  We investigate and model pressure effects on the turbulent burning velocity
over a wide range of pressures and turbulence intensities with the direct
numerical simulation (DNS) of statistically planar turbulent premixed flames
for lean hydrogen/air mixture. DNS results indicate that the stretch factor has
an impact on the turbulent burning velocity and flame surface area at elevated
pressures. In particular, the enhanced stretch factor at high pressures
increases the ratio of turbulent and laminar burning velocities, diminishing
the "bending" effect. Based on a good consistency between turbulent and laminar
burning velocities with respect to flame stretch, a lookup table formed by
laminar flame data is employed to model the stretch factor in turbulent flames
at various pressures. A predictive model for the turbulent burning velocity is
then developed by combining sub models of the stretch factor and flame surface
area. The overall good agreement between model predictions and DNS results
demonstrates that the proposed model is able to quantitatively predict the
turbulent burning velocity over a wide range of pressures and turbulent
intensities in homogeneous isotropic turbulence.
