Hybrid RANS-LES methods can be very useful when high detailed insight into turbulent flow is required, in which instantaneous fluctuations play a critical role. For example when a high-accuracy prediction of complex flow separation is needed, or for insight into thermal fatigue due to fluctuating flows at different temperature, or for the approximation of acoustic noises levels via measurement of fluctuating pressure. Compared to the full deployment of Large Eddy Simulation (LES), the Hybrid methods are designed to retain an economical RANS turbulence model in regions where they are expected to perform well; limiting the use of Eddy Simulation approaches to specific areas where more detail/accuracy is needed.
We report progress in an approach known as Embedded Simulation (ES), whereby we prescribe the limits of these regions in advance and use synthetic turbulence methods to pass from the time-averaged RANS fields into the fluctuating fields (where one can use either LES, or even the DDES schemes as necessary. We demonstrate how this can be achieved today using existing tools in STAR-CCM+, and also provide insight into the more advanced ES approaches currently under development that will provide a comprehensive and semi-automated usage of ES methods in the future.