PUbic( repo tnq burden for this C0144711011o t informaton i$ estimated toApproved for public release; distribution unlimited. ABSTRACT (Maximum 200 words)Fluid dynamic turbulence is one of the most challenging computational physics problems because of the extremely wide range of time and space scales involved, the strong nonlinearity of the government equations, and the many practical and important applications. While most linear fluid instabilities are well understood, the nonlinear interactions among them makes even the relatively simple limit of homogeneous isotropic turbulence difficult to treat physically, mathematically, and computationally. Turbulence is modeled computationally by a twostage bootstrap process. The first stage, Direct Numerical Simulations, attempts to resolve the relevant physical time and space scales but its application is limited to diffusive flows with a relatively small Reynolds number (Re). Using Direct Numerical Simulation to provide a database, in turn, allows calibration of phenomenological turbulence models for engineering applications. Large Eddy Simulation incorporates a form of turbulence modelling applicable when the large-scale flows of interest are intrinsically time dependent, thus throwing common statistical models into question. A promising approach to Large Eddy Simulation involves the use of high-resolution monotone computational fluid dynamics algorithms such as Flux-Corrected Transport or the Piecewise Parabolic Method which have intrinsic subgrid turbulence models coupled naturally to the resolves scales in the computed flow. The physical considerations underlying and evidence supporting this Monotone Integrated Large Eddy Simulation approach are discussed.

▪ Abstract  Noncircular jets have been the topic of extensive research in the last fifteen years. These jets were identified as an efficient technique of passive flow control that allows significant improvements of performance in various practical systems at a relatively low cost because noncircular jets rely solely on changes in the geometry of the nozzle. The applications of noncircular jets discussed in this review include improved large- and small-scale mixing in low- and high-speed flows, and enhanced combustor performance, by improving combustion efficiency, reducing combustion instabilities and undesired emissions. Additional applications include noise suppression, heat transfer, and thrust vector control (TVC). The flow patterns associated with noncircular jets involve mechanisms of vortex evolution and interaction, flow instabilities, and fine-scale turbulence augmentation. Stability theory identified the effects of initial momentum thickness distribution, aspect ratio, and radius of curvature on the initial flow evolution. Experiments revealed complex vortex evolution and interaction related to self-induction and interaction between azimuthal and axial vortices, which lead to axis switching in the mean flow field. Numerical simulations described the details and clarified mechanisms of vorticity dynamics and effects of heat release and reaction on noncircular jet behavior. The research on noncircular jets has also led to technology transfer. A topic that started as an academic curiosity—an interesting flow phenomenon—subsequently has had various industrial applications. The investigations reviewed include experimental, theoretical, numerical, and technological aspects of the subject.

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