A method for the large-eddy simulation (LES) of wildfire spread over complex terrain is presented. In this scheme, a cut-cell immersed boundary method (CC-IBM) is used to render the complex terrain, defined by a tessellation, on a rectilinear Cartesian grid. Discretization of scalar transport equations for chemical species is done via a finite volume scheme on cut-cells defined by the intersection of the terrain geometry and the Cartesian cells. Momentum transport and heat transfer close to the immersed terrain are handled using dynamic wall models and a direct forcing immersed boundary method. A new “open” convective inflow/outflow method for specifying atmospheric wind boundary conditions is presented. Additionally, three basic approaches have been explored to model fire spread: (1) Representing the vegetation as a collection of Lagrangian particles, (2) representing the vegetation as a semi-porous boundary, and (3) representing the fire spread using a level set method, in which the fire spreads as a function of terrain slope, vegetation type, and wind speed. Several test and validation cases are reported to demonstrate the capabilities of this novel wildfire simulation methodology.

Interest in the development of super-maneuverable, micro-air-vehicles has led to the re-examination of basic flight modes, particularly, those that are inspired by biological observations. The majority of experimental and numerical studies related to flapping flight have explored the relationships between the thrust coefficient (and propulsive efficiency) and wing geometry and kinematics. Relatively speaking, the wing flexibility and the interplay between kinematics and flexibility have received less attention, and currently, it remains unclear as to if they can be exploited to achieve a better performance during low Reynolds number flapping flight. To bridge this gap. the role of flexibility and fluid-structure interactions in flapping flight have been numerically investigated by using a two-dimensional, two-component wing system with a torsion spring. One of the primary outcomes of this work is that nonlinear resonances play an important role in determining the performance of a flapping wing system, mainly through the formation of leading, trailing edge, and end of stroke vortices and interactions amongst them.