Both in-tube and unconfined experimental evidence showed strong dependence of micrometric aluminum-air detonability on initial pressure and highly nonlinear behavior of abrupt deflagration-to-detonation transition, thus indicating dependence of the aluminum reaction mechanism of the detonation waves on chemical kinetics. On the other hand, the observed aluminum-air detonation manifested itself in a weak transverse wave structure, as revealed by the small-amplitude oscillation that rapidly degenerates behind the shock front in the pressure histories. This suggests a functional dependence that is weaker than the nonlinear Arrhenius kinetic behavior for the later aluminum combustion. Hence, a surface kinetic oxidation and diffusion hybrid reaction model with a degree of condensed detonation products was suggested, and the unsteady two-phase fluid dynamics modeling showed the success of the hybrid reaction model, capable of capturing both the kinetics-limited transient processes of detonation initiation, abrupt deflagration-to-detonation transition and detonation instability, and the diffusion-limited combustion of aluminum in the long reaction zone, supporting the weak transverse wave structure.Nomenclature a e = equilibrium sound speed, m=s a g = phase-frozen sound speed, m=s C = mole concentration, mol=m 3 C D = drag coefficient D = detonation velocity, m=s D g = gas-phase diffusivity, m 2 =s d p = particle diameter, m E = activation energy, J=mol e = specific internal energy, J=kg f p = rate of momentum transfer between the solid and the gas phase, N=m 3 J p = rate of mass transfer between the particles and the gas phase, kg=m 3 s K = diffusion reaction coefficient, s=m 2 k = mass depletion flux, kg=m 2 s k d = rate coefficient of diffusion reaction, kg m=mol s k s = rate coefficient of kinetic reaction, kg m=mol s k 0 = kinetic reaction coefficient, kg m=mol s L b = latent heats of evaporation, J=mol L m = latent heats of melting, J=mol Nu = Nusselt number n p = particle number density, 1=m 3 Pr = gas-phase Prandtl number p = pressure, N=m 2 Q p = rate of heat transfer between the particles and the gas phase, J=m 3 s q p = heat release of particles, J=kg R = universal gas constant, J=mol K Re = two-phase Reynolds number r p = particle radius, m T = temperature, K T ign = particle ignition temperature, K t b = particle burning time, s u = flow velocity, m=s W = molecular weight, g=mol w = species reaction rate, kg=m 3 s x = distance in the shock-propagation direction, m Y = mass fraction of species g = thermal conductivity of the gas phase, W=m K = stoichiometric coefficient = material density, kg=m 3 = partial density or mass concentration, kg=m 3 = volume fraction p = rate of particle number production, 1=m 3 s Subscripts g = gas-phase index oxi = index for oxidizing gases p = particle-phase index s = index for particle surface 0 = initial state
