This seminar will start by establishing and comparing the fundamental assumptions supporting RANS and LES and, in doing so, will highlight what the true potential of LES is, as well as its limitations. It will continue by way of a short review of the most common LES formulations before allowing time for the presentation of two key applications. The software and hardware requirement of running a LES simulation will also be reviewed as we move towards the end of the day to add a cost dimension to the information pack provided.