Can turbulence alone turn an unconfined premixed flame into detonation?

For a premixed fuel-air flame (for example stoichiometric $\mathrm{H_2}$-air or $\mathrm{CH_4}$-air) in homogeneous isotropic turbulence with no walls or obstacles, determine whether deflagration-to-detonation transition (DDT) occurs, and the threshold in turbulent intensity $u'/S_L$ and integral scale $L/\delta_L$ ($S_L$ laminar flame speed, $\delta_L$ laminar flame thickness). Test the proposed route in which the turbulent flame speed exceeds the Chapman-Jouguet deflagration speed (the fastest steady deflagration allowed by conservation laws), so pressure builds up in the flame brush and forms shocks that trigger detonation. An answer is a verified criterion for unconfined DDT as a function of mixture and turbulence.

Experiments with turbulent premixed flames free of walls and obstacles that observe or exclude DDT at controlled $u'/S_{L}$ and $L$, matched by fully resolved simulations with detailed chemistry.