High fidelity numerical simulations of gas turbine flows.

Traditionally the so called Reynolds-Averaged Navier-Stokes (RANS) and Unsteady RANS (URANS) have been the main numerical tools for computing gas turbine flows due to their computational efficiency and reasonable accuracy. However, the limitations of RANS and URANS to resolve appropriate details and capture some essential flow features associated with turbulence are also well known, in some cases such as transition they could fail to predict the flow behaviors completely. Therefore, the desire for greater accuracy has led to the development and application of high fidelity numerical simulation tools for gas turbine flows. Two conventional such tools are Direct Numerical Simulation (DNS) which captures directly all details of turbulent flow in space and time, and Large Eddy Simulation (LES) which computes large scale motions of turbulent flow directly in space and time while the small scale motions are modelled. DNS is computationally very expensive and even with the available most powerful supercomputers today or in the foreseeable future it is still prohibitive to apply DNS for gas turbine flows. LES is the most promising simulation tool which has already reasonably widely used for gas turbine flows. This paper will very briefly review first the applications of LES in turbomachinery flows and then focus on two gas turbine combustor related flow cases, demonstrating the superiority of LES in those cases where the RANS performs poorlyN/