  Flow past a high-lift low-pressure turbine (LPT) blade in a cascade could be
quite complex as phenomena like separation and transition are often involved.
For a highly loadedT106A blade at a high incidence and relatively low Reynolds
number(25, 000 < Re < 1, 00, 000), separation-induced transition is observed on
the suction side of the blade, making it a challenging problem for model-based
simulations. In this work, computations for this flow are carried out using
RANS and hybrid LES/RANS approaches. The RANS simulations are performed with
six popular low- Re turbulence models. While turbulence models by themselves
fail to predict any separation on the T106A blade, the four-equation
Langtry-Menter transition model predicts a short separation bubble. The
characteristic of this bubble, however, is very different from what is observed
in experiments and DNS, and therefore transition is not accurately predicted.
An embedded hybrid LES/RANS approach, Limited numerical scales(LNS), with an
automatic switch to LES in sufficiently resolved grids, is then used for
predictions on the sameRANS grid. With the statistical turbulence on fine
grids, LES-like behavior of LNS results in an unphysical drop in Reynolds
stresses as the turbulent fluctuations are not appropriately represented on the
resolved scale. Therefore, the LNS results are very similar to those obtained
with turbulence models. However, when synthetic turbulence with correct
statistical characteristics is used to stimulate the large eddies in the
embedded LES zone, LNS is able to predict separation and recovers a solution
very close to DNS and experimental results.
