Abstract
WindNinja is a high-resolution diagnostic wind model developed for use
by operational wildland fire management. The original version of
WindNinja employed a numerical solver to enforce conservation of mass
(COM). Because the COM solver is fast-running, requires little technical
experience to run, and predicts ridgetop speed up and channeling effects
well, it is widely used by the operational fire community. The COM
solver has limitations, however, in regions where momentum effects
dominate the flow, such as in regions of flow separation, which can
occur on the lee-side of terrain obstacles. Recently, a second solver
has been incorporated into WindNinja which enforces conservation of mass
and momentum using computational fluid dynamics (CFD) techniques based
on the Reynolds-Averaged Navier-Stokes (RANS) equations. In this work we
compare simulations from the CFD solver to measurements made during
three field campaigns (Askervein Hill, Bolund Hill, and Big Southern
Butte) as well as to simulations from the COM solver and an LES model.
Evaluations focus on near-surface winds during high-wind periods, which
are of particular interest to wildland fire managers.