Direct Numerical Simulation
High-fidelity numerical simulation is one predictive approach to gaining physical insight into the details of combustion. CRF scientists have developed direct numerical simulations (DNSs) of turbulent flames with detailed descriptions of chemistry. These first-principles simulations provide data to validate mixing and combustion models in engineering-level simulations of combustion devices, in addition to fundamental insight into complex turbulence/chemistry interactions in flames.
Appealing because of its accuracy and simplicity, DNS fully resolves the finest spatial and temporal details of a turbulent combustion process. DNS is usually limited to a particular physical aspect of a turbulent combustion process and simple ‘building block’ flows such as homogeneous turbulence or shear layers. Other high-fidelity simulation approaches, such as those using adaptive mesh refinement and/or vortex methods, are useful for investigations of unsteady laminar combustion where there is a wide separation of the spatial scales of the problem. All of these approaches can benefit by direct comparisons with carefully designed ‘building block’ experiments. High-fidelity simulation approaches also allow validation of submodels of combustion processes. Successful submodels then enable efficient computational prediction of these detailed processes when they are coupled to simulations on larger domains. The goal of the larger, or device-scale, simulation is to be realistic over the time frame and volume needed to understand performance.