Transition Prediction in Low Pressure Turbine (LPT) Using Gamma Theta Model and Passive Control of Separation

The boundary layer of low-pressure turbine blades has received a great deal of attention due to advent of high lift and ultra high lift LP turbines. At cruising condition, Reynolds number is very low in engine and LP turbine performance suffers mainly from losses due to the laminar separation bubble on suction surface. In this paper, T106A low pressure turbine profile has been used to study the behavior of boundary layer and subsequently, flow is controlled using the passive technique. Unsteady Reynolds Averaged Navier Stokes equations were solved using SST Gamma-Theta transition model for turbulence closure. Hybrid mesh topology has been used to discretize the computational domain, with highly resolved structured mesh in boundary layer (Y+ < 1) and unstructured mesh in the rest of domain. Simulations were performed using commercial CFD code ANSYS FLUENT ® at Reynolds number 91000 (based on inlet velocity and chord length) and turbulence intensity of 0.4%. To study the effect of dimple on the flow separation, dimple has been positioned at different axial location on the suction side. It was found that shifting the dimple downstream results in controlled flow and reduced loss coefficient as compared to the case when no dimple is applied.Copyright © 2011 by ASME