Computationally simulating premixed hydrogen-air combustion in micro-channels (length scale = 1.4 mm), I obtained a positive correlation between Flame propagating Speed and thermal flame thickness. While analytically we have an inverse relation for laminar flame speed and its flame thickness. Shouldn't this basic correlations be same even if a lot of assumptions used in analytical formulation.
Detailed Chemistry simulations were used.
The obtained data and formula attached below
The correlation model has many assumptions that may not hold well for confined H2-Air flames. I recall some of the assumptions are equal (and constant) specific heats and unity Lewis #'s. (I can't find my Turns so please correct me if I'm wrong on those.) Le for the H2-Air mix can be pretty far from 1 (depending on the equivalence-ratio) and the Cp for H2 is much higher than Air (at ~300k). These may cause some mismatches between the simulation and model. Also, does the model account for your wall heat loss? This may be a big issue since you have an isothermal wall and not an adiabatic wall. So I would check the assumptions for the correlation model and make sure they are appropriate.
The correlation model has many assumptions that may not hold well for confined H2-Air flames. I recall some of the assumptions are equal (and constant) specific heats and unity Lewis #'s. (I can't find my Turns so please correct me if I'm wrong on those.) Le for the H2-Air mix can be pretty far from 1 (depending on the equivalence-ratio) and the Cp for H2 is much higher than Air (at ~300k). These may cause some mismatches between the simulation and model. Also, does the model account for your wall heat loss? This may be a big issue since you have an isothermal wall and not an adiabatic wall. So I would check the assumptions for the correlation model and make sure they are appropriate.
I would support Christophers view. The analytical solution is based on a 1-D analysis, steady-state, perfect gas, constant cp and alpha, Lewis number =1, single step irreversible chemistry, no radiation, no heat loss; hydrogen diffuses very fast and you have probably a lot of heat loss towards walls and 3-D effects, maybe not even a thin flame. So the theory does not apply.
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