Generating realistic turbulent inflow conditions for large eddy simulations (LES) and other large-scale-resolving approaches is essential to fully exploit the ever-increasing capabilities of modern computers in solving fluid flow problems of engineering interest. This research area has received much attention during the last two decades, and will continue to grow as LES is applied to an even wider range of flows. It is deceptively difficult to generate inlet turbulence that is appropriate for a specific problem being simulated and various methods have been designed to improve this "appropriateness". We present a review of such turbulent inflow boundary conditions, broadly classified into library-based methods, recycling-rescaling-based methods, and synthetic turbulence generators. The last category is given more attention to cover a variety of creative approaches that are found in the literature, as well as due to its practicality. Selection of a particular method for a particular application is a compromise between the required fidelity and the allowable complexity and computational expense. An example case study is presented to illustrate the issues involved in the selection and adaptation process.
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