  Flamelet-based methods are extensively used in modeling turbulent hydrocarbon
flames. However, these models have yet to be established for (lean) premixed
hydrogen flames. While flamelet models exist for laminar thermo-diffusively
unstable hydrogen flames, for which consideration of curvature effects has
resulted in improved model predictions, it is still unclear whether these
models are directly applicable to turbulent hydrogen flames. Therefore, a
detailed assessment of stretch effects on thermochemical states in a turbulent
lean premixed hydrogen-air slot flame through finite-rate chemistry simulations
is conducted. Strain and curvature are examined individually using a
composition space model, revealing their distinct influences on thermochemical
states. An a-priori analysis confirms that the previously developed tabulated
manifolds fall short of capturing all turbulent flame phenomena, necessitating
a novel manifold incorporating both strain and curvature variations. These
results underscore the significance of these variations in developing
manifold-based combustion models for turbulent lean hydrogen flames.
