Progress and challenges in large eddy simulation of gas turbine flows.

Abstract

Gas turbine flows are complex and very difficult to be predicted accurately not only due to that they are inherently unsteady but also because the presence of many complex flow phenomena such as transition, separation, substantial secondary flow, combustion and so on. Those complex flow phenomena cannot be captured accurately by the traditional Reynolds-Averaged Navier-Stokes (RANS) and Unsteady RANS (URANS) methods although they have been the main numerical tools for computing gas turbine flows in the past decades due to their computational efficiency and reasonable accuracy. Therefore, the desire for greater accuracy has led to the development and application of high fidelity numerical simulation tools for gas turbine flows. Two such tools available 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, summarizing the current status of LES applications in gas turbines and pointing out the challenges that we are facing.