adaptive mesh refinement provides adequate resolution of flames, boundary layers, acoustic waves, and all of their interactions. The influence of tube length scale and aspect ratio was examined for a range of tube sizes that produce tulip flames (TFs) and series of distorted tulip flames (DTFs). The simulations show that pressure waves and acoustic properties of the tube play an important role in the flame evolution, specifically in the formation and evolution of the series of increasingly wrinkled DTFs. A time scale and pressure wave analysis of the results, combined with a linear analysis to give the growth rate of the Rayleigh–Taylor instability (RTI), shows that the RTI is a primary cause for the initiation of DTFs.

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Effects of pressure waves on the stability of flames propagating in tubes

Effect of decreasing blockage ratio on DDT in small channels with obstacles

A model for predicting the behaviour of a compressible flow laden with shocks interacting with granular material has been developed and tested. The model consists of two sets of coupled Euler equations, one for the gas phase and the other for the granular phase. Drag, convective, heat transfer and non-conservative terms couple the two sets of governing equations. Intergranular stress acting on the grains is modelled using granular kinetic theory in dilute regimes where particle collisions are dominant and frictional–collisional pressure in dense regions where layers of granular material slide over one another. The two-phase granular–gaseous model, as a result, is valid from dilute to densely packed granular regimes. The solution of these nonlinearly coupled Euler equations is challenging due to the presence of the non-conservative nozzling and work terms. A numerical technique, based on Godunov’s method, was designed for solving these equations. This method takes advantage of particle incompressibility to simplify the nozzling terms. It also uses the observation that a Riemann problem is valid in the region where gas can flow between particles and can be used to provide a physically accurate approximation of the non-conservative terms. The model and solution method are verified by comparisons to test problems involving granular shocks and two-phase shock-tube problems, and they are validated against experimental measurements of shock and dense particle-curtain interactions and transmitted oblique granular shocks.

Ryan W. Houim

Papers

Formation and evolution of distorted tulip flames

A low-dissipation and time-accurate method for compressible multi-component flow with variable specific heat ratios

Effects of pressure waves on the stability of flames propagating in tubes

Effect of decreasing blockage ratio on DDT in small channels with obstacles

A multiphase model for compressible granular–gaseous flows: formulation and initial tests