  Modeling the effect of complex terrain on high Reynolds number flows is
important to improve our understanding of flow dynamics in wind farms and the
dispersion of pollen and pollutants in hilly or mountainous terrain as well as
the flow in urban areas. Unfortunately, simulating high Reynolds number flows
over complex terrain is still a big challenge. Therefore, we present a
simplified version of the wall modeled immersed boundary method by Chester et
al. (J. Comput. Phys. 2007; 225: 427-448). By preventing the extrapolation and
iteration steps in the original method, the proposed approach is much easier to
implement and more computationally efficient. Furthermore, the proposed method
only requires information that is available to each processor and thus is much
more efficient for simulations performed on a large number of cores. These are
crucial considerations for algorithms that are deployed on modern
supercomputers and will allow much higher grid resolutions to be considered. We
validate our method against wind tunnel measurements for turbulent flows over
wall-mounted cubes, a two dimensional ridge, and a three-dimensional hill. We
find very good agreement between the simulation results and the measurement
data, which shows this method is suitable to model high Reynolds number flows
over complex terrain.
