Simulation of Turbulent Flow and Complex Chemistry by Local Integral Moment (LIM) Modeling

A local integral moment (LIM) model is presented for simulations of gas combustion in turbulent flows. The LIM model, which is fundamentally different f rom existing codes, is based on the fact that molecular mixing processes in turbulent flows are concentrated on universal, self-similar, small-scale structures. The model incorporates this experimentally proven simplification through a local parabolization of the governing transport equations on the time-evolving material surface on which the gradients are concentrated. This leads to a closed set of equations governing the local integral moments along the layer-normal direction at each point on the surface, effectively trans forming the original partial differential equations to a set of ordinary differential equations that can be solved on a time-evolving surface. The scalar field constructed from the integral moments on this surface gives the chemical species fields via a strained diffusion and reaction layer formulation. Results from numerous test cases indicate that the LIM model allows accurate, relatively economical calculations of complex flows with complex chemistry.