Large Eddy Simulation of Turbine Aerodynamics by Explicit Filtering

A large eddy simulation (LES) has been performed of the flow through a turbine cascade, named T106C, with an explicit filtering method. This flow has emerged as a benchmark for assessing newer types of computations like LES. The explicit filtering method is implemented using 6th-order compact differences for derivatives, and 10th-order filtering for sub-grid-scale, functional modeling. LES with a uniform inflow, and one with turbulent fluctuations (from a precursor, forced, homogeneous, isotropic turbulence simulation) were performed. Broadly, the surface pressure distribution agrees with experiment as in other simulations. The effect of inflow turbulence has only minor effects on gross parameters like surface pressure distribution, wake profiles of losses, and skin friction distribution. Examination of 2nd invariant of the velocity gradient tensor Q shows the structural development of bypass transition over the suction surface terminated by a reattaching shear layer carrying spanwise rollers. These rollers break down continuously into smaller structures travelling into the wake